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Sample records for introgression barriers revealed

  1. Potential chromosomal introgression barriers revealed by linkage analysis in a hybrid of Pinus massoniana and P. hwangshanensis.

    Science.gov (United States)

    Li, Shuxian; Chen, Ying; Gao, Handong; Yin, Tongming

    2010-02-25

    Exploring the genetic mechanisms underlying speciation is a hot topic in modern genetics and evolutionary studies. Distortion of marker transmission ratio is frequently ascribed to selection against alleles that cause hybrid incompatibility. The natural introgression between P. massoniana and P. hwangshanensis and their distribution ranges lead to the emergence of the two species as desirable organisms to study the genetic mechanisms for speciation. Using seeds sampled from trees at different elevations, we consistently detected sharp decreases in seed germination rates of trees in the hybrid zone, which might be due largely to the hybrid incompatibility. A genetic map was established using 192 megagametophytes from a single tree in the hybrid zone of the two species. Segregation distortion analysis revealed that the percentage of significant-segregation-distortion (SSD) markers was extremely high, accounting for more than 25% of the segregating markers. The extension range, the distortion direction, and the distortion intensity of SSD markers also varied dramatically on different linkage groups. In this study, we display the potential chromosomal introgression barriers between P. massoniana and P. hwangshanensis. Our study provides a valuable platform for conducting genome-wide association of hybrid incompatible QTLs and/or candidate genes with marker transmission ratio distortion in the hybrid.

  2. Potential chromosomal introgression barriers revealed by linkage analysis in a hybrid of Pinus massoniana and P. hwangshanensis

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    Yin Tongming

    2010-02-01

    Full Text Available Abstract Background Exploring the genetic mechanisms underlying speciation is a hot topic in modern genetics and evolutionary studies. Distortion of marker transmission ratio is frequently ascribed to selection against alleles that cause hybrid incompatibility. The natural introgression between P. massoniana and P. hwangshanensis and their distribution ranges lead to the emergence of the two species as desirable organisms to study the genetic mechanisms for speciation. Results Using seeds sampled from trees at different elevations, we consistently detected sharp decreases in seed germination rates of trees in the hybrid zone, which might be due largely to the hybrid incompatibility. A genetic map was established using 192 megagametophytes from a single tree in the hybrid zone of the two species. Segregation distortion analysis revealed that the percentage of significant-segregation-distortion (SSD markers was extremely high, accounting for more than 25% of the segregating markers. The extension range, the distortion direction, and the distortion intensity of SSD markers also varied dramatically on different linkage groups. Conclusions In this study, we display the potential chromosomal introgression barriers between P. massoniana and P. hwangshanensis. Our study provides a valuable platform for conducting genome-wide association of hybrid incompatible QTLs and/or candidate genes with marker transmission ratio distortion in the hybrid.

  3. Multilocus phylogeography of the common lizard Zootoca vivipara at the Ibero-Pyrenean suture zone reveals lowland barriers and high-elevation introgression.

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    Milá, Borja; Surget-Groba, Yann; Heulin, Benoît; Gosá, Alberto; Fitze, Patrick S

    2013-09-10

    The geographic distribution of evolutionary lineages and the patterns of gene flow upon secondary contact provide insight into the process of divergence and speciation. We explore the evolutionary history of the common lizard Zootoca vivipara (= Lacerta vivipara) in the Iberian Peninsula and test the role of the Pyrenees and the Cantabrian Mountains in restricting gene flow and driving lineage isolation and divergence. We also assess patterns of introgression among lineages upon secondary contact, and test for the role of high-elevation trans-mountain colonisations in explaining spatial patterns of genetic diversity. We use mtDNA sequence data and genome-wide AFLP loci to reconstruct phylogenetic relationships among lineages, and measure genetic structure. The main genetic split in mtDNA corresponds generally to the French and Spanish sides of the Pyrenees as previously reported, in contrast to genome-wide AFLP data, which show a major division between NW Spain and the rest. Both types of markers support the existence of four distinct and geographically congruent genetic groups, which are consistent with major topographic barriers. Both datasets reveal the presence of three independent contact zones between lineages in the Pyrenean region, one in the Basque lowlands, one in the low-elevation mountains of the western Pyrenees, and one in the French side of the central Pyrenees. The latter shows genetic evidence of a recent, high-altitude trans-Pyrenean incursion from Spain into France. The distribution and age of major lineages is consistent with a Pleistocene origin and a role for both the Pyrenees and the Cantabrian Mountains in driving isolation and differentiation of Z. vivipara lineages at large geographic scales. However, mountain ranges are not always effective barriers to dispersal, and have not prevented a recent high-elevation trans-Pyrenean incursion that has led to asymmetrical introgression among divergent lineages. Cytonuclear discordance in patterns

  4. Reticulate Speciation and Barriers to Introgression in the Anopheles gambiae Species Complex

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    Crawford, Jacob E.; Riehle, Michelle M.; Guelbeogo, Wamdaogo M.; Gneme, Awa; Sagnon, N'Fale; Vernick, Kenneth D.; Nielsen, Rasmus; Lazzaro, Brian P.

    2015-01-01

    Speciation as a process remains a central focus of evolutionary biology, but our understanding of the genomic architecture and prevalence of speciation in the face of gene flow remains incomplete. The Anopheles gambiae species complex of malaria mosquitoes is a radiation of ecologically diverse taxa. This complex is well-suited for testing for evidence of a speciation continuum and genomic barriers to introgression because its members exhibit partially overlapping geographic distributions as well as varying levels of divergence and reproductive isolation. We sequenced 20 genomes from wild A. gambiae s.s., Anopheles coluzzii, Anopheles arabiensis, and compared these with 12 genomes from the “GOUNDRY” subgroup of A. gambiae s.l. Amidst a backdrop of strong reproductive isolation, we find strong evidence for a speciation continuum with introgression of autosomal chromosomal regions among species and subgroups. The X chromosome, however, is strongly differentiated among all taxa, pointing to a disproportionately large effect of X chromosome genes in driving speciation among anophelines. Strikingly, we find that autosomal introgression has occurred from contemporary hybridization between A. gambiae and A. arabiensis despite strong divergence (∼5× higher than autosomal divergence) and isolation on the X chromosome. In addition to the X, we find strong evidence that lowly recombining autosomal regions, especially pericentromeric regions, serve as barriers to introgression secondarily to the X. We show that speciation with gene flow results in genomic mosaicism of divergence and introgression. Such a reticulate gene pool connecting vector taxa across the speciation continuum has important implications for malaria control efforts. PMID:26615027

  5. Interspecies introgressive hybridization in spiny frogsQuasipaa(Family Dicroglossidae) revealed by analyses on multiple mitochondrial and nuclear genes.

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    Zhang, Qi-Peng; Hu, Wen-Fang; Zhou, Ting-Ting; Kong, Shen-Shen; Liu, Zhi-Fang; Zheng, Rong-Quan

    2018-01-01

    Introgression may lead to discordant patterns of variation among loci and traits. For example, previous phylogeographic studies on the genus Quasipaa detected signs of genetic introgression from genetically and morphologically divergent Quasipaa shini or Quasipaa spinosa . In this study, we used mitochondrial and nuclear DNA sequence data to verify the widespread introgressive hybridization in the closely related species of the genus Quasipaa , evaluate the level of genetic diversity, and reveal the formation mechanism of introgressive hybridization. In Longsheng, Guangxi Province, signs of asymmetrical nuclear introgression were detected between Quasipaa boulengeri and Q. shini . Unidirectional mitochondrial introgression was revealed from Q. spinosa to Q. shini . By contrast, bidirectional mitochondrial gene introgression was detected between Q. spinosa and Q. shini in Lushan, Jiangxi Province. Our study also detected ancient hybridizations between a female Q. spinosa and a male Q. jiulongensis in Zhejiang Province. Analyses on mitochondrial and nuclear genes verified three candidate cryptic species in Q. spinosa , and a cryptic species may also exist in Q. boulengeri . However, no evidence of introgressive hybridization was found between Q. spinosa and Q. boulengeri . Quasipaa exilispinosa from all the sampling localities appeared to be deeply divergent from other communities. Our results suggest widespread introgressive hybridization in closely related species of Quasipaa and provide a fundamental basis for illumination of the forming mechanism of introgressive hybridization, classification of species, and biodiversity assessment in Quasipaa .

  6. The myth of natural barriers. Is transgene introgression by genetically modified crops an environmental risk?

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    Guarnieri, Vincenzo; Benessia, Alice; Camino, Elena; Barbiero, Giuseppe

    2008-01-01

    Genetically modified (GM) crops under open field conditions are a complex and controversial issue. Ecologists are discussing about the possibility that a transgene belonging to GM plants could spread to native populations through a process known as introgression the stable incorporation of a gene in the host genome able to generate a differentiated population. The ecological consequences of a transgene introgression in plants or bacteria are not yet well understood, but could be significant. In this critical review we consider vertical and horizontal introgression. We analyse the biochemical and genetic constraints, and environmental factors that limit the possibility of transgene spread; meanwhile we show cases in which the natural barriers are overcome. Then we discuss the overall management of GM crops, noting the shortcomings and approximations of risk assessment based on linear thinking typical of the biomolecular approach. Finally we suggest to explicitly weight facts together with values and we encourage the undertaking of an ecological perspective, encompassing the complexity of (non-linear) relations between organisms and the environment.

  7. Population Genomics Reveals Speciation and Introgression between Brown Norway Rats and Their Sibling Species.

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    Teng, Huajing; Zhang, Yaohua; Shi, Chengmin; Mao, Fengbiao; Cai, Wanshi; Lu, Liang; Zhao, Fangqing; Sun, Zhongsheng; Zhang, Jianxu

    2017-09-01

    Murine rodents are excellent models for study of adaptive radiations and speciation. Brown Norway rats (Rattus norvegicus) are successful global colonizers and the contributions of their domesticated laboratory strains to biomedical research are well established. To identify nucleotide-based speciation timing of the rat and genomic information contributing to its colonization capabilities, we analyzed 51 whole-genome sequences of wild-derived Brown Norway rats and their sibling species, R. nitidus, and identified over 20 million genetic variants in the wild Brown Norway rats that were absent in the laboratory strains, which substantially expand the reservoir of rat genetic diversity. We showed that divergence of the rat and its siblings coincided with drastic climatic changes that occurred during the Middle Pleistocene. Further, we revealed that there was a geographically widespread influx of genes between Brown Norway rats and the sibling species following the divergence, resulting in numerous introgressed regions in the genomes of admixed Brown Norway rats. Intriguing, genes related to chemical communications among these introgressed regions appeared to contribute to the population-specific adaptations of the admixed Brown Norway rats. Our data reveals evolutionary history of the Brown Norway rat, and offers new insights into the role of climatic changes in speciation of animals and the effect of interspecies introgression on animal adaptation. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  8. Multi-locus phylogeny reveals instances of mitochondrial introgression and unrecognized diversity in Kenyan barbs (Cyprininae: Smiliogastrini).

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    Schmidt, Ray C; Bart, Henry L; Nyingi, Wanja Dorothy

    2017-06-01

    The phylogenetics and taxonomic status of small African barbs (Cyprininae: Smiliogastrini) remains unresolved despite the recent decision to elevate the genus name Enteromius for the group. The main barrier to understanding the origin of African small barbs and evolutionary relationships within the group is the poor resolution of phylogenies published to date. These phylogenies usually rely on mitochondrial markers and have limited taxon sampling. Here we investigate the phylogenetic relationships of small barbs of Kenya utilizing cytochrome b, Growth Hormone (GH) intron 2, and RAG1 markers from multiple populations of many species in the region. This multi-locus study produced well-supported phylogenies and revealed additional issues that complicate understanding the relationships among East African barbs. We observed widespread mtDNA introgression within the Kenyan barbs, highlighting the need to include nuclear markers in phylogenetic studies of the group. The GH intron 2 resolved heterospecific individuals and aided in inferring the species level phylogeny. The study reveals unrecognized diversity within the group, including within species reported to occur throughout East Africa, and it provides the groundwork for future taxonomic work in the region and across Africa. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Interspecific introgression in cetaceans: DNA markers reveal post-F1 status of a pilot whale.

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    Laura Miralles

    Full Text Available Visual species identification of cetacean strandings is difficult, especially when dead specimens are degraded and/or species are morphologically similar. The two recognised pilot whale species (Globicephala melas and Globicephala macrorhynchus are sympatric in the North Atlantic Ocean. These species are very similar in external appearance and their morphometric characteristics partially overlap; thus visual identification is not always reliable. Genetic species identification ensures correct identification of specimens. Here we have employed one mitochondrial (D-Loop region and eight nuclear loci (microsatellites as genetic markers to identify six stranded pilot whales found in Galicia (Northwest Spain, one of them of ambiguous phenotype. DNA analyses yielded positive amplification of all loci and enabled species identification. Nuclear microsatellite DNA genotypes revealed mixed ancestry for one individual, identified as a post-F1 interspecific hybrid employing two different Bayesian methods. From the mitochondrial sequence the maternal species was Globicephala melas. This is the first hybrid documented between Globicephala melas and G. macrorhynchus, and the first post-F1 hybrid genetically identified between cetaceans, revealing interspecific genetic introgression in marine mammals. We propose to add nuclear loci to genetic databases for cetacean species identification in order to detect hybrid individuals.

  10. Genomic markers reveal introgressive hybridization in the Indo-West Pacific mangroves: a case study.

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    Mei Sun

    2011-05-01

    Full Text Available Biodiversity of mangrove ecosystems is difficult to assess, at least partly due to lack of genetic verification of morphology-based documentation of species. Natural hybridization, on the one hand, plays an important role in evolution as a source of novel gene combinations and a mechanism of speciation. However, on the other hand, recurrent introgression allows gene flow between species and could reverse the process of genetic differentiation among populations required for speciation. To understand the dynamic evolutionary consequences of hybridization, this study examines genomic structure of hybrids and parental species at the population level. In the Indo-West Pacific, Bruguiera is one of the dominant mangrove genera and species ranges overlap extensively with one another. Morphological intermediates between sympatric Bruguiera gymnorrhiza and Bruguiera sexangula have been reported as a variety of B. sexangula or a new hybrid species, B. × rhynchopetala. However, the direction of hybridization and extent of introgression are unclear. A large number of species-specific inter-simple sequence repeat (ISSR markers were found in B. gymnorrhiza and B. sexangula, and the additive ISSR profiling of B. × rhynchopetala ascertained its hybrid status and identified its parental origin. The varying degree of scatterness among hybrid individuals in Principal Coordinate Analysis and results from NewHybrids analysis indicate that B. × rhynchopetala comprises different generations of introgressants in addition to F(1s. High genetic relatedness between B. × rhynchopetala and B. gymnorrhiza based on nuclear and chloroplast sequences suggests preferential hybrid backcrosses to B. gymnorrhiza. We conclude that B. × rhynchopetala has not evolved into an incipient hybrid species, and its persistence can be explained by recurrent hybridization and introgression. Genomic data provide insights into the hybridization dynamics of mangrove plants. Such information

  11. European flint landraces grown in situ reveal adaptive introgression from modern maize.

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    Elena Bitocchi

    Full Text Available We have investigated the role of selection in the determination of the detected levels of introgression from modern maize hybrid varieties into maize landraces still cultivated in situ in Italy. We exploited the availability of a historical collection of landraces undertaken before the introduction and widespread use of modern maize, to analyse genomic changes that have occurred in these maize landraces over 50 years of co-existence with hybrid varieties. We have combined a previously published SSR dataset (n=21 with an AFLP loci dataset (n=168 to provide higher resolution power and to obtain a more detailed picture. We show that selection pressures for adaptation have favoured new alleles introduced by migration from hybrids. This shows the potential for analysis of historical introgression even over this short period of 50 years, for an understanding of the evolution of the genome and for the identification of its functionally important regions. Moreover, this demonstrates that landraces grown in situ represent almost unique populations for use for such studies when the focus is on the domesticated plant. This is due to their adaptation, which has arisen from their dynamic evolution under a continuously changing agro-ecological environment, and their capture of new alleles from hybridisation. We have also identified loci for which selection has inhibited introgression from modern germplasm and has enhanced the distinction between landraces and modern maize. These loci indicate that selection acted in the past, during the formation of the flint and dent gene pools. In particular, the locus showing the strongest signals of selection is a Misfit transposable element. Finally, molecular characterisation of the same samples with two different molecular markers has allowed us to compare their performances. Although the genetic-diversity and population-structure analyses provide the same global qualitative pattern, which thus provides the same

  12. Interspecies introgressive hybridization in spiny frogs Quasipaa (Family Dicroglossidae) revealed by analyses on multiple mitochondrial and nuclear genes

    OpenAIRE

    Zhang, Qi‐Peng; Hu, Wen‐Fang; Zhou, Ting‐Ting; Kong, Shen‐Shen; Liu, Zhi‐Fang; Zheng, Rong‐Quan

    2017-01-01

    Abstract Introgression may lead to discordant patterns of variation among loci and traits. For example, previous phylogeographic studies on the genus Quasipaa detected signs of genetic introgression from genetically and morphologically divergent Quasipaa shini or Quasipaa spinosa. In this study, we used mitochondrial and nuclear DNA sequence data to verify the widespread introgressive hybridization in the closely related species of the genus Quasipaa, evaluate the level of genetic diversity, ...

  13. Genome-wide SNP analysis reveals recent genetic introgression from domestic pigs into Northwest European wild boar populations

    NARCIS (Netherlands)

    Goedbloed, D.J.; Megens, H.J.W.C.; Hooft, van W.F.; Herrero-Medrano, J.; Lutz, W.; Alexandri, P.; Crooijmans, R.P.M.A.; Groenen, M.A.M.; Wieren, van S.E.; Ydenberg, R.C.; Prins, H.H.T.

    2013-01-01

    Present-day genetic introgression from domestic pigs into European wild boar has been suggested in various studies. However, no hybrids have been identified beyond doubt mainly because available methods were unable to quantify the extent of introgression and rule out natural processes. Genetic

  14. Integrative Taxonomy of Southeast Asian Snail-Eating Turtles (Geoemydidae: Malayemys Reveals a New Species and Mitochondrial Introgression.

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    Flora Ihlow

    Full Text Available Based on an integrative taxonomic approach, we examine the differentiation of Southeast Asian snail-eating turtles using information from 1863 bp of mitochondrial DNA, 12 microsatellite loci, morphology and a correlative species distribution model. Our analyses reveal three genetically distinct groups with limited mitochondrial introgression in one group. All three groups exhibit distinct nuclear gene pools and distinct morphology. Two of these groups correspond to the previously recognized species Malayemys macrocephala (Chao Phraya Basin and M. subtrijuga (Lower Mekong Basin. The third and genetically most divergent group from the Khorat Basin represents a previously unrecognized species, which is described herein. Although Malayemys are extensively traded and used for religious release, only few studied turtles appear to be translocated by humans. Historic fluctuations in potential distributions were assessed using species distribution models (SDMs. The Last Glacial Maximum (LGM projection of the predictive SDMs suggests two distinct glacial distribution ranges, implying that the divergence of M. macrocephala and M. subtrijuga occurred in allopatry and was triggered by Pleistocene climate fluctuations. Only the projection derived from the global circulation model MIROC reveals a distinct third glacial distribution range for the newly discovered Malayemys species.

  15. Rangewide genetic analysis of Lesser Prairie-Chicken reveals population structure, range expansion, and possible introgression

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    Oyler-McCance, Sara J.; DeYoung, Randall W; Fike, Jennifer; Hagen, Christian A.; Johnson, Jeff A.; Larsson, Lena C.; Patten, Michael

    2016-01-01

    The distribution of the Lesser Prairie-Chicken (Tympanuchus pallidicinctus) has been markedly reduced due to loss and fragmentation of habitat. Portions of the historical range, however, have been recolonized and even expanded due to planting of conservation reserve program (CRP) fields that provide favorable vegetation structure for Lesser Prairie-Chickens. The source population(s) feeding the range expansion is unknown, yet has resulted in overlap between Lesser and Greater Prairie-Chickens (T. cupido) increasing the potential for hybridization. Our objectives were to characterize connectivity and genetic diversity among populations, identify source population(s) of recent range expansion, and examine hybridization with the Greater Prairie-Chicken. We analyzed 640 samples from across the range using 13 microsatellites. We identified three to four populations corresponding largely to ecoregions. The Shinnery Oak Prairie and Sand Sagebrush Prairie represented genetically distinct populations (F ST > 0.034 and F ST > 0.023 respectively). The Shortgrass/CRP Mosaic and Mixed Grass ecoregions appeared admixed (F ST = 0.009). Genetic diversity was similar among ecoregions and N e ranged from 142 (95 % CI 99–236) for the Shortgrass/CRP Mosaic to 296 (95 % CI 233–396) in the Mixed Grass Prairie. No recent migration was detected among ecoregions, except asymmetric dispersal from both the Mixed Grass Prairie and to a lesser extent the Sand Sagebrush Prairie north into adjacent Shortgrass/CRP Mosaic (m = 0.207, 95 % CI 0.116–0.298, m = 0.097, 95 % CI 0.010–0.183, respectively). Indices investigating potential hybridization in the Shortgrass/CRP Mosaic revealed that six of the 13 individuals with hybrid phenotypes were significantly admixed suggesting hybridization. Continued monitoring of diversity within and among ecoregions is warranted as are actions promoting genetic connectivity and range expansion.

  16. Genomic diversity and introgression in O. sativa reveal the impact of domestication and breeding on the rice genome.

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    Keyan Zhao

    2010-05-01

    Full Text Available The domestication of Asian rice (Oryza sativa was a complex process punctuated by episodes of introgressive hybridization among and between subpopulations. Deep genetic divergence between the two main varietal groups (Indica and Japonica suggests domestication from at least two distinct wild populations. However, genetic uniformity surrounding key domestication genes across divergent subpopulations suggests cultural exchange of genetic material among ancient farmers.In this study, we utilize a novel 1,536 SNP panel genotyped across 395 diverse accessions of O. sativa to study genome-wide patterns of polymorphism, to characterize population structure, and to infer the introgression history of domesticated Asian rice. Our population structure analyses support the existence of five major subpopulations (indica, aus, tropical japonica, temperate japonica and GroupV consistent with previous analyses. Our introgression analysis shows that most accessions exhibit some degree of admixture, with many individuals within a population sharing the same introgressed segment due to artificial selection. Admixture mapping and association analysis of amylose content and grain length illustrate the potential for dissecting the genetic basis of complex traits in domesticated plant populations.Genes in these regions control a myriad of traits including plant stature, blast resistance, and amylose content. These analyses highlight the power of population genomics in agricultural systems to identify functionally important regions of the genome and to decipher the role of human-directed breeding in refashioning the genomes of a domesticated species.

  17. Genomic Analysis Reveals Hypoxia Adaptation in the Tibetan Mastiff by Introgression of the Gray Wolf from the Tibetan Plateau.

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    Miao, Benpeng; Wang, Zhen; Li, Yixue

    2017-03-01

    The Tibetan Mastiff (TM), a native of the Tibetan Plateau, has quickly adapted to the extreme highland environment. Recently, the impact of positive selection on the TM genome was studied and potential hypoxia-adaptive genes were identified. However, the origin of the adaptive variants remains unknown. In this study, we investigated the signature of genetic introgression in the adaptation of TMs with dog and wolf genomic data from different altitudes in close geographic proximity. On a genome-wide scale, the TM was much more closely related to other dogs than wolves. However, using the 'ABBA/BABA' test, we identified genomic regions from the TM that possibly introgressed from Tibetan gray wolf. Several of the regions, including the EPAS1 and HBB loci, also showed the dominant signature of selective sweeps in the TM genome. We validated the introgression of the two loci by excluding the possibility of convergent evolution and ancestral polymorphisms and examined the haplotypes of all available canid genomes. The estimated time of introgression based on a non-coding region of the EPAS1 locus mostly overlapped with the Paleolithic era. Our results demonstrated that the introgression of hypoxia adaptive genes in wolves from the highland played an important role for dogs living in hypoxic environments, which indicated that domestic animals could acquire local adaptation quickly by secondary contact with their wild relatives. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  18. Introgression evidence and phylogenetic relationships among three (ParaMisgurnus species as revealed by mitochondrial and nuclear DNA markers

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    Jakovlić I.

    2013-01-01

    Full Text Available The taxonomy of (ParaMisgurnus genera is still debated. We therefore used mitochondrial and nuclear DNA markers to analyze the phylogenetic relationships among Misgurnus anguillicaudatus, Paramisgurnus dabryanus and Misgurnus fossilis. Differing phylogenetic signals from mitochondrial and nuclear marker data suggest an introgression event in the history of M. anguillicaudatus and M. mohoity. No substantial genetic evidence was found that Paramisgurnus dabryanus should be classified as a separate genus.

  19. Cultivar-Based Introgression Mapping Reveals Wild Species-Derived Pm-0, the Major Powdery Mildew Resistance Locus in Squash

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    Holdsworth, William L.; LaPlant, Kyle E.; Bell, Duane C.; Jahn, Molly M.; Mazourek, Michael

    2016-01-01

    Powdery mildew is a major fungal disease on squash and pumpkin (Cucurbita spp.) in the US and throughout the world. Genetic resistance to the disease is not known to occur naturally within Cucurbita pepo and only infrequently in Cucurbita moschata, but has been achieved in both species through the introgression of a major resistance gene from the wild species Cucurbita okeechobeensis subsp. martinezii. At present, this gene, Pm-0, is used extensively in breeding, and is found in nearly all powdery mildew-resistant C. pepo and C. moschata commercial cultivars. In this study, we mapped C. okeechobeensis subsp. martinezii-derived single nucleotide polymorphism (SNP) alleles in a set of taxonomically and morphologically diverse and resistant C. pepo and C. moschata cultivars bred at Cornell University that, by common possession of Pm-0, form a shared-trait introgression panel. High marker density was achieved using genotyping-by-sequencing, which yielded over 50,000 de novo SNP markers in each of the three Cucurbita species genotyped. A single 516.4 kb wild-derived introgression was present in all of the resistant cultivars and absent in a diverse set of heirlooms that predated the Pm-0 introgression. The contribution of this interval to powdery mildew resistance was confirmed by association mapping in a C. pepo cultivar panel that included the Cornell lines, heirlooms, and 68 additional C. pepo cultivars and with an independent F2 population derived from C. okeechobeensis subsp. martinezii x C. moschata. The interval was refined to a final candidate interval of 76.4 kb and CAPS markers were developed inside this interval to facilitate marker-assisted selection. PMID:27936008

  20. The high-quality genome of Brassica napus cultivar 'ZS11' reveals the introgression history in semi-winter morphotype.

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    Sun, Fengming; Fan, Guangyi; Hu, Qiong; Zhou, Yongming; Guan, Mei; Tong, Chaobo; Li, Jiana; Du, Dezhi; Qi, Cunkou; Jiang, Liangcai; Liu, Weiqing; Huang, Shunmou; Chen, Wenbin; Yu, Jingyin; Mei, Desheng; Meng, Jinling; Zeng, Peng; Shi, Jiaqin; Liu, Kede; Wang, Xi; Wang, Xinfa; Long, Yan; Liang, Xinming; Hu, Zhiyong; Huang, Guodong; Dong, Caihua; Zhang, He; Li, Jun; Zhang, Yaolei; Li, Liangwei; Shi, Chengcheng; Wang, Jiahao; Lee, Simon Ming-Yuen; Guan, Chunyun; Xu, Xun; Liu, Shengyi; Liu, Xin; Chalhoub, Boulos; Hua, Wei; Wang, Hanzhong

    2017-11-01

    Allotetraploid oilseed rape (Brassica napus L.) is an agriculturally important crop. Cultivation and breeding of B. napus by humans has resulted in numerous genetically diverse morphotypes with optimized agronomic traits and ecophysiological adaptation. To further understand the genetic basis of diversification and adaptation, we report a draft genome of an Asian semi-winter oilseed rape cultivar 'ZS11' and its comprehensive genomic comparison with the genomes of the winter-type cultivar 'Darmor-bzh' as well as two progenitors. The integrated BAC-to-BAC and whole-genome shotgun sequencing strategies were effective in the assembly of repetitive regions (especially young long terminal repeats) and resulted in a high-quality genome assembly of B. napus 'ZS11'. Within a short evolutionary period (~6700 years ago), semi-winter-type 'ZS11' and the winter-type 'Darmor-bzh' maintained highly genomic collinearity. Even so, certain genetic differences were also detected in two morphotypes. Relative to 'Darmor-bzh', both two subgenomes of 'ZS11' are closely related to its progenitors, and the 'ZS11' genome harbored several specific segmental homoeologous exchanges (HEs). Furthermore, the semi-winter-type 'ZS11' underwent potential genomic introgressions with B. rapa (A r ). Some of these genetic differences were associated with key agronomic traits. A key gene of A03.FLC3 regulating vernalization-responsive flowering time in 'ZS11' was first experienced HE, and then underwent genomic introgression event with A r , which potentially has led to genetic differences in controlling vernalization in the semi-winter types. Our observations improved our understanding of the genetic diversity of different B. napus morphotypes and the cultivation history of semi-winter oilseed rape in Asia. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

  1. Cotton fiber elongation network revealed by expression profiling of longer fiber lines introgressed with different Gossypium barbadense chromosome segments.

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    Fang, Lei; Tian, Ruiping; Li, Xinghe; Chen, Jiedan; Wang, Sen; Wang, Peng; Zhang, Tianzhen

    2014-10-02

    Cotton fiber, a highly elongated, thickened single cell of the seed epidermis, is a powerful cell wall research model. Fiber length, largely determined during the elongation stage, is a key property of fiber quality. Several studies using expressed sequence tags and microarray analysis have identified transcripts that accumulate preferentially during fiber elongation. To further show the mechanism of fiber elongation, we used Digital Gene Expression Tag Profiling to compare transcriptome data from longer fiber chromosome introgressed lines (CSILs) containing segments of various Gossypium barbadense chromosomes with data from its recurrent parent TM-1 during fiber elongation (from 5 DPA to 20 DPA). A large number of differentially expressed genes (DEGs) involved in carbohydrate, fatty acid and secondary metabolism, particularly cell wall biosynthesis, were highly upregulated during the fiber elongation stage, as determined by functional enrichment and pathway analysis. Furthermore, DEGs related to hormone responses and transcription factors showed upregulated expression levels in the CSILs. Moreover, metabolic and regulatory network analysis indicated that the same pathways were differentially altered, and distinct pathways exhibited altered gene expression, in the CSILs. Interestingly, mining of upregulated DEGs in the introgressed segments of these CSILs based on D-genome sequence data showed that these lines were enriched in glucuronosyltransferase, inositol-1, 4, 5-trisphosphate 3-kinase and desulfoglucosinolate sulfotransferase activity. These results were similar to the results of transcriptome analysis. This report provides an integrative network about the molecular mechanisms controlling fiber length, which are mainly tied to carbohydrate metabolism, cell wall biosynthesis, fatty acid metabolism, secondary metabolism, hormone responses and Transcription factors. The results of this study provide new insights into the critical factors associated with cell

  2. Introgression of mitochondrial DNA among Myodes voles: consequences for energetics?

    Directory of Open Access Journals (Sweden)

    Boratyński Zbyszek

    2011-12-01

    Full Text Available Abstract Background Introgression of mitochondrial DNA (mtDNA is among the most frequently described cases of reticulate evolution. The tendency of mtDNA to cross interspecific barriers is somewhat counter-intuitive considering the key function of enzymes that it encodes in the oxidative-phosphorylation process, which could give rise to hybrid dysfunction. How mtDNA reticulation affects the evolution of metabolic functions is, however, uncertain. Here we investigated how morpho-physiological traits vary in natural populations of a common rodent (the bank vole, Myodes glareolus and whether this variation could be associated with mtDNA introgression. First, we confirmed that M. glareolus harbour mtDNA introgressed from M. rutilus by analyzing mtDNA (cytochrome b, 954 bp and nuclear DNA (four markers; 2333 bp in total sequence variation and reconstructing loci phylogenies among six natural populations in Finland. We then studied geographic variation in body size and basal metabolic rate (BMR among the populations of M. glareolus and tested its relationship with mtDNA type. Results Myodes glareolus and its arctic neighbour, M. rutilus, are reciprocally monophyletic at the analyzed nuclear DNA loci. In contrast, the two northernmost populations of M. glareolus have a fixed mitotype that is shared with M. rutilus, likely due to introgressive hybridization. The analyses of phenotypic traits revealed that the body mass and whole-body, but not mass corrected, BMR are significantly reduced in M. glareolus females from northern Finland that also have the introgressed mitotype. Restricting the analysis to the single population where the mitotypes coexist, the association of mtDNA type with whole-body BMR remained but those with mass corrected BMR and body mass did not. Mitochondrial sequence variation in the introgressed haplotypes is compatible with demographic growth of the populations, but may also be a result of positive selection. Conclusion Our

  3. Recent introgressive hybridization revealed by exclusive mtDNA transfer from Oreochromis leucostictus (Trewavas, 1933) to Oreochromis niloticus (Linnaeus, 1758) in Lake Baringo, Kenya

    OpenAIRE

    Nyingi, Dorothy W.; Agnèse, Jean-François

    2007-01-01

    Nuclear DNA and mtDNA polymorphisms were surveyed in various species of East African Oreochromis. In Lake Baringo, where only Oreochromis niloticus baringoensis is present, alien mtDNA haplotypes were observed, apparently the result of introgressive hybridization with Oreochromis leucostictus. This introgression is not accompanied by any substantial or recorded transfer of nuclear genes into O. n. baringoensis.

  4. Introgressive hybridization of Schistosoma haematobium group species in Senegal: species barrier break down between ruminant and human schistosomes.

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    Bonnie L Webster

    Full Text Available BACKGROUND: Schistosomes are dioecious parasitic flatworms, which live in the vasculature of their mammalian definitive hosts. They are the causative agent of schistosomiasis, a disease of considerable medical and veterinary importance in tropical and subtropical regions. Schistosomes undergo a sexual reproductive stage within their mammalian host enabling interactions between different species, which may result in hybridization if the species involved are phylogenetically close. In Senegal, three closely related species in the Schistosoma haematobium group are endemic: S. haematobium, which causes urogenital schistosomiasis in humans, and S. bovis and S. curassoni, which cause intestinal schistosomiasis in cows, sheep and goats. METHODOLOGY/PRINCIPAL FINDINGS: Large-scale multi-loci molecular analysis of parasite samples collected from children and domestic livestock across Senegal revealed that interactions and hybridization were taking place between all three species. Evidence of hybridization between S. haematobium/S. curassoni and S. haematobium/S. bovis was commonly found in children from across Senegal, with 88% of the children surveyed in areas of suspected species overlap excreting hybrid miracidia. No S. haematobium worms or hybrids thereof were found in ruminants, although S. bovis and S. curassoni hybrid worms were found in cows. Complementary experimental mixed species infections in laboratory rodents confirmed that males and females of each species readily pair and produce viable hybrid offspring. CONCLUSIONS/SIGNIFICANCE: THESE DATA PROVIDE INDISPUTABLE EVIDENCE FOR: the high occurrence of bidirectional hybridization between these Schistosoma species; the first conclusive evidence for the natural hybridisation between S. haematobium and S. curassoni; and demonstrate that the transmission of the different species and their hybrids appears focal. Hybridization between schistosomes has been known to influence the disease epidemiology

  5. Genome re-sequencing of semi-wild soybean reveals a complex Soja population structure and deep introgression.

    Science.gov (United States)

    Qiu, Jie; Wang, Yu; Wu, Sanling; Wang, Ying-Ying; Ye, Chu-Yu; Bai, Xuefei; Li, Zefeng; Yan, Chenghai; Wang, Weidi; Wang, Ziqiang; Shu, Qingyao; Xie, Jiahua; Lee, Suk-Ha; Fan, Longjiang

    2014-01-01

    Semi-wild soybean is a unique type of soybean that retains both wild and domesticated characteristics, which provides an important intermediate type for understanding the evolution of the subgenus Soja population in the Glycine genus. In this study, a semi-wild soybean line (Maliaodou) and a wild line (Lanxi 1) collected from the lower Yangtze regions were deeply sequenced while nine other semi-wild lines were sequenced to a 3-fold genome coverage. Sequence analysis revealed that (1) no independent phylogenetic branch covering all 10 semi-wild lines was observed in the Soja phylogenetic tree; (2) besides two distinct subpopulations of wild and cultivated soybean in the Soja population structure, all semi-wild lines were mixed with some wild lines into a subpopulation rather than an independent one or an intermediate transition type of soybean domestication; (3) high heterozygous rates (0.19-0.49) were observed in several semi-wild lines; and (4) over 100 putative selective regions were identified by selective sweep analysis, including those related to the development of seed size. Our results suggested a hybridization origin for the semi-wild soybean, which makes a complex Soja population structure.

  6. Genome re-sequencing of semi-wild soybean reveals a complex Soja population structure and deep introgression.

    Directory of Open Access Journals (Sweden)

    Jie Qiu

    Full Text Available Semi-wild soybean is a unique type of soybean that retains both wild and domesticated characteristics, which provides an important intermediate type for understanding the evolution of the subgenus Soja population in the Glycine genus. In this study, a semi-wild soybean line (Maliaodou and a wild line (Lanxi 1 collected from the lower Yangtze regions were deeply sequenced while nine other semi-wild lines were sequenced to a 3-fold genome coverage. Sequence analysis revealed that (1 no independent phylogenetic branch covering all 10 semi-wild lines was observed in the Soja phylogenetic tree; (2 besides two distinct subpopulations of wild and cultivated soybean in the Soja population structure, all semi-wild lines were mixed with some wild lines into a subpopulation rather than an independent one or an intermediate transition type of soybean domestication; (3 high heterozygous rates (0.19-0.49 were observed in several semi-wild lines; and (4 over 100 putative selective regions were identified by selective sweep analysis, including those related to the development of seed size. Our results suggested a hybridization origin for the semi-wild soybean, which makes a complex Soja population structure.

  7. Multiple mitochondrial introgression events and heteroplasmy in trypanosoma cruzi revealed by maxicircle MLST and next generation sequencing.

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    Louisa A Messenger

    Full Text Available Mitochondrial DNA is a valuable taxonomic marker due to its relatively fast rate of evolution. In Trypanosoma cruzi, the causative agent of Chagas disease, the mitochondrial genome has a unique structural organization consisting of 20-50 maxicircles (∼20 kb and thousands of minicircles (0.5-10 kb. T. cruzi is an early diverging protist displaying remarkable genetic heterogeneity and is recognized as a complex of six discrete typing units (DTUs. The majority of infected humans are asymptomatic for life while 30-35% develop potentially fatal cardiac and/or digestive syndromes. However, the relationship between specific clinical outcomes and T. cruzi genotype remains elusive. The availability of whole genome sequences has driven advances in high resolution genotyping techniques and re-invigorated interest in exploring the diversity present within the various DTUs.To describe intra-DTU diversity, we developed a highly resolutive maxicircle multilocus sequence typing (mtMLST scheme based on ten gene fragments. A panel of 32 TcI isolates was genotyped using the mtMLST scheme, GPI, mini-exon and 25 microsatellite loci. Comparison of nuclear and mitochondrial data revealed clearly incongruent phylogenetic histories among different geographical populations as well as major DTUs. In parallel, we exploited read depth data, generated by Illumina sequencing of the maxicircle genome from the TcI reference strain Sylvio X10/1, to provide the first evidence of mitochondrial heteroplasmy (heterogeneous mitochondrial genomes in an individual cell in T. cruzi.mtMLST provides a powerful approach to genotyping at the sub-DTU level. This strategy will facilitate attempts to resolve phenotypic variation in T. cruzi and to address epidemiologically important hypotheses in conjunction with intensive spatio-temporal sampling. The observations of both general and specific incidences of nuclear-mitochondrial phylogenetic incongruence indicate that genetic recombination

  8. Repeated adaptive introgression at a gene under multiallelic balancing selection.

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    Vincent Castric

    2008-08-01

    Full Text Available Recently diverged species typically have incomplete reproductive barriers, allowing introgression of genetic material from one species into the genomic background of the other. The role of natural selection in preventing or promoting introgression remains contentious. Because of genomic co-adaptation, some chromosomal fragments are expected to be selected against in the new background and resist introgression. In contrast, natural selection should favor introgression for alleles at genes evolving under multi-allelic balancing selection, such as the MHC in vertebrates, disease resistance, or self-incompatibility genes in plants. Here, we test the prediction that negative, frequency-dependent selection on alleles at the multi-allelic gene controlling pistil self-incompatibility specificity in two closely related species, Arabidopsis halleri and A. lyrata, caused introgression at this locus at a higher rate than the genomic background. Polymorphism at this gene is largely shared, and we have identified 18 pairs of S-alleles that are only slightly divergent between the two species. For these pairs of S-alleles, divergence at four-fold degenerate sites (K = 0.0193 is about four times lower than the genomic background (K = 0.0743. We demonstrate that this difference cannot be explained by differences in effective population size between the two types of loci. Rather, our data are most consistent with a five-fold increase of introgression rates for S-alleles as compared to the genomic background, making this study the first documented example of adaptive introgression facilitated by balancing selection. We suggest that this process plays an important role in the maintenance of high allelic diversity and divergence at the S-locus in flowering plant families. Because genes under balancing selection are expected to be among the last to stop introgressing, their comparison in closely related species provides a lower-bound estimate of the time since the

  9. Systematic design for trait introgression projects.

    Science.gov (United States)

    Cameron, John N; Han, Ye; Wang, Lizhi; Beavis, William D

    2017-10-01

    Using an Operations Research approach, we demonstrate design of optimal trait introgression projects with respect to competing objectives. We demonstrate an innovative approach for designing Trait Introgression (TI) projects based on optimization principles from Operations Research. If the designs of TI projects are based on clear and measurable objectives, they can be translated into mathematical models with decision variables and constraints that can be translated into Pareto optimality plots associated with any arbitrary selection strategy. The Pareto plots can be used to make rational decisions concerning the trade-offs between maximizing the probability of success while minimizing costs and time. The systematic rigor associated with a cost, time and probability of success (CTP) framework is well suited to designing TI projects that require dynamic decision making. The CTP framework also revealed that previously identified 'best' strategies can be improved to be at least twice as effective without increasing time or expenses.

  10. High rates of hybridisation reveal fragile reproductive barriers between endangered Australian sea snakes

    DEFF Research Database (Denmark)

    Sanders, Kate L; Redsted Rasmussen, Arne; Guinea, Michael L.

    2014-01-01

    designations, but revealed high frequencies of hybrids on all four reefs and individuals of pure A. fuscus ancestry only at Scott and (historically) Ashmore. Most unexpectedly, 95% of snakes sampled at Hibernia were hybrids that resembled A. laevis in phenotype, revealing a collapse of reproductive barriers...... (‘reverse speciation’) at this reef. These results have dire implications for the conservation status of A. fuscus, and highlight the fragility of reproductive barriers in a recent marine radiation....

  11. Tracking the progression of speciation: variable patterns of introgression across the genome provide insights on the species delimitation between progenitor-derivative spruces (Picea mariana × P. rubens).

    Science.gov (United States)

    de Lafontaine, Guillaume; Prunier, Julien; Gérardi, Sébastien; Bousquet, Jean

    2015-10-01

    The genic species concept implies that while most of the genome can be exchanged somewhat freely between species through introgression, some genomic regions remain impermeable to interspecific gene flow. Hence, interspecific differences can be maintained despite ongoing gene exchange within contact zones. This study assessed the heterogeneous patterns of introgression at gene loci across the hybrid zone of an incipient progenitor-derivative species pair, Picea mariana (black spruce) and Picea rubens (red spruce). The spruce taxa likely diverged in geographic isolation during the Pleistocene and came into secondary contact during late Holocene. A total of 300 SNPs distributed across the 12 linkage groups (LG) of black spruce were genotyped for 385 individual trees from 33 populations distributed across the allopatric zone of each species and within the zone of sympatry. An integrative framework combining three population genomic approaches was used to scan the genomes, revealing heterogeneous patterns of introgression. A total of 23 SNPs scattered over 10 LG were considered impermeable to introgression and putatively under diverging selection. These loci revealed the existence of impermeable genomic regions forming the species boundary and are thus indicative of ongoing speciation between these two genetic lineages. Another 238 SNPs reflected selectively neutral diffusion across the porous species barrier. Finally, 39 highly permeable SNPs suggested ancestral polymorphism along with balancing selection. The heterogeneous patterns of introgression across the genome indicated that the speciation process between black spruce and red spruce is young and incomplete, albeit some interspecific differences are maintained, allowing ongoing species divergence even in sympatry. The approach developed in this study can be used to track the progression of ongoing speciation processes. © 2015 John Wiley & Sons Ltd.

  12. Quantifying introgression risk with realistic population genetics.

    Science.gov (United States)

    Ghosh, Atiyo; Meirmans, Patrick G; Haccou, Patsy

    2012-12-07

    Introgression is the permanent incorporation of genes from the genome of one population into another. This can have severe consequences, such as extinction of endemic species, or the spread of transgenes. Quantification of the risk of introgression is an important component of genetically modified crop regulation. Most theoretical introgression studies aimed at such quantification disregard one or more of the most important factors concerning introgression: realistic genetical mechanisms, repeated invasions and stochasticity. In addition, the use of linkage as a risk mitigation strategy has not been studied properly yet with genetic introgression models. Current genetic introgression studies fail to take repeated invasions and demographic stochasticity into account properly, and use incorrect measures of introgression risk that can be manipulated by arbitrary choices. In this study, we present proper methods for risk quantification that overcome these difficulties. We generalize a probabilistic risk measure, the so-called hazard rate of introgression, for application to introgression models with complex genetics and small natural population sizes. We illustrate the method by studying the effects of linkage and recombination on transgene introgression risk at different population sizes.

  13. Introgressive hybridization: brown bears as vectors for polar bear alleles.

    Science.gov (United States)

    Hailer, Frank

    2015-03-01

    The dynamics and consequences of introgression can inform about numerous evolutionary processes. Biologists have therefore long been interested in hybridization. One challenge, however, lies in the identification of nonadmixed genotypes that can serve as a baseline for accurate quantification of admixture. In this issue of Molecular Ecology, Cahill et al. (2015) analyse a genomic data set of 28 polar bears, eight brown bears and one American black bear. Polar bear alleles are found to be introgressed into brown bears not only near a previously identified admixture zone on the Alaskan Admiralty, Baranof and Chichagof (ABC) Islands, but also far into the North American mainland. Elegantly contrasting admixture levels at autosomal and X chromosomal markers, Cahill and colleagues infer that male-biased dispersal has spread these introgressed alleles away from the Late Pleistocene contact zone. Compared to a previous study on the ABC Island population in which an Alaskan brown bear served as a putatively admixture-free reference, Cahill et al. (2015) utilize a newly sequenced Swedish brown bear as admixture baseline. This approach reveals that brown bears have been impacted by introgression from polar bears to a larger extent (up to 8.8% of their genome), than previously known, including the bear that had previously served as admixture baseline. No evidence for introgression of brown bear into polar bear is found, which the authors argue could be a consequence of selection. Besides adding new exciting pieces to the puzzle of polar/brown bear evolutionary history, the study by Cahill and colleagues highlights that wildlife genomics is moving from analysing single genomes towards a landscape genomics approach. © 2015 John Wiley & Sons Ltd.

  14. Quantifying introgression risk with realistic population genetics

    NARCIS (Netherlands)

    Ghosh, A.; Meirmans, P.G.; Haccou, P.

    2012-01-01

    Introgression is the permanent incorporation of genes from the genome of one population into another. This can have severe consequences, such as extinction of endemic species, or the spread of transgenes. Quantification of the risk of introgression is an important component of genetically modified

  15. Widespread introgression of mountain hare genes into Fennoscandian brown hare populations.

    Science.gov (United States)

    Levänen, Riikka; Thulin, Carl-Gustaf; Spong, Göran; Pohjoismäki, Jaakko L O

    2018-01-01

    In Fennoscandia, mountain hare (Lepus timidus) and brown hare (Lepus europaeus) hybridize and produce fertile offspring, resulting in gene flow across the species barrier. Analyses of maternally inherited mitochondrial DNA (mtDNA) show that introgression occur frequently, but unavailability of appropriate nuclear DNA markers has made it difficult to evaluate the scale- and significance for the species. The extent of introgression has become important as the brown hare is continuously expanding its range northward, at the apparent expense of the mountain hare, raising concerns about possible competition. We report here, based on analysis of 6833 SNP markers, that the introgression is highly asymmetrical in the direction of gene flow from mountain hare to brown hare, and that the levels of nuclear gene introgression are independent of mtDNA introgression. While it is possible that brown hares obtain locally adapted alleles from the resident mountain hares, the low levels of mountain hare alleles among allopatric brown hares suggest that hybridization is driven by stochastic processes. Interspecific geneflow with the brown hare is unlikely to have major impacts on mountain hare in Fennoscandia, but direct competition may.

  16. High rates of hybridisation reveal fragile reproductive barriers between endangered Australian sea snakes

    DEFF Research Database (Denmark)

    Sanders, Kate L; Redsted Rasmussen, Arne; Guinea, Michael L.

    2014-01-01

    species have disappeared from Ashmore, the largest of these reefs, over the last 15 years, including two critically endangered Aipysurus species that have also disappeared from neighbouring Hibernia Reef. A third Timor Sea endemic, Aipysurusfuscus, is now known only from Scott and Hibernia reefs, where......The viviparous sea snakes include 62 ecologically diverse species, many of which are of very recent evolutionary origin and have overlapping distributions. Peak sea snake diversity and endemism is recorded from the isolated emergent reefs of the Timor Sea in Northwest Australia. However, nine...... significant and asymmetrical levels of gene flow following species divergence, and highest rates of introgression from the large A. laevis population into the much smaller A. fuscus population. Population assignment analyses recovered two ancestral clusters that broadly corresponded to morphological species...

  17. Superresolution and Fluorescence Dynamics Evidence Reveal That Intact Liposomes Do Not Cross the Human Skin Barrier.

    Directory of Open Access Journals (Sweden)

    Jes Dreier

    Full Text Available In this study we use the combination of super resolution optical microscopy and raster image correlation spectroscopy (RICS to study the mechanism of action of liposomes as transdermal drug delivery systems in human skin. Two different compositions of liposomes were applied to newly excised human skin, a POPC liposome and a more flexible liposome containing the surfactant sodium cholate. Stimulated emission depletion microscopy (STED images of intact skin and cryo-sections of skin treated with labeled liposomes were recorded displaying an optical resolution low enough to resolve the 100 nm liposomes in the skin. The images revealed that virtually none of the liposomes remained intact beneath the skin surface. RICS two color cross correlation diffusion measurements of double labeled liposomes confirmed these observations. Our results suggest that the liposomes do not act as carriers that transport their cargo directly through the skin barrier, but mainly burst and fuse with the outer lipid layers of the stratum corneum. It was also found that the flexible liposomes showed a greater delivery of the fluorophore into the stratum corneum, indicating that they functioned as chemical permeability enhancers.

  18. Biosensor Technology Reveals the Disruption of the Endothelial Barrier Function and the Subsequent Death of Blood Brain Barrier Endothelial Cells to Sodium Azide and Its Gaseous Products

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    Dan T. Kho

    2017-09-01

    Full Text Available Herein we demonstrate the sensitive nature of human blood-brain barrier (BBB endothelial cells to sodium azide and its gaseous product. Sodium azide is known to be acutely cytotoxic at low millimolar concentrations, hence its use as a biological preservative (e.g., in antibodies. Loss of barrier integrity was noticed in experiments using Electric Cell-substrate Impedance Sensing (ECIS biosensor technology, to measure endothelial barrier integrity continuously in real-time. Initially the effect of sodium azide was observed as an artefact where it was present in antibodies being employed in neutralisation experiments. This was confirmed where antibody clones that were azide-free did not mediate loss of barrier function. A delayed loss of barrier function in neighbouring wells implied the influence of a liberated gaseous product. ECIS technology demonstrated that the BBB endothelial cells had a lower level of direct sensitivity to sodium azide of ~3 µM. Evidence of gaseous toxicity was consistently observed at 30 µM and above, with disrupted barrier function and cell death in neighbouring wells. We highlight the ability of this cellular biosensor technology to reveal both the direct and gaseous toxicity mediated by sodium azide. The sensitivity and temporal dimension of ECIS technology was instrumental in these observations. These findings have substantial implications for the wide use of sodium azide in biological reagents, raising issues of their application in live-cell assays and with regard to the protection of the user. This research also has wider relevance highlighting the sensitivity of brain endothelial cells to a known mitochondrial disruptor. It is logical to hypothesise that BBB endothelial dysfunction due to mitochondrial dys-regulation could have an important but underappreciated role in a range of neurological diseases.

  19. Biosensor Technology Reveals the Disruption of the Endothelial Barrier Function and the Subsequent Death of Blood Brain Barrier Endothelial Cells to Sodium Azide and Its Gaseous Products.

    Science.gov (United States)

    Kho, Dan T; Johnson, Rebecca H; O'Carroll, Simon J; Angel, Catherine E; Graham, E Scott

    2017-09-21

    Herein we demonstrate the sensitive nature of human blood-brain barrier (BBB) endothelial cells to sodium azide and its gaseous product. Sodium azide is known to be acutely cytotoxic at low millimolar concentrations, hence its use as a biological preservative (e.g., in antibodies). Loss of barrier integrity was noticed in experiments using Electric Cell-substrate Impedance Sensing (ECIS) biosensor technology, to measure endothelial barrier integrity continuously in real-time. Initially the effect of sodium azide was observed as an artefact where it was present in antibodies being employed in neutralisation experiments. This was confirmed where antibody clones that were azide-free did not mediate loss of barrier function. A delayed loss of barrier function in neighbouring wells implied the influence of a liberated gaseous product. ECIS technology demonstrated that the BBB endothelial cells had a lower level of direct sensitivity to sodium azide of ~3 µM. Evidence of gaseous toxicity was consistently observed at 30 µM and above, with disrupted barrier function and cell death in neighbouring wells. We highlight the ability of this cellular biosensor technology to reveal both the direct and gaseous toxicity mediated by sodium azide. The sensitivity and temporal dimension of ECIS technology was instrumental in these observations. These findings have substantial implications for the wide use of sodium azide in biological reagents, raising issues of their application in live-cell assays and with regard to the protection of the user. This research also has wider relevance highlighting the sensitivity of brain endothelial cells to a known mitochondrial disruptor. It is logical to hypothesise that BBB endothelial dysfunction due to mitochondrial dys-regulation could have an important but underappreciated role in a range of neurological diseases.

  20. Detecting slow introgression of invasive alleles in an extensively restocked game bird

    Directory of Open Access Journals (Sweden)

    Ines eSanchez-Donoso

    2014-04-01

    Full Text Available Interbreeding of two species in the wild implies introgression of alleles from one species into the other only when admixed individuals survive and successfully backcross with the parental species. Consequently, estimating the proportion of first generation hybrids in a population may not inform about the evolutionary impact of hybridization. Samples obtained over a long time span may offer a more accurate view of the spreading of introgressed alleles in a species’ gene pool. Common quail (Coturnix coturnix populations in Europe have been restocked extensively with farm quails of hybrid origin (crosses with Japanese quails, C. japonica. We genetically monitored a common quail population over 15 years to investigate whether genetic introgression is occurring and used simulations to investigate our power to detect it. Our results revealed that some introgression has occurred, but we did not observe a significant increase over time in the proportion of admixed individuals. However, simulations showed that the degree of admixture may be larger than anticipated due to the limited power of analyses over a short time span, and that observed data was compatible with a low rate of introgression, probably resulting from reduced fitness of admixed individuals. Simulations predicted this could result in extensive admixture in the near future.

  1. Widespread hybridization and bidirectional introgression in sympatric species of coral reef fish.

    Science.gov (United States)

    Harrison, Hugo B; Berumen, Michael L; Saenz-Agudelo, Pablo; Salas, Eva; Williamson, David H; Jones, Geoffrey P

    2017-10-01

    Coral reefs are highly diverse ecosystems, where numerous closely related species often coexist. How new species arise and are maintained in these high geneflow environments have been long-standing conundrums. Hybridization and patterns of introgression between sympatric species provide a unique insight into the mechanisms of speciation and the maintenance of species boundaries. In this study, we investigate the extent of hybridization between two closely related species of coral reef fish: the common coral trout (Plectropomus leopardus) and the bar-cheek coral trout (Plectropomus maculatus). Using a complementary set of 25 microsatellite loci, we distinguish pure genotype classes from first- and later-generation hybrids, identifying 124 interspecific hybrids from a collection of 2,991 coral trout sampled in inshore and mid-shelf reefs of the southern Great Barrier Reef. Hybrids were ubiquitous among reefs, fertile and spanned multiple generations suggesting both ecological and evolutionary processes are acting to maintain species barriers. We elaborate on these finding to investigate the extent of genomic introgression and admixture from 2,271 SNP loci recovered from a ddRAD library of pure and hybrid individuals. An analysis of genomic clines on recovered loci indicates that 261 SNP loci deviate from a model of neutral introgression, of which 132 indicate a pattern of introgression consistent with selection favouring both hybrid and parental genotypes. Our findings indicate genome-wide, bidirectional introgression between two sympatric species of coral reef fishes and provide further support to a growing body of evidence for the role of hybridization in the evolution of coral reef fishes. © 2017 John Wiley & Sons Ltd.

  2. Widespread hybridization and bidirectional introgression in sympatric species of coral reef fish

    KAUST Repository

    Harrison, Hugo B.

    2017-10-28

    Coral reefs are highly diverse ecosystems, where numerous closely related species often coexist. How new species arise and are maintained in these high geneflow environments have been long-standing conundrums. Hybridization and patterns of introgression between sympatric species provide a unique insight into the mechanisms of speciation and the maintenance of species boundaries. In this study, we investigate the extent of hybridization between two closely related species of coral reef fish: the common coral trout (Plectropomus leopardus) and the bar-cheek coral trout (Plectropomus maculatus). Using a complementary set of 25 microsatellite loci, we distinguish pure genotype classes from first- and later-generation hybrids, identifying 124 interspecific hybrids from a collection of 2,991 coral trout sampled in inshore and mid-shelf reefs of the southern Great Barrier Reef. Hybrids were ubiquitous among reefs, fertile and spanned multiple generations suggesting both ecological and evolutionary processes are acting to maintain species barriers. We elaborate on these finding to investigate the extent of genomic introgression and admixture from 2,271 SNP loci recovered from a ddRAD library of pure and hybrid individuals. An analysis of genomic clines on recovered loci indicates that 261 SNP loci deviate from a model of neutral introgression, of which 132 indicate a pattern of introgression consistent with selection favouring both hybrid and parental genotypes. Our findings indicate genome-wide, bidirectional introgression between two sympatric species of coral reef fishes and provide further support to a growing body of evidence for the role of hybridization in the evolution of coral reef fishes.

  3. Modern elite rice varieties of the 'Green Revolution' have retained a large introgression from wild rice around the Pi33 rice blast resistance locus.

    Science.gov (United States)

    Ballini, Elsa; Berruyer, Romain; Morel, Jean-Benoît; Lebrun, Marc-Henri; Nottéghem, Jean-Loup; Tharreau, Didier

    2007-01-01

    During the breeding process of cultivated crops, resistance genes to pests and diseases are commonly introgressed from wild species. The size of these introgressions is predicted by theoretical models but has rarely been measured in cultivated varieties. By combining resistance tests with isogenic strains, genotyping and sequencing of different rice accessions, it was shown that, in the elite rice variety IR64, the resistance conferring allele of the rice blast resistance gene Pi33 was introgressed from the wild rice Oryza rufipogon (accession IRGC101508). Further characterization of this introgression revealed a large introgression at this locus in IR64 and the related variety IR36. The introgressed fragment represents approximately half of the short arm of rice chromosome 8. This is the first report of a large introgression in a cultivated variety of rice. Such a large introgression is likely to have been maintained during backcrossing only if a selection pressure was exerted on this genomic region. The possible traits that were selected are discussed.

  4. Mating, hybridisation and introgression in Lasius ants

    NARCIS (Netherlands)

    Have, van der T.M.; Pedersen, J.S.; Boomsma, J.J.

    2011-01-01

    Recent reviews have shown that hybridisation among ant species is likely to be more common than previously appreciated. but that documented cases of introgression remain rare. After molecular phylogenetic work had shown that European Lasius niger (LINNAEUS, 1758) and L. psammophilus SEIFERT, 1992

  5. Genomic contributions in livestock gene introgression programmes

    Directory of Open Access Journals (Sweden)

    Hospital Frédéric

    2005-05-01

    Full Text Available Abstract The composition of the genome after introgression of a marker gene from a donor to a recipient breed was studied using analytical and simulation methods. Theoretical predictions of proportional genomic contributions, including donor linkage drag, from ancestors used at each generation of crossing after an introgression programme agreed closely with simulated results. The obligate drag, the donor genome surrounding the target locus that cannot be removed by subsequent selection, was also studied. It was shown that the number of backcross generations and the length of the chromosome affected proportional genomic contributions to the carrier chromosomes. Population structure had no significant effect on ancestral contributions and linkage drag but it did have an effect on the obligate drag whereby larger offspring groups resulted in smaller obligate drag. The implications for an introgression programme of the number of backcross generations, the population structure and the carrier chromosome length are discussed. The equations derived describing contributions to the genome from individuals from a given generation provide a framework to predict the genomic composition of a population after the introgression of a favourable donor allele. These ancestral contributions can be assigned a value and therefore allow the prediction of genetic lag.

  6. Sequence-based SSR marker development and their application in defining the Introgressions of LA0716 (Solanum pennellii in the background of cv. M82 (Solanum lycopersicum.

    Directory of Open Access Journals (Sweden)

    Wenbo Long

    Full Text Available The introgression lines (ILs from cv. M82 (Solanum lycopersicum × LA0716 (S. pennellii have been proven to be exceptionally useful for genetic analysis and gene cloning. The introgressions were originally defined by RFLP markers at their development. The objectives of this study are to develop polymorphic SSR markers, and to re-define the DNA introgression from LA0716 in the ILs. Tomato sequence data was scanned by software to generate SSR markers. In total, 829 SSRs, which could be robustly amplified by PCR, were developed. Among them, 658 SSRs were dinucleotide repeats, 162 were trinucleotide repeats, and nine were tetranucleotide repeats. The 829 SSRs together with 96 published RFLPs were integrated into the physical linkage map of S. lycopersicum. Introgressions of DNA fragments from LA0716 were re-defined among the 75 ILs using the newly developed SSRs. A specific introgression of DNA fragment from LA0716 was identified in 72 ILs as described previously by RFLP, whereas the specific DNA introgression described previously were not detected in the ILs LA4035, LA4059 and LA4091. The physical location of each investigated DNA introgression was finely determined by SSR mapping. Among the 72 ILs, eight ILs showed a shorter and three ILs (IL3-2, IL12-3 and IL12-3-1 revealed a longer DNA introgression than that framed by RFLPs. Furthermore, 54 previously undefined segments were found in 21 ILs, ranging from 1 to 11 DNA introgressions per IL. Generally, the newly developed SSRs provide additional markers for genetic studies of tomatoes, and the fine definition of DNA introgressions from LA0716 would facilitate the use of the ILs for genetic analysis and gene cloning.

  7. Reindeer introgression and the population genetics of caribou in southwestern Alaska.

    Science.gov (United States)

    Colson, Kevin E; Mager, Karen H; Hundertmark, Kris J

    2014-01-01

    Alaska caribou (Rangifer tarandus granti) in southwestern Alaska are a poorly understood system, with differing descriptions of their regional population structure, population abundance that has varied greatly through time and instances of the release of domestic reindeer (R. t. tarandus) into their range. Here, we use 21 microsatellites and 297 individuals to investigate the genetic population structure of herds and examine for population bottlenecks. Then, using genetic characteristics of existing reindeer populations, we examine introgression into the wild caribou populations. Caribou of the area are genetically diverse (H E between 0.69 and 0.84), with diversity decreasing along the Alaska Peninsula (AP). Using G ST and Jost's D, we find extensive structuring among all herds; Migrate-n finds that AP herds share few effective migrants with other herds, with Southern AP and Unimak Island herds having the least. Bayesian clustering techniques are able to resolve all but Denali and Mulchatna caribou herds. Using a conservative assignment threshold of q reindeer ≥ 0.2, 3% of caribou show signs of domestic introgression. Denali herd has the most introgressed individuals (6.9%); those caribou herds that were historically adjacent to smaller reindeer herds, or were historically without adjacent herding, show no admixture. This domestic introgression persists despite the lack of managed reindeer in the region since the 1940s. Our results suggest that despite previous movement data indicating metapopulation-like dispersal in this region, there may be unknown barriers to reproduction by dispersing individuals. Finally, our results support findings that wild and domestic Rangifer can hybridize and show this introgression may persist dozens of generations after domestics are no longer present. © The American Genetic Association 2014. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  8. Genetic structure of Miscanthus sinensis and Miscanthus sacchariflorus in Japan indicates a gradient of bidirectional but asymmetric introgression

    Science.gov (United States)

    Clark, Lindsay V.; Stewart, J. Ryan; Nishiwaki, Aya; Toma, Yo; Kjeldsen, Jens Bonderup; Jørgensen, Uffe; Zhao, Hua; Peng, Junhua; Yoo, Ji Hye; Heo, Kweon; Yu, Chang Yeon; Yamada, Toshihiko

    2015-01-01

    Unilateral introgression from diploids to tetraploids has been hypothesized to be an important evolutionary mechanism in plants. However, few examples have been definitively identified, perhaps because data of sufficient depth and breadth were difficult to obtain before the advent of affordable high-density genotyping. Throughout Japan, tetraploid Miscanthus sacchariflorus and diploid Miscanthus sinensis are common, and occasionally hybridize. In this study, 667 M. sinensis and 78 M. sacchariflorus genotypes from Japan were characterized using 20 704 SNPs and ten plastid microsatellites. Similarity of SNP genotypes between diploid and tetraploid M. sacchariflorus indicated that the tetraploids originated through autopolyploidy. Structure analysis indicated a gradient of introgression from diploid M. sinensis into tetraploid M. sacchariflorus throughout Japan; most tetraploids had some M. sinensis DNA. Among phenotypically M. sacchariflorus tetraploids, M. sinensis ancestry averaged 7% and ranged from 1–39%, with introgression greatest in southern Japan. Unexpectedly, rare (~1%) diploid M. sinensis individuals from northern Japan were found with 6–27% M. sacchariflorus ancestry. Population structure of M. sinensis in Japan included three groups, and was driven primarily by distance, and secondarily by geographic barriers such as mountains and straits. Miscanthus speciation is a complex and dynamic process. In contrast to limited introgression between diploid M. sacchariflorus and M. sinensis in northern China, selection for adaptation to a moderate maritime climate probably favoured cross-ploidy introgressants in southern Japan. These results will help guide the selection of Miscanthus accessions for the breeding of biomass cultivars. PMID:25618143

  9. Genome patterns of selection and introgression of haplotypes in natural populations of the house mouse (Mus musculus.

    Directory of Open Access Journals (Sweden)

    Fabian Staubach

    Full Text Available General parameters of selection, such as the frequency and strength of positive selection in natural populations or the role of introgression, are still insufficiently understood. The house mouse (Mus musculus is a particularly well-suited model system to approach such questions, since it has a defined history of splits into subspecies and populations and since extensive genome information is available. We have used high-density single-nucleotide polymorphism (SNP typing arrays to assess genomic patterns of positive selection and introgression of alleles in two natural populations of each of the subspecies M. m. domesticus and M. m. musculus. Applying different statistical procedures, we find a large number of regions subject to apparent selective sweeps, indicating frequent positive selection on rare alleles or novel mutations. Genes in the regions include well-studied imprinted loci (e.g. Plagl1/Zac1, homologues of human genes involved in adaptations (e.g. alpha-amylase genes or in genetic diseases (e.g. Huntingtin and Parkin. Haplotype matching between the two subspecies reveals a large number of haplotypes that show patterns of introgression from specific populations of the respective other subspecies, with at least 10% of the genome being affected by partial or full introgression. Using neutral simulations for comparison, we find that the size and the fraction of introgressed haplotypes are not compatible with a pure migration or incomplete lineage sorting model. Hence, it appears that introgressed haplotypes can rise in frequency due to positive selection and thus can contribute to the adaptive genomic landscape of natural populations. Our data support the notion that natural genomes are subject to complex adaptive processes, including the introgression of haplotypes from other differentiated populations or species at a larger scale than previously assumed for animals. This implies that some of the admixture found in inbred strains of mice

  10. Changes in the Chemical Barrier Composition of Tears in Alzheimer's Disease Reveal Potential Tear Diagnostic Biomarkers.

    Directory of Open Access Journals (Sweden)

    Gergő Kalló

    Full Text Available Alzheimer's disease (AD is one of the most common neurodegenerative diseases, with increasing prevalence affecting millions of people worldwide. Currently, only autopsy is able to confirm the diagnosis with a 100% certainty, therefore, biomarkers from body fluids obtained by non-invasive means provide an attractive alternative for the diagnosis of Alzheimer`s disease. Global changes of the protein profile were examined by quantitative proteomics; firstly, electrophoresis and LC-MS/MS were used, thereafter, SRM-based targeted proteomics method was developed and applied to examine quantitative changes of tear proteins. Alterations in the tear flow rate, total tear protein concentration and composition of the chemical barrier specific to AD were demonstrated, and the combination of lipocalin-1, dermcidin, lysozyme-C and lacritin was shown to be a potential biomarker, with an 81% sensitivity and 77% specificity.

  11. Influenza vaccination among Saudi Hajj pilgrims: Revealing the uptake and vaccination barriers.

    Science.gov (United States)

    Alfelali, Mohammad; Barasheed, Osamah; Badahdah, Al-Mamoon; Bokhary, Hamid; Azeem, Mohammed I; Habeebullah, Turki; Bakarman, Marwan; Asghar, Atif; Booy, Robert; Rashid, Harunor

    2018-04-12

    Hajj is the world's largest annual mass gathering that attracts two to three million Muslims from around the globe to a religious assemblage in Makkah, Saudi Arabia. The risk of acquisition and transmission of influenza among Hajj pilgrims is high. Therefore, influenza vaccination is recommended, and was monitored frequently among pilgrims from different countries. However, the vaccination uptake among Saudi pilgrims has not been assessed in recent years. This analysis aims to evaluate influenza vaccine uptake among Saudi Hajj pilgrims, and identify the key barriers to vaccination. Data on influenza vaccination were obtained from Saudi pilgrims who took part in a large trial during the Hajj of 2013, 2014 and 2015. Pilgrims were met and recruited in Mina, Makkah during the peak period of Hajj and were asked to complete a baseline questionnaire that recorded their influenza vaccination history, including reason(s) for non-receipt of vaccine. A total of 6974 Saudi pilgrims aged between 18 and 95 (median 34) years were recruited; male to female ratio was 1:1.2. Of the total, 90.8% declared their influenza vaccination history, 51.3% of them reported receiving influenza vaccine before travel to Hajj. The vaccination rates for the years 2013, 2014 and 2015 were 21.4%, 48.2% and 58.1%, respectively (P natural immunity (15.8%) and being busy (15.5%) were the main reasons for non-receipt. These data from a convenience sample indicate that influenza vaccine uptake among Saudi Hajj pilgrims is increasing over years but still needs further improvement. Lack of awareness and misperceptions are the main barriers. Education of Saudi pilgrims and health professionals is required to raise awareness about influenza vaccination. Further studies are needed to understand pilgrims' misperceptions. Copyright © 2018 Elsevier Ltd. All rights reserved.

  12. Comparative transmission genetics of introgressed chromatin in Gossypium (cotton) polyploids.

    Science.gov (United States)

    Waghmare, Vijay N; Rong, Junkang; Rogers, Carl J; Bowers, John E; Chee, Peng W; Gannaway, John R; Katageri, Ishwarappa; Paterson, Andrew H

    2016-04-01

    Introgression is widely acknowledged as a potential source of valuable genetic variation, and growing effort is being invested in analysis of interspecific crosses conferring transgressive variation. Experimental backcross populations provide an opportunity to study transmission genetics following interspecific hybridization, identifying opportunities and constraints to introgressive crop improvement. The evolutionary consequences of introgression have been addressed at the theoretical level, however, issues related to levels and patterns of introgression among (plant) species remain inadequately explored, including such factors as polyploidization, subgenome interaction inhabiting a common nucleus, and the genomic distribution and linkage relationships of introgressant alleles. We analyze introgression into the polyploid Gossypium hirsutum (upland cotton) from its sister G. tomentosum and compare the level and pattern with that of G. barbadense representing a different clade tracing to the same polyploidization. Across the genome, recurrent backcrossing to Gossypium hirsutum yielded only one-third of the expected average frequency of the G. tomentosum allele, although one unusual region showed preferential introgression. Although a similar rate of introgression is found in the two subgenomes of polyploid (AtDt) G. hirsutum, a preponderance of multilocus interactions were largely within the Dt subgenome. Skewed G. tomentosum chromatin transmission is polymorphic among two elite G. hirsutum genotypes, which suggests that genetic background may profoundly affect introgression of particular chromosomal regions. Only limited correspondence is found between G. hirsutum chromosomal regions that are intolerant to introgression from the two species, G. barbadense and G. tomentosum, concentrated near possible inversion polymorphisms. Complex transmission of introgressed chromatin highlights the challenges to utilization of exotic germplasm in crop improvement. © 2016

  13. Great Barrier Reef coral luminescence reveals rainfall variability over northeastern Australia since the 17th century

    Science.gov (United States)

    Lough, Janice M.

    2011-06-01

    Northeast tropical Queensland rainfall is concentrated in the summer half year and characterized by high interannual variability, partly related to El Niño-Southern Oscillation (ENSO) events. This results in highly variable river flows affecting nearshore coral reefs of the Great Barrier Reef, Australia. Freshwater flood events are recorded in long-lived, annually banded massive coral skeletons as luminescent lines. Quantitative measurements of luminescence intensity were made for 20 Porites coral cores from nearshore reef sites between 11°S and 23°S. Seventeen of the coral luminescence series were significantly correlated with an instrumental record of northeast Queensland summer rainfall and were used to develop seven significantly calibrated and verified rainfall reconstructions based on between 17 (starting 1891) and 1 (starting 1639) coral series. The longest reconstruction, based on more than one coral, provides insights into northeast Queensland rainfall variability from the late 17th century. Comparisons with various independent climate proxies are equivocal: the magnitude and significance of relationships with, for example, a proxy ENSO index vary through time. An extended drier period reconstructed from approximately the 1760s to the 1850s is associated with lower interannual rainfall variability. Since the late 19th century average rainfall and its variability have significantly increased, with wet and dry extremes becoming more frequent than in earlier centuries. This suggests that a warming global climate maybe associated with more variable tropical Queensland rainfall.

  14. Localizing introgression on the chromosome of rice by genomic in ...

    African Journals Online (AJOL)

    USER

    2010-07-26

    Jul 26, 2010 ... Genomic in situ hybridization was used to detect introgressed segment from Oryza australinesis onto ... Figure 1. Fluorescence in situ hybridization to root tip preparation from an introgression line of rice derived from the cross of O. sativa x ... IR65682-136-4-3-2, derived from interspecific cross O. sativa x O.

  15. Archaic adaptive introgression in TBX15/WARS2

    DEFF Research Database (Denmark)

    Racimo, Fernando; Gokhman, David; Fumagalli, Matteo

    2017-01-01

    to the sequence in the Denisovan genome, and was likely introgressed from an archaic population. The region contains two genes, WARS2 and TBX15, and has previously been associated with adipose tissue differentiation and body-fat distribution in humans. We show that the adaptively introgressed allele has been...

  16. Introgression of Crop Alleles into Wild or Weedy Populations

    NARCIS (Netherlands)

    Ellstrand, N.C.; Meirmans, P.; Rong, J.; Bartsch, D.; Ghosh, A.; de Jong, T.J.; Haccou, P.; Lu, B-R.; Snow, A.A.; Stewart, C.N.; Strasburg, J.L.; van Tienderen, P.H.; Vrieling, K; Hooftman, D.A.P.

    2013-01-01

    The evolutionary significance of introgression has been discussed for decades. Questions about potential impacts of transgene flow into wild and weedy populations brought renewed attention to the introgression of crop alleles into those populations. In the past two decades, the field has advanced

  17. Introgression in Lake Malaŵi

    DEFF Research Database (Denmark)

    Stauffer, Jay R.; Madsen, Henry; Rollinson, David

    2014-01-01

    For the last 15 years, we have studied the relationships among cichlid snail-eating fishes, intermediate snail-host density, and the prevalence of human infection of Schistosoma haematobium in Lake Malaŵi and concluded that the increase of human infection is correlated with the decrease in snail...... with the indigenous strain of S. haematobium, which ultimately produced via introgression a strain that can use both B. globosus and B. nyassanus as intermediate hosts. This actively evolving situation involving intermediate snail-host switching and decline of Trematocranus placodon, a natural cichlid snail predator...

  18. Superresolution and Fluorescence Dynamics Evidence Reveal That Intact Liposomes Do Not Cross the Human Skin Barrier

    DEFF Research Database (Denmark)

    Dreier, Jes; Sørensen, Jens A; Brewer, Jonathan R

    2016-01-01

    In this study we use the combination of super resolution optical microscopy and raster image correlation spectroscopy (RICS) to study the mechanism of action of liposomes as transdermal drug delivery systems in human skin. Two different compositions of liposomes were applied to newly excised human...... skin, a POPC liposome and a more flexible liposome containing the surfactant sodium cholate. Stimulated emission depletion microscopy (STED) images of intact skin and cryo-sections of skin treated with labeled liposomes were recorded displaying an optical resolution low enough to resolve the 100 nm...... liposomes in the skin. The images revealed that virtually none of the liposomes remained intact beneath the skin surface. RICS two color cross correlation diffusion measurements of double labeled liposomes confirmed these observations. Our results suggest that the liposomes do not act as carriers...

  19. Annual layers revealed by GPR in the subsurface of a prograding coastal barrier, southwest Washington, U.S.A

    Science.gov (United States)

    Moore, L.J.; Jol, H.M.; Kruse, S.; Vanderburgh, S.; Kaminsky, G.M.

    2004-01-01

    The southwest Washington coastline has experienced extremely high rates of progradation during the late Holocene. Subsurface stratigraphy, preserved because of progradation and interpreted using ground-penetrating radar (GPR), has previously been used successfully to document coastal response to prehistoric storm and earthquake events. New GPR data collected at Ocean Shores, Washington, suggest that the historic stratigraphy of the coastal barrier in this area represents a higher resolution record of coastal behavior than previously thought. GPR records for this location at 200 MHz reveal a series of gently sloping, seaward-dipping reflections with slopes similar to the modern beach and spacings on the order of 20-45 cm. Field evidence and model results suggest that thin (1-10 cm), possibly magnetite-rich, heavy-mineral lags or low-porosity layers left by winter storms and separated by thick (20-40 cm) summer progradational sequences are responsible for generating the GPR reflections. These results indicate that a record of annual progradation is preserved in the subsurface of the prograding barrier and can be quantified using GPR. Such records of annual coastal behavior, where available, will be invaluable in understanding past coastal response to climatic and tectonic forcing. ?? 2004.

  20. RNA Virus Evolution via a Quasispecies-Based Model Reveals a Drug Target with a High Barrier to Resistance

    Directory of Open Access Journals (Sweden)

    Richard J. Bingham

    2017-11-01

    Full Text Available The rapid occurrence of therapy-resistant mutant strains provides a challenge for anti-viral therapy. An ideal drug target would be a highly conserved molecular feature in the viral life cycle, such as the packaging signals in the genomes of RNA viruses that encode an instruction manual for their efficient assembly. The ubiquity of this assembly code in RNA viruses, including major human pathogens, suggests that it confers selective advantages. However, their impact on viral evolution cannot be assessed in current models of viral infection that lack molecular details of virus assembly. We introduce here a quasispecies-based model of a viral infection that incorporates structural and mechanistic knowledge of packaging signal function in assembly to construct a phenotype-fitness map, capturing the impact of this RNA code on assembly yield and efficiency. Details of viral replication and assembly inside an infected host cell are coupled with a population model of a viral infection, allowing the occurrence of therapy resistance to be assessed in response to drugs inhibiting packaging signal recognition. Stochastic simulations of viral quasispecies evolution in chronic HCV infection under drug action and/or immune clearance reveal that drugs targeting all RNA signals in the assembly code collectively have a high barrier to drug resistance, even though each packaging signal in isolation has a lower barrier than conventional drugs. This suggests that drugs targeting the RNA signals in the assembly code could be promising routes for exploitation in anti-viral drug design.

  1. RNA Virus Evolution via a Quasispecies-Based Model Reveals a Drug Target with a High Barrier to Resistance.

    Science.gov (United States)

    Bingham, Richard J; Dykeman, Eric C; Twarock, Reidun

    2017-11-17

    The rapid occurrence of therapy-resistant mutant strains provides a challenge for anti-viral therapy. An ideal drug target would be a highly conserved molecular feature in the viral life cycle, such as the packaging signals in the genomes of RNA viruses that encode an instruction manual for their efficient assembly. The ubiquity of this assembly code in RNA viruses, including major human pathogens, suggests that it confers selective advantages. However, their impact on viral evolution cannot be assessed in current models of viral infection that lack molecular details of virus assembly. We introduce here a quasispecies-based model of a viral infection that incorporates structural and mechanistic knowledge of packaging signal function in assembly to construct a phenotype-fitness map, capturing the impact of this RNA code on assembly yield and efficiency. Details of viral replication and assembly inside an infected host cell are coupled with a population model of a viral infection, allowing the occurrence of therapy resistance to be assessed in response to drugs inhibiting packaging signal recognition. Stochastic simulations of viral quasispecies evolution in chronic HCV infection under drug action and/or immune clearance reveal that drugs targeting all RNA signals in the assembly code collectively have a high barrier to drug resistance, even though each packaging signal in isolation has a lower barrier than conventional drugs. This suggests that drugs targeting the RNA signals in the assembly code could be promising routes for exploitation in anti-viral drug design.

  2. Massive invasion of exotic Barbus barbus and introgressive hybridization with endemic Barbus plebejus in Northern Italy: where, how and why?

    Science.gov (United States)

    Meraner, A; Venturi, A; Ficetola, G F; Rossi, S; Candiotto, A; Gandolfi, A

    2013-11-01

    Biological invasions and introgressive hybridization are major drivers for the decline of native freshwater fish. However, the magnitude of the problem across a native species range, the mechanisms shaping introgression as well as invader's dispersal and the relative role of biological invasions in the light of multiple environmental stressors are rarely described. Here, we report extensive (N = 665) mtDNA sequence and (N = 692) microsatellite genotypic data of 32 Northern Adriatic sites aimed to unravel the invasion of the European Barbus barbus in Italy and the hybridization and decline of the endemic B. plebejus. We highlight an exceptionally fast breakthrough of B. barbus within the Po River basin, leading to widespread introgressive hybridization with the endemic B. plebejus within few generations. In contrast, adjacent drainage systems are still unaffected from B. barbus invasion. We show that barriers to migration are inefficient to halt the invasion process and that propagule pressure, and not environmental quality, is the major driver responsible for B. barbus success. Both introgressive hybridization and invader's dispersal are facilitated by ongoing fisheries management practices. Therefore, immediate changes in fisheries management (i.e. stocking and translocation measures) and a detailed conservation plan, focussed on remnant purebred B. plebejus populations, are urgently needed. © 2013 John Wiley & Sons Ltd.

  3. Mining for Candidate Genes in an Introgression Line by Using RNA Sequencing: The Anthocyanin Overaccumulation Phenotype in Brassica

    Directory of Open Access Journals (Sweden)

    Lulu Xie

    2016-08-01

    Full Text Available Introgression breeding is a widely used method for the genetic improvement of crop plants; however, the mechanism underlying candidate gene flow patterns during hybridization is poorly understood. In this study, we used a powerful pipeline to investigate a Chinese cabbage (Brassica rapa L. ssp. pekinensis introgression line with the anthocyanin overaccumulation phenotype. Our purpose was to analyze the gene flow patterns during hybridization and elucidate the genetic factors responsible for the accumulation of this important pigment compound. We performed RNA-seq analysis by using two pipelines, one with and one without a reference sequence, to obtain transcriptome data. We identified 930 significantly differentially expressed genes (DEGs between the purple-leaf introgression line and B. rapa green cultivar, namely, 389 up-regulated and 541 down-regulated DEGs that mapped to the B. rapa reference genome. Since only one anthocyanin pathway regulatory gene was identified, i.e., Bra037887 (bHLH, we mined unmapped reads, revealing 2,031 de novo assembled unigenes, including c3563g1i2. Phylogenetic analysis suggested that c3563g1i2, which was transferred from the Brassica B genome of the donor parental line Brassica juncea, may represent an R2R3-MYB transcription factor that participates in the ternary transcriptional activation complex responsible for the anthocyanin overaccumulation phenotype of the B. rapa introgression line. We also identified genes involved in cold and light reaction pathways that were highly upregulated in the introgression line, as confirmed using quantitative real-time PCR analysis. The results of this study shed light on the mechanisms underlying the purple leaf trait in Brassica plants and may facilitate the use of introgressive hybridization for many traits of interest.

  4. "There is no carnival without samba": Revealing barriers hampering biodiversity-based R&D and eco-design in Brazil.

    Science.gov (United States)

    Jabbour, Charbel Jose Chiappetta; Jugend, Daniel; Jabbour, Ana Beatriz Lopes de Sousa; Govindan, Kannan; Kannan, Devika; Leal Filho, Walter

    2018-01-15

    Considering the unique relevance of Brazilian biodiversity, this research aims to investigate the main barriers to biodiversity-based R&D and eco-design development in a leading national company which has been commended for its innovation and sustainability. The methodology for this research was based on on-location visits, in-depth interviews, and consensus building among R&D, sustainability, and quality managers. A multi-criteria decision-making (MCDM) approach was adopted through interpretive structural modelling (ISM), a method that assists decision makers to transform complex models with unclear data into structural models. Some of the most influential barriers to biodiversity-based eco-design initiatives are "lack of legal incentive", "not enough demand from the market", and "not enough available knowledge/scientific data." The most relevant barrier was "no legal incentive" from government. Consequently, managers should concentrate their efforts in tackling those barriers that may affect other barriers known as 'key barriers'. Government should work decisively toward promoting a framework of legal incentives for bio-based eco-design; otherwise, metaphorically, "there is not carnival without the samba singer who pushes the rhythm". The results given here reveal the barriers for bio-based eco-design in a Brazilian leading company, and this is the first work combining ISM to barriers to biodiversity R&D and eco-design. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Adaptive introgression across species boundaries in Heliconius butterflies.

    Directory of Open Access Journals (Sweden)

    Carolina Pardo-Diaz

    Full Text Available It is widely documented that hybridisation occurs between many closely related species, but the importance of introgression in adaptive evolution remains unclear, especially in animals. Here, we have examined the role of introgressive hybridisation in transferring adaptations between mimetic Heliconius butterflies, taking advantage of the recent identification of a gene regulating red wing patterns in this genus. By sequencing regions both linked and unlinked to the red colour locus, we found a region that displays an almost perfect genotype by phenotype association across four species, H. melpomene, H. cydno, H. timareta, and H. heurippa. This particular segment is located 70 kb downstream of the red colour specification gene optix, and coalescent analysis indicates repeated introgression of adaptive alleles from H. melpomene into the H. cydno species clade. Our analytical methods complement recent genome scale data for the same region and suggest adaptive introgression has a crucial role in generating adaptive wing colour diversity in this group of butterflies.

  6. Genetic and epigenetic changes in somatic hybrid introgression lines between wheat and tall wheatgrass.

    Science.gov (United States)

    Liu, Shuwei; Li, Fei; Kong, Lina; Sun, Yang; Qin, Lumin; Chen, Suiyun; Cui, Haifeng; Huang, Yinghua; Xia, Guangmin

    2015-04-01

    Broad phenotypic variations were induced in derivatives of an asymmetric somatic hybridization of bread wheat (Triticum aestivum) and tall wheatgrass (Thinopyrum ponticum Podp); however, how these variations occurred was unknown. We explored the nature of these variations by cytogenetic assays and DNA profiling techniques to characterize six genetically stable somatic introgression lines. Karyotyping results show the six lines similar to their wheat parent, but GISH analysis identified the presence of a number of short introgressed tall wheatgrass chromatin segments. DNA profiling revealed many genetic and epigenetic differences, including sequences deletions, altered regulation of gene expression, changed patterns of cytosine methylation, and the reactivation of retrotransposons. Phenotypic variations appear to result from altered repetitive sequences combined with the epigenetic regulation of gene expression and/or retrotransposon transposition. The extent of genetic and epigenetic variation due to the maintenance of parent wheat cells in tissue culture was assessed and shown to be considerably lower than had been induced in the introgression lines. Asymmetric somatic hybridization provides appropriate material to explore the nature of the genetic and epigenetic variations induced by genomic shock. Copyright © 2015 by the Genetics Society of America.

  7. High-throughput phenotyping to detect drought tolerance QTL in wild barley introgression lines.

    Directory of Open Access Journals (Sweden)

    Nora Honsdorf

    Full Text Available Drought is one of the most severe stresses, endangering crop yields worldwide. In order to select drought tolerant genotypes, access to exotic germplasm and efficient phenotyping protocols are needed. In this study the high-throughput phenotyping platform "The Plant Accelerator", Adelaide, Australia, was used to screen a set of 47 juvenile (six week old wild barley introgression lines (S42ILs for drought stress responses. The kinetics of growth development was evaluated under early drought stress and well watered treatments. High correlation (r=0.98 between image based biomass estimates and actual biomass was demonstrated, and the suitability of the system to accurately and non-destructively estimate biomass was validated. Subsequently, quantitative trait loci (QTL were located, which contributed to the genetic control of growth under drought stress. In total, 44 QTL for eleven out of 14 investigated traits were mapped, which for example controlled growth rate and water use efficiency. The correspondence of those QTL with QTL previously identified in field trials is shown. For instance, six out of eight QTL controlling plant height were also found in previous field and glasshouse studies with the same introgression lines. This indicates that phenotyping juvenile plants may assist in predicting adult plant performance. In addition, favorable wild barley alleles for growth and biomass parameters were detected, for instance, a QTL that increased biomass by approximately 36%. In particular, introgression line S42IL-121 revealed improved growth under drought stress compared to the control Scarlett. The introgression line showed a similar behavior in previous field experiments, indicating that S42IL-121 may be an attractive donor for breeding of drought tolerant barley cultivars.

  8. Evolutionary analyses of non-genealogical bonds produced by introgressive descent.

    Science.gov (United States)

    Bapteste, Eric; Lopez, Philippe; Bouchard, Frédéric; Baquero, Fernando; McInerney, James O; Burian, Richard M

    2012-11-06

    All evolutionary biologists are familiar with evolutionary units that evolve by vertical descent in a tree-like fashion in single lineages. However, many other kinds of processes contribute to evolutionary diversity. In vertical descent, the genetic material of a particular evolutionary unit is propagated by replication inside its own lineage. In what we call introgressive descent, the genetic material of a particular evolutionary unit propagates into different host structures and is replicated within these host structures. Thus, introgressive descent generates a variety of evolutionary units and leaves recognizable patterns in resemblance networks. We characterize six kinds of evolutionary units, of which five involve mosaic lineages generated by introgressive descent. To facilitate detection of these units in resemblance networks, we introduce terminology based on two notions, P3s (subgraphs of three nodes: A, B, and C) and mosaic P3s, and suggest an apparatus for systematic detection of introgressive descent. Mosaic P3s correspond to a distinct type of evolutionary bond that is orthogonal to the bonds of kinship and genealogy usually examined by evolutionary biologists. We argue that recognition of these evolutionary bonds stimulates radical rethinking of key questions in evolutionary biology (e.g., the relations among evolutionary players in very early phases of evolutionary history, the origin and emergence of novelties, and the production of new lineages). This line of research will expand the study of biological complexity beyond the usual genealogical bonds, revealing additional sources of biodiversity. It provides an important step to a more realistic pluralist treatment of evolutionary complexity.

  9. High-throughput phenotyping to detect drought tolerance QTL in wild barley introgression lines

    KAUST Repository

    Honsdorf, Nora

    2014-05-13

    Drought is one of the most severe stresses, endangering crop yields worldwide. In order to select drought tolerant genotypes, access to exotic germplasm and efficient phenotyping protocols are needed. In this study the high-throughput phenotyping platform "The Plant Accelerator", Adelaide, Australia, was used to screen a set of 47 juvenile (six week old) wild barley introgression lines (S42ILs) for drought stress responses. The kinetics of growth development was evaluated under early drought stress and well watered treatments. High correlation (r = 0.98) between image based biomass estimates and actual biomass was demonstrated, and the suitability of the system to accurately and non-destructively estimate biomass was validated. Subsequently, quantitative trait loci (QTL) were located, which contributed to the genetic control of growth under drought stress. In total, 44 QTL for eleven out of 14 investigated traits were mapped, which for example controlled growth rate and water use efficiency. The correspondence of those QTL with QTL previously identified in field trials is shown. For instance, six out of eight QTL controlling plant height were also found in previous field and glasshouse studies with the same introgression lines. This indicates that phenotyping juvenile plants may assist in predicting adult plant performance. In addition, favorable wild barley alleles for growth and biomass parameters were detected, for instance, a QTL that increased biomass by approximately 36%. In particular, introgression line S42IL-121 revealed improved growth under drought stress compared to the control Scarlett. The introgression line showed a similar behavior in previous field experiments, indicating that S42IL-121 may be an attractive donor for breeding of drought tolerant barley cultivars. © 2014 Honsdorf et al.

  10. High-throughput phenotyping to detect drought tolerance QTL in wild barley introgression lines.

    Science.gov (United States)

    Honsdorf, Nora; March, Timothy John; Berger, Bettina; Tester, Mark; Pillen, Klaus

    2014-01-01

    Drought is one of the most severe stresses, endangering crop yields worldwide. In order to select drought tolerant genotypes, access to exotic germplasm and efficient phenotyping protocols are needed. In this study the high-throughput phenotyping platform "The Plant Accelerator", Adelaide, Australia, was used to screen a set of 47 juvenile (six week old) wild barley introgression lines (S42ILs) for drought stress responses. The kinetics of growth development was evaluated under early drought stress and well watered treatments. High correlation (r=0.98) between image based biomass estimates and actual biomass was demonstrated, and the suitability of the system to accurately and non-destructively estimate biomass was validated. Subsequently, quantitative trait loci (QTL) were located, which contributed to the genetic control of growth under drought stress. In total, 44 QTL for eleven out of 14 investigated traits were mapped, which for example controlled growth rate and water use efficiency. The correspondence of those QTL with QTL previously identified in field trials is shown. For instance, six out of eight QTL controlling plant height were also found in previous field and glasshouse studies with the same introgression lines. This indicates that phenotyping juvenile plants may assist in predicting adult plant performance. In addition, favorable wild barley alleles for growth and biomass parameters were detected, for instance, a QTL that increased biomass by approximately 36%. In particular, introgression line S42IL-121 revealed improved growth under drought stress compared to the control Scarlett. The introgression line showed a similar behavior in previous field experiments, indicating that S42IL-121 may be an attractive donor for breeding of drought tolerant barley cultivars.

  11. Genomic change, retrotransposon mobilization and extensive cytosine methylation alteration in Brassica napus introgressions from two intertribal hybridizations.

    Directory of Open Access Journals (Sweden)

    Xueli Zhang

    Full Text Available Hybridization and introgression represent important means for the transfer and/or de novo origination of traits and play an important role in facilitating speciation and plant breeding. Two sets of introgression lines in Brassica napus L. were previously established by its intertribal hybridizations with two wild species and long-term selection. In this study, the methods of amplified fragment length polymorphisms (AFLP, sequence-specific amplification polymorphism (SSAP and methylation-sensitive amplified polymorphism (MSAP were used to determine their genomic change, retrotransposon mobilization and cytosine methylation alteration in these lines. The genomic change revealed by the loss or gain of AFLP bands occurred for ∼10% of the total bands amplified in the two sets of introgressions, while no bands specific for wild species were detected. The new and absent SSAP bands appeared for 9 out of 11 retrotransposons analyzed, with low frequency of new bands and their total percentage of about 5% in both sets. MSAP analysis indicated that methylation changes were common in these lines (33.4-39.8% and the hypermethylation was more frequent than hypomethylation. Our results suggested that certain extents of genetic and epigenetic alterations were induced by hybridization and alien DNA introgression. The cryptic mechanism of these changes and potential application of these lines in breeding were also discussed.

  12. Paracellular barrier and channel functions of TJ claudins in organizing biological systems: advances in the field of barriology revealed in knockout mice.

    Science.gov (United States)

    Tamura, Atsushi; Tsukita, Sachiko

    2014-12-01

    Claudin was first identified as a four-transmembrane protein in the tight junctions (TJs) between epithelial cells. The claudin family has 27 members, which are specifically expressed depending on the epithelial cell type. Accumulating evidence has revealed that claudins are responsible for the paracellular barrier that prevents molecules from passing through epithelial cell sheets. In addition, the extracellular domains of some claudins enable them to act as a permselective paracellular channel for specific molecules, including ions and/or non-ionic solutes. Recent studies using claudin knockout mice revealed that the loss of claudins' specific paracellular barrier and/or channel functions affects specific biological functions and leads to pathological states. In this review, considering recent findings in vivo, we describe how, sometimes in concert with canonical transporters and channels, the paracellular barrier and channel functions of claudins sophisticatedly organize biological systems. Copyright © 2014. Published by Elsevier Ltd.

  13. A coculture model mimicking the intestinal mucosa reveals a regulatory role for myofibroblasts in immune-mediated barrier disruption

    NARCIS (Netherlands)

    Willemsen, L. E. M.; Schreurs, C. C. H. M.; Kroes, H.; Spillenaar Bilgen, E. J.; van Deventer, S. J. H.; van Tol, E. A. F.

    2002-01-01

    The pathogenesis of Crohn's disease involves a mucosal inflammatory response affecting the barrier function of the gut. Myofibroblasts directly underlining the intestinal epithelium may have a regulatory role in immune-mediated barrier disruption. A coculture system of T84 epithelial and CCD-18Co

  14. The Strength of Selection against Neanderthal Introgression.

    Directory of Open Access Journals (Sweden)

    Ivan Juric

    2016-11-01

    Full Text Available Hybridization between humans and Neanderthals has resulted in a low level of Neanderthal ancestry scattered across the genomes of many modern-day humans. After hybridization, on average, selection appears to have removed Neanderthal alleles from the human population. Quantifying the strength and causes of this selection against Neanderthal ancestry is key to understanding our relationship to Neanderthals and, more broadly, how populations remain distinct after secondary contact. Here, we develop a novel method for estimating the genome-wide average strength of selection and the density of selected sites using estimates of Neanderthal allele frequency along the genomes of modern-day humans. We confirm that East Asians had somewhat higher initial levels of Neanderthal ancestry than Europeans even after accounting for selection. We find that the bulk of purifying selection against Neanderthal ancestry is best understood as acting on many weakly deleterious alleles. We propose that the majority of these alleles were effectively neutral-and segregating at high frequency-in Neanderthals, but became selected against after entering human populations of much larger effective size. While individually of small effect, these alleles potentially imposed a heavy genetic load on the early-generation human-Neanderthal hybrids. This work suggests that differences in effective population size may play a far more important role in shaping levels of introgression than previously thought.

  15. Effects of asymmetric nuclear introgression, introgressive mitochondrial sweep, and purifying selection on phylogenetic reconstruction and divergence estimates in the Pacific clade of Locustella warblers.

    Science.gov (United States)

    Drovetski, Sergei V; Semenov, Georgy; Red'kin, Yaroslav A; Sotnikov, Vladimir N; Fadeev, Igor V; Koblik, Evgeniy A

    2015-01-01

    When isolated but reproductively compatible populations expand geographically and meet, simulations predict asymmetric introgression of neutral loci from a local to invading taxon. Genetic introgression may affect phylogenetic reconstruction by obscuring topology and divergence estimates. We combined phylogenetic analysis of sequences from one mtDNA and 12 nuDNA loci with analysis of gene flow among 5 species of Pacific Locustella warblers to test for presence of genetic introgression and its effects on tree topology and divergence estimates. Our data showed that nuDNA introgression was substantial and asymmetrical among all members of superspecies groups whereas mtDNA showed no introgression except a single species pair where the invader's mtDNA was swept by mtDNA of the local species. This introgressive sweep of mtDNA had the opposite direction of the nuDNA introgression and resulted in the paraphyly of the local species' mtDNA haplotypes with respect to those of the invader. Тhe multilocus nuDNA species tree resolved all inter- and intraspecific relationships despite substantial introgression. However, the node ages on the species tree may be underestimated as suggested by the differences in node age estimates based on non-introgressing mtDNA and introgressing nuDNA. In turn, the introgressive sweep and strong purifying selection appear to elongate internal branches in the mtDNA gene tree.

  16. Marked hybridization and introgression in Ophrys sect. Pseudophrys in the western Iberian Peninsula.

    Science.gov (United States)

    Cotrim, Helena; Monteiro, Filipa; Sousa, Eva; Pinto, Manuel J; Fay, Michael F

    2016-04-01

    Orchids in the genus Ophrys represent extraordinary cases of tight coevolution between plants and their pollinators, and as a result, they present opportunities for studying hybridization, or a lack thereof, during speciation. However, few studies assess the real effect of hybridization in diversification. The three most representative species of section Pseudophrys in the western Iberian Peninsula-O. dyris, O. fusca, and O. lutea-were chosen to study evolutionary relationships and examine speciation. Using eight specific nuclear microsatellite loci, 357 individuals from 28 locations were studied; 142 of these samples were also studied with four plastid microsatellite loci. Data were analyzed using Bayesian cluster analysis, a median-joint network, and multivariate analysis. Many O. dyris and O. fusca specimens had three or four alleles and were therefore treated as tetraploid. Ophrys dyris is poorly genetically separated from O. fusca, and pure populations are rare. Ophrys fusca and O. lutea are distinct, but hybrids/introgressed individuals were detected in most of the populations and supported by plastid haplotypes. Ophrys fusca is subdivided into three well-delimited genetic lineages with a strict geographic correspondence confirmed by plastid haplotypes. Because postzygotic barriers are weak, leakage in this highly specialized orchid-pollinator system contributes to hybridization and introgression. These leakages may have occurred during periods of past climate change, promoting homogenization and the potential for generations of new biodiversity via production of novel genotypes/phenotypes interacting with pollinators. © 2016 Botanical Society of America.

  17. Historical and current introgression in a Mesoamerican hummingbird species complex: a biogeographic perspective

    Directory of Open Access Journals (Sweden)

    Rosa Alicia Jiménez

    2016-01-01

    Full Text Available The influence of geologic and Pleistocene glacial cycles might result in morphological and genetic complex scenarios in the biota of the Mesoamerican region. We tested whether berylline, blue-tailed and steely-blue hummingbirds, Amazilia beryllina, Amazilia cyanura and Amazilia saucerottei, show evidence of historical or current introgression as their plumage colour variation might suggest. We also analysed the role of past and present climatic events in promoting genetic introgression and species diversification. We collected mitochondrial DNA (mtDNA sequence data and microsatellite loci scores for populations throughout the range of the three Amazilia species, as well as morphological and ecological data. Haplotype network, Bayesian phylogenetic and divergence time inference, historical demography, palaeodistribution modelling, and niche divergence tests were used to reconstruct the evolutionary history of this Amazilia species complex. An isolation-with-migration coalescent model and Bayesian assignment analysis were assessed to determine historical introgression and current genetic admixture. mtDNA haplotypes were geographically unstructured, with haplotypes from disparate areas interdispersed on a shallow tree and an unresolved haplotype network. Assignment analysis of the nuclear genome (nuDNA supported three genetic groups with signs of genetic admixture, corresponding to: (1 A. beryllina populations located west of the Isthmus of Tehuantepec; (2 A. cyanura populations between the Isthmus of Tehuantepec and the Nicaraguan Depression (Nuclear Central America; and (3 A. saucerottei populations southeast of the Nicaraguan Depression. Gene flow and divergence time estimates, and demographic and palaeodistribution patterns suggest an evolutionary history of introgression mediated by Quaternary climatic fluctuations. High levels of gene flow were indicated by mtDNA and asymmetrical isolation-with-migration, whereas the microsatellite analyses

  18. Historical and current introgression in a Mesoamerican hummingbird species complex: a biogeographic perspective

    Science.gov (United States)

    Jiménez, Rosa Alicia

    2016-01-01

    The influence of geologic and Pleistocene glacial cycles might result in morphological and genetic complex scenarios in the biota of the Mesoamerican region. We tested whether berylline, blue-tailed and steely-blue hummingbirds, Amazilia beryllina, Amazilia cyanura and Amazilia saucerottei, show evidence of historical or current introgression as their plumage colour variation might suggest. We also analysed the role of past and present climatic events in promoting genetic introgression and species diversification. We collected mitochondrial DNA (mtDNA) sequence data and microsatellite loci scores for populations throughout the range of the three Amazilia species, as well as morphological and ecological data. Haplotype network, Bayesian phylogenetic and divergence time inference, historical demography, palaeodistribution modelling, and niche divergence tests were used to reconstruct the evolutionary history of this Amazilia species complex. An isolation-with-migration coalescent model and Bayesian assignment analysis were assessed to determine historical introgression and current genetic admixture. mtDNA haplotypes were geographically unstructured, with haplotypes from disparate areas interdispersed on a shallow tree and an unresolved haplotype network. Assignment analysis of the nuclear genome (nuDNA) supported three genetic groups with signs of genetic admixture, corresponding to: (1) A. beryllina populations located west of the Isthmus of Tehuantepec; (2) A. cyanura populations between the Isthmus of Tehuantepec and the Nicaraguan Depression (Nuclear Central America); and (3) A. saucerottei populations southeast of the Nicaraguan Depression. Gene flow and divergence time estimates, and demographic and palaeodistribution patterns suggest an evolutionary history of introgression mediated by Quaternary climatic fluctuations. High levels of gene flow were indicated by mtDNA and asymmetrical isolation-with-migration, whereas the microsatellite analyses found evidence

  19. Mapping of barley alpha-amylases and outer subsite mutants reveals dynamic high-affinity subsites and barriers in the long substrate binding cleft

    DEFF Research Database (Denmark)

    Kandra, L.; Abou Hachem, Maher; Gyemant, G.

    2006-01-01

    Subsite affinity maps of long substrate binding clefts in barley alpha-amylases, obtained using a series of maltooligosaccharides of degree of polymerization of 3-12, revealed unfavorable binding energies at the internal subsites -3 and -5 and at subsites -8 and +3/+4 defining these subsites...... as binding barriers. Barley a-amylase I mutants Y105A and T212Y at subsite -6 and +4 resulted in release or anchoring of bound substrate, thus modifying the affinities of other high-affinity subsites (-2 and +2) and barriers. The double mutant Y105A-T212Y displayed a hybrid subsite affinity profile......, converting barriers to binding areas. These findings highlight the dynamic binding energy distribution and the versatility of long maltooligosaccharide derivatives in mapping extended binding clefts in a-amylases....

  20. Mating, hybridisation and introgression in Lasius ants (Hymenoptera: Formicidae)

    DEFF Research Database (Denmark)

    Van der Have, Tom; Pedersen, Jes Søe; Boomsma, Jacobus Jan

    2011-01-01

    Recent reviews have shown that hybridisation among ant species is likely to be more common than previously appreci-ated, but that documented cases of introgression remain rare. After molecular phylogenetic work had shown that Euro-pean Lasius niger (LINNAEUS, 1758) and L. psammophilus SEIFERT, 1992...... (formerly L. alienus (FOERSTER, 1850)) are unlikely to be very closely related, we decided to analyse an old data set confirming the conclusion by PEARSON (1983) that these two ants can indeed form viable hybrids. We show that signatures of introgression can be detected in a Danish site...... sympatrically. This would imply that multiple accessible field sites are available to study the molecular details of hybridisation and in-trogression between two ant species that have variable degrees of sympatry throughout their distributional ranges...

  1. Bidirectional introgressive hybridization between a cattle and human schistosome species.

    Science.gov (United States)

    Huyse, Tine; Webster, Bonnie L; Geldof, Sarah; Stothard, J Russell; Diaw, Oumar T; Polman, Katja; Rollinson, David

    2009-09-01

    Schistosomiasis is a disease of great medical and veterinary importance in tropical and subtropical regions, caused by parasitic flatworms of the genus Schistosoma (subclass Digenea). Following major water development schemes in the 1980s, schistosomiasis has become an important parasitic disease of children living in the Senegal River Basin (SRB). During molecular parasitological surveys, nuclear and mitochondrial markers revealed unexpected natural interactions between a bovine and human Schistosoma species: S. bovis and S. haematobium, respectively. Hybrid schistosomes recovered from the urine and faeces of children and the intermediate snail hosts of both parental species, Bulinus truncatus and B. globosus, presented a nuclear ITS rRNA sequence identical to S. haematobium, while the partial mitochondrial cox1 sequence was identified as S. bovis. Molecular data suggest that the hybrids are not 1st generation and are a result of parental and/or hybrid backcrosses, indicating a stable hybrid zone. Larval stages with the reverse genetic profile were also found and are suggested to be F1 progeny. The data provide indisputable evidence for the occurrence of bidirectional introgressive hybridization between a bovine and a human Schistosoma species. Hybrid species have been found infecting B. truncatus, a snail species that is now very abundant throughout the SRB. The recent increase in urinary schistosomiasis in the villages along the SRB could therefore be a direct effect of the increased transmission through B. truncatus. Hybridization between schistosomes under laboratory conditions has been shown to result in heterosis (higher fecundity, faster maturation time, wider intermediate host spectrum), having important implications on disease prevalence, pathology and treatment. If this new hybrid exhibits the same hybrid vigour, it could develop into an emerging pathogen, necessitating further control strategies in zones where both parental species overlap.

  2. Broadening the genetic base of Abyssinian mustard (Brassica carinata A. Braun through introgression of genes from related allotetraploid species

    Directory of Open Access Journals (Sweden)

    Farooq A. Sheikh

    2014-07-01

    Full Text Available Brassica carinata (BBCC, 2n=34 has still to emerge as a major oilseed crop owing to poor agronomic attributes like long stature, long maturity duration and low seed yield. The restricted amount of genetic variability available in natural B. carinata necessitates utilization of new sources of variability for broadening its genetic base. Interspecific hybridization followed by selection in selfed and back cross progenies was employed to generate useful variability into B. carinata cv ˈPC5ˈ from elite lines of Brassica napus (AACC, 2n=38 and Brassica juncea (AABB, 2n=36. The morphological evaluation of 24 stable introgressed progenies revealed wide range of variability for key economic traits. The progenies with mean maturity duration of 161 ± 2.1 days, short stature of 139.5 ± 6.5 cm and seed yield per plant of 18.6 ± 2.0 g in comparison to the corresponding figures of 168 ± 4.6 days, 230.6 ± 12.7 cm and 12.0 ± 2.4 g in ˈPC5ˈ (recurrent parent were recovered. Diversity analysis at morphological level revealed that 22 out of 24 stable introgressed progenies were grouped with B. carinata ˈPC5ˈ at average taxonomic distance of 1.19. The diversity at molecular level using 25 polymorphic and reproducible RAPD primers revealed that 19 out of 21 introgressed progenies grouped with B. carinata ˈPC5ˈ at a similarity coefficient of 0.68. The clusters in general represent a wide range of genetic diversity in the back cross lines of B. carinata as a result of introgression of genes from elite lines of B. napus and B. juncea parents.

  3. Introgression Browser: High throughput whole-genome SNP visualization

    NARCIS (Netherlands)

    Aflitos, S.A.; Sanchez Perez, G.F.; Ridder, de D.; Fransz, P.; Schranz, M.E.; Jong, de J.H.S.G.M.; Peters, S.A.

    2015-01-01

    Breeding by introgressive hybridization is a pivotal strategy to broaden the genetic basis of crops. Usually, the desired traits are monitored in consecutive crossing generations by marker-assisted selection, but their analyses fail in chromosome regions where crossover recombinants are rare or not

  4. Introgression browser: high-throughput whole-genome SNP visualization

    NARCIS (Netherlands)

    Alves Aflitos, S.; Sanchez-Perez, G.; de Ridder, D.; Fransz, P.; Schranz, M.E.; de Jong, H.; Peters, S.A.

    2015-01-01

    Breeding by introgressive hybridization is a pivotal strategy to broaden the genetic basis of crops. Usually, the desired traits are monitored in consecutive crossing generations by marker-assisted selection, but their analyses fail in chromosome regions where crossover recombinants are rare or not

  5. A molecular cytogenetic analysis of introgression in Alstroemeria

    NARCIS (Netherlands)

    Kamstra, S.A.

    1999-01-01

    This thesis describes the results of a molecular cytogenetic investigation of the process of introgression in Alstroemeria . The aim of this study was to transfer chromosomes or genes from one Alstroemeria species into another. For this, two

  6. Introgression and selection shaped the evolutionary history of sympatric sister-species of coral reef fishes (genus: Haemulon)

    KAUST Repository

    Bernal, Moisés A.

    2016-11-22

    Closely related marine species with large overlapping ranges provide opportunities to study mechanisms of speciation, particularly when there is evidence of gene flow between such lineages. Here, we focus on a case of hybridization between the sympatric sister-species Haemulon maculicauda and H. flaviguttatum, using Sanger sequencing of mitochondrial and nuclear loci, as well as 2422 single nucleotide polymorphisms (SNPs) obtained via restriction site-associated DNA sequencing (RADSeq). Mitochondrial markers revealed a shared haplotype for COI and low divergence for CytB and CR between the sister-species. On the other hand, complete lineage sorting was observed at the nuclear loci and most of the SNPs. Under neutral expectations, the smaller effective population size of mtDNA should lead to fixation of mutations faster than nDNA. Thus, these results suggest that hybridization in the recent past (0.174-0.263Ma) led to introgression of the mtDNA, with little effect on the nuclear genome. Analyses of the SNP data revealed 28 loci potentially under divergent selection between the two species. The combination of mtDNA introgression and limited nuclear DNA introgression provides a mechanism for the evolution of independent lineages despite recurrent hybridization events. This study adds to the growing body of research that exemplifies how genetic divergence can be maintained in the presence of gene flow between closely related species.

  7. Natural hybridization and asymmetric introgression at the distribution margin of two Buddleja species with a large overlap.

    Science.gov (United States)

    Liao, Rong-Li; Ma, Yong-Peng; Gong, Wei-Chang; Chen, Gao; Sun, Wei-Bang; Zhou, Ren-Chao; Marczewski, Tobias

    2015-06-18

    Natural hybridization in plants is universal and plays an important role in evolution. Based on morphology it has been presumed that hybridization occurred in the genus Buddleja, though genetic studies confirming this assumption have not been conducted to date. The two species B. crispa and B. officinalis overlap in their distributions over a wide range in South-West China, and we aimed to provide genetic evidence for ongoing hybridization in this study. We investigated the occurrence of hybrids between the two species at the southern-most edge of the distribution of B. crispa using five nuclear loci and pollination experiments. The genetic data suggest substantial differentiation between the two species as species-specific alleles are separated by at least 7-28 mutations. The natural hybrids found were nearly all F1s (21 of 23), but backcrosses were detected, and some individuals, morphologically indistinguishable from the parental species, showed introgression. Pollen viability test shows that the percentage of viable pollen grains was 50 ± 4% for B. crispa, and 81 ± 2% for B. officinalis. This difference is highly significant (t = 7.382, p < 0.0001). Hand cross-pollination experiments showed that B. crispa is not successful as pollen-parent, but B. officinalis is able to pollinate B. crispa to produce viable hybrid seed. Inter-specific seed-set is low (8 seeds per fruit, as opposed to about 65 for intra-specific pollinations), suggesting post-zygotic reproductive barriers. In addition, one of the reference populations also suggests a history of introgression at other localities. The occurrence of morphologically intermediate individuals between B. crispa and B. officinalis at Xishan Mountain is unequivocally linked to hybridization and almost all examined individuals of the putative hybrids were likely F1s. Despite pollination experiments indicating higher chances for introgression into B. officinalis (hybrids only produced viable seed when

  8. Efficient anchoring of alien chromosome segments introgressed into bread wheat by new Leymus racemosus genome-based markers.

    Science.gov (United States)

    Edet, Offiong Ukpong; Kim, June-Sik; Okamoto, Masanori; Hanada, Kousuke; Takeda, Tomoyuki; Kishii, Masahiro; Gorafi, Yasir Serag Alnor; Tsujimoto, Hisashi

    2018-03-27

    The tertiary gene pool of bread wheat, to which Leymus racemosus belongs, has remained underutilized due to the current limited genomic resources of the species that constitute it. Continuous enrichment of public databases with useful information regarding these species is, therefore, needed to provide insights on their genome structures and aid successful utilization of their genes to develop improved wheat cultivars for effective management of environmental stresses. We generated de novo DNA and mRNA sequence information of L. racemosus and developed 110 polymorphic PCR-based markers from the data, and to complement the PCR markers, DArT-seq genotyping was applied to develop additional 9990 SNP markers. Approximately 52% of all the markers enabled us to clearly genotype 22 wheat-L. racemosus chromosome introgression lines, and L. racemosus chromosome-specific markers were highly efficient in detailed characterization of the translocation and recombination lines analyzed. A further analysis revealed remarkable transferability of the PCR markers to three other important Triticeae perennial species: L. mollis, Psathyrostachys huashanica and Elymus ciliaris, indicating their suitability for characterizing wheat-alien chromosome introgressions carrying chromosomes of these genomes. The efficiency of the markers in characterizing wheat-L. racemosus chromosome introgression lines proves their reliability, and their high transferability further broadens their scope of application. This is the first report on sequencing and development of markers from L. racemosus genome and the application of DArT-seq to develop markers from a perennial wild relative of wheat, marking a paradigm shift from the seeming concentration of the technology on cultivated species. Integration of these markers with appropriate cytogenetic methods would accelerate development and characterization of wheat-alien chromosome introgression lines.

  9. Multilocus Analysis of Divergence and Introgression in Sympatric and Allopatric Sibling Species of the Lutzomyia longipalpis Complex in Brazil

    Science.gov (United States)

    Mazzoni, Camila J.; Souza, Nataly A.; Machado, Ricardo C.; Bruno, Rafaela V.

    2013-01-01

    Background Lutzomyia longipalpis, the main vector of visceral leishmaniasis in Latin America, is a complex of sibling species. In Brazil, a number of very closely related sibling species have been revealed by the analyses of copulation songs, sex pheromones and molecular markers. However, the level of divergence and gene flow between the sibling species remains unclear. Brazilian populations of this vector can be divided in two main groups: one producing Burst-type songs and the Cembrene-1 pheromone and a second more diverse group producing various Pulse song subtypes and different pheromones. Methodology/Principal Findings We analyzed 21 nuclear loci in two pairs of Brazilian populations: two sympatric populations from the Sobral locality (1S and 2S) in northeastern Brazil and two allopatric populations from the Lapinha and Pancas localities in southeastern Brazil. Pancas and Sobral 2S are populations of the Burst/Cembrene-1 species while Lapinha and Sobral 1S are two putative incipient species producing the same pheromone and similar Pulse song subtypes. The multilocus analysis strongly suggests the occurrence of gene flow during the divergence between the sibling species, with different levels of introgression between loci. Moreover, this differential introgression is asymmetrical, with estimated gene flow being higher in the direction of the Burst/Cembrene-1 species. Conclusions/Significance The results indicate that introgressive hybridization has been a crucial phenomenon in shaping the genome of the L. longipalpis complex. This has possible epidemiological implications and is particularly interesting considering the potential for increased introgression caused by man-made environmental changes and the current trend of leishmaniasis urbanization in Brazil. PMID:24147172

  10. Sexual selection drives asymmetric introgression in wall lizards.

    Science.gov (United States)

    While, Geoffrey M; Michaelides, Sozos; Heathcote, Robert J P; MacGregor, Hannah E A; Zajac, Natalia; Beninde, Joscha; Carazo, Pau; Pérez I de Lanuza, Guillem; Sacchi, Roberto; Zuffi, Marco A L; Horváthová, Terézia; Fresnillo, Belén; Schulte, Ulrich; Veith, Michael; Hochkirch, Axel; Uller, Tobias

    2015-12-01

    Hybridisation is increasingly recognised as an important cause of diversification and adaptation. Here, we show how divergence in male secondary sexual characters between two lineages of the common wall lizard (Podarcis muralis) gives rise to strong asymmetries in male competitive ability and mating success, resulting in asymmetric hybridisation upon secondary contact. Combined with no negative effects of hybridisation on survival or reproductive characters in F1-hybrids, these results suggest that introgression should be asymmetric, resulting in the displacement of sexual characters of the sub-dominant lineage. This prediction was confirmed in two types of secondary contact, across a natural contact zone and in two introduced populations. Our study illustrates how divergence in sexually selected traits via male competition can determine the direction and extent of introgression, contributing to geographic patterns of genetic and phenotypic diversity. © 2015 John Wiley & Sons Ltd/CNRS.

  11. Detection of the introgression loci in Triticum aestivum transferred ...

    African Journals Online (AJOL)

    Significant changes of the distribution frequency for the same introgression loci between BC1F2 and BC1F2-F7 populations were observed, and seven selective advantage loci from A. tauschii (Xgdm128-3D, Xgdm8-3D, Xgdm72-3D, Xgwm341-3D, Xgdm63-5D, Xgdm132-6D and Xgdm36-6D) were found, which ...

  12. Chemical communication, sexual selection, and introgression in wall lizards.

    Science.gov (United States)

    MacGregor, Hannah E A; Lewandowsky, Rachel A M; d'Ettorre, Patrizia; Leroy, Chloé; Davies, Noel W; While, Geoffrey M; Uller, Tobias

    2017-10-01

    Divergence in communication systems should influence the likelihood that individuals from different lineages interbreed, and consequently shape the direction and rate of hybridization. Here, we studied the role of chemical communication in hybridization, and its contribution to asymmetric and sexually selected introgression between two lineages of the common wall lizard (Podarcis muralis). Males of the two lineages differed in the chemical composition of their femoral secretions. Chemical profiles provided information regarding male secondary sexual characters, but the associations were variable and inconsistent between lineages. In experimental contact zones, chemical composition was weakly associated with male reproductive success, and did not predict the likelihood of hybridization. Consistent with these results, introgression of chemical profiles in a natural hybrid zone resembled that of neutral nuclear genetic markers overall, but one compound in particular (tocopherol methyl ether) matched closely the introgression of visual sexual characters. These results imply that associations among male chemical profiles, sexual characters, and reproductive success largely reflect transient and environmentally driven effects, and that genetic divergence in chemical composition is largely neutral. We therefore suggest that femoral secretions in wall lizards primarily provide information about residency and individual identity rather than function as sexual signals. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  13. Extensive hybridization and introgression between Melastoma candidum and M. sanguineum.

    Directory of Open Access Journals (Sweden)

    Ting Liu

    Full Text Available Natural hybridization can lead to various evolutionary outcomes in plants, including hybrid speciation and interspecific gene transfer. It can also cause taxonomic problems, especially in plant genera containing multiple species. In this study, the hybrid status of Melastoma affine, the most widespread taxon in this genus, and introgression between its putative parental species, M. candidum and M. sanguineum, were assessed on two sites, Hainan and Guangdong, using 13 SSR markers and sequences of a chloroplast intergenic spacer. Bayesian-based STRUCTURE analysis detected two most likely distinct clusters for the three taxa, and 76.0% and 73.9% of the morphologically identified individuals of M. candidum and M. sanguineum were correctly assigned, respectively. 74.5% of the M. affine individuals had a membership coefficient to either parental species between 0.1 and 0.9, suggesting admixture between M. candidum and M. sanguineum. Furthermore, NewHybrids analysis suggested that most individuals of M. affine were F2 hybrids or backcross hybrids to M. candidum, and that there was extensive introgression between M. candidum and M. sanguineum. These SSR data thus provides convincing evidence for hybrid origin of M. affine and extensive introgression between M. candidum and M. sanguineum. Chloroplast DNA results were consistent with this conclusion. Much higher hybrid frequency on the more disturbed Guangdong site suggests that human disturbance might offer suitable habitats for the survival of hybrids, a hypothesis that is in need of further testing.

  14. U-Th dating reveals regional-scale decline of branching Acropora corals on the Great Barrier Reef over the past century

    Science.gov (United States)

    Clark, Tara R.; Roff, George; Zhao, Jian-xin; Feng, Yue-xing; Done, Terence J.; McCook, Laurence J.; Pandolfi, John M.

    2017-09-01

    Hard coral cover on the Great Barrier Reef (GBR) is on a trajectory of decline. However, little is known about past coral mortality before the advent of long-term monitoring (circa 1980s). Using paleoecological analysis and high-precision uranium-thorium (U-Th) dating, we reveal an extensive loss of branching Acropora corals and changes in coral community structure in the Palm Islands region of the central GBR over the past century. In 2008, dead coral assemblages were dominated by large, branching Acropora and living coral assemblages by genera typically found in turbid inshore environments. The timing of Acropora mortality was found to be occasionally synchronous among reefs and frequently linked to discrete disturbance events, occurring in the 1920s to 1960s and again in the 1980s to 1990s. Surveys conducted in 2014 revealed low Acropora cover (shifted baseline.

  15. SNP Discovery for mapping alien introgressions in wheat.

    Science.gov (United States)

    Tiwari, Vijay K; Wang, Shichen; Sehgal, Sunish; Vrána, Jan; Friebe, Bernd; Kubaláková, Marie; Chhuneja, Praveen; Doležel, Jaroslav; Akhunov, Eduard; Kalia, Bhanu; Sabir, Jamal; Gill, Bikram S

    2014-04-10

    Monitoring alien introgressions in crop plants is difficult due to the lack of genetic and molecular mapping information on the wild crop relatives. The tertiary gene pool of wheat is a very important source of genetic variability for wheat improvement against biotic and abiotic stresses. By exploring the 5Mg short arm (5MgS) of Aegilops geniculata, we can apply chromosome genomics for the discovery of SNP markers and their use for monitoring alien introgressions in wheat (Triticum aestivum L). The short arm of chromosome 5Mg of Ae. geniculata Roth (syn. Ae. ovata L.; 2n = 4x = 28, UgUgMgMg) was flow-sorted from a wheat line in which it is maintained as a telocentric chromosome. DNA of the sorted arm was amplified and sequenced using an Illumina Hiseq 2000 with ~45x coverage. The sequence data was used for SNP discovery against wheat homoeologous group-5 assemblies. A total of 2,178 unique, 5MgS-specific SNPs were discovered. Randomly selected samples of 59 5MgS-specific SNPs were tested (44 by KASPar assay and 15 by Sanger sequencing) and 84% were validated. Of the selected SNPs, 97% mapped to a chromosome 5Mg addition to wheat (the source of t5MgS), and 94% to 5Mg introgressed from a different accession of Ae. geniculata substituting for chromosome 5D of wheat. The validated SNPs also identified chromosome segments of 5MgS origin in a set of T5D-5Mg translocation lines; eight SNPs (25%) mapped to TA5601 [T5DL · 5DS-5MgS(0.75)] and three (8%) to TA5602 [T5DL · 5DS-5MgS (0.95)]. SNPs (gsnp_5ms83 and gsnp_5ms94), tagging chromosome T5DL · 5DS-5MgS(0.95) with the smallest introgression carrying resistance to leaf rust (Lr57) and stripe rust (Yr40), were validated in two released germplasm lines with Lr57 and Yr40 genes. This approach should be widely applicable for the identification of species/genome-specific SNPs. The development of a large number of SNP markers will facilitate the precise introgression and monitoring of alien segments in crop

  16. SNP Discovery for mapping alien introgressions in wheat

    Science.gov (United States)

    2014-01-01

    Background Monitoring alien introgressions in crop plants is difficult due to the lack of genetic and molecular mapping information on the wild crop relatives. The tertiary gene pool of wheat is a very important source of genetic variability for wheat improvement against biotic and abiotic stresses. By exploring the 5Mg short arm (5MgS) of Aegilops geniculata, we can apply chromosome genomics for the discovery of SNP markers and their use for monitoring alien introgressions in wheat (Triticum aestivum L). Results The short arm of chromosome 5Mg of Ae. geniculata Roth (syn. Ae. ovata L.; 2n = 4x = 28, UgUgMgMg) was flow-sorted from a wheat line in which it is maintained as a telocentric chromosome. DNA of the sorted arm was amplified and sequenced using an Illumina Hiseq 2000 with ~45x coverage. The sequence data was used for SNP discovery against wheat homoeologous group-5 assemblies. A total of 2,178 unique, 5MgS-specific SNPs were discovered. Randomly selected samples of 59 5MgS-specific SNPs were tested (44 by KASPar assay and 15 by Sanger sequencing) and 84% were validated. Of the selected SNPs, 97% mapped to a chromosome 5Mg addition to wheat (the source of t5MgS), and 94% to 5Mg introgressed from a different accession of Ae. geniculata substituting for chromosome 5D of wheat. The validated SNPs also identified chromosome segments of 5MgS origin in a set of T5D-5Mg translocation lines; eight SNPs (25%) mapped to TA5601 [T5DL · 5DS-5MgS(0.75)] and three (8%) to TA5602 [T5DL · 5DS-5MgS (0.95)]. SNPs (gsnp_5ms83 and gsnp_5ms94), tagging chromosome T5DL · 5DS-5MgS(0.95) with the smallest introgression carrying resistance to leaf rust (Lr57) and stripe rust (Yr40), were validated in two released germplasm lines with Lr57 and Yr40 genes. Conclusion This approach should be widely applicable for the identification of species/genome-specific SNPs. The development of a large number of SNP markers will facilitate the precise introgression and

  17. Combined amplicon pyrosequencing assays reveal presence of the apicomplexan "type-N" (cf. Gemmocystis cylindrus and Chromera velia on the Great Barrier Reef, Australia.

    Directory of Open Access Journals (Sweden)

    Jan Slapeta

    Full Text Available BACKGROUND: The coral is predominantly composed of the metabolically dependent coral host and the photosynthetic dinoflagellate Symbiodinium sp. The system as a whole interacts with symbiotic eukaryotes, bacteria and viruses. Gemmocystiscylindrus (cf. "type-N" symbiont belonging to the obligatory parasitic phylum Apicomplexa (Alveolata is ubiquitous in the Caribbean coral, but its presence in the Great Barrier Reef coral has yet to be documented. Approaches allowing identification of the healthy community from the pathogenic or saprobic organisms are needed for sustainable coral reef monitoring. METHODS & PRINCIPAL FINDINGS: We investigated the diversity of eukaryotes associated with a common reef-building corals from the southern Great Barrier Reef. We used three tag encoded 454 amplicon pyrosequencing assays targeting eukaryote small-subunit rRNA gene to demonstrate the presence of the apicomplexan type-N and a photosynthetic sister species to Apicomplexa-Chromeravelia. Amplicon pyrosequencing revealed presence of the small-subunit rRNA genes of known eukaryotic pathogens (Cryptosporidium and Cryptococcus. We therefore conducted bacterial tag encoded amplicon pyrosequencing assay for small-subunit rRNA gene to support effluent exposure of the coral. Bacteria of faecal origin (Enterobacteriales formed 41% of total sequences in contrast to 0-2% of the coral-associated bacterial communities with and without C. velia, respectively. SIGNIFICANCE: This is the first time apicomplexan type-N has been detected in the Great Barrier Reef. Eukaryote tag encoded amplicon pyrosequencing assays demonstrate presence of apicomplexan type-N and C. Velia in total coral DNA. The data highlight the need for combined approaches for eukaryotic diversity studies coupled with bacterial community assessment to achieve a more realistic goals of defining the holobiont community and assessing coral disease. With increasing evidence of Apicomplexa in coral reef

  18. Molecular Characterization of Barrier Properties in Follicle-Associated Epithelium of Porcine Peyer's Patches Reveals Major Sealing Function of Claudin-4

    Directory of Open Access Journals (Sweden)

    Judith Radloff

    2017-08-01

    Full Text Available The pig represents a preferred model for the analysis of intestinal immunology. However, the barrier of the follicle-associated epithelium (FAE covering porcine Peyer's patches (PP has not yet been characterized in detail. This study aimed to perform this characterization in order to pave the way toward an understanding of the functional contribution of epithelial barrier properties in gut immunology. Porcine tissue specimens were taken from the distal small intestine in order to obtain electrophysiological data of PP FAE and neighboring villous epithelium (VE, employing the Ussing chamber technique. Transepithelial resistance (TER and paracellular fluorescein flux were measured, and tissues were morphometrically compared. In selfsame tissues, expression and localization of major tight junction (TJ proteins (claudin-1, -2, -3, -4, -5, and -8 were analyzed. PP FAE specimens showed a higher TER and a lower apparent permeability for sodium fluorescein than VE. Immunoblotting revealed an expression of all claudins within both epithelia, with markedly stronger expression of the sealing TJ protein claudin-4 in PP FAE compared with the neighboring VE. Immunohistochemistry confirmed the expression and localization of all claudins in both PP FAE and VE, with stronger claudin-4 abundance in PP FAE. The results are in accordance with the physiological function of the FAE, which strongly regulates and limits antigen uptake determining a mandatory transcellular route for antigen presentation, highlighting the importance of this structure for the first steps of the intestinal immune response. Thus, this study provides detailed insights into the specific barrier properties of the porcine FAE covering intestinal PP, at the interface of intestinal immunology and barriology.

  19. Combined amplicon pyrosequencing assays reveal presence of the apicomplexan "type-N" (cf. Gemmocystis cylindrus) and Chromera velia on the Great Barrier Reef, Australia.

    Science.gov (United States)

    Slapeta, Jan; Linares, Marjorie C

    2013-01-01

    The coral is predominantly composed of the metabolically dependent coral host and the photosynthetic dinoflagellate Symbiodinium sp. The system as a whole interacts with symbiotic eukaryotes, bacteria and viruses. Gemmocystiscylindrus (cf. "type-N" symbiont) belonging to the obligatory parasitic phylum Apicomplexa (Alveolata) is ubiquitous in the Caribbean coral, but its presence in the Great Barrier Reef coral has yet to be documented. Approaches allowing identification of the healthy community from the pathogenic or saprobic organisms are needed for sustainable coral reef monitoring. We investigated the diversity of eukaryotes associated with a common reef-building corals from the southern Great Barrier Reef. We used three tag encoded 454 amplicon pyrosequencing assays targeting eukaryote small-subunit rRNA gene to demonstrate the presence of the apicomplexan type-N and a photosynthetic sister species to Apicomplexa-Chromeravelia. Amplicon pyrosequencing revealed presence of the small-subunit rRNA genes of known eukaryotic pathogens (Cryptosporidium and Cryptococcus). We therefore conducted bacterial tag encoded amplicon pyrosequencing assay for small-subunit rRNA gene to support effluent exposure of the coral. Bacteria of faecal origin (Enterobacteriales) formed 41% of total sequences in contrast to 0-2% of the coral-associated bacterial communities with and without C. velia, respectively. This is the first time apicomplexan type-N has been detected in the Great Barrier Reef. Eukaryote tag encoded amplicon pyrosequencing assays demonstrate presence of apicomplexan type-N and C. Velia in total coral DNA. The data highlight the need for combined approaches for eukaryotic diversity studies coupled with bacterial community assessment to achieve a more realistic goals of defining the holobiont community and assessing coral disease. With increasing evidence of Apicomplexa in coral reef environments, it is important not only to understand the evolution of these

  20. Mapping of stripe rust resistance gene in an Aegilops caudate introgression line in wheat and its genetic association with leaf rust resistance.

    Science.gov (United States)

    Toor, Puneet Inder; Kaur, Satinder; Bansal, Mitaly; Yadav, Bharat; Chhuneja, Parveen

    2016-12-01

    A pair of stripe rust and leaf rust resistance genes was introgressed from Aegilops caudata, a nonprogenitor diploid species with the CC genome, to cultivated wheat. Inheritance and genetic mapping of stripe rust resistance gene in backcrossrecombinant inbred line (BC-RIL) population derived from the cross of a wheat-Ae. caudata introgression line (IL) T291- 2(pau16060) with wheat cv. PBW343 is reported here. Segregation of BC-RILs for stripe rust resistance depicted a single major gene conditioning adult plant resistance (APR) with stripe rust reaction varying from TR-20MS in resistant RILs signifying the presence of some minor genes as well. Genetic association with leaf rust resistance revealed that two genes are located at a recombination distance of 13%. IL T291-2 had earlier been reported to carry introgressions on wheat chromosomes 2D, 3D, 4D, 5D, 6D and 7D. Genetic mapping indicated the introgression of stripe rust resistance gene on wheat chromosome 5DS in the region carrying leaf rust resistance gene LrAc, but as an independent introgression. Simple sequence repeat (SSR) and sequence-tagged site (STS) markers designed from the survey sequence data of 5DS enriched the target region harbouring stripe and leaf rust resistance genes. Stripe rust resistance locus, temporarily designated as YrAc, mapped at the distal most end of 5DS linked with a group of four colocated SSRs and two resistance gene analogue (RGA)-STS markers at a distance of 5.3 cM. LrAc mapped at a distance of 9.0 cM from the YrAc and at 2.8 cM from RGA-STS marker Ta5DS_2737450, YrAc and LrAc appear to be the candidate genes for marker-assisted enrichment of the wheat gene pool for rust resistance.

  1. Introgression of a leaf rust resistance gene from Aegilops caudata to ...

    Indian Academy of Sciences (India)

    wheat were undertaken. An F2 population derived from the cross of Triticum aestivum cv. WL711 – Ae. caudata introgression line T291-2 with wheat cultivar PBW343 segregated for a single dominant leaf rust resistance gene at the seedling and adult plant stages. Progeny testing in F3 confirmed the introgression of a single ...

  2. Genetic introgression of farmed salmon in native populations: quantifying the relative influence of population size and frequency of escapees

    OpenAIRE

    Heino, Mikko Petteri; Svåsand, Terje; Wennevik, Vidar; Glover, Kevin

    2015-01-01

    - Farmed escapees may threaten the genetic integrity of native salmon populations through interbreeding. However, introgression requires survival until maturation, successful reproduction and successful early development. These traits are often compromised in domesticated animals selected for high performance in captivity. This makes it difficult to predict introgression levels in native populations. A recent study estimated genetic introgression of farmed escaped Atlantic salmon Salmo sal...

  3. Progressive introgression between ¤Brassica napus¤ (oilseed rape) and ¤B-rapa¤

    DEFF Research Database (Denmark)

    Hansen, L.B.; Siegismund, H.R.; Bagger Jørgensen, Rikke

    2003-01-01

    We have earlier shown extensive introgression between oilseed rape (Brassica napus) and B. rapa in a weedy population using AFLP markers specific for the nuclear genomes. In order to describe the progress of this introgression, we examined 117 offspring from 12 maternal plants from the introgress...

  4. Introgression between cultivars and wild populations of Momordica charantia L. (Cucurbitaceae) in Taiwan.

    Science.gov (United States)

    Liao, Pei-Chun; Tsai, Chi-Chu; Chou, Chang-Hung; Chiang, Yu-Chung

    2012-01-01

    The landrace strains of Momordica charantia are widely cultivated vegetables throughout the tropics and subtropics, but not in Taiwan, a continental island in Southeast Asia, until a few hundred years ago. In contrast, the related wild populations with smaller fruit sizes are native to Taiwan. Because of the introduction of cultivars for agricultural purposes, these two accessions currently exhibit a sympatric or parapatric distribution in Taiwan. In this study, the cultivars and wild samples from Taiwan, India, and Korea were collected for testing of their hybridization and evolutionary patterns. The cpDNA marker showed a clear distinction between accessions of cultivars and wild populations of Taiwan and a long divergence time. In contrast, an analysis of eight selectively neutral nuclear microsatellite loci did not reveal a difference between the genetic structures of these two accessions. A relatively short divergence time and frequent but asymmetric gene flows were estimated based on the isolation-with-migration model. Historical and current introgression from cultivars to wild populations of Taiwan was also inferred using MIGRATE-n and BayesAss analyses. Our results showed that these two accessions shared abundant common ancestral polymorphisms, and the timing of the divergence and colonization of the Taiwanese wild populations is consistent with the geohistory of the Taiwan Strait land bridge of the Last Glacial Maximum (LGM). Long-term and recurrent introgression between accessions indicated the asymmetric capacity to receive foreign genes from other accessions. The modern introduction of cultivars of M. charantia during the colonization of Taiwan by the Han Chinese ethnic group enhanced the rate of gene replacement in the native populations and resulted in the loss of native genes.

  5. Historical introgression and the persistence of ghost alleles in the intermediate horseshoe bat (Rhinolophus affinis).

    Science.gov (United States)

    Mao, Xiuguang; He, Guimei; Hua, Panyu; Jones, Gareth; Zhang, Shuyi; Rossiter, Stephen J

    2013-02-01

    Phylogenetic conflicts between genetic markers can help to disentangle complex histories of phylogeography and introgression among taxa. We previously proposed that the Chinese mainland subspecies of the intermediate horseshoe bat Rhinolophus affinis himalayanus colonized Hainan Island to form the subspecies R. a. hainanus. Subsequent recolonization of the mainland formed a third taxon, R. a macrurus, and a secondary contact zone with the ancestral himalayanus. To test for historical and recurrent genetic exchange between these mainland subspecies, we sampled populations of each from two parapatric zones and undertook analyses using one mtDNA marker, three nuclear genes and 14 microsatellites. Nuclear DNA, echolocation call frequencies and morphological data all recovered two taxa; however, a mtDNA phylogeny revealed two himalayanus clades, of which one clustered with macrurus, as well as some shared or related mtDNA haplotypes in eastern populations. Isolation-with-migration (IM) models suggested some mtDNA gene flow from macrurus to himalayanus. However, strong population structure in himalayanus raises the possibility that macrurus captured mtDNA from a coastal population of himalayanus that has since become rare or extinct. To reconcile these two sets of results, we suggest that the IM estimates might reflect historical mtDNA gene flow among populations of himalayanus, before mtDNA was subsequently captured by macrurus. Finally, microsatellite-based ABC analyses supported the island origin of macrurus; however, mtDNA-based ABC analyses suggest this taxon might have evolved on the mainland. Our findings highlight the importance of understanding population history and structure for interpreting hybridization and introgression events. © 2012 Blackwell Publishing Ltd.

  6. Blood-brain barrier specific permeability assay reveals N-methylated tyramine derivatives in standardised leaf extracts and herbal products of Ginkgo biloba.

    Science.gov (United States)

    Könczöl, Árpád; Rendes, Kata; Dékány, Miklós; Müller, Judit; Riethmüller, Eszter; Balogh, György Tibor

    2016-11-30

    The linkage between the central nervous system availability and neuropharmacological activity of the constituents of Ginkgo biloba L. extracts (GBE) is still incomplete. In this study, the in vitro blood-brain barrier (BBB) permeability profile of the standardised GBE was investigated by the parallel artificial membrane permeability assay (PAMPA). Biomarkers, such as terpene trilactones, flavonoid aglycones and ginkgotoxin exerted moderate or good BBB-permeability potential (BBB+), while glycosides and biflavones were predicted as unable to pass the BBB. N-methyltyramine (NMT) and N,N-dimethyltyramine or hordenine (Hor) were identified among BBB+ compounds, while subsequent direct HRMS analysis revealed tyramine (Tyr) and N,N,N-trimethyltyramine or candicine (Can) in GBE as trace constituents. Distribution of Tyr, NMT, Hor and Can was determined by a validated ion-exchange mechanism-based liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS) method in G. biloba samples, such as herbal drugs and dietary supplements. The total content of the four tyramine derivatives in various GBEs ranged from 7.3 up to 6357μg/g dry extract with NMT and Hor as most abundant ones. Considering the pharmacological activities and the revealed fluctuation in the concentration of the analysed adrenergic protoalkaloids, the presented rapid LC-ESI-MS method is proposed for monitoring of the levels of Tyr, NMT, Hor and Can in G. biloba products. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Discordant introgression in a rapidly expanding hybrid swarm

    Science.gov (United States)

    Ward, Jessica L.; Blum, Mike J.; Walters, David M.; Porter, Brady A.; Burkhead, Noel; Freeman, Byron

    2012-01-01

    The erosion of species boundaries can involve rapid evolutionary change. Consequently, many aspects of the process remain poorly understood, including the formation, expansion, and evolution of hybrid swarms. Biological invasions involving hybridization present exceptional opportunities to study the erosion of species boundaries because timelines of interactions and outcomes are frequently well known. Here, we examined clinal variation across codominant and maternally inherited genetic markers as well as phenotypic traits to characterize the expansion and evolution of a hybrid swarm between native Cyprinella venusta and invasive Cyprinella lutrensis minnows. Discordant introgression of phenotype, microsatellite multilocus genotype, and mtDNA haplotype indicates that the observable expansion of the C. venusta x C. lutrensis hybrid swarm is a false invasion front. Both parental and hybrid individuals closely resembling C. lutrensis are numerically dominant in the expansion wake, indicating that the non-native parental phenotype may be selectively favored. These findings show that cryptic introgression can extend beyond the phenotypic boundaries of hybrid swarms and that hybrid swarms likely expand more rapidly than can be documented from phenotypic variation alone. Similarly, dominance of a single parental phenotype following an introduction event may lead to instances of species erosion being mistaken for species displacement without hybridization.

  8. Fine scale mapping of genomic introgressions within the Drosophila yakuba clade.

    Directory of Open Access Journals (Sweden)

    David A Turissini

    2017-09-01

    Full Text Available The process of speciation involves populations diverging over time until they are genetically and reproductively isolated. Hybridization between nascent species was long thought to directly oppose speciation. However, the amount of interspecific genetic exchange (introgression mediated by hybridization remains largely unknown, although recent progress in genome sequencing has made measuring introgression more tractable. A natural place to look for individuals with admixed ancestry (indicative of introgression is in regions where species co-occur. In west Africa, D. santomea and D. yakuba hybridize on the island of São Tomé, while D. yakuba and D. teissieri hybridize on the nearby island of Bioko. In this report, we quantify the genomic extent of introgression between the three species of the Drosophila yakuba clade (D. yakuba, D. santomea, D. teissieri. We sequenced the genomes of 86 individuals from all three species. We also developed and applied a new statistical framework, using a hidden Markov approach, to identify introgression. We found that introgression has occurred between both species pairs but most introgressed segments are small (on the order of a few kilobases. After ruling out the retention of ancestral polymorphism as an explanation for these similar regions, we find that the sizes of introgressed haplotypes indicate that genetic exchange is not recent (>1,000 generations ago. We additionally show that in both cases, introgression was rarer on X chromosomes than on autosomes which is consistent with sex chromosomes playing a large role in reproductive isolation. Even though the two species pairs have stable contemporary hybrid zones, providing the opportunity for ongoing gene flow, our results indicate that genetic exchange between these species is currently rare.

  9. Fine scale mapping of genomic introgressions within the Drosophila yakuba clade.

    Science.gov (United States)

    Turissini, David A; Matute, Daniel R

    2017-09-01

    The process of speciation involves populations diverging over time until they are genetically and reproductively isolated. Hybridization between nascent species was long thought to directly oppose speciation. However, the amount of interspecific genetic exchange (introgression) mediated by hybridization remains largely unknown, although recent progress in genome sequencing has made measuring introgression more tractable. A natural place to look for individuals with admixed ancestry (indicative of introgression) is in regions where species co-occur. In west Africa, D. santomea and D. yakuba hybridize on the island of São Tomé, while D. yakuba and D. teissieri hybridize on the nearby island of Bioko. In this report, we quantify the genomic extent of introgression between the three species of the Drosophila yakuba clade (D. yakuba, D. santomea), D. teissieri). We sequenced the genomes of 86 individuals from all three species. We also developed and applied a new statistical framework, using a hidden Markov approach, to identify introgression. We found that introgression has occurred between both species pairs but most introgressed segments are small (on the order of a few kilobases). After ruling out the retention of ancestral polymorphism as an explanation for these similar regions, we find that the sizes of introgressed haplotypes indicate that genetic exchange is not recent (>1,000 generations ago). We additionally show that in both cases, introgression was rarer on X chromosomes than on autosomes which is consistent with sex chromosomes playing a large role in reproductive isolation. Even though the two species pairs have stable contemporary hybrid zones, providing the opportunity for ongoing gene flow, our results indicate that genetic exchange between these species is currently rare.

  10. Genetic dissection of maize phenology using an intraspecific introgression library

    Directory of Open Access Journals (Sweden)

    Sanguineti Maria C

    2011-01-01

    Full Text Available Abstract Background Collections of nearly isogenic lines where each line carries a delimited portion of a donor source genome into a common recipient genetic background are known as introgression libraries and have already shown to be instrumental for the dissection of quantitative traits. By means of marker-assisted backcrossing, we have produced an introgression library using the extremely early-flowering maize (Zea mays L. variety Gaspé Flint and the elite line B73 as donor and recipient genotypes, respectively, and utilized this collection to investigate the genetic basis of flowering time and related traits of adaptive and agronomic importance in maize. Results The collection includes 75 lines with an average Gaspé Flint introgression length of 43.1 cM. The collection was evaluated for flowering time, internode length, number of ears, number of nodes (phytomeres, number of nodes above the ear, number and proportion of nodes below the ear and plant height. Five QTLs for flowering time were mapped, all corresponding to major QTLs for number of nodes. Three additional QTLs for number of nodes were mapped. Besides flowering time, the QTLs for number of nodes drove phenotypic variation for plant height and number of nodes below and above the top ear, but not for internode length. A number of apparently Mendelian-inherited phenotypes were also observed. Conclusions While the inheritance of flowering time was dominated by the well-known QTL Vgt1, a number of other important flowering time QTLs were identified and, thanks to the type of plant material here utilized, immediately isogenized and made available for fine mapping. At each flowering time QTL, early flowering correlated with fewer vegetative phytomeres, indicating the latter as a key developmental strategy to adapt the maize crop from the original tropical environment to the northern border of the temperate zone (southern Canada, where Gaspé Flint was originally cultivated. Because of

  11. Water deficit affects primary metabolism differently in two Lolium multiflorum/Festuca arundinacea introgression forms with a distinct capacity for photosynthesis and membrane regeneration.

    Directory of Open Access Journals (Sweden)

    Dawid Perlikowski

    2016-07-01

    Full Text Available Understanding how plants respond to drought at different levels of cell metabolism is an important aspect of research on the mechanisms involved in stress tolerance. Furthermore, a dissection of drought tolerance into its crucial components by the use of plant introgression forms facilitates to analyze this trait more deeply. The important components of plant drought tolerance are the capacity for photosynthesis under drought conditions, and the ability of cellular membrane regeneration after stress cessation. Two closely related introgression forms of Lolium multiflorum/Festuca arundinacea, differing in the level of photosynthetic capacity during stress, and in the ability to regenerate their cellular membranes after stress cessation, were used as forage grass models in a primary metabolome profiling and in an evaluation of chloroplast 1,6-bisphosphate aldolase accumulation level and activity, during 11 days of water deficit, followed by 10 days of rehydration. It was revealed here that the introgression form, characterized by the ability to regenerate membranes after rehydration, contained higher amounts of proline, melibiose, galactaric acid, myo-inositol and myo-inositol-1-phosphate involved in osmoprotection and stress signaling under drought. Moreover, during the rehydration period, this form also maintained elevated accumulation levels of most the primary metabolites, analyzed here. The other introgression form, characterized by the higher capacity for photosynthesis, revealed a higher accumulation level and activity of chloroplast aldolase under drought conditions, and higher accumulation levels of most photosynthetic products during control and drought periods. The potential impact of the observed metabolic alterations on cellular membrane recovery after stress cessation, and on a photosynthetic capacity under drought conditions in grasses, are discussed.

  12. Introgression between ecologically distinct species following increased salinity in the Colorado Delta- Worldwide implications for impacted estuary diversity

    Directory of Open Access Journals (Sweden)

    Clive L.F. Lau

    2017-12-01

    Full Text Available We investigate hybridization and introgression between ecologically distinct sister species of silverside fish in the Gulf of California through combined analysis of morphological, sequence, and genotypic data. Water diversions in the past century turned the Colorado River Delta from a normal estuary to a hypersaline inverse estuary, raising concerns for the local fauna, much of which is endangered. Salinity differences are known to generate ecological species pairs and we anticipated that loss of the fresher-water historic salinity regime could alter the adaptive factors maintaining distinction between the broadly distributed Gulf-endemic Colpichthys regis and the narrowly restricted Delta-endemic Colpichthys hubbsi, the species that experienced dramatic environmental change. In this altered environmental context, these long-isolated species (as revealed by Cytochrome b sequences show genotypic (RAG1, microsatellites evidence of active hybridization where the species ranges abut, as well as directional introgression from C. regis into the range center of C. hubbsi. Bayesian group assignment (STRUCTURE on six microsatellite loci and multivariate analyses (DAPC on both microsatellites and phenotypic data further support substantial recent admixture between the sister species. Although we find no evidence for recent population decline in C. hubbsi based on mitochondrial sequence, introgression may be placing an ancient ecological species at risk of extinction. Such introgressive extinction risk should also pertain to other ecological species historically sustained by the now changing Delta environment. More broadly, salinity gradient associated ecological speciation is evident in silverside species pairs in many estuarine systems around the world. Ecological species pairs among other taxa in such systems are likely poorly understood or cryptic. As water extraction accelerates in river systems worldwide, salinity gradients will necessarily be

  13. Introgression between ecologically distinct species following increased salinity in the Colorado Delta- Worldwide implications for impacted estuary diversity.

    Science.gov (United States)

    Lau, Clive L F; Jacobs, David K

    2017-01-01

    We investigate hybridization and introgression between ecologically distinct sister species of silverside fish in the Gulf of California through combined analysis of morphological, sequence, and genotypic data. Water diversions in the past century turned the Colorado River Delta from a normal estuary to a hypersaline inverse estuary, raising concerns for the local fauna, much of which is endangered. Salinity differences are known to generate ecological species pairs and we anticipated that loss of the fresher-water historic salinity regime could alter the adaptive factors maintaining distinction between the broadly distributed Gulf-endemic Colpichthys regis and the narrowly restricted Delta-endemic Colpichthys hubbsi , the species that experienced dramatic environmental change. In this altered environmental context, these long-isolated species (as revealed by Cytochrome b sequences) show genotypic (RAG1, microsatellites) evidence of active hybridization where the species ranges abut, as well as directional introgression from C. regis into the range center of C. hubbsi . Bayesian group assignment (STRUCTURE) on six microsatellite loci and multivariate analyses (DAPC) on both microsatellites and phenotypic data further support substantial recent admixture between the sister species. Although we find no evidence for recent population decline in C. hubbsi based on mitochondrial sequence, introgression may be placing an ancient ecological species at risk of extinction. Such introgressive extinction risk should also pertain to other ecological species historically sustained by the now changing Delta environment. More broadly, salinity gradient associated ecological speciation is evident in silverside species pairs in many estuarine systems around the world. Ecological species pairs among other taxa in such systems are likely poorly understood or cryptic. As water extraction accelerates in river systems worldwide, salinity gradients will necessarily be altered, impacting

  14. Dynamic genome wide expression profiling of Drosophila head development reveals a novel role of Hunchback in retinal glia cell development and blood-brain barrier integrity.

    Directory of Open Access Journals (Sweden)

    Montserrat Torres-Oliva

    2018-01-01

    Full Text Available Drosophila melanogaster head development represents a valuable process to study the developmental control of various organs, such as the antennae, the dorsal ocelli and the compound eyes from a common precursor, the eye-antennal imaginal disc. While the gene regulatory network underlying compound eye development has been extensively studied, the key transcription factors regulating the formation of other head structures from the same imaginal disc are largely unknown. We obtained the developmental transcriptome of the eye-antennal discs covering late patterning processes at the late 2nd larval instar stage to the onset and progression of differentiation at the end of larval development. We revealed the expression profiles of all genes expressed during eye-antennal disc development and we determined temporally co-expressed genes by hierarchical clustering. Since co-expressed genes may be regulated by common transcriptional regulators, we combined our transcriptome dataset with publicly available ChIP-seq data to identify central transcription factors that co-regulate genes during head development. Besides the identification of already known and well-described transcription factors, we show that the transcription factor Hunchback (Hb regulates a significant number of genes that are expressed during late differentiation stages. We confirm that hb is expressed in two polyploid subperineurial glia cells (carpet cells and a thorough functional analysis shows that loss of Hb function results in a loss of carpet cells in the eye-antennal disc. Additionally, we provide for the first time functional data indicating that carpet cells are an integral part of the blood-brain barrier. Eventually, we combined our expression data with a de novo Hb motif search to reveal stage specific putative target genes of which we find a significant number indeed expressed in carpet cells.

  15. Dynamic genome wide expression profiling of Drosophila head development reveals a novel role of Hunchback in retinal glia cell development and blood-brain barrier integrity

    Science.gov (United States)

    Torres-Oliva, Montserrat; Schneider, Julia; Wiegleb, Gordon

    2018-01-01

    Drosophila melanogaster head development represents a valuable process to study the developmental control of various organs, such as the antennae, the dorsal ocelli and the compound eyes from a common precursor, the eye-antennal imaginal disc. While the gene regulatory network underlying compound eye development has been extensively studied, the key transcription factors regulating the formation of other head structures from the same imaginal disc are largely unknown. We obtained the developmental transcriptome of the eye-antennal discs covering late patterning processes at the late 2nd larval instar stage to the onset and progression of differentiation at the end of larval development. We revealed the expression profiles of all genes expressed during eye-antennal disc development and we determined temporally co-expressed genes by hierarchical clustering. Since co-expressed genes may be regulated by common transcriptional regulators, we combined our transcriptome dataset with publicly available ChIP-seq data to identify central transcription factors that co-regulate genes during head development. Besides the identification of already known and well-described transcription factors, we show that the transcription factor Hunchback (Hb) regulates a significant number of genes that are expressed during late differentiation stages. We confirm that hb is expressed in two polyploid subperineurial glia cells (carpet cells) and a thorough functional analysis shows that loss of Hb function results in a loss of carpet cells in the eye-antennal disc. Additionally, we provide for the first time functional data indicating that carpet cells are an integral part of the blood-brain barrier. Eventually, we combined our expression data with a de novo Hb motif search to reveal stage specific putative target genes of which we find a significant number indeed expressed in carpet cells. PMID:29360820

  16. Rapid and targeted introgression of fgr gene through marker-assisted backcrossing in rice (Oryza sativa L.).

    Science.gov (United States)

    Cheng, Acga; Ismail, Ismanizan; Osman, Mohamad; Hashim, Habibuddin; Mohd Zainual, Nur Samahah

    2017-12-01

    While it is crucial for developing countries like Malaysia to achieve self-sufficiency in rice (Oryza sativa L.), it is equally critical to be able to produce high-quality rice, specifically fragrant rice, which demands are often met through importation. The present study was aimed at developing high-yielding fragrant rice, in a timely and cost-effective manner. A marker-assisted backcross (MABC) approach was optimised to introgress the fragrance gene (fgr) into two high-yielding Malaysian varieties, MR84 and MR219, within two years utilising less than 50 molecular markers. Coupled with phenotypic screening, one single foreground marker (fgr-SNP) and 48 background markers were selected and utilised, revealing recovery of at least 90% of recurrent parent genome (RPG) in merely two backcross generations. Collectively, the yield potential of the developed BC 2 F 2 lines (BLs) was higher (P > 0.05) than the donor parent, MRQ74, and similar (P < 0.05) to both the recurrent parents, MR84 and MR219. In addition, some of the developed BLs showed good grain quality, such as having long grain. We believe that this is the first report comprising the validation and utilisation of the single functional marker system (fgr-SNP) in introgressing the fgr gene into different rice varieties.

  17. Introgressive hybridization as a promoter of genome reshuffling in natural homoploid fish hybrids (Cyprinidae, Leuciscinae)

    Czech Academy of Sciences Publication Activity Database

    Pereira, C. S.; Aboim, M. A.; Ráb, Petr; Collares-Pereira, M. J.

    2014-01-01

    Roč. 112, č. 3 (2014), s. 343-350 ISSN 0018-067X Institutional support: RVO:67985904 Keywords : comparative genome hybridization * hybrid zones * introgression Subject RIV: EG - Zoology Impact factor: 3.805, year: 2014

  18. Propagule pressure and stream characteristics influence introgression: Cutthroat and rainbow trout in British Columbia

    Science.gov (United States)

    Bennett, S.N.; Olson, J.R.; Kershner, J.L.; Corbett, P.

    2010-01-01

    Hybridization and introgression between introduced and native salmonids threaten the continued persistence of many inland cutthroat trout species. Environmental models have been developed to predict the spread of introgression, but few studies have assessed the role of propagule pressure. We used an extensive set of fish stocking records and geographic information system (GIS) data to produce a spatially explicit index of potential propagule pressure exerted by introduced rainbow trout in the Upper Kootenay River, British Columbia, Canada. We then used logistic regression and the information-theoretic approach to test the ability of a set of environmental and spatial variables to predict the level of introgression between native westslope cutthroat trout and introduced rainbow trout. Introgression was assessed using between four and seven co-dominant, diagnostic nuclear markers at 45 sites in 31 different streams. The best model for predicting introgression included our GIS propagule pressure index and an environmental variable that accounted for the biogeoclimatic zone of the site (r2 = 0.62). This model was 1.4 times more likely to explain introgression than the next-best model, which consisted of only the propagule pressure index variable. We created a composite model based on the model-averaged results of the seven top models that included environmental, spatial, and propagule pressure variables. The propagule pressure index had the highest importance weight (0.995) of all variables tested and was negatively related to sites with no introgression. This study used an index of propagule pressure and demonstrated that propagule pressure had the greatest influence on the level of introgression between a native and introduced trout in a human-induced hybrid zone. ?? 2010 by the Ecological Society of America.

  19. Postglacial species displacement in Triturus newts deduced from asymmetrically introgressed mitochondrial DNA and ecological niche models

    Science.gov (United States)

    2012-01-01

    Background If the geographical displacement of one species by another is accompanied by hybridization, mitochondrial DNA can introgress asymmetrically, from the outcompeted species into the invading species, over a large area. We explore this phenomenon using the two parapatric crested newt species, Triturus macedonicus and T. karelinii, distributed on the Balkan Peninsula in south-eastern Europe, as a model. Results We first delimit a ca. 54,000 km2 area in which T. macedonicus contains T. karelinii mitochondrial DNA. This introgression zone bisects the range of T. karelinii, cutting off a T. karelinii enclave. The high similarity of introgressed mitochondrial DNA haplotypes with those found in T. karelinii suggests a recent transfer across the species boundary. We then use ecological niche modeling to explore habitat suitability of the location of the present day introgression zone under current, mid-Holocene and Last Glacial Maximum conditions. This area was inhospitable during the Last Glacial Maximum for both species, but would have been habitable at the mid-Holocene. Since the mid-Holocene, habitat suitability generally increased for T. macedonicus, whereas it decreased for T. karelinii. Conclusion The presence of a T. karelinii enclave suggests that T. karelinii was the first to colonize the area where the present day introgression zone is positioned after the Last Glacial Maximum. Subsequently, we propose T. karelinii was outcompeted by T. macedonicus, which captured T. karelinii mitochondrial DNA via introgressive hybridization in the process. Ecological niche modeling suggests that this replacement was likely facilitated by a shift in climate since the mid-Holocene. We suggest that the northwestern part of the current introgression zone was probably never inhabited by T. karelinii itself, and that T. karelinii mitochondrial DNA spread there through T. macedonicus exclusively. Considering the spatial distribution of the introgressed mitochondrial DNA and

  20. Genomic signatures of adaptive introgression from European mouflon into domestic sheep.

    Science.gov (United States)

    Barbato, Mario; Hailer, Frank; Orozco-terWengel, Pablo; Kijas, James; Mereu, Paolo; Cabras, Pierangela; Mazza, Raffaele; Pirastru, Monica; Bruford, Michael W

    2017-08-08

    Mouflon (Ovis aries musimon) became extinct from mainland Europe after the Neolithic, but remnant populations from the Mediterranean islands of Corsica and Sardinia have been used for reintroductions across Europe since the 19 th -century. Mouflon x sheep hybrids are larger-bodied than mouflon, potentially showing increased male reproductive success, but little is known about genomic levels of admixture, or about the adaptive significance of introgression between resident mouflon and local sheep breeds. Here we analysed Ovine medium-density SNP array genotypes of 92 mouflon from six geographic regions, along with data from 330 individuals of 16 domestic sheep breeds. We found lower levels of genetic diversity in mouflon than in domestic sheep, consistent with past bottlenecks in mouflon. Introgression signals were bidirectional and affected most mouflon and sheep populations, being strongest in one Sardinian mouflon population. Developing and using a novel approach to identify chromosomal regions with consistent introgression signals, we infer adaptive introgression from mouflon to domestic sheep related to immunity mechanisms, but not in the opposite direction. Further, we infer that Soay and Sarda sheep carry introgressed mouflon alleles involved in bitter taste perception and/or innate immunity. Our results illustrate the potential for adaptive introgression even among recently diverged populations.

  1. Gene introgression from common wheat into Aegilops L.

    Directory of Open Access Journals (Sweden)

    Bo Yuan

    2017-05-01

    Full Text Available Group of experiments were carried out to verify possibility of gene introgression from common wheat into Aegilops. The artificial indoor crossbreed was conducted using 7 genotypes from 4 wheat relative species as female, and common wheat as male. The experiment result shows that different species has variable cross ability. Among the 4 Aegilops species, the highest cross rate is from the combination of Aegilops tauschii × Triticum aestivum (46.49% for genotype Ae42, 22.58% for Y92, the second is from Aegilops ovata × T. aestivum (14.76% for Y100, 12.11% for Ae23, the third is from Aegilops cylindrica × T. aestivum (2.23% for Ae7, 8.50% for Y145, and the lowest is from Aegilops speltoides × T. aestivum (0.19%. Hybrid embryos from different combinations have different ability of callus initiation and germination. The hybrid embryos from A. ovata/T. aestivum and Ae. tauschii/T. aestivum have a higher level of callus initiation and germination. Ae. cylindrica/T. aestivum has a middle level, while the Ae. speltoides has a lower level. The interspecific hybrids between Aegilops and common wheat have so low fertility. In back-crosses, the seed-set rate of hybrids of Ae. ovata/T. aestivum is 3.71% and 4.36% respectively back-crossed with male and female parents, while for hybrids of Ae. cylindrica/T. aestivum, they were 0 and 0.33% respectively, and for Ae. tauschii/T. aestivum, 0.33% and 0 respectively. On selfing of the hybrids, the seed-set rate is 0 (no seed set from 9750 florets for the combination of Ae. cylindrica/T. aestivum, 0.044% (3 selfed seeds out of 6870 florets for Ae. ovata/T. aestivum and 0 (no seed set from 7253 florets for Ae. tauschii/T. aestivum. The research suggests that the probability of gene introgression from T. aestivum into Aegilops species is very low in nature.

  2. Transcriptome alteration in a rice introgression line with enhanced alkali tolerance.

    Science.gov (United States)

    Zhang, Yunhong; Lin, Xiuyun; Ou, Xiufang; Hu, Lanjuan; Wang, Jinming; Yang, Chunwu; Wang, Shucai; Liu, Bao

    2013-07-01

    Alkali stress inhibits plant growth and development and thus limits crop productivity. To investigate the possible genetic basis of alkali tolerance in rice, we generated an introgressed rice line (K83) with significantly enhanced tolerance to alkali stress compared to its recipient parental cultivar (Jijing88). By using microarray analysis, we examined the global gene expression profiles of K83 and Jijing88, and found that more than 1200 genes were constitutively and differentially expressed in K83 in comparison to Jijing88 with 572 genes up- and 654 down-regulated. Upon alkali treatment, a total of 347 genes were found up- and 156 down-regulated in K83 compared to 591 and 187, respectively, in Jijing88. Among the up-regulated genes in both K83 and Jijing88, only 34 were constitutively up-regulated in K83, suggesting that both the constitutive differentially expressed genes in K83 and those induced by alkali treatment are most likely responsible for enhanced alkali tolerance. A gene ontology analysis based on all annotated, differentially expressed genes revealed that genes with expression alterations were enriched in pathways involved in metabolic processes, catalytic activity, and transport and transcription factor activities, suggesting that these pathways are associated with alkali stress tolerance in rice. Our results illuminated the novel genetic aspects of alkali tolerance in rice and established a repertory of potential target genes for biotechnological manipulations that can be used to generate alkali-tolerant rice cultivars. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  3. Cellular immune surveillance of central nervous system bypasses blood-brain barrier and blood-cerebrospinal-fluid barrier: revealed with the New Marburg cerebrospinal-fluid model in healthy humans.

    Science.gov (United States)

    Kleine, Tilmann O

    2015-03-01

    In healthy human brain/spinal cord, blood capillaries and venules are locked differently with junctions and basement membrane (blood-brain barrier, blood-venule barrier). In choroid plexus, epithelial tight junctions and basement membrane lock blood-cerebrospinal-fluid (CSF) barrier. Lymphocytic cell data, quantified with multicolour flow-cytometry or immuno-cytochemical methods in sample pairs of lumbar CSF, ventrictricular CSF and peripheral venous blood, are taken from references; similarly, data of thoracic duct chyle and blood sample pairs. Through three circumventricular organs (median eminence, organum vasculosum lamina terminalis, area postrema), 15-30 μl blood are pressed by blood pressure through fenestrated capillaries, matrix/basement membrane spaces and ependyma cell lacks into ventricular/suboccipital CSF to generate CD3(+) , CD4(+) , CD8(+) , CD3(+) HLA-DR(+) , CD16(+) 56(+) 3(-) NK, CD19(+) 3(-) B subsets; some B, few NK cells adhere in circumventricular organs. Into lumbar CSF, 10-15 μl thoracic chyle with five lymphocyte subsets (without CD3(+) HLA-DR(+) cells) reflux, when CSF drains out with to-and-fro movements of chyle/CSF along nerve roots. Lymphocytes in lumbar CSF represent a mixture of blood and lymph lymphocytic cells with similar HLA-DR(+) CD3(+) cell counts in ventricular and lumbar CSF, higher CD3(+) , CD4(+) , CD8(+) subsets in lumbar CSF, and few NK and B cells due to absorption in circumventricular organs. The Marburg CSF Model reflects origin and turnover of lymphatic cells in CSF realistically; the model differs from ligand-multistep processes of activated lymphocytes through blood-brain-, blood-venule-, and blood-CSF-barriers; because transfer of inactivated native lymphocytes through the barriers is not found with healthy humans, although described so in literature. © 2015 International Society for Advancement of Cytometry.

  4. Genetic and epigenetic alterations of Brassica nigra introgression lines from somatic hybridization: a resource for cauliflower improvement

    Directory of Open Access Journals (Sweden)

    Guixiang Wang

    2016-08-01

    Full Text Available Broad phenotypic variations were obtained previously in derivatives from the asymmetric somatic hybridization of cauliflower ‘Korso’ (Brassica oleracea var. botrytis, 2n = 18, CC genome and black mustard ‘G1/1’ (Brassica nigra, 2n = 16, BB genome. However, the mechanisms underlying these variations were unknown. In this study, 28 putative introgression lines (ILs were pre-selected according to a series of morphological (leaf shape and color, plant height and branching, curd features, and flower traits and physiological (black rot/club root resistance characters. Multi-color fluorescence in situ hybridization revealed that these plants contained 18 chromosomes derived from ‘Korso’. Molecular marker (65 simple sequence repeats and 77 amplified fragment length polymorphisms analysis identified the presence of ‘G1/1’ DNA segments (average 7.5%. Additionally, DNA profiling revealed many genetic and epigenetic differences among the ILs, including sequence alterations, deletions, and variation in patterns of cytosine methylation. The frequency of fragments lost (5.1% was significantly higher than presence of novel bands (1.4%, and the presence of fragments specific to B. carinata (BBCC 2n = 34 were common (average 15.5%. Methylation-sensitive amplified polymorphism analysis indicated that methylation changes were common and that hypermethylation (12.4% was more frequent than hypomethylation (4.8%. Our results suggested that asymmetric somatic hybridization and alien DNA introgression induced genetic and epigenetic alterations. Thus, these ILs represent an important, novel germplasm resource for cauliflower improvement that can be mined for diverse traits of interest to breeders and researchers.

  5. Gene Introgression in Weeds Depends on Initial Gene Location in the Crop:Brassica napus-Raphanus raphanistrumModel.

    Science.gov (United States)

    Adamczyk-Chauvat, Katarzyna; Delaunay, Sabrina; Vannier, Anne; François, Caroline; Thomas, Gwenaëlle; Eber, Frédérique; Lodé, Maryse; Gilet, Marie; Huteau, Virginie; Morice, Jérôme; Nègre, Sylvie; Falentin, Cyril; Coriton, Olivier; Darmency, Henri; Alrustom, Bachar; Jenczewski, Eric; Rousseau-Gueutin, Mathieu; Chèvre, Anne-Marie

    2017-07-01

    The effect of gene location within a crop genome on its transfer to a weed genome remains an open question for gene flow assessment. To elucidate this question, we analyzed advanced generations of intergeneric hybrids, derived from an initial pollination of known oilseed rape varieties ( Brassica napus , AACC, 2 n  = 38) by a local population of wild radish ( Raphanus raphanistrum , RrRr, 2 n  = 18). After five generations of recurrent pollination, 307 G5 plants with a chromosome number similar to wild radish were genotyped using 105 B. napus specific markers well distributed along the chromosomes. They revealed that 49.8% of G5 plants carried at least one B. napus genomic region. According to the frequency of B. napus markers (0-28%), four classes were defined: Class 1 (near zero frequency), with 75 markers covering ∼70% of oilseed rape genome; Class 2 (low frequency), with 20 markers located on 11 genomic regions; Class 3 (high frequency), with eight markers on three genomic regions; and Class 4 (higher frequency), with two adjacent markers detected on A10. Therefore, some regions of the oilseed rape genome are more prone than others to be introgressed into wild radish. Inheritance and growth of plant progeny revealed that genomic regions of oilseed rape could be stably introduced into wild radish and variably impact the plant fitness (plant height and seed number). Our results pinpoint that novel technologies enabling the targeted insertion of transgenes should select genomic regions that are less likely to be introgressed into the weed genome, thereby reducing gene flow. Copyright © 2017 by the Genetics Society of America.

  6. Introgression of leginsulin, a cysteine-rich protein, and high-protein trait from an Asian soybean plant introduction genotype into a North American experimental soybean line.

    Science.gov (United States)

    Krishnan, Hari B; Kim, Won-Seok; Oehrle, Nathan W; Alaswad, Alaa A; Baxter, Ivan; Wiebold, William J; Nelson, Randall L

    2015-03-25

    Soybean is an important protein source for both humans and animals. However, soybean proteins are relatively poor in the sulfur-containing amino acids, cysteine and methionine. Improving the content of endogenous proteins rich in sulfur-containing amino acids could enhance the nutritive value of soybean meal. Leginsulin, a cysteine-rich peptide, predominantly accumulates in Asian soybean accessions but not in most North American cultivars. By screening diverse soybean accessions from the USDA Soybean Germplasm Collection, we were able to identify one plant introduction, PI 427138, as a high-protein line with relatively high amounts of both elemental sulfur and leginsulin. We introgressed these desirable traits from PI 427138 into an experimental line with the aim of improving the overall protein content and quality of seed proteins. Biochemical characterization of inbred progenies from the cross of LD00-3309 with PI 427138 grown at six locations revealed stable ingression of high protein, high elemental sulfur, and high leginsulin accumulation. Comparison of soybean seed proteins resolved by high-resolution 2-D gel electrophoresis in combination with Delta2D image analysis software revealed preferential accumulation of a few glycinin subunits contributed to the increased protein content in the introgressed lines. Amino acid analysis revealed that even though the leginsulin introgressed lines had higher protein, leginsulin, and elemental sulfur, the overall concentration of sulfur-containing amino acids was not significantly altered when compared with the parental lines. The experimental soybean lines developed during this study (Leg-3, Leg-7, and Leg-8) lack A5, A4, and B3 glycinin subunits and could be utilized in breeding programs to develop high-quality tofu cultivars.

  7. Sperm-related phenotypes implicated in both maintenance and breakdown of a natural species barrier in the house mouse

    Science.gov (United States)

    Albrechtová, Jana; Albrecht, Tomáš; Baird, Stuart J. E.; Macholán, Miloš; Rudolfsen, Geir; Munclinger, Pavel; Tucker, Priscilla K.; Piálek, Jaroslav

    2012-01-01

    The house mouse hybrid zone (HMHZ) is a species barrier thought to be maintained by a balance between dispersal and natural selection against hybrids. While the HMHZ is characterized by frequency discontinuities for some sex chromosome markers, there is an unexpected large-scale regional introgression of a Y chromosome across the barrier, in defiance of Haldane's rule. Recent work suggests that a major force maintaining the species barrier acts through sperm traits. Here, we test whether the Y chromosome penetration of the species barrier acts through sperm traits by assessing sperm characteristics of wild-caught males directly in a field laboratory set up in a Y introgression region of the HMHZ, later calculating the hybrid index of each male using 1401 diagnostic single nucleotide polymorphisms (SNPs). We found that both sperm count (SC) and sperm velocity were significantly reduced across the natural spectrum of hybrids. However, SC was more than rescued in the presence of the invading Y. Our results imply an asymmetric advantage for Y chromosome introgression consistent with the observed large-scale introgression. We suggest that selection on sperm-related traits probably explains a large component of patterns observed in the natural hybrid zone, including the Y chromosome penetration. PMID:23055063

  8. Sperm-related phenotypes implicated in both maintenance and breakdown of a natural species barrier in the house mouse

    Czech Academy of Sciences Publication Activity Database

    Albrechtová, Jana; Albrecht, Tomáš; Baird, S. J. E.; Macholán, Miloš; Rudolfsen, G.; Munclinger, P.; Tucker, P. K.; Piálek, Jaroslav

    2012-01-01

    Roč. 279, č. 1748 (2012), s. 4803-4810 ISSN 0962-8452 R&D Projects: GA ČR GA206/08/0640; GA MŠk LC06073 Institutional support: RVO:68081766 ; RVO:67985904 Keywords : sperm * hybrid zone * species barrier * Y introgression * male fitness Subject RIV: EG - Zoology Impact factor: 5.683, year: 2012

  9. Detection of nitrogen deficiency QTL in juvenile wild barley introgression lines growing in a hydroponic system.

    Science.gov (United States)

    Hoffmann, Astrid; Maurer, Andreas; Pillen, Klaus

    2012-10-20

    In this report we studied the genetic regulation of juvenile development of wild barley introgression lines (S42ILs) under two contrasting hydroponic nitrogen (N) supplies. Ten shoot and root related traits were examined among 42 S42ILs and the recurrent parent 'Scarlett'. The traits included tiller number, leaf number, plant height, leaf and root length, leaf to root length ratio, shoots and root dry weight, shoot to root weight ratio, and chlorophyll content. Our aims were (1) to test the suitability of a hydroponic system for early detection of favourable S42ILs, (2) to locate quantitative trait loci (QTL) that control the examined traits, (3) to identify favourable wild barley alleles that improve trait performances in regard to N treatment and, finally, (4) to validate the identified QTL through comparison with previously reported QTL originating from the same parental cross. The phenotypic data were analysed in a mixed model association study to detect QTL. The post-hoc Dunnett test identified 28 S42ILs that revealed significant (P hydroponic N study corresponded to QTL that were also detected in field trials with adult plants of a similar S42IL set or of the original S42 population. For instance, S42IL-135, -136 and -137, revealed increasing Hsp effects for tiller number, leaf number, leaf length, plant height and leaf to root ratio on the long arm of chromosome 7H. These QTL correspond to QTL for ears per plant and plant height that were previously detected in field trials conducted with the same S42ILs or with the S42 population. Our results suggest that the QTL we identified under hydroponic N cultivation partly correspond to QTL detected in field experiments. Due to this finding, screening of plants in early developmental stages grown in a hydroponic system may be a fast and cost effective method for early QTL detection and marker-assisted allelic selection, potentially speeding up elite barley breeding programs.

  10. Molecular cytogenetic characterization of alien introgressions with gene Fhb3 for resistance to Fusarium head blight disease of wheat

    Science.gov (United States)

    Fusarium head blight (FHB) resistance was identified in the alien species Leymus racemosus, and wheat-Leymus introgression lines with FHB resistance were reported previously. Detailed molecular cytogenetic analysis of alien introgressions T01, T09, and T14 and the mapping of Fhb3, a new gene for FHB...

  11. Molecular evidence for hybridization and introgression in the neotropical coastal desert-endemic Palaua (Malveae, Malvaceae).

    Science.gov (United States)

    Schneider, Julio V; Schulte, Katharina; Aguilar, Javier Fuertes; Huertas, Marilú L

    2011-09-01

    Recent years have seen an increasing awareness of the importance of hybridization and introgression in plant evolution. Both processes were also invoked to have had a strong impact in the evolution of Palaua, based on morphological intermediacy. Here, we used nuclear ITS and cellulose synthase DNA sequences to assess previous phylogenetic hypotheses and to uncover previously undescribed reticulate evolution in Palaua. Both nuclear regions recovered largely the same reticulate pattern, showing that interspecific crosses occurred between distantly related species of the Dissecta and Integrifolia clade. Hybridization between species occurred only in a narrow contact zone. Moreover, many sequences of Palaua dissecta were placed in the strongly divergent Integrifolia clade, a pattern that is best explained by introgression. These results support our view that the strong interannual fluctuations of humidity and habitat expansion provide opportunities for the isolation of taxa, establishment of hybrid species, and for introgression between incompletely reproductively isolated taxa following recurrent contact. Copyright © 2011 Elsevier Inc. All rights reserved.

  12. Huntington’s Disease iPSC-Derived Brain Microvascular Endothelial Cells Reveal WNT-Mediated Angiogenic and Blood-Brain Barrier Deficits

    Directory of Open Access Journals (Sweden)

    Ryan G. Lim

    2017-05-01

    Full Text Available Brain microvascular endothelial cells (BMECs are an essential component of the blood-brain barrier (BBB that shields the brain against toxins and immune cells. While BBB dysfunction exists in neurological disorders, including Huntington’s disease (HD, it is not known if BMECs themselves are functionally compromised to promote BBB dysfunction. Further, the underlying mechanisms of BBB dysfunction remain elusive given limitations with mouse models and post-mortem tissue to identify primary deficits. We undertook a transcriptome and functional analysis of human induced pluripotent stem cell (iPSC-derived BMECs (iBMEC from HD patients or unaffected controls. We demonstrate that HD iBMECs have intrinsic abnormalities in angiogenesis and barrier properties, as well as in signaling pathways governing these processes. Thus, our findings provide an iPSC-derived BBB model for a neurodegenerative disease and demonstrate autonomous neurovascular deficits that may underlie HD pathology with implications for therapeutics and drug delivery.

  13. Genomic analysis reveals selection for Asian genes in European pigs following human-mediated introgression

    NARCIS (Netherlands)

    Bosse, M.; Megens, H.J.W.C.; Frantz, L.A.F.; Madsen, O.; Paudel, Y.; Duijvestein, N.; Crooijmans, R.P.M.A.; Groenen, M.

    2014-01-01

    The independent domestication of local wild boar populations in Asia and Europe about 10,000 years ago led to distinct European and Asian pig breeds, each with very different phenotypic characteristics. During the Industrial Revolution, Chinese breeds were imported to Europe to improve commercial

  14. Nuclear markers reveal a complex introgression pattern among marine turtle species on the Brazilian coast.

    Science.gov (United States)

    Vilaça, Sibelle T; Vargas, Sarah M; Lara-Ruiz, Paula; Molfetti, Érica; Reis, Estéfane C; Lôbo-Hajdu, Gisele; Soares, Luciano S; Santos, Fabrício R

    2012-09-01

    Surprisingly, a high frequency of interspecific sea turtle hybrids has been previously recorded in a nesting site along a short stretch of the Brazilian coast. Mitochondrial DNA data indicated that as much as 43% of the females identified as Eretmochelys imbricata are hybrids in this area (Bahia State of Brazil). It is a remarkable find, because most of the nesting sites surveyed worldwide, including some in northern Brazil, presents no hybrids, and rare Caribbean sites present no more than 2% of hybrids. Thus, a detailed understanding of the hybridization process is needed to evaluate natural or anthropogenic causes of this regional phenomenon in Brazil, which could be an important factor affecting the conservation of this population. We analysed a set of 12 nuclear markers to investigate the pattern of hybridization involving three species of sea turtles: hawksbill (E. imbricata), loggerhead (Caretta caretta) and olive ridley (Lepidochelys olivacea). Our data indicate that most of the individuals in the crossings L. olivacea × E. imbricata and L. olivacea × C. caretta are F1 hybrids, whereas C. caretta × E. imbricata crossings present F1 and backcrosses with both parental species. In addition, the C. caretta × E. imbricata hybridization seems to be gender and species biased, and we also found one individual with evidence of multispecies hybridization among C. caretta × E. imbricata × Chelonia mydas. The overall results also indicate that hybridization in this area is a recent phenomenon, spanning at least two generations or ~40 years. © 2012 Blackwell Publishing Ltd.

  15. Introgression from domestic goat generated variation at the major histocompatibility complex of Alpine ibex.

    Directory of Open Access Journals (Sweden)

    Christine Grossen

    2014-06-01

    Full Text Available The major histocompatibility complex (MHC is a crucial component of the vertebrate immune system and shows extremely high levels of genetic polymorphism. The extraordinary genetic variation is thought to be ancient polymorphisms maintained by balancing selection. However, introgression from related species was recently proposed as an additional mechanism. Here we provide evidence for introgression at the MHC in Alpine ibex (Capra ibex ibex. At a usually very polymorphic MHC exon involved in pathogen recognition (DRB exon 2, Alpine ibex carried only two alleles. We found that one of these DRB alleles is identical to a DRB allele of domestic goats (Capra aegagrus hircus. We sequenced 2489 bp of the coding and non-coding regions of the DRB gene and found that Alpine ibex homozygous for the goat-type DRB exon 2 allele showed nearly identical sequences (99.8% to a breed of domestic goats. Using Sanger and RAD sequencing, microsatellite and SNP chip data, we show that the chromosomal region containing the goat-type DRB allele has a signature of recent introgression in Alpine ibex. A region of approximately 750 kb including the DRB locus showed high rates of heterozygosity in individuals carrying one copy of the goat-type DRB allele. These individuals shared SNP alleles both with domestic goats and other Alpine ibex. In a survey of four Alpine ibex populations, we found that the region surrounding the DRB allele shows strong linkage disequilibria, strong sequence clustering and low diversity among haplotypes carrying the goat-type allele. Introgression at the MHC is likely adaptive and introgression critically increased MHC DRB diversity in the genetically impoverished Alpine ibex. Our finding contradicts the long-standing view that genetic variability at the MHC is solely a consequence of ancient trans-species polymorphism. Introgression is likely an underappreciated source of genetic diversity at the MHC and other loci under balancing selection.

  16. Historical introgression of the downy mildew resistance gene Rpv12 from the Asian species Vitis amurensis into grapevine varieties.

    Directory of Open Access Journals (Sweden)

    Silvia Venuti

    Full Text Available The Amur grape (Vitis amurensis Rupr. thrives naturally in cool climates of Northeast Asia. Resistance against the introduced pathogen Plasmopara viticola is common among wild ecotypes that were propagated from Manchuria into Chinese vineyards or collected by Soviet botanists in Siberia, and used for the introgression of resistance into wine grapes (Vitis vinifera L.. A QTL analysis revealed a dominant gene Rpv12 that explained 79% of the phenotypic variance for downy mildew resistance and was inherited independently of other resistance genes. A Mendelian component of resistance-a hypersensitive response in leaves challenged with P. viticola-was mapped in an interval of 0.2 cM containing an array of coiled-coil NB-LRR genes on chromosome 14. We sequenced 10-kb genic regions in the Rpv12(+ haplotype and identified polymorphisms in 12 varieties of V. vinifera using next-generation sequencing. The combination of two SNPs in single-copy genes flanking the NB-LRR cluster distinguished the resistant haplotype from all others found in 200 accessions of V. vinifera, V. amurensis, and V. amurensis x V. vinifera crosses. The Rpv12(+ haplotype is shared by 15 varieties, the most ancestral of which are the century-old 'Zarja severa' and 'Michurinets'. Before this knowledge, the chromosome segment around Rpv12(+ became introgressed, shortened, and pyramided with another downy mildew resistance gene from North American grapevines (Rpv3 only by phenotypic selection. Rpv12(+ has an additive effect with Rpv3(+ to protect vines against natural infections, and confers foliar resistance to strains that are virulent on Rpv3(+ plants.

  17. Introgression Between Cultivars and Wild Populations of Momordica charantia L. (Cucurbitaceae in Taiwan

    Directory of Open Access Journals (Sweden)

    Yu-Chung Chiang

    2012-05-01

    Full Text Available The landrace strains of Momordica charantia are widely cultivated vegetables throughout the tropics and subtropics, but not in Taiwan, a continental island in Southeast Asia, until a few hundred years ago. In contrast, the related wild populations with smaller fruit sizes are native to Taiwan. Because of the introduction of cultivars for agricultural purposes, these two accessions currently exhibit a sympatric or parapatric distribution in Taiwan. In this study, the cultivars and wild samples from Taiwan, India, and Korea were collected for testing of their hybridization and evolutionary patterns. The cpDNA marker showed a clear distinction between accessions of cultivars and wild populations of Taiwan and a long divergence time. In contrast, an analysis of eight selectively neutral nuclear microsatellite loci did not reveal a difference between the genetic structures of these two accessions. A relatively short divergence time and frequent but asymmetric gene flows were estimated based on the isolation-with-migration model. Historical and current introgression from cultivars to wild populations of Taiwan was also inferred using MIGRATE-n and BayesAss analyses. Our results showed that these two accessions shared abundant common ancestral polymorphisms, and the timing of the divergence and colonization of the Taiwanese wild populations is consistent with the geohistory of the Taiwan Strait land bridge of the Last Glacial Maximum (LGM. Long-term and recurrent introgression between accessions indicated the asymmetric capacity to receive foreign genes from other accessions. The modern introduction of cultivars of M. charantia during the colonization of Taiwan by the Han Chinese ethnic group enhanced the rate of gene replacement in the native populations and resulted in the loss of native genes.

  18. Variability and performance evaluation of introgressed Nigerian dura x Deli dura oil palm progenies.

    Science.gov (United States)

    Noh, A; Rafii, M Y; Mohd Din, A; Kushairi, A; Norziha, A; Rajanaidu, N; Latif, M A; Malek, M A

    2014-04-03

    Twelve introgressed oil palm (Elaeis guineensis) progenies of Nigerian dura x Deli dura were evaluated for bunch yield, yield attributes, bunch quality components and vegetative characters at the Malaysian Palm Oil Board Research Station, in Keratong, Pahang, Malaysia. Analysis of variance revealed significant to highly significant genotypic differences, indicating sufficient genetic variability among the progenies for bunch yield and its attributes, vegetative characters and bunch quality components, except fruit to bunch ratio. Fresh fruit bunch yield ranged from 167 kg·palm(-1)·year(-1) in PK1330 to 212 kg·palm(-1)·year(-1) in PK1351, with a mean yield of 192 kg·palm(-1)·year(-1). Among the progeny, PK1313 had the highest oil to bunch ratio (19.36%), due to its high mesocarp to fruit ratio, fruit to bunch ratio and low shell to fruit ratio. Among the progenies, PK1313 produced the highest oil yield of 31.4 kg·palm(-1)·year(-1), due to a high mesocarp to fruit ratio (61.2%) and a low shell to fruit ratio (30.7%), coupled with high fruit to bunch ratio (65.6%). PK1330 was found promising for selection, as it had desirable vegetative characters, including smaller petiole cross section (27.15 cm2), short rachis length (4.83 m), short palm height (1.85 m), and the lowest leaf number (164.6), as these vegetative characters are prerequisites for selecting palms for high density planting and high yield per hectare. The genetic variability among the progenies was found to be high, indicating ample scope for further breeding, followed by selection.

  19. Detection of nitrogen deficiency QTL in juvenile wild barley introgression lines growing in a hydroponic system

    Directory of Open Access Journals (Sweden)

    Hoffmann Astrid

    2012-10-01

    Full Text Available Abstract Background In this report we studied the genetic regulation of juvenile development of wild barley introgression lines (S42ILs under two contrasting hydroponic nitrogen (N supplies. Ten shoot and root related traits were examined among 42 S42ILs and the recurrent parent ‘Scarlett’. The traits included tiller number, leaf number, plant height, leaf and root length, leaf to root length ratio, shoots and root dry weight, shoot to root weight ratio, and chlorophyll content. Our aims were (1 to test the suitability of a hydroponic system for early detection of favourable S42ILs, (2 to locate quantitative trait loci (QTL that control the examined traits, (3 to identify favourable wild barley alleles that improve trait performances in regard to N treatment and, finally, (4 to validate the identified QTL through comparison with previously reported QTL originating from the same parental cross. Results The phenotypic data were analysed in a mixed model association study to detect QTL. The post-hoc Dunnett test identified 28 S42ILs that revealed significant (P Hsp effects for tiller number, leaf number, leaf length, plant height and leaf to root ratio on the long arm of chromosome 7H. These QTL correspond to QTL for ears per plant and plant height that were previously detected in field trials conducted with the same S42ILs or with the S42 population. Conclusion Our results suggest that the QTL we identified under hydroponic N cultivation partly correspond to QTL detected in field experiments. Due to this finding, screening of plants in early developmental stages grown in a hydroponic system may be a fast and cost effective method for early QTL detection and marker-assisted allelic selection, potentially speeding up elite barley breeding programs.

  20. Genomic Signatures of Selective Pressures and Introgression from Archaic Hominins at Human Innate Immunity Genes.

    Science.gov (United States)

    Deschamps, Matthieu; Laval, Guillaume; Fagny, Maud; Itan, Yuval; Abel, Laurent; Casanova, Jean-Laurent; Patin, Etienne; Quintana-Murci, Lluis

    2016-01-07

    Human genes governing innate immunity provide a valuable tool for the study of the selective pressure imposed by microorganisms on host genomes. A comprehensive, genome-wide study of how selective constraints and adaptations have driven the evolution of innate immunity genes is missing. Using full-genome sequence variation from the 1000 Genomes Project, we first show that innate immunity genes have globally evolved under stronger purifying selection than the remainder of protein-coding genes. We identify a gene set under the strongest selective constraints, mutations in which are likely to predispose individuals to life-threatening disease, as illustrated by STAT1 and TRAF3. We then evaluate the occurrence of local adaptation and detect 57 high-scoring signals of positive selection at innate immunity genes, variation in which has been associated with susceptibility to common infectious or autoimmune diseases. Furthermore, we show that most adaptations targeting coding variation have occurred in the last 6,000-13,000 years, the period at which populations shifted from hunting and gathering to farming. Finally, we show that innate immunity genes present higher Neandertal introgression than the remainder of the coding genome. Notably, among the genes presenting the highest Neandertal ancestry, we find the TLR6-TLR1-TLR10 cluster, which also contains functional adaptive variation in Europeans. This study identifies highly constrained genes that fulfill essential, non-redundant functions in host survival and reveals others that are more permissive to change-containing variation acquired from archaic hominins or adaptive variants in specific populations-improving our understanding of the relative biological importance of innate immunity pathways in natural conditions. Copyright © 2016 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

  1. Population diversity and evidence of introgression among the black oaks of California

    Science.gov (United States)

    Richard S. Dodd; Nasser Kashani; Zara Afzal-Rafii

    2002-01-01

    The black oaks of California include 4 tree species (California black oak, coast live oak, Shreve oak, interior live oak) that are known to hybridize. Complex patterns of population variation within each species are likely to result from these hybrid combinations and from subsequent introgressions. We have been studying population variation using biochemical and...

  2. Introgression of Clearfield(TM) rice crop traits into weedy red rice outcrosses

    Science.gov (United States)

    Studies were conducted to determine the impact of introgression of crop alleles into weedy rice populations. Seeds of 89 weedy rice accessions collected from Arkansas fields in 11 counties, with a history of Clearfield(TM) rice production, were planted in 2011 and treated with two applications of im...

  3. Introgression of bacterial blight (BB) resistance genes Xa7 and Xa21 ...

    African Journals Online (AJOL)

    Yihui1577 is an elite restorer line widely used in hybrid rice production in China, however, both the restorer and their derived hybrids are susceptible to bacterial blight (BB) caused by Xathomonas oryzae pv. oryzae (Xoo). In order to overcome this problem, we had introgressed two resistant genes Xa7 and Xa21 into ...

  4. Mapping and introgression of QTL for yield and related traits in two ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Genetics; Volume 93; Issue 3. Mapping and introgression of QTL for yield and related traits in two backcross populations derived from Oryza sativa cv. Swarna and two accessions of O. nivara. B. P. Mallikarjuna Swamy K. Kaladhar G. Ashok Reddy B. C. Viraktamath N. Sarla. Research Article ...

  5. Introgression of stay-green trait into a Kenyan farmer prefered ...

    African Journals Online (AJOL)

    Introgression of stay-green trait into a Kenyan farmer prefered sorghum variety. K Ngugi, W Kimani, D Kiambi. Abstract. Backcross breeding enables breeders to transfer a desired trait from a Genetic Improvement of Kenyan sorghum variety for drought resistance donor parent, into the favoured genetic background of a ...

  6. Evaluation de l'introgression du caractère croissance lente de ...

    African Journals Online (AJOL)

    Evaluation de l'introgression du caractère croissance lente de quelques géniteurs Akpadanou (origine Bénin) chez quelques géniteurs améliorés de palmier à huile ( E. guineensis Jacq.) de l'origine La Mé (Côte d'Ivoire)

  7. Enhancing introgression of the opaque-2 trait into elite maize lines ...

    African Journals Online (AJOL)

    To improve on the efficiency of Quality Protein Maize (QPM) breeding in Uganda, the utility of three simple sequence repeats (SSR) markers (phi057, phi 112 and umc1066) in selection and introgression of the opaque-2 (o2) gene was investigated. Genomic DNA of six normal and seven (QPM) lines was analysed using a ...

  8. Evaluating the use of ABBA-BABA statistics to locate introgressed loci.

    Science.gov (United States)

    Martin, Simon H; Davey, John W; Jiggins, Chris D

    2015-01-01

    Several methods have been proposed to test for introgression across genomes. One method tests for a genome-wide excess of shared derived alleles between taxa using Patterson's D statistic, but does not establish which loci show such an excess or whether the excess is due to introgression or ancestral population structure. Several recent studies have extended the use of D by applying the statistic to small genomic regions, rather than genome-wide. Here, we use simulations and whole-genome data from Heliconius butterflies to investigate the behavior of D in small genomic regions. We find that D is unreliable in this situation as it gives inflated values when effective population size is low, causing D outliers to cluster in genomic regions of reduced diversity. As an alternative, we propose a related statistic ƒ(d), a modified version of a statistic originally developed to estimate the genome-wide fraction of admixture. ƒ(d) is not subject to the same biases as D, and is better at identifying introgressed loci. Finally, we show that both D and ƒ(d) outliers tend to cluster in regions of low absolute divergence (d(XY)), which can confound a recently proposed test for differentiating introgression from shared ancestral variation at individual loci. © The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  9. Introgression of a leaf rust resistance gene from Aegilops caudata to ...

    Indian Academy of Sciences (India)

    Keywords. alien introgression; molecular mapping; leaf rust; Puccinia triticina; Triticum aestivum; Aegilops caudata. Abstract. Rusts are the most important biotic constraints limiting wheat productivity worldwide. Deployment of cultivars with broad spectrum rust resistance is the only environmentally viable option to combat ...

  10. Chromosome engineering for alien gene introgression in wheat: Progress and prospective

    Science.gov (United States)

    Chromosome engineering is a useful strategy for introgression of desirable genes from wild relatives into cultivated wheat. However, it has been a challenge to transfer a small amount of alien chromatin containing the gene of interest from one genome to another non-homologous genome through classic...

  11. Mapping and introgression of QTL for yield and related traits in two ...

    Indian Academy of Sciences (India)

    The major-effect QTL reported in this study are useful for marker-assisted breeding and are also suitable for further fine mapping and .... cross family and the control (Swarna) consisted of 30 plants planted in three rows of 10 ...... 2010 Chromosome segment substitution lines: a powerful tool for the introgression of valuable ...

  12. Yield QTL analysis of Oryza sativa x O. glumaepatula introgression lines

    Directory of Open Access Journals (Sweden)

    Priscila Nascimento Rangel

    2013-03-01

    Full Text Available The objective of this work was to evaluate the yield performance of two generations (BC2F2 and BC2F9 of introgression lines developed from the interspecific cross between Oryza sativa and O. glumaepatula, and to identify the SSR markers associated to yield. The wild accession RS‑16 (O. glumaepatula was used as donor parent in the backcross with the high yielding cultivar Cica‑8 (O. sativa. A set of 114 BC2F1 introgression lines was genotyped with 141 polymorphic SSR loci distributed across the whole rice genome. Molecular analysis showed that in average 22% of the O. glumaepatula genome was introgressed into BC2F1 generation. Nine BC2F9 introgression lines had a significantly higher yield than the genitor Cica‑8, thus showing a positive genome interaction among cultivated rice and the wild O. glumaepatula. Seven QTL were identified in the overall BC2F2, with one marker interval (4879‑EST20 of great effect on yield. The alleles with positive effect on yield came from the cultivated parent Cica‑8.

  13. Mapping and introgression of QTL for yield and related traits in two ...

    Indian Academy of Sciences (India)

    further fine mapping and candidate gene identification. [Swamy B. P. M., Kaladhar K., Reddy G. A., Viraktamath B. C. and Sarla N. 2014 Mapping and introgression of QTL for yield and related traits in two backcross populations derived from Oryza sativa cv. Swarna and two accessions of O. nivara. J. Genet. 93, 643–654].

  14. Low-field EPR studies of levels near the top of the barrier in Mn 12-acetate reveal a new magnetization relaxation pathway

    Science.gov (United States)

    Rakvin, Boris; Žilić, Dijana; Dalal, Naresh S.; Harter, Andrew; Sanakis, Yiannis

    2006-07-01

    We show that X-band electron paramagnetic resonance (EPR) measurements using a dual-mode resonance cavity can directly probe the levels near the top of the magnetization reversal barrier in the single-molecule magnet (SMM) Mn 12-acetate. The observed transitions are much sharper than those reported in high-field EPR studies. The observed temperature dependence of the line positions points to the presence of a spin-diffusional mode. The correlation time for such fluctuations is of the order of 6×10 -8 s at 10 K, and follows an Arrhenius activation energy of 35-40 K. These results open a new avenue for understanding the mechanism of tunneling and spin-lattice relaxations in these SMMs.

  15. Solid-State17O NMR Reveals Hydrogen-Bonding Energetics: Not All Low-Barrier Hydrogen Bonds Are Strong.

    Science.gov (United States)

    Lu, Jiasheng; Hung, Ivan; Brinkmann, Andreas; Gan, Zhehong; Kong, Xianqi; Wu, Gang

    2017-05-22

    While NMR and IR spectroscopic signatures and structural characteristics of low-barrier hydrogen bond (LBHB) formation are well documented in the literature, direct measurement of the LBHB energy is difficult. Here, we show that solid-state 17 O NMR spectroscopy can provide unique information about the energy required to break a LBHB. Our solid-state 17 O NMR data show that the HB enthalpy of the O⋅⋅⋅H⋅⋅⋅N LBHB formed in crystalline nicotinic acid is only 7.7±0.5 kcal mol -1 , suggesting that not all LBHBs are particularly strong. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Health Access Livelihood Framework Reveals Potential Barriers in the Control of Schistosomiasis in the Dongting Lake Area of Hunan Province, China

    Science.gov (United States)

    McManus, Donald P.; Raso, Giovanna; Utzinger, Jürg; Xiao, Shui-Yuan; Yu, Dong-Bao; Zhao, Zheng-Yuan; Li, Yue-Sheng

    2013-01-01

    Background Access to health care is a major requirement in improving health and fostering socioeconomic development. In the People's Republic of China (P.R. China), considerable changes have occurred in the social, economic, and health systems with a shift from a centrally planned to a socialist market economy. This brought about great benefits and new challenges, particularly for vertical disease control programs, including schistosomiasis. We explored systemic barriers in access to equitable and effective control of schistosomiasis. Methodology Between August 2002 and February 2003, 66 interviews with staff from anti-schistosomiasis control stations and six focus group discussions with health personnel were conducted in the Dongting Lake area, Hunan Province. Additionally, 79 patients with advanced schistosomiasis japonica were interviewed. The health access livelihood framework was utilized to examine availability, accessibility, affordability, adequacy, and acceptability of schistosomiasis-related health care. Principal Findings We found sufficient availability of infrastructure and human resources at most control stations. Many patients with advanced schistosomiasis resided in non-endemic or moderately endemic areas, however, with poor accessibility to disease-specific knowledge and specialized health services. Moreover, none of the patients interviewed had any form of health insurance, resulting in high out-of-pocket expenditure or unaffordable care. Reports on the adequacy and acceptability of care were mixed. Conclusions/Significance There is a need to strengthen health awareness and schistosomiasis surveillance in post-transmission control settings, as well as to reduce diagnostic and treatment costs. Further studies are needed to gain a multi-layered, in-depth understanding of remaining barriers, so that the ultimate goal of schistosomiasis elimination in P.R. China can be reached. PMID:23936580

  17. Health access livelihood framework reveals potential barriers in the control of schistosomiasis in the Dongting Lake area of Hunan Province, China.

    Directory of Open Access Journals (Sweden)

    Julie Balen

    Full Text Available Access to health care is a major requirement in improving health and fostering socioeconomic development. In the People's Republic of China (P.R. China, considerable changes have occurred in the social, economic, and health systems with a shift from a centrally planned to a socialist market economy. This brought about great benefits and new challenges, particularly for vertical disease control programs, including schistosomiasis. We explored systemic barriers in access to equitable and effective control of schistosomiasis.Between August 2002 and February 2003, 66 interviews with staff from anti-schistosomiasis control stations and six focus group discussions with health personnel were conducted in the Dongting Lake area, Hunan Province. Additionally, 79 patients with advanced schistosomiasis japonica were interviewed. The health access livelihood framework was utilized to examine availability, accessibility, affordability, adequacy, and acceptability of schistosomiasis-related health care.We found sufficient availability of infrastructure and human resources at most control stations. Many patients with advanced schistosomiasis resided in non-endemic or moderately endemic areas, however, with poor accessibility to disease-specific knowledge and specialized health services. Moreover, none of the patients interviewed had any form of health insurance, resulting in high out-of-pocket expenditure or unaffordable care. Reports on the adequacy and acceptability of care were mixed.There is a need to strengthen health awareness and schistosomiasis surveillance in post-transmission control settings, as well as to reduce diagnostic and treatment costs. Further studies are needed to gain a multi-layered, in-depth understanding of remaining barriers, so that the ultimate goal of schistosomiasis elimination in P.R. China can be reached.

  18. Building barriers.

    Science.gov (United States)

    Turksen, Kursad

    2017-10-02

    Formation of tissue barriers starts in early development where it is critical for normal cell fate selection, differentiation and organogenesis. Barrier maintenance is critical to the ongoing function of organs during adulthood and aging. Dysfunctional tissue barrier formation and function at any stage of the organismal life cycle underlies many disease states.

  19. Microsatellites Reveal Genetic Homogeneity among Outbreak Populations of Crown-of-Thorns Starfish (Acanthaster cf. solaris) on Australia’s Great Barrier Reef

    KAUST Repository

    Harrison, Hugo

    2017-03-10

    Specific patterns in the initiation and spread of reef-wide outbreaks of crown-of-thorns starfish are important, both to understand potential causes (or triggers) of outbreaks and to develop more effective and highly targeted management and containment responses. Using analyses of genetic diversity and structure (based on 17 microsatellite loci), this study attempted to resolve the specific origin for recent outbreaks of crown-of-thorns on Australia’s Great Barrier Reef (GBR). We assessed the genetic structure amongst 2705 starfish collected from 13 coral reefs in four regions that spanned ~1000 km of the GBR. Our results indicate that populations sampled across the full length of the GBR are genetically homogeneous (G’ST = −0.001; p = 0.948) with no apparent genetic structure between regions. Approximate Bayesian computational analyses suggest that all sampled populations had a common origin and that current outbreaking populations of crown-of-thorns starfish (CoTS) in the Swains are not independent of outbreak populations in the northern GBR. Despite hierarchical sampling and large numbers of CoTS genotyped from individual reefs and regions, limited genetic structure meant we were unable to determine a putative source population for the current outbreak of CoTS on the GBR. The very high genetic homogeneity of sampled populations and limited evidence of inbreeding indicate rapid expansion in population size from multiple, undifferentiated latent populations.

  20. Quantifying rates of cell migration and cell proliferation in co-culture barrier assays reveals how skin and melanoma cells interact during melanoma spreading and invasion.

    Science.gov (United States)

    Haridas, Parvathi; Penington, Catherine J; McGovern, Jacqui A; McElwain, D L Sean; Simpson, Matthew J

    2017-06-21

    Malignant spreading involves the migration of cancer cells amongst other native cell types. For example, in vivo melanoma invasion involves individual melanoma cells migrating through native skin, which is composed of several distinct subpopulations of cells. Here, we aim to quantify how interactions between melanoma and fibroblast cells affect the collective spreading of a heterogeneous population of these cells in vitro. We perform a suite of circular barrier assays that includes: (i) monoculture assays with fibroblast cells; (ii) monoculture assays with SK-MEL-28 melanoma cells; and (iii) a series of co-culture assays initiated with three different ratios of SK-MEL-28 melanoma cells and fibroblast cells. Using immunostaining, detailed cell density histograms are constructed to illustrate how the two subpopulations of cells are spatially arranged within the spreading heterogeneous population. Calibrating the solution of a continuum partial differential equation to the experimental results from the monoculture assays allows us to estimate the cell diffusivity and the cell proliferation rate for the melanoma and the fibroblast cells, separately. Using the parameter estimates from the monoculture assays, we then make a prediction of the spatial spreading in the co-culture assays. Results show that the parameter estimates obtained from the monoculture assays lead to a reasonably accurate prediction of the spatial arrangement of the two subpopulations in the co-culture assays. Overall, the spatial pattern of spreading of the melanoma cells and the fibroblast cells is very similar in monoculture and co-culture conditions. Therefore, we find no clear evidence of any interactions other than cell-to-cell contact and crowding effects. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Enhanced virulence of sheep-passaged bovine spongiform encephalopathy agent is revealed by decreased polymorphism barriers in prion protein conversion studies.

    Science.gov (United States)

    Priem, Jan; Langeveld, Jan P M; van Keulen, Lucien J M; van Zijderveld, Fred G; Andreoletti, Olivier; Bossers, Alex

    2014-03-01

    Bovine spongiform encephalopathy (BSE) can be efficiently transmitted to small ruminants (sheep and goats) with certain prion protein (PrP) genotypes. Polymorphisms in PrP of both the host and donor influence the transmission efficiency of transmissible spongiform encephalopathies (TSEs) in general. These polymorphisms in PrP also modulate the PrP conversion underlying TSE agent replication. Here we demonstrate that single-round protein misfolding cyclic amplification (PMCA) can be used to assess species and polymorphism barriers at the molecular level. We assessed those within and between the ovine and bovine species in vitro using a variety of natural scrapie and experimentally generated cross-species BSE agents. These BSE agents include ovBSE-ARQ isolates (BSE derived from sheep having the ARQ/ARQ PrP genotype), and two unique BSE-derived variants: BSE passaged in VRQ/VRQ sheep and a cow BSE agent isolate generated by back-transmission of ovBSE-ARQ into its original host. PMCA allowed us to quantitatively determine PrP conversion profiles that correlated with known in vivo transmissibility and susceptibility in the two ruminant species in which strain-specific molecular signatures, like its molecular weight after protease digestion, were maintained. Furthermore, both BSE agent isolates from ARQ and VRQ sheep demonstrated a surprising transmission profile in which efficient transmissions to both sheep and bovine variants was combined. Finally, all data support the notion that ARQ-derived sheep BSE points to a significant increase in virulence compared to all other tested scrapie- and BSE-derived variants reflected by the increased conversion efficiencies of previously inefficient convertible PrP variants (including the so-called "resistant" sheep ARR variant). Prion diseases such as scrapie in sheep and goats, BSE in cattle, and Creutzfeldt-Jakob disease (CJD) in humans are fatal neurodegenerative diseases caused by prions. BSE is known to be transmissible to a

  2. The elusive nature of adaptive mitochondrial DNA evolution of an Arctic lineage prone to frequent introgression

    DEFF Research Database (Denmark)

    Melo-Ferreira, Jose; Vilela, Joana; Fonseca, Miguel M.

    2014-01-01

    understood. Hares (Lepus spp.) are privileged models to study the impact of natural selection on mitogenomic evolution because 1) species are adapted to contrasting environments, including arctic, with different metabolic pressures, and 2) mtDNA introgression from arctic into temperate species is widespread....... Here, we analyzed the sequences of 11 complete mitogenomes (ten newly obtained) of hares of temperate and arctic origins (including two of arctic origin introgressed into temperate species). The analysis of patterns of codon substitutions along the reconstructed phylogeny showed evidence for positive...... lie on complex interactions with nuclear encoded peptides. Also, a cloverleaf structure was detected in the control region only from the arctic mtDNA lineage, which may influence mtDNA replication and transcription. These results suggest that adaptation impacted the evolution of hare mtDNA and may...

  3. Evolutionary neutrality of mtDNA introgression: evidence from complete mitogenome analysis in roe deer.

    Science.gov (United States)

    Matosiuk, M; Sheremetyeva, I N; Sheremetyev, I S; Saveljev, A P; Borkowska, A

    2014-11-01

    Introgressive hybridization offers a unique platform for studying the molecular basis of natural selection acting on mitogenomes. Most of the mtDNA protein-coding genes are extremely conserved; however, some of the observed variations have potentially adaptive significance. Here, we evaluated whether the evolution of mtDNA in closely related roe deer species affected by widespread mtDNA introgression is neutral or adaptive. We characterized and compared 16 complete mitogenomes of European (Capreolus capreolus) and Siberian (C. pygargus) roe deer, including four of Siberian origin introgressed into European species. The average sequence divergence of species-specific lineages was estimated at 2.8% and varied across gene classes. Only 21 of 315 fixed differences identified in protein-coding genes represented nonsynonymous changes. Only three of them were determined to have arisen in the C. pygargus lineage since the time to the most recent common ancestor (TMRCA) of both Capreolus species, reflecting a decelerated evolutionary ratio. The almost four-fold higher dN /dS ratio described for the European roe deer lineage is constrained by overall purifying selection, especially pronounced in the ND4 and ND5 genes. We suggest that the highly divergent C. capreolus lineage could have maintained a capability for genomic incorporation of the well-preserved and almost ancestral type of mtDNA present in C. pygargus. Our analyses did not indicate any signs of positive selection for Siberian roe deer mtDNA, suggesting that the present widespread introgression is evolutionarily neutral. © 2014 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

  4. Assessing multilocus introgression patterns: a case study on the mouse X chromosome in Central Europe

    Czech Academy of Sciences Publication Activity Database

    Macholán, Miloš; Baird, S. J. E.; Dufková, Petra; Munclinger, P.; Vošlajerová Bímová, Barbora; Piálek, Jaroslav

    2011-01-01

    Roč. 65, č. 5 (2011), s. 1428-1446 ISSN 0014-3820 R&D Projects: GA ČR GA206/08/0640 Institutional research plan: CEZ:AV0Z50450515; CEZ:AV0Z60930519 Keywords : genetic conflict * hybrid zone movement * sex biased introgression * mice * X chromosome Subject RIV: EG - Zoology Impact factor: 5.146, year: 2011

  5. Introgression of Chromosome 3Ns from Psathyrostachys huashanica into Wheat Specifying Resistance to Stripe Rust

    Science.gov (United States)

    Kang, Houyang; Wang, Yi; Fedak, George; Cao, Wenguang; Zhang, Haiqin; Fan, Xing; Sha, Lina; Xu, Lili; Zheng, Youliang; Zhou, Yonghong

    2011-01-01

    Wheat stripe rust is a destructive disease in the cool and humid wheat-growing areas of the world. Finding diverse sources of stripe rust resistance is critical for increasing genetic diversity of resistance for wheat breeding programs. Stripe rust resistance was identified in the alien species Psathyrostachys huashanica, and a wheat- P. huashanica amphiploid line (PHW-SA) with stripe rust resistance was reported previously. In this study, a P. huashanica 3Ns monosomic addition line (PW11) with superior resistance to stripe rust was developed, which was derived from the cross between PHW-SA and wheat J-11. We evaluated the alien introgressions PW11-2, PW11-5 and PW11-8 which were derived from line PW11 for reaction to new Pst race CYR32, and used molecular and cytogenetic tools to characterize these lines. The introgressions were remarkably resistant to CYR32, suggesting that the resistance to stripe rust of the introgressions thus was controlled by gene(s) located on P. huashanica chromosome 3Ns. All derived lines were cytologically stable in term of meiotic chromosome behavior. Two 3Ns chromosomes of P. huashanica were detected in the disomic addition line PW11-2. Chromosomes 1B of substitution line PW11-5 had been replaced by a pair of P. huashanica 3Ns chromosomes. In PW11-8, a small terminal segment from P. huashanica chromosome arm 3NsS was translocated to the terminal region of wheat chromosomes 3BL. Thus, this translocated chromosome is designated T3BL-3NsS. These conclusions were further confirmed by SSR analyses. Two 3Ns-specific markers Xgwm181 and Xgwm161 will be useful to rapidly identify and trace the translocated fragments. These introgressions, which had significant characteristics of resistance to stripe rust, could be utilized as novel germplasms for wheat breeding. PMID:21760909

  6. Panmixia and Limited Interspecific Introgression in Coyotes (Canis latrans) from West Virginia and Virginia, USA.

    Science.gov (United States)

    Bohling, Justin H; Mastro, Lauren L; Adams, Jennifer R; Gese, Eric M; Owen, Sheldon F; Waits, Lisette P

    2017-09-01

    The expansion of coyotes (Canis latrans) into the eastern United States has had major consequences for ecological communities and wildlife managers. Despite this, there has been little investigation of the genetics of coyotes across much of this region, especially outside of the northeast. Understanding patterns of genetic structure and interspecific introgression would provide insights into the colonization history of the species, its response to the modern environment, and interactions with other canids. We examined the genetic characteristics of 121 coyotes from the mid-Atlantic states of West Virginia and Virginia by genotyping 17 polymorphic nuclear DNA microsatellite loci. These genotypes were compared with those from other canid populations to evaluate the extent of genetic introgression. We conducted spatial clustering analyses and spatial autocorrelation to assess genetic structure among sampled coyotes. Coyotes across the 2 states had high genetic diversity, and we found no evidence of genetic structure. Six to sixteen percent of individuals displayed some evidence of genetic introgression from other species depending on the method and criteria used, but the population possessed predominantly coyote ancestry. Our findings suggested introgression from other canid populations has played less of a role in shaping the genetic character of coyotes in these states compared with populations closer to the Canadian border. Coyotes appear to display a panmictic population structure despite high habitat heterogeneity and heavy human influence in the spatial environment, underscoring the adaptability of the species. Published by Oxford University Press on behalf of The American Genetic Association 2017. This work is written by (a) US Government employee(s) and is in the public domain in the US.

  7. A Phylogenetic Synthesis for Oceanic Dolphins: Total Evidence, Cytonuclear Discordance, and Possible Introgressive Hybridization

    OpenAIRE

    Haisten, David

    2016-01-01

    Introgressive hybridization is increasingly being detected in vertebrate taxa but was thought to be rare in mammals. Recent evidence suggests that this view might not correct and cetaceans may be pre-disposed for the capacity to hybridize. Numerous instances of cetacean (dolphins, whales, and porpoises) hybridization have been reported both in captivity and in the wild, many of which occurred in oceanic dolphins: family Delphinidae. The rapid radiation of Delphinidae commenced during the Mio...

  8. Detecting genetic introgression: high levels of intersubspecific recombination found in Xylella fastidiosa in Brazil.

    Science.gov (United States)

    Nunney, Leonard; Yuan, Xiaoli; Bromley, Robin E; Stouthamer, Richard

    2012-07-01

    Documenting the role of novel mutation versus homologous recombination in bacterial evolution, and especially in the invasion of new hosts, is central to understanding the long-term dynamics of pathogenic bacteria. We used multilocus sequence typing (MLST) to study this issue in Xylella fastidiosa subsp. pauca from Brazil, a bacterium causing citrus variegated chlorosis (CVC) and coffee leaf scorch (CLS). All 55 citrus isolates typed (plus one coffee isolate) defined three similar sequence types (STs) dominated by ST11 (85%), while the remaining 22 coffee isolates defined two STs, mainly ST16 (74%). This low level of variation masked unusually large allelic differences (>1% divergence with no intermediates) at five loci (leuA, petC, malF, cysG, and holC). We developed an introgression test to detect whether these large differences were due to introgression via homologous recombination from another X. fastidiosa subspecies. Using additional sequencing around these loci, we established that the seven randomly chosen MLST targets contained seven regions of introgression totaling 2,172 bp of 4,161 bp (52%), only 409 bp (10%) of which were detected by other recombination tests. This high level of introgression suggests the hypothesis that X. fastidiosa subsp. pauca became pathogenic on citrus and coffee (crops cultivated in Brazil for several hundred years) only recently after it gained genetic variation via intersubspecific recombination, facilitating a switch from native hosts. A candidate donor is the subspecies infecting plum in the region since 1935 (possibly X. fastidiosa subsp. multiplex). This hypothesis predicts that nonrecombinant native X. fastidiosa subsp. pauca (not yet isolated) does not cause disease in citrus or coffee.

  9. Detection of alien genetic introgressions in bread wheat using dot-blot genomic hybridisation.

    Science.gov (United States)

    Rey, María-Dolores; Prieto, Pilar

    2017-01-01

    Simple, reliable methods for the identification of alien genetic introgressions are required in plant breeding programmes. The use of genomic dot-blot hybridisation allows the detection of small Hordeum chilense genomic introgressions in the descendants of genetic crosses between wheat and H. chilense addition or substitution lines in wheat when molecular markers are difficult to use. Based on genomic in situ hybridisation, DNA samples from wheat lines carrying putatively H. chilense introgressions were immobilised on a membrane, blocked with wheat genomic DNA and hybridised with biotin-labelled H. chilense genomic DNA as a probe. This dot-blot screening reduced the number of plants necessary to be analysed by molecular markers or in situ hybridisation, saving time and money. The technique was sensitive enough to detect a minimum of 5 ng of total genomic DNA immobilised on the membrane or about 1/420 dilution of H. chilense genomic DNA in the wheat background. The robustness of the technique was verified by in situ hybridisation. In addition, the detection of other wheat relative species such as Hordeum vulgare , Secale cereale and Agropyron cristatum in the wheat background was also reported .

  10. Expanding Maize Genetic Resources with Predomestication Alleles: Maize–Teosinte Introgression Populations

    Directory of Open Access Journals (Sweden)

    Zhengbin Liu

    2016-03-01

    Full Text Available Teosinte ( subsp. H. H. Iltis & Doebley has greater genetic diversity than maize inbreds and landraces ( subsp. . There are, however, limited genetic resources to efficiently evaluate and tap this diversity. To broaden resources for genetic diversity studies in maize, we developed and evaluated 928 near-isogenic introgression lines (NILs from 10 teosinte accessions in the B73 background. Joint linkage analysis of the 10 introgression populations identified several large-effect quantitative trait loci (QTL for days to anthesis (DTA, kernel row number (KRN, and 50-kernel weight (Wt50k. Our results confirm prior reports of kernel domestication loci and identify previously uncharacterized QTL with a range of allelic effects enabling future research into the genetic basis of these traits. Additionally, we used a targeted set of NILs to validate the effects of a KRN QTL located on chromosome 2. These introgression populations offer novel tools for QTL discovery and validation as well as a platform for initiating fine mapping.

  11. Evidence for introgressive hybridization of captive markhor (Capra falconeri) with domestic goat: cautions for reintroduction.

    Science.gov (United States)

    Hammer, Sabine E; Schwammer, Harald M; Suchentrunk, Franz

    2008-04-01

    Markhors (Capra falconeri) are among the most endangered mammal species, and several conservation measures, including ex situ breeding, are implemented to prevent their extinction. We studied sequence diversity and differentiation of the first hypervariable segment of the mitochondrial DNA control region among C. f. heptneri and C. f. megaceros kept in four zoos in relationship to lineages of other wild and domestic goats, to assess for the first time the level of molecular distinctness and variability among those subspecies, and to check for possible introgression by related Capra taxa, such as domestic goats. Levels of differentiation between some Capra falconeri lineages and modern domestic goats were similar to levels between other wild goat species (i.e., Capra aegagrus, Capra ibex) and domestic goats. Among pure markhor lineages, paraphyly was observed for C. f. heptneri, suggesting occurrence of shared ancestral polymorphism among markhor subspecies and/or ancient or recent gene exchange between subspecies. Interestingly, 35.7% of all studied markhors from three zoos are introgressed by the domestic goat. Furthermore, despite relatively small breeding group sizes, markhors have maintained a relatively high proportion of mtDNA variation within zoo groups. In any case, the existence of markhors introgressed with domestic goat DNA in zoos should be considered when selecting markhors for ex situ breeding programs with the aim of building up a stock for later reintroduction into the wild.

  12. Extensive Rangewide Mitochondrial Introgression Indicates Substantial Cryptic Hybridization in the Golden-winged Warbler (Vermivora chrysoptera

    Directory of Open Access Journals (Sweden)

    Rachel Vallender

    2009-12-01

    Full Text Available Widespread population declines of the Golden-winged Warbler (Vermivora chrysoptera are thought to be due in part to hybridization with the expanding Blue-winged Warbler (V. pinus, which predictably replaces Golden-winged Warblers at breeding sites in which the two species come into contact. However, the mechanism by which this replacement occurs remains unresolved. Recent genetic work has indicated that, even in areas where the two species have been in contact for a short period, introgression of Blue-winged mitochondrial (mtDNA and nuclear genes into Golden-winged individuals is common. To explore this process on a broader scale, we screened more than 750 individuals from nine U.S. states and three provinces to examine geographic patterns of mtDNA introgression. The only population in which all phenotypic Golden-winged Warblers had Golden-winged mtDNA haplotypes, and in which there are no breeding Blue-winged or hybrid individuals, was in the province of Manitoba, near the northwestern edge of the species' breeding distribution. The near ubiquity of mitochondrial introgression suggests that there are far fewer genetically pure populations of Golden-winged Warblers than previously believed, a finding with important implications for this threatened species.

  13. Reticulate phylogeny of gastropod-shell-breeding cichlids from Lake Tanganyika – the result of repeated introgressive hybridization

    Directory of Open Access Journals (Sweden)

    Blanc Michel

    2007-01-01

    Full Text Available Abstract Background The tribe Lamprologini is the major substrate breeding lineage of Lake Tanganyika's cichlid species flock. Among several different life history strategies found in lamprologines, the adaptation to live and breed in empty gastropod shells is probably the most peculiar. Although shell-breeding arose several times in the evolutionary history of the lamprologines, all obligatory and most facultative shell-breeders belong to the so called "ossified group", a monophyletic lineage within the lamprologine cichlids. Since their distinctive life style enables these species to live and breed in closest vicinity, we hypothesized that these cichlids might be particularly prone to accidental hybridization, and that introgression might have affected the evolutionary history of this cichlid lineage. Results Our analyses revealed discrepancies between phylogenetic hypotheses based on mitochondrial and nuclear (AFLP data. While the nuclear phylogeny was congruent with morphological, behavioral and ecological characteristics, several species – usually highly specialized shell-breeders – were placed at contradicting positions in the mitochondrial phylogeny. The discordant phylogenies strongly suggest repeated incidents of introgressive hybridization between several distantly related shell-breeding species, which reticulated the phylogeny of this group of cichlids. Long interior branches and high bootstrap support for many interior nodes in the mitochondrial phylogeny argue against a major effect of ancient incomplete lineage sorting on the phylogenetic reconstruction. Moreover, we provide morphological and genetic (mtDNA and microsatellites evidence for ongoing hybridization among distantly related shell-breeders. In these cases, the territorial males of the inferred paternal species are too large to enter the shells of their mate, such that they have to release their sperm over the entrance of the shell to fertilize the eggs. With sperm

  14. Evaluation of genetic introgression from domesticated pigs into the Ryukyu wild boar population on Iriomote Island in Japan.

    Science.gov (United States)

    Murakami, K; Yoshikawa, S; Konishi, S; Ueno, Y; Watanabe, S; Mizoguchi, Y

    2014-08-01

    We evaluated genetic introgression from domesticated pigs into the Ryukyu wild boar (RWB) population on Iriomote Island based on their genetic structure and diversity. We used a combination of mitochondrial DNA D-loop region (596 bp) polymorphisms and 23 microsatellite markers. RWBs (n = 130) were collected from 18 locations on Iriomote Island and compared with 66 reference samples of European and Asian domestic pigs. We identified six distinct haplotypes, involving 22 single nucleotide polymorphisms (including one insertion) in the RWB population. The phylogenetic tree had two branches: the RWB group and domestic lineage. Fourteen of 130 RWBs (10.8%) belonged to the European domestic lineage, including 11 RWBs from the Panari Islands, northwest of Iriomote Main Island (IMI). The heterozygosity values, total number of alleles, number of effective alleles and polymorphism information content of the RWB groups were lower than those of the European domestic groups. The RWB population on IMI had a lower heterozygous deficiency index (FIS = 0.059) than did the other populations, which indicates that this population was more inbred. There was a large genetic distance (FST = 0.560) between RWBs on IMI and the Meishan populations. Structure analysis using the 23 microsatellite markers revealed that 16 RWBs had an admixture pattern between RWB and domesticated pig breeds. These results suggest that gene flow may have occurred from domestic pigs to RWBs and demonstrate that there was low genetic variation in the IMI population. © 2014 Stichting International Foundation for Animal Genetics.

  15. Distinguishing contemporary hybridization from past introgression with postgenomic ancestry-informative SNPs in strongly differentiated Ciona species.

    Science.gov (United States)

    Bouchemousse, Sarah; Liautard-Haag, Cathy; Bierne, Nicolas; Viard, Frédérique

    2016-11-01

    Biological introductions bring into contact species that can still hybridize. The evolutionary outcomes of such secondary contacts may be diverse (e.g. adaptive introgression from or into the introduced species) but are not yet well examined in the wild. The recent secondary contact between the non-native sea squirt Ciona robusta (formerly known as C. intestinalis type A) and its native congener C. intestinalis (formerly known as C. intestinalis type B), in the Western English Channel, provides an excellent case study to examine. To examine contemporary hybridization between the two species, we developed a panel of 310 ancestry-informative SNPs from a population transcriptomic study. Hybridization rates were examined on 449 individuals sampled in eight sites from the sympatric range and five sites from allopatric ranges. The results clearly showed an almost complete absence of contemporary hybridization between the two species in syntopic localities, with only one-first-generation hybrid and no other genotype compatible with recent backcrosses. Despite the almost lack of contemporary hybridization, shared polymorphisms were observed in sympatric and allopatric populations of both species. Furthermore, one allopatric population from SE Pacific exhibited a higher rate of shared polymorphisms compared to all other C. robusta populations. Altogether, these results indicate that the observed level of shared polymorphism is more probably the outcome of ancient gene flow spread afterwards at a worldwide scale. They also emphasize efficient reproductive barriers preventing hybridization between introduced and native species, which suggests hybridization should not impede too much the expansion and the establishment of the non-native species in its introduction range. © 2016 John Wiley & Sons Ltd.

  16. Evidence to support natural hybridization between Anopheles sinensis and Anopheles kleini (Diptera: Culicidae): possibly a significant mechanism for gene introgression in sympatric populations

    Science.gov (United States)

    2014-01-01

    Background Malaria caused by Plasmodium vivax is still a public health problem in the Republic of Korea (ROK), particularly regarding the recent re-emergence of this malarial species near the demilitarized zone in northwestern Paju City, Gyeonggi-do Province. Currently, at least 4 species (An. kleini, An. pullus, An. belenrae and An. lesteri) of the Hyrcanus Group are reported as possible natural vectors of vivax malaria in the ROK, and An. sinensis, which is the most dominant species, has long been incriminated as an important natural vector of this P. vivax. However, An. sinensis was ranked recently as a low potential vector. According to the discovery of natural hybrids between An. sinensis (a low potential vector for P. vivax) and An. kleini (a high potential vector for P. vivax) in Paju City, intensive investigation of this phenomenon is warranted under laboratory conditions. Methods Mosquitoes were collected during 2010-2012 from Paju City, ROK. Hybridization experiments used iso-female line colonies of these anophelines together with DNA analysis of ribosomal DNA [second internal transcribed spacer (ITS2)] and mitochondrial DNA [cytochrome c oxidase subunit I (COI)] of the parental colonies, F1-hybrids and repeated backcross progenies were performed intensively by using a PCR-based assay and pyrosequencing technology. Results The results from hybridization experiments and molecular investigations revealed that the mitochondrial COI gene was introgressed from An. sinensis into An. kleini. The An. sinensis progenies obtained from consecutive repeated backcrosses in both directions, i.e., F2-11 progeny [(An. sinensis x An. kleini) x An. sinensis] and F3-5 progeny [(An. kleini x An. sinensis) x An. kleini] provided good supportive evidence. Conclusions This study revealed introgression of the mitochondrial COI gene between An. sinensis and An. kleini through consecutive repeated backcrosses under laboratory conditions. This new body of knowledge will be

  17. Development and characterization of Brassica juncea--fruticulosa introgression lines exhibiting resistance to mustard aphid (Lipaphis erysimi Kalt).

    Science.gov (United States)

    Atri, Chhaya; Kumar, Bharti; Kumar, Hitesh; Kumar, Sarwan; Sharma, Sanjula; Banga, Surinder S

    2012-11-27

    Mustard aphid is a major pest of Brassica oilseeds. No source for aphid resistance is presently available in Brassica juncea. A wild crucifer, Brassica fruticulosa is known to be resistant to mustard aphid. An artificially synthesized amphiploid, AD-4 (B. fruticulosa × B. rapa var. brown sarson) was developed for use as a bridge species to transfer fruticulosa resistance to B. juncea. Using the selfed backcross we could select a large number of lines with resistance to mustard aphid. This paper reports cytogenetic stability of introgression lines, molecular evidence for alien introgression and their reaction to mustard aphid infestation. Majority of introgression lines had expected euploid chromosome number(2n= 36), showed normal meiosis and high pollen grain fertility. Well-distributed and transferable simple-sequence repeats (SSR) markers for all the 18 B. juncea chromosomes helped to characterize introgression events. Average proportions of recipient and donor genome in the substitution lines were 49.72 and 35.06%, respectively. Minimum alien parent genome presence (27.29%) was observed in the introgression line, Ad3K-280 . Introgressed genotypes also varied for their resistance responses to mustard aphid infestations under artificial release conditions for two continuous seasons. Some of the test genotypes showed consistent resistant reaction. B.juncea-fruticulosa introgression set may prove to be a very powerful breeding tool for aphid resistance related QTL/gene discovery and fine mapping of the desired genes/QTLs to facilitate marker assisted transfer of identified gene(s) for mustard aphid resistance in the background of commercial mustard genotypes.

  18. Development of a genetic sexing strain in Bactrocera carambolae (Diptera: Tephritidae) by introgression of sex sorting components from B. dorsalis, Salaya1 strain.

    Science.gov (United States)

    Isasawin, Siriwan; Aketarawong, Nidchaya; Lertsiri, Sittiwat; Thanaphum, Sujinda

    2014-01-01

    The carambola fruit fly, Bactrocera carambolae Drew & Hancock is a high profile key pest that is widely distributed in the southwestern ASEAN region. In addition, it has trans-continentally invaded Suriname, where it has been expanding east and southward since 1975. This fruit fly belongs to Bactrocera dorsalis species complex. The development and application of a genetic sexing strain (Salaya1) of B. dorsalis sensu stricto (s.s.) (Hendel) for the sterile insect technique (SIT) has improved the fruit fly control. However, matings between B. dorsalis s.s. and B. carambolae are incompatible, which hinder the application of the Salaya1 strain to control the carambola fruit fly. To solve this problem, we introduced genetic sexing components from the Salaya1 strain into the B. carambolae genome by interspecific hybridization. Morphological characteristics, mating competitiveness, male pheromone profiles, and genetic relationships revealed consistencies that helped to distinguish Salaya1 and B. carambolae strains. A Y-autosome translocation linking the dominant wild-type allele of white pupae gene and a free autosome carrying a recessive white pupae homologue from the Salaya1 strain were introgressed into the gene pool of B. carambolae. A panel of Y-pseudo-linked microsatellite loci of the Salaya1 strain served as markers for the introgression experiments. This resulted in a newly derived genetic sexing strain called Salaya5, with morphological characteristics corresponding to B. carambolae. The rectal gland pheromone profile of Salaya5 males also contained a distinctive component of B. carambolae. Microsatellite DNA analyses confirmed the close genetic relationships between the Salaya5 strain and wild B. carambolae populations. Further experiments showed that the sterile males of Salaya5 can compete with wild males for mating with wild females in field cage conditions. Introgression of sex sorting components from the Salaya1 strain to a closely related B. carambolae

  19. Rapid and targeted introgression of genes into popular wheat cultivars using marker-assisted background selection.

    Directory of Open Access Journals (Sweden)

    Harpinder S Randhawa

    Full Text Available A marker-assisted background selection (MABS-based gene introgression approach in wheat (Triticum aestivum L. was optimized, where 97% or more of a recurrent parent genome (RPG can be recovered in just two backcross (BC generations. A four-step MABS method was developed based on 'Plabsim' computer simulations and wheat genome structure information. During empirical optimization of this method, double recombinants around the target gene were selected in a step-wise fashion during the two BC cycles followed by selection for recurrent parent genotype on non-carrier chromosomes. The average spacing between carrier chromosome markers was <4 cM. For non-carrier chromosome markers that flanked each of the 48 wheat gene-rich regions, this distance was approximately 12 cM. Employed to introgress seedling stripe rust (Puccinia striiformis f. sp. tritici resistance gene Yr15 into the spring wheat cultivar 'Zak', marker analysis of 2,187 backcross-derived progeny resulted in the recovery of a BC(2F(2ratio3 plant with 97% of the recurrent parent genome. In contrast, only 82% of the recurrent parent genome was recovered in phenotypically selected BC(4F(7 plants developed without MABS. Field evaluation results from 17 locations indicated that the MABS-derived line was either equal or superior to the recurrent parent for the tested agronomic characteristics. Based on these results, MABS is recommended as a strategy for rapidly introgressing a targeted gene into a wheat genotype in just two backcross generations while recovering 97% or more of the recurrent parent genotype.

  20. Introgression of Physiological Traits for a Comprehensive Improvement of Drought Adaptation in Crop Plants

    Directory of Open Access Journals (Sweden)

    Sheshshayee M. Sreeman

    2018-04-01

    Full Text Available Burgeoning population growth, industrial demand, and the predicted global climate change resulting in erratic monsoon rains are expected to severely limit fresh water availability for agriculture both in irrigated and rainfed ecosystems. In order to remain food and nutrient secure, agriculture research needs to focus on devising strategies to save water in irrigated conditions and to develop superior cultivars with improved water productivity to sustain yield under rainfed conditions. Recent opinions accruing in the scientific literature strongly favor the adoption of a “trait based” crop improvement approach for increasing water productivity. Traits associated with maintenance of positive tissue turgor and maintenance of increased carbon assimilation are regarded as most relevant to improve crop growth rates under water limiting conditions and to enhance water productivity. The advent of several water saving agronomic practices notwithstanding, a genetic enhancement strategy of introgressing distinct physiological, morphological, and cellular mechanisms on to a single elite genetic background is essential for achieving a comprehensive improvement in drought adaptation in crop plants. The significant progress made in genomics, though would provide the necessary impetus, a clear understanding of the “traits” to be introgressed is the most essential need of the hour. Water uptake by a better root architecture, water conservation by preventing unproductive transpiration are crucial for maintaining positive tissue water relations. Improved carbon assimilation associated with carboxylation capacity and mesophyll conductance is important in sustaining crop growth rates under water limited conditions. Besides these major traits, we summarize the available information in literature on classifying various drought adaptive traits. We provide evidences that Water-Use Efficiency when introgressed with moderately higher transpiration, would

  1. Introgressive hybridization of human and rodent schistosome parasites in western Kenya.

    Science.gov (United States)

    Steinauer, Michelle L; Hanelt, Ben; Mwangi, Ibrahim N; Maina, Geoffrey M; Agola, Lelo E; Kinuthia, Joseph M; Mutuku, Martin W; Mungai, Ben N; Wilson, Wade D; Mkoji, Gerald M; Loker, Eric S

    2008-12-01

    Hybridization and introgression can have important consequences for the evolution, ecology and epidemiology of pathogenic organisms. We examined the dynamics of hybridization between a trematode parasite of humans, Schistosoma mansoni, and its sister species, S. rodhaini, a rodent parasite, in a natural hybrid zone in western Kenya. Using microsatellite markers, rDNA and mtDNA, we showed that hybrids between the two species occur in nature, are fertile and produce viable offspring through backcrosses with S. mansoni. Averaged across collection sites, individuals of hybrid ancestry comprised 7.2% of all schistosomes collected, which is a large proportion given that one of the parental species, S. rodhaini, comprised only 9.1% of the specimens. No F1 individuals were collected and all hybrids represented backcrosses with S. mansoni that were of the first or successive generations. The direction of introgression appears highly asymmetric, causing unidirectional gene flow from the rodent parasite, S. rodhaini, to the human parasite, S. mansoni. Hybrid occurrence was seasonal and most hybrids were collected during the month of September over a 2-year period, a time when S. rodhaini was also abundant. We also examined the sex ratios and phenotypic differences between the hybrids and parental species, including the number of infective stages produced in the snail host and the time of day the infective stages emerge. No statistical differences were found in any of these characteristics, and most of the hybrids showed an emergence pattern similar to that of S. mansoni. One individual, however, showed a bimodal emergence pattern that was characteristic of both parental species. In conclusion, these species maintain their identity despite hybridization, although introgression may cause important alterations of the biology and epidemiology of schistosomiasis in this region.

  2. Introgression of physiological traits for a comprehensive improvement of drought adaptation in crop plants

    Science.gov (United States)

    Sreeman, Sheshshayee M.; Vijayaraghavareddy, Preethi; Sreevathsa, Rohini; Rajendrareddy, Sowmya; Arakesh, Smitharani; Bharti, Pooja; Dharmappa, Prathibha; Soolanayakanahally, Raju

    2018-04-01

    Burgeoning population growth, industrial demand and the predicted global climate change resulting in erratic monsoon rains are expected to severely limit fresh water availability for agriculture both in irrigated and rainfed ecosystems. In order to remain food and nutrient secure, agriculture research needs to focus on devising strategies to save water in irrigated conditions and to develop superior cultivars with improved water productivity to sustain yield under rainfed conditions. Recent opinions accruing in the scientific literature strongly favour the adoption of a “trait based” approach for increasing water productivity especially the traits associated with maintenance of positive tissue turgor and maintenance of increased carbon assimilation as the most relevant traits to improve crop growth rates under water limiting conditions and to enhance water productivity. The advent of several water saving agronomic practices notwithstanding, a genetic enhancement strategy of introgressing distinct physiological, morphological and cellular mechanisms on to a single elite genetic background is essential for achieving a comprehensive improvement in drought adaptation in crop plants. The significant progress made in genomics, though would provide the necessary impetus, a clear understanding of the “traits” to be introgressed is the most essential need of the hour. Water uptake by a better root architecture, water conservation by preventing unproductive transpiration is crucial for maintaining positive tissue water relations. Improved carbon assimilation associated with carboxylation capacity and mesophyll conductance is equally important in sustaining crop growth rates under water limited conditions. Besides these major traits, we summarized the available information in literature on classifying various drought adaptive traits. We provide evidences that water-use efficiency when introgressed with moderately higher transpiration, would significantly enhance

  3. Sequence-Based Introgression Mapping Identifies Candidate White Mold Tolerance Genes in Common Bean

    Directory of Open Access Journals (Sweden)

    Sujan Mamidi

    2016-07-01

    Full Text Available White mold, caused by the necrotrophic fungus (Lib. de Bary, is a major disease of common bean ( L.. WM7.1 and WM8.3 are two quantitative trait loci (QTL with major effects on tolerance to the pathogen. Advanced backcross populations segregating individually for either of the two QTL, and a recombinant inbred (RI population segregating for both QTL were used to fine map and confirm the genetic location of the QTL. The QTL intervals were physically mapped using the reference common bean genome sequence, and the physical intervals for each QTL were further confirmed by sequence-based introgression mapping. Using whole-genome sequence data from susceptible and tolerant DNA pools, introgressed regions were identified as those with significantly higher numbers of single-nucleotide polymorphisms (SNPs relative to the whole genome. By combining the QTL and SNP data, WM7.1 was located to a 660-kb region that contained 41 gene models on the proximal end of chromosome Pv07, while the WM8.3 introgression was narrowed to a 1.36-Mb region containing 70 gene models. The most polymorphic candidate gene in the WM7.1 region encodes a BEACH-domain protein associated with apoptosis. Within the WM8.3 interval, a receptor-like protein with the potential to recognize pathogen effectors was the most polymorphic gene. The use of gene and sequence-based mapping identified two candidate genes whose putative functions are consistent with the current model of pathogenicity.

  4. The in silico identification and characterization of a bread wheat/Triticum militinae introgression line

    Czech Academy of Sciences Publication Activity Database

    Abrouk, Michael; Balcárková, Barbora; Šimková, Hana; Komínková, Eva; Martis, M.M.; Jakobson, I.; Timofejeva, L.; Rey, Elodie; Vrána, Jan; Kilian, A.; Jarve, K.; Doležel, Jaroslav; Valárik, Miroslav

    2017-01-01

    Roč. 15, č. 2 (2017), s. 249-256 ISSN 1467-7644 R&D Projects: GA MŠk(CZ) LO1204; GA ČR(CZ) GA14-07164S Institutional support: RVO:61389030 Keywords : crop improvement * powdery mildew * common wheat * chromosomes * genome * resistance * plant * recombination * evolution * barley * GenomeZipper * alien introgression * comparative analysis * chromosome rearrangement * chromosome translocation * linkage drag Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Plant sciences, botany Impact factor: 7.443, year: 2016

  5. Evaluation de l'introgression du caractère croissance lente de ...

    African Journals Online (AJOL)

    Evaluation de l'introgression du caractère croissance lente de quelques géniteurs Akpadanou (origine Bénin) chez quelques géniteurs améliorés de palmier à ... de sélection, à terme, de matériel végétal à croissance en hauteur fortement réduite et possédant un bon niveau de production de régimes et d'huile de palme.

  6. Adaptive introgression from distant Caribbean islands contributed to the diversification of a microendemic adaptive radiation of trophic specialist pupfishes.

    Directory of Open Access Journals (Sweden)

    Emilie J Richards

    2017-08-01

    Full Text Available Rapid diversification often involves complex histories of gene flow that leave variable and conflicting signatures of evolutionary relatedness across the genome. Identifying the extent and source of variation in these evolutionary relationships can provide insight into the evolutionary mechanisms involved in rapid radiations. Here we compare the discordant evolutionary relationships associated with species phenotypes across 42 whole genomes from a sympatric adaptive radiation of Cyprinodon pupfishes endemic to San Salvador Island, Bahamas and several outgroup pupfish species in order to understand the rarity of these trophic specialists within the larger radiation of Cyprinodon. 82% of the genome depicts close evolutionary relationships among the San Salvador Island species reflecting their geographic proximity, but the vast majority of variants fixed between specialist species lie in regions with discordant topologies. Top candidate adaptive introgression regions include signatures of selective sweeps and adaptive introgression of genetic variation from a single population in the northwestern Bahamas into each of the specialist species. Hard selective sweeps of genetic variation on San Salvador Island contributed 5 times more to speciation of trophic specialists than adaptive introgression of Caribbean genetic variation; however, four of the 11 introgressed regions came from a single distant island and were associated with the primary axis of oral jaw divergence within the radiation. For example, standing variation in a proto-oncogene (ski known to have effects on jaw size introgressed into one San Salvador Island specialist from an island 300 km away approximately 10 kya. The complex emerging picture of the origins of adaptive radiation on San Salvador Island indicates that multiple sources of genetic variation contributed to the adaptive phenotypes of novel trophic specialists on the island. Our findings suggest that a suite of factors

  7. Geography disentangles introgression from ancestral polymorphism in Lake Malawi cichlids.

    Science.gov (United States)

    Mims, Meryl C; Darrin Hulsey, C; Fitzpatrick, Benjamin M; Streelman, J Todd

    2010-03-01

    Phenotypically diverse Lake Malawi cichlids exhibit similar genomes. The extensive sharing of genetic polymorphism among forms has both intrigued and frustrated biologists trying to understand the nature of diversity in this and other rapidly evolving systems. Shared polymorphism might result from hybridization and/or the retention of ancestrally polymorphic alleles. To examine these alternatives, we used new genomic tools to characterize genetic differentiation in widespread, geographically structured populations of Labeotropheus fuelleborni and Metriaclima zebra. These phenotypically distinct species share mitochondrial DNA (mtDNA) haplotypes and show greater mtDNA differentiation among localities than between species. However, Bayesian analysis of nuclear single nucleotide polymorphism (SNP) data revealed two distinct genetic clusters corresponding perfectly to morphologically diagnosed L. fuelleborni and M. zebra. This result is a function of the resolving power of the multi-locus dataset, not a conflict between nuclear and mitochondrial partitions. Locus-by-locus analysis showed that mtDNA differentiation between species (F(CT)) was nearly identical to the median single-locus SNP F(CT). Finally, we asked whether there is evidence for gene flow at sites of co-occurrence. We used simulations to generate a null distribution for the level of differentiation between co-occurring populations of L. fuelleborni and M. zebra expected if there was no hybridization. The null hypothesis was rejected for the SNP data; populations that co-occur at rock reef sites were slightly more similar than expected by chance, suggesting recent gene flow. The coupling of numerous independent markers with extensive geographic sampling and simulations utilized here provides a framework for assessing the prevalence of gene flow in recently diverged species.

  8. Introgressing subgenome components from Brassica rapa and B. carinata to B. juncea for broadening its genetic base and exploring intersubgenomic heterosis

    Directory of Open Access Journals (Sweden)

    Zili Wei

    2016-11-01

    Full Text Available Brassica juncea (AjAjBjBj, is an allotetraploid that arose from two diploid species, B. rapa (ArAr and B. nigra (BnBn. It is an old oilseed crop with unique favorable traits, but the genetic improvement on this species is limited. We developed an approach to broaden its genetic base within several generations by intensive selection. The Ar subgenome from the Asian oil crop B. rapa (ArAr and the Bc subgenome from the African oil crop B. carinata (BcBcCcCc were combined in a synthesized allohexaploid (ArArBcBcCcCc, which was crossed with traditional B. juncea to generate pentaploid F1 hybrids (ArAjBcBjCc, with subsequent self-pollination to obtain newly synthesized B. juncea (Ar/jAr/jBc/jBc/j. After intensive cytological screening and phenotypic selection of fertility and agronomic traits, a population of new-type B. juncea was obtained and was found to be genetically stable at the F6 generation. The new-type B. juncea possesses good fertility and rich genetic diversity and is distinctly divergent but not isolated from traditional B. juncea, as revealed by population genetic analysis with molecular markers. More than half of its genome was modified, showing exotic introgression and novel variation. In addition to the improvement in some traits of the new-type B. juncea lines, a considerable potential for heterosis was observed in inter-subgenomic hybrids between new-type B. juncea lines and traditional B. juncea accessions. The new-type B. juncea exhibited a stable chromosome number and a novel genome composition through multiple generations, providing insight into how to significantly broaden the genetic base of crops with subgenome introgression from their related species and the potential of exploring inter-subgenomic heterosis for hybrid breeding.

  9. Barrier Systems

    NARCIS (Netherlands)

    Heteren, S. van

    2015-01-01

    Barrier-system dynamics are a function of antecedent topography and substrate lithology, Relative sea-level (RSL) changes, sediment availability and type, climate, vegetation type and cover, and various aero- and hydrodynamic processes during fair-weather conditions and extreme events. Global change

  10. Genome Targeted Introgression of Resistance to African Stem Rust fromAegilops sharonensisinto Bread Wheat.

    Science.gov (United States)

    Millet, Eitan; Steffenson, Brian J; Prins, Renée; Sela, Hanan; Przewieslik-Allen, Alexandra M; Pretorius, Zacharias A

    2017-11-01

    Many accessions of the wheat wild relative Sharon goatgrass ( Eig., ) are resistant to African races of the stem rust pathogen (i.e., Ug99 group races), which currently threaten wheat production worldwide. A procedure was designed to introgress the respective resistances to specific bread wheat genomes by producing plants homozygous for the A and B genomes and hemizygous for the D and S genomes or homozygous for the A and D genomes and hemizygous for the B and S genomes. In these genotypes, which lack the allele, homeologous pairing was expected mainly between chromosomes of the D and S genomes or B and S genomes, respectively. An antigametocidal (AG) wheat mutant () was used to overcome gametocidal effects. Wheat lines initially found resistant at the seedling stage were also highly resistant at the adult plant stage in rust nurseries established in the field. DNA of 41 selected homozygous resistant lines, analyzed by the Axiom wheat 820K SNP array, showed alien chromatin mainly in wheat chromosomes 1B, 1D, and 5B. This work suggests that, in most cases, it is possible to target introgressions into the homeologous chromosome of a selected genome of bread wheat. Copyright © 2017 Crop Science Society of America.

  11. Introgression of Black Rot Resistance from Brassica carinata to Cauliflower (Brassica oleracea botrytis Group) through Embryo Rescue

    Science.gov (United States)

    Sharma, Brij B.; Kalia, Pritam; Singh, Dinesh; Sharma, Tilak R.

    2017-01-01

    Black rot caused by Xanthomonas campestris pv. campestris (Xcc) is a very important disease of cauliflower (Brassica oleracea botrytis group) resulting into 10–50% yield losses every year. Since there is a dearth of availability of resistance to black rot disease in B. oleracea (C genome), therefore exploration of A and B genomes was inevitable as they have been reported to be potential reservoirs of gene(s) for resistance to black rot. To utilize these sources, interspecific hybrid and backcross progeny (B1) were generated between cauliflower “Pusa Sharad” and Ethiopian mustard “NPC-9” employing in vitro embryo rescue technique. Direct ovule culture method was better than siliqua culture under different temperature regime periods. Hybridity testing of F1 inter-specific plants was carried out using co-dominant SSR marker and Brassica B and C genome-specific (DB and DC) primers. Meiosis in the di-genomic (BCC) interspecific hybrid of B. oleracea botrytis group (2n = 18, CC) × B. carinata (2n = 4x = 34, BBCC) was higly disorganized and cytological analysis of pollen mother cells revealed chromosomes 2n = 26 at metaphase-I. Fertile giant pollen grain formation was observed frequently in interspecific F1 hybrid and BC1 plants. The F1 inter-specific plants were found to be resistant to Xcc race 1. Segregation distortion was observed in BC1 generation for black rot resistance and different morphological traits. The At1g70610 marker analysis confirmed successful introgression of black rot resistance in interspecific BC1 population. This effort will go a long way in pyramiding gene(s) for resistance against black rot in Cole crops, especially cauliflower and cabbage for developing durable resistance, thus minimize dependency on bactericides. PMID:28769959

  12. Red pericarp introgression lines derived from interspecific crosses of rice: physicochemical characteristics, antioxidative properties and phenolic content.

    Science.gov (United States)

    Sharma, Neerja; Kaur, Rimaljeet; Mangat, Gurjit S; Singh, Kuldeep

    2014-11-01

    Antioxidative properties and physicochemical characteristics of introgression lines (ILs) and their recurrent parents were analyzed. In addition, catalase (CAT) and superoxide dismutase (SOD) activities and free radical-scavenging capacity were evaluated, since these are important antioxidative properties for developing nutraceutical and functional foods. Comparative analysis of the brown and milled rice fractions of ILs with their respective recurrent parents revealed 2.26- and 1.22-fold increase in total phenolics, 1.95- and 2.09-fold increase in flavonoids, 8.38- and 6.80-fold increase in proanthocyanidins and 1.55- and 1.20-fold increase in tannins in brown and milled rice fractions respectively. Higher CAT (1.36- and 1.89-fold) and SOD (1.71- and 2.02-fold) activities and Trolox equivalent antioxidant capacity (TEAC, 7.13- and 1.98-fold) were observed in brown and milled rice fractions respectively of ILs compared with their respective recurrent parents. A high and positive correlation was obtained between TEAC and total phenols (0.73, P ≤ 0.01), flavonoids (0.66, P ≤ 0.05) and proanthocyanidins (0.69, P ≤ 0.05). The yield parameters and physicochemical characteristics of the grains, in general, were comparable in the ILs and their respective recurrent parents. The ILs of rice reported in the present study exhibited significant positive differences in the content of phenolic constituents and antioxidant properties with good grain quality characteristics over their recurrent parents, indicating their potential as a natural source of phytochemicals for nutraceutical and functional food development. © 2014 Society of Chemical Industry.

  13. Transcriptomic analysis of fiber strength in upland cotton chromosome introgression lines carrying different Gossypium barbadense chromosomal segments.

    Directory of Open Access Journals (Sweden)

    Lei Fang

    Full Text Available Fiber strength is the key trait that determines fiber quality in cotton, and it is closely related to secondary cell wall synthesis. To understand the mechanism underlying fiber strength, we compared fiber transcriptomes from different G. barbadense chromosome introgression lines (CSILs that had higher fiber strengths than their recipient, G. hirsutum acc. TM-1. A total of 18,288 differentially expressed genes (DEGs were detected between CSIL-35431 and CSIL-31010, two CSILs with stronger fiber and TM-1 during secondary cell wall synthesis. Functional classification and enrichment analysis revealed that these DEGs were enriched for secondary cell wall biogenesis, glucuronoxylan biosynthesis, cellulose biosynthesis, sugar-mediated signaling pathways, and fatty acid biosynthesis. Pathway analysis showed that these DEGs participated in starch and sucrose metabolism (328 genes, glycolysis/gluconeogenesis (122 genes, phenylpropanoid biosynthesis (101 genes, and oxidative phosphorylation (87 genes, etc. Moreover, the expression of MYB- and NAC-type transcription factor genes were also dramatically different between the CSILs and TM-1. Being different to those of CSIL-31134, CSIL-35431 and CSIL-31010, there were many genes for fatty acid degradation and biosynthesis, and also for carbohydrate metabolism that were down-regulated in CSIL-35368. Metabolic pathway analysis in the CSILs showed that different pathways were changed, and some changes at the same developmental stage in some pathways. Our results extended our understanding that carbonhydrate metabolic pathway and secondary cell wall biosynthesis can affect the fiber strength and suggested more genes and/or pathways be related to complex fiber strength formation process.

  14. Introgression of Black Rot Resistance from Brassica carinata to Cauliflower (Brassica oleracea botrytis Group through Embryo Rescue

    Directory of Open Access Journals (Sweden)

    Brij B. Sharma

    2017-07-01

    Full Text Available Black rot caused by Xanthomonas campestris pv. campestris (Xcc is a very important disease of cauliflower (Brassica oleracea botrytis group resulting into 10–50% yield losses every year. Since there is a dearth of availability of resistance to black rot disease in B. oleracea (C genome, therefore exploration of A and B genomes was inevitable as they have been reported to be potential reservoirs of gene(s for resistance to black rot. To utilize these sources, interspecific hybrid and backcross progeny (B1 were generated between cauliflower “Pusa Sharad” and Ethiopian mustard “NPC-9” employing in vitro embryo rescue technique. Direct ovule culture method was better than siliqua culture under different temperature regime periods. Hybridity testing of F1 inter-specific plants was carried out using co-dominant SSR marker and Brassica B and C genome-specific (DB and DC primers. Meiosis in the di-genomic (BCC interspecific hybrid of B. oleracea botrytis group (2n = 18, CC × B. carinata (2n = 4x = 34, BBCC was higly disorganized and cytological analysis of pollen mother cells revealed chromosomes 2n = 26 at metaphase-I. Fertile giant pollen grain formation was observed frequently in interspecific F1 hybrid and BC1 plants. The F1 inter-specific plants were found to be resistant to Xcc race 1. Segregation distortion was observed in BC1 generation for black rot resistance and different morphological traits. The At1g70610 marker analysis confirmed successful introgression of black rot resistance in interspecific BC1 population. This effort will go a long way in pyramiding gene(s for resistance against black rot in Cole crops, especially cauliflower and cabbage for developing durable resistance, thus minimize dependency on bactericides.

  15. Maize x Teosinte Hybrid Cobs Do Not Prevent Crop Gene Introgression.

    Science.gov (United States)

    Chavez, Nancy B; Flores, Jose J; Martin, Joseph; Ellstrand, Norman C; Guadagnuolo, Roberto; Heredia, Sylvia; Welles, Shana R

    2012-06-01

    Maize x Teosinte Hybrid Cobs Do Not Prevent Crop Gene Introgression. Whether introgression from crops to wild relatives can occur is an important component of transgene risk assessment. In the case of maize, which co-occurs with its wild relative teosinte in Mexico, the possibility of introgression has been controversial. Maize is cross-compatible with teosinte, and spontaneous hybridization is known to occur. Some scientists have hypothesized that the maize x teosinte cob infructescence will prevent progeny dispersal, thus preventing introgression. Motivated by a prior study where we found maize x teosinte hybrid fruits naturally dispersed under field conditions, we tested whether hybrid cobs hold their fruits as tightly as maize cobs. We found the force required to detach hybrid fruits was substantially and significantly less than that for maize. Consequently, we expect that introgression of transgenes from maize into teosinte in Mexico should occur largely unimpeded by the hybrid cob.La mazorca o elote híbrido de maíz x teocintle no impide la introgresión de genes transgénicos provenientes del cultivo. La introgresión entre el maíz cultivado y el maíz silvestre, o teocintle, es un componente importante en la evaluación ambiental relacionada con los riesgos de la introducción de genes transgénicos. La posibilidad de introgresión entre el maíz domesticado y el teocintle ha sido un tema controversial, en particular en México, donde maíz y teocintle coexisten. El maíz es compatible con el teocintle y la hibridización espontánea ocurre entre ellos. Algunos científicos han planteado como hipótesis que al cruzar el maíz con teocintle, la estructura interna de la infrutescencia que sujeta los frutos conocida como la mazorca de maíz o el elote, impide la dispersión de la progenie evitando que la introgresión ocurra. Los resultados de un estudio previo evidencian la dispersión de los frutos híbridos del maíz x teocintle en condiciones naturales

  16. Seismic waves and seismic barriers

    Science.gov (United States)

    Kuznetsov, S. V.

    2011-05-01

    The basic idea of seismic barrier is to protect an area occupied by a building or a group of buildings from seismic waves. Depending on nature of seismic waves that are most probable in a specific region, different kinds of seismic barriers are suggested. For example, vertical barriers resembling a wall in a soil can protect from Rayleigh and bulk waves. The FEM simulation reveals that to be effective, such a barrier should be (i) composed of layers with contrast physical properties allowing "trapping" of the wave energy inside some of the layers, and (ii) depth of the barrier should be comparable or greater than the considered seismic wave length. Another type of seismic barrier represents a relatively thin surface layer that prevents some types of surface seismic waves from propagating. The ideas for these barriers are based on one Chadwick's result concerning non-propagation condition for Rayleigh waves in a clamped half-space, and Love's theorem that describes condition of non-existence for Love waves. The numerical simulations reveal that to be effective the length of the horizontal barriers should be comparable to the typical wavelength.

  17. Transgressive variation for yield components and dynamic traits in Jefferson (Oryza sativa) x O. rufipogon introgression lines

    Science.gov (United States)

    Alleles from wild progenitors of crops can be a source of transgressive variation in modern cultivars. Introgressions from the Oryza rufipogon donor (IRGC104591) in an O. sativa tropical japonica cultivar (Jefferson) were shown to confer a yield advantage in multi-location field trials. Yield loci...

  18. [Comparative cytological and molecular analysis of introgressive common wheat lines containing genetic material of Triticum timopheevii Zhur].

    Science.gov (United States)

    Gordeeva, E I; Leonova, I N; Kalinina, N P; Salina, E A; Budashkina, E b

    2009-12-01

    A total of 40 introgressive lines of common wheat (2n = 42) Triticum aestivum L x T. timopheevii Zhuk., resistant to brown rust and partly to powdery mildew, were examined. Based on cytological analysis of meiosis in pollen mother cells (PMC), hybrid lines were subdivided into two groups characterized by either stable or unstable meiosis. In cytologically stable lines, chromosome configuration at the MI stage of meiosis was mostly bivalent (21II) with small proportion of defect cells (almost 10%), which at most contained two univalents (20II + + 21). Cytologically unstable group was comprised of the lines, containing high proportions of cells with abnormal chromosome pairing in meiotic PMC, as well as the cells with multivalents, and the lines containing aneuploid plants. Localization of the T. timopheevii fragments performed with the use of SSR markers showed that the lines with unstable meiosis were characterized by higher numbers of introgressions compared to stable lines. The influence of certain chromosomes of T. timopheevii on chromosome pairing stability was also demonstrated. In cytologically unstable lines, the increased frequency of 2A substitutions along with the high frequency of introgression of T. timopheevii genetic material into chromosome 7A was observed. Multivalents were scored in all cases of introgression in chromosome 7A. It was suggested that the reason for the genome instability in hybrid forms lied in insufficient compensating ability of certain T. timopheevii chromosomes and/or their parts, involved into recombination processes.

  19. Asymmetric introgression in the horticultural living fossil cycas sect. Asiorientales using a genome-wide scanning approach.

    Science.gov (United States)

    Chiang, Yu-Chung; Huang, Bing-Hong; Chang, Chun-Wen; Wan, Yu-Ting; Lai, Shih-Jie; Huang, Shong; Liao, Pei-Chun

    2013-04-15

    The Asian cycads are mostly allopatric, distributed in small population sizes. Hybridization between allopatric species provides clues in determining the mechanism of species divergence. Horticultural introduction provides the chance of interspecific gene flow between allopatric species. Two allopatrically eastern Asian Cycas sect. Asiorientales species, C. revoluta and C. taitungensis, which are widely distributed in Ryukyus and Fujian Province and endemic to Taiwan, respectively, were planted in eastern Taiwan for horticultural reason. Higher degrees of genetic admixture in cultivated samples than wild populations in both cycad species were detected based on multilocus scans by neutral AFLP markers. Furthermore, bidirectional but asymmetric introgression by horticultural introduction of C. revoluta is evidenced by the reanalyses of species associated loci, which are assumed to be diverged after species divergence. Partial loci introgressed from native cycad to the invaders were also detected at the loci of strong species association. Consistent results tested by all neutral loci, and the species-associated loci, specify the recent introgression from the paradox of sharing of ancestral polymorphisms. Phenomenon of introgression of cultivated cycads implies niche conservation among two geographic-isolated cycads, even though the habitats of the extant wild populations of two species are distinct.

  20. The complex biogeography of the plant pathogen Xylella fastidiosa: genetic evidence of introductions and Subspecific introgression in Central America.

    Directory of Open Access Journals (Sweden)

    Leonard Nunney

    Full Text Available The bacterium Xylella fastidiosa is a plant pathogen with a history of economically damaging introductions of subspecies to regions where its other subspecies are native. Genetic evidence is presented demonstrating the introduction of two new taxa into Central America and their introgression into the native subspecies, X. fastidiosa subsp. fastidiosa. The data are from 10 genetic outliers detected by multilocus sequence typing (MLST of isolates from Costa Rica. Six (five from oleander, one from coffee defined a new sequence type (ST53 that carried alleles at six of the eight loci sequenced (five of the seven MLST loci diagnostic of the South American subspecies Xylella fastidiosa subsp. pauca which causes two economically damaging plant diseases, citrus variegated chlorosis and coffee leaf scorch. The two remaining loci of ST53 carried alleles from what appears to be a new South American form of X. fastidiosa. Four isolates, classified as X. fastidiosa subsp. fastidiosa, showed a low level of introgression of non-native DNA. One grapevine isolate showed introgression of an allele from X. fastidiosa subsp. pauca while the other three (from citrus and coffee showed introgression of an allele with similar ancestry to the alleles of unknown origin in ST53. The presence of X. fastidiosa subsp. pauca in Central America is troubling given its disease potential, and establishes another route for the introduction of this economically damaging subspecies into the US or elsewhere, a threat potentially compounded by the presence of a previously unknown form of X. fastidiosa.

  1. The complex biogeography of the plant pathogen Xylella fastidiosa: genetic evidence of introductions and Subspecific introgression in Central America.

    Science.gov (United States)

    Nunney, Leonard; Ortiz, Beatriz; Russell, Stephanie A; Ruiz Sánchez, Rebeca; Stouthamer, Richard

    2014-01-01

    The bacterium Xylella fastidiosa is a plant pathogen with a history of economically damaging introductions of subspecies to regions where its other subspecies are native. Genetic evidence is presented demonstrating the introduction of two new taxa into Central America and their introgression into the native subspecies, X. fastidiosa subsp. fastidiosa. The data are from 10 genetic outliers detected by multilocus sequence typing (MLST) of isolates from Costa Rica. Six (five from oleander, one from coffee) defined a new sequence type (ST53) that carried alleles at six of the eight loci sequenced (five of the seven MLST loci) diagnostic of the South American subspecies Xylella fastidiosa subsp. pauca which causes two economically damaging plant diseases, citrus variegated chlorosis and coffee leaf scorch. The two remaining loci of ST53 carried alleles from what appears to be a new South American form of X. fastidiosa. Four isolates, classified as X. fastidiosa subsp. fastidiosa, showed a low level of introgression of non-native DNA. One grapevine isolate showed introgression of an allele from X. fastidiosa subsp. pauca while the other three (from citrus and coffee) showed introgression of an allele with similar ancestry to the alleles of unknown origin in ST53. The presence of X. fastidiosa subsp. pauca in Central America is troubling given its disease potential, and establishes another route for the introduction of this economically damaging subspecies into the US or elsewhere, a threat potentially compounded by the presence of a previously unknown form of X. fastidiosa.

  2. A model for population growth of laboratory animals subjected to marker-assisted introgression : how many animals do we need?

    NARCIS (Netherlands)

    Koudande, O.D.; Thomson, P.C.; Arendonk, van J.A.M.

    1999-01-01

    This study provides methods for calculating the mean and variance of the number of animals with the desired genotype in each backcross generation for a marker-assisted introgression experiment. The ultimate goal is to produce animals which are homozygous for the desired loci. The methods have been

  3. Identification of a Rice stripe necrosis virus resistance locus and yield component QTLs using Oryza sativa × O. glaberrima introgression lines

    Directory of Open Access Journals (Sweden)

    Prado Gustavo

    2010-01-01

    Full Text Available Abstract Background Developing new population types based on interspecific introgressions has been suggested by several authors to facilitate the discovery of novel allelic sources for traits of agronomic importance. Chromosome segment substitution lines from interspecific crosses represent a powerful and useful genetic resource for QTL detection and breeding programs. Results We built a set of 64 chromosome segment substitution lines carrying contiguous chromosomal segments of African rice Oryza glaberrima MG12 (acc. IRGC103544 in the genetic background of Oryza sativa ssp. tropical japonica (cv. Caiapó. Well-distributed simple-sequence repeats markers were used to characterize the introgression events. Average size of the substituted chromosomal segments in the substitution lines was about 10 cM and covered the whole donor genome, except for small regions on chromosome 2 and 4. Proportions of recurrent and donor genome in the substitution lines were 87.59% and 7.64%, respectively. The remaining 4.78% corresponded to heterozygotes and missing data. Strong segregation distortion was found on chromosomes 3 and 6, indicating the presence of interspecific sterility genes. To illustrate the advantages and the power of quantitative trait loci (QTL detection using substitution lines, a QTL detection was performed for scored traits. Transgressive segregation was observed for several traits measured in the population. Fourteen QTLs for plant height, tiller number per plant, panicle length, sterility percentage, 1000-grain weight and grain yield were located on chromosomes 1, 3, 4, 6 and 9. Furthermore, a highly significant QTL controlling resistance to the Rice stripe necrosis virus was located between SSR markers RM202-RM26406 (44.5-44.8 cM on chromosome 11. Conclusions Development and phenotyping of CSSL libraries with entire genome coverage represents a useful strategy for QTL discovery. Mapping of the RSNV locus represents the first identification

  4. Study on the introgression of beef breeds in Canchim cattle using single nucleotide polymorphism markers.

    Directory of Open Access Journals (Sweden)

    Marcos Eli Buzanskas

    Full Text Available The aim of this study was to evaluate the level of introgression of breeds in the Canchim (CA: 62.5% Charolais-37.5% Zebu and MA genetic group (MA: 65.6% Charolais-34.4% Zebu cattle using genomic information on Charolais (CH, Nelore (NE, and Indubrasil (IB breeds. The number of animals used was 395 (CA and MA, 763 (NE, 338 (CH, and 37 (IB. The Bovine50SNP BeadChip from Illumina panel was used to estimate the levels of introgression of breeds considering the Maximum likelihood, Bayesian, and Single Regression method. After genotype quality control, 32,308 SNPs were considered in the analysis. Furthermore, three thresholds to prune out SNPs in linkage disequilibrium higher than 0.10, 0.05, and 0.01 were considered, resulting in 15,286, 7,652, and 1,582 SNPs, respectively. For k = 2, the proportion of taurine and indicine varied from the expected proportion based on pedigree for all methods studied. For k = 3, the Regression method was able to differentiate the animals in three main clusters assigned to each purebred breed, showing more reasonable according to its biological viewpoint. Analyzing the data considering k = 2 seems to be more appropriate for Canchim-MA animals due to its biological interpretation. The usage of 32,308 SNPs in the analyses resulted in similar findings between the estimated and expected breed proportions. Using the Regression approach, a contribution of Indubrasil was observed in Canchim-MA when k = 3 was considered. Genetic parameter estimation could account for this breed composition information as a source of variation in order to improve the accuracy of genetic models. Our findings may help assemble appropriate reference populations for genomic prediction for Canchim-MA in order to improve prediction accuracy. Using the information on the level of introgression in each individual could also be useful in breeding or crossing design to improve individual heterosis in crossbred cattle.

  5. Co-introgression of Y-chromosome haplogroups and the sickle cell gene across Africa's Sahel.

    Science.gov (United States)

    Bereir, Rihab E; Hassan, Hisham Y; Salih, Niven A; Underhill, Peter A; Cavalli-Sforza, Luigi L; Hussain, Ayman A; Kwiatkowski, Dominic; Ibrahim, Muntaser E

    2007-11-01

    The Sahel that extends from the Atlantic Ocean to the Ethiopian highland is a historical reservoir of Africa's cultures and grandest populations and a known arena of ancient and recent migrations. We are interested in the issue whether such migrations were also carriers of genetic traits and whether this introgression could be associated with population genetic markers. Based on analysis of Y-chromosome haplogroups, we present evidence that the sickle gene, one of the major protective polymorphisms known in malaria, has in fact found its way only recently to the gene pool of the populations in eastern Sahel. We discuss the possible dynamics of the process and give estimates of the age of the introduction of the S allele into eastern Sahel.

  6. Historical introgression drives pervasive mitochondrial admixture between two species of pelagic sharks.

    Science.gov (United States)

    Corrigan, Shannon; Maisano Delser, Pierpaolo; Eddy, Corey; Duffy, Clinton; Yang, Lei; Li, Chenhong; Bazinet, Adam L; Mona, Stefano; Naylor, Gavin J P

    2017-05-01

    We use a genomic sampling of both nuclear and mitochondrial DNA markers to examine a pattern of genetic admixture between Carcharhinus galapagensis (Galapagos sharks) and Carcharhinus obscurus (dusky sharks), two well-known and closely related sharks that have been recognized as valid species for more than 100years. We describe widespread mitochondrial-nuclear discordance in which these species are readily distinguishable based on 2152 nuclear single nucleotide polymorphisms from 910 independent autosomal regions, but show pervasive mitochondrial admixture. The species are superficially morphologically cryptic as adults but show marked differences in internal anatomy, as well as niche separation. There was no indication of ongoing hybridization between the species. We conclude that the observed mitochondrial-nuclear discordance is likely due to historical mitochondrial introgression following a range expansion. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Species-specific markers provide molecular genetic evidence for natural introgression of bullhead catfishes in Hungary

    Science.gov (United States)

    Béres, Beatrix; Kánainé Sipos, Dóra; Müller, Tamás; Staszny, Ádám; Farkas, Milán; Bakos, Katalin; Urbányi, Béla

    2017-01-01

    Since three bullhead catfish species were introduced to Europe in the late 19th century, they have spread to most European countries. In Hungary, the brown bullhead (Ameiurus nebulosus) was more widespread in the 1970s–1980s, but the black bullhead (Ameiurus melas) has gradually supplanted since their second introduction in 1980. The introgressive hybridization of the two species has been presumed based on morphological examinations, but it has not previously been supported by genetic evidence. In this study, 11 different Hungarian habitats were screened with a new species-specific nuclear genetic, duplex PCR based, marker system to distinguish the introduced catfish species, Ameiurus nebulosus, Ameiurus melas, and Ameiurus natalis, as well as the hybrids of the first two. More than 460 specimens were analyzed using the above markers and additional mitochondrial sequence analyses were also conducted on >25% of the individuals from each habitat sampled. The results showed that only 7.9% of the specimens from two habitats belonged to Ameiurus nebulosus, and 92.1% were classified as Ameiurus melas of all habitats, whereas the presence of Ameiurus natalis was not detected. Two specimens (>0.4%) showed the presence of both nuclear genomes and they were identified as hybrids of Ameiurus melas and Ameiurus nebulosus. An additional two individuals showed contradicting results from the nuclear and mitochondrial assays as a sign of a possible footprint of introgressive hybridization that might have happened two or more generations before. Surprisingly, the level of hybridization was much smaller than expected based on the analyses of the North American continent’s indigenous stock from the hybrid zones. This phenomenon has been observed in several invasive fish species and it is regarded as an added level of complexity in the management of their rapid adaptation. PMID:28265489

  8. Genetic diversity, introgression and relationships among West/Central African cattle breeds.

    Science.gov (United States)

    Ibeagha-Awemu, Eveline Mengwi; Jann, Oliver Carl; Weimann, Christina; Erhardt, Georg

    2004-01-01

    Genetic diversity, introgression and relationships were studied in 521 individuals from 9 African Bos indicus and 3 Bos taurus cattle breeds in Cameroon and Nigeria using genotype information on 28 markers (16 microsatellite, 7 milk protein and 5 blood protein markers). The genotypes of 13 of the 16 microsatellite markers studied on three European (German Angus, German Simmental and German Yellow) and two Indian (Nelore and Ongole) breeds were used to assess the relationships between them and the African breeds. Diversity levels at microsatellite loci were higher in the zebu than in the taurine breeds and were generally similar for protein loci in the breeds in each group. Microsatellite allelic distribution displayed groups of alleles specific to the Indian zebu, African taurine and European taurine. The level of the Indian zebu genetic admixture proportions in the African zebus was higher than the African taurine and European taurine admixture proportions, and ranged from 58.1% to 74.0%. The African taurine breed, Muturu was free of Indian zebu genes while its counter Namchi was highly introgressed (30.2%). Phylogenic reconstruction and principal component analysis indicate close relationships among the zebu breeds in Cameroon and Nigeria and a large genetic divergence between the main cattle groups--African taurine, European taurine and Indian zebu, and a central position for the African zebus. The study presents the first comprehensive information on the hybrid composition of the individual cattle breeds of Cameroon and Nigeria and the genetic relationships existing among them and other breeds outside of Africa. Strong evidence supporting separate domestication events for the Bos species is also provided.

  9. Introgression study reveals two quantitative trait loci involved in interspecific variation in memory retention among Nasonia wasp species

    NARCIS (Netherlands)

    Hoedjes, K.M.; Smid, H.M.; Vet, L.E.M.; Werren, J.H.

    2014-01-01

    Genes involved in the process of memory formation have been studied intensively in model organisms; however, little is known about the mechanisms that are responsible for natural variation in memory dynamics. There is substantial variation in memory retention among closely related species in the

  10. A study of the deep structure of the energy landscape of glassy polystyrene: the exponential distribution of the energy barriers revealed by high-field electron spin resonance spectroscopy

    International Nuclear Information System (INIS)

    Bercu, V; Martinelli, M; Massa, C A; Pardi, L A; Leporini, D

    2004-01-01

    The reorientation of one small paramagnetic molecule (spin probe) in glassy polystyrene (PS) is studied by high-field electron spin resonance spectroscopy at two different Larmor frequencies (190 and 285 GHz). The exponential distribution of the energy barriers for the rotational motion of the spin probe is unambiguously evidenced at both 240 and 270 K. The same shape for the distribution of the energy barriers of PS was evidenced by the master curves provided by previous mechanical and light scattering studies. The breadth of the energy barrier distribution of the spin probe is in the range of the estimates of the breadth of the PS energy barrier distribution. The evidence that the deep structure of the energy landscape of PS exhibits the exponential shape of the energy barrier distribution agrees with the results from extreme-value statistics (Bouchaud and Mezard 1997 J. Phys. A: Math. Gen. 30 7997) and the trap model by Bouchaud and co-workers (1996 J. Phys. A: Math. Gen. 29 3847, 2001 Phys. Rev. B 64 104417). (letter to the editor)

  11. Differential patterns of hybridization and introgression between the swallowtails Papilio machaon and P. hospiton from Sardinia and Corsica islands (Lepidoptera, Papilionidae).

    Science.gov (United States)

    Cianchi, R; Ungaro, A; Marini, M; Bullini, L

    2003-06-01

    Proportions of hybridization and introgression between the swallowtails Papilio hospiton, endemic to Sardinia and Corsica, and the holarctic Papilio machaon, were characterized using nine fully diagnostic and two differentiated allozyme loci and a mitochondrial DNA marker. Very low frequencies of F1 hybrids were detected in both Sardinia (0-4%, average 1.4%) and Corsica (0-3%, average 0.5%), as well as of first generation backcrosses (B1). No F2 were observed, in agreement with the hybrid breakdown detected in laboratory crosses. In spite of this minimal current gene exchange, specimens carrying introgressed alleles were found in high proportions in P. machaon but in lower proportions in P. hospiton. Introgression apparently occurred through past hybridization and repeated backcrossing, as evidenced by hybrid index scores and Bayesian assignment tests. Levels of introgression were low (0-1%) at two sex-linked loci and mitochondrial DNA, limited (0.4-2%) at three autosomal loci coding for dimeric enzymes, and high (up to 43%) at four autosomal loci coding for monomeric enzymes. Accordingly, selective filters are acting against foreign alleles, with differential effectiveness depending on the loci involved. The low levels of introgression at sex-linked loci and mitochondrial DNA are in agreement with Haldane's rule and suggest that introgression in P. machaon proceeds mainly through males, owing to a lower fitness of hybrid females. Papilio machaon populations showed higher levels of introgression in Sardinia than in Corsica. The role of reinforcement in the present reproductive isolation between P. machaon and P. hospiton is examined, as well as the evolutionary effects of introgressive hybridization between the two species.

  12. Genetic structure of Miscanthus sinensis and M. sacchariflorus in Japan indicates a gradient of bidirectional but asymmetric introgression

    DEFF Research Database (Denmark)

    Clark, Lindsay V; Stewart, J Ryan; Nishiwaki, Aya

    2015-01-01

    Unilateral introgression from diploids to tetraploids has been hypothesized to be an important evolutionary mechanism in plants. However, few examples have been definitively identified, perhaps because data of sufficient depth and breadth were difficult to obtain before the advent of affordable h...... in northern China, selection for adaptation to a moderate maritime climate probably favoured cross-ploidy introgressants in southern Japan. These results will help guide the selection of Miscanthus accessions for the breeding of biomass cultivars....

  13. Development and bin mapping of gene-associated interspecific SNPs for cotton (Gossypium hirsutum L.) introgression breeding efforts.

    Science.gov (United States)

    Hulse-Kemp, Amanda M; Ashrafi, Hamid; Zheng, Xiuting; Wang, Fei; Hoegenauer, Kevin A; Maeda, Andrea B V; Yang, S Samuel; Stoffel, Kevin; Matvienko, Marta; Clemons, Kimberly; Udall, Joshua A; Van Deynze, Allen; Jones, Don C; Stelly, David M

    2014-10-30

    Cotton (Gossypium spp.) is the largest producer of natural fibers for textile and is an important crop worldwide. Crop production is comprised primarily of G. hirsutum L., an allotetraploid. However, elite cultivars express very small amounts of variation due to the species monophyletic origin, domestication and further bottlenecks due to selection. Conversely, wild cotton species harbor extensive genetic diversity of prospective utility to improve many beneficial agronomic traits, fiber characteristics, and resistance to disease and drought. Introgression of traits from wild species can provide a natural way to incorporate advantageous traits through breeding to generate higher-producing cotton cultivars and more sustainable production systems. Interspecific introgression efforts by conventional methods are very time-consuming and costly, but can be expedited using marker-assisted selection. Using transcriptome sequencing we have developed the first gene-associated single nucleotide polymorphism (SNP) markers for wild cotton species G. tomentosum, G. mustelinum, G. armourianum and G. longicalyx. Markers were also developed for a secondary cultivated species G. barbadense cv. 3-79. A total of 62,832 non-redundant SNP markers were developed from the five wild species which can be utilized for interspecific germplasm introgression into cultivated G. hirsutum and are directly associated with genes. Over 500 of the G. barbadense markers have been validated by whole-genome radiation hybrid mapping. Overall 1,060 SNPs from the five different species have been screened and shown to produce acceptable genotyping assays. This large set of 62,832 SNPs relative to cultivated G. hirsutum will allow for the first high-density mapping of genes from five wild species that affect traits of interest, including beneficial agronomic and fiber characteristics. Upon mapping, the markers can be utilized for marker-assisted introgression of new germplasm into cultivated cotton and in

  14. Introgression between ecologically distinct species following increased salinity in the Colorado Delta- Worldwide implications for impacted estuary diversity

    OpenAIRE

    Lau, Clive L.F.; Jacobs, David K.

    2017-01-01

    We investigate hybridization and introgression between ecologically distinct sister species of silverside fish in the Gulf of California through combined analysis of morphological, sequence, and genotypic data. Water diversions in the past century turned the Colorado River Delta from a normal estuary to a hypersaline inverse estuary, raising concerns for the local fauna, much of which is endangered. Salinity differences are known to generate ecological species pairs and we anticipated that lo...

  15. Introgression of domesticated alleles into a wild trout genotype and the impact on seasonal survival in natural lakes

    OpenAIRE

    Vandersteen, Wendy; Biro, Pete; Harris, Les; Devlin, Robert

    2011-01-01

    We tested the fitness consequences of introgression of fast-growing domesticated fish into a wild population. Fry from wild and domesticated rainbow trout (Oncorhynchus mykiss) crosses, F1 hybrids, and first- and second-generation backcrosses were released into two natural lakes. Parentage analysis using microsatellite loci facilitated the identification of survivors, so fitness was estimated in nature from the first-feeding stage. Results indicated that under certain conditions, domesticated...

  16. Alien DNA introgression and wheat DNA rearrangements in a stable wheat line derived from the early generation of distant hybridization.

    Science.gov (United States)

    Zhang, Lianquan; Liu, Dengcai; Yan, Zehong; Zheng, Youliang

    2005-10-01

    Polyploidy has been found to be common in plants. Bread or common wheat (Triticum aestivum L., 2n=42) is a good example of allopolyploid made up of three diploid genomes A, B and D. In recent years, by the study of mimicking the origination of common wheat, it was found that changes of DNA sequence and gene expression occurred at the early stages of artificial allohexaploid between tetraploid wheat and Aegilops tauschii, which was probably favorable to genetic diploidization of new synthetic hexaploid wheat. Common wheat 99L2 is a new line stable in genetic, which was derived from the early self-pollinated generation of wide hybrids between common wheat and rye. In this study, it was found that at least two rye DNA segments had been introgressed into 99L2. This result suggested that a mechanism of alien DNA introgression may exist, which was different from the traditional mechanism of chromosome pairing and DNA recombination between wheat and alien species. Meanwhile, during the introgression process of alien rye DNA segments, the changes in DNA sequences of wheat itself occurred.

  17. Crop to wild introgression in lettuce: following the fate of crop genome segments in backcross populations

    Directory of Open Access Journals (Sweden)

    Uwimana Brigitte

    2012-03-01

    Full Text Available Abstract Background After crop-wild hybridization, some of the crop genomic segments may become established in wild populations through selfing of the hybrids or through backcrosses to the wild parent. This constitutes a possible route through which crop (transgenes could become established in natural populations. The likelihood of introgression of transgenes will not only be determined by fitness effects from the transgene itself but also by the crop genes linked to it. Although lettuce is generally regarded as self-pollinating, outbreeding does occur at a low frequency. Backcrossing to wild lettuce is a likely pathway to introgression along with selfing, due to the high frequency of wild individuals relative to the rarely occurring crop-wild hybrids. To test the effect of backcrossing on the vigour of inter-specific hybrids, Lactuca serriola, the closest wild relative of cultivated lettuce, was crossed with L. sativa and the F1 hybrid was backcrossed to L. serriola to generate BC1 and BC2 populations. Experiments were conducted on progeny from selfed plants of the backcrossing families (BC1S1 and BC2S1. Plant vigour of these two backcrossing populations was determined in the greenhouse under non-stress and abiotic stress conditions (salinity, drought, and nutrient deficiency. Results Despite the decreasing contribution of crop genomic blocks in the backcross populations, the BC1S1 and BC2S1 hybrids were characterized by a substantial genetic variation under both non-stress and stress conditions. Hybrids were identified that performed equally or better than the wild genotypes, indicating that two backcrossing events did not eliminate the effect of the crop genomic segments that contributed to the vigour of the BC1 and BC2 hybrids. QTLs for plant vigour under non-stress and the various stress conditions were detected in the two populations with positive as well as negative effects from the crop. Conclusion As it was shown that the crop

  18. [Development and study of spring bread wheat variety Pamyati Maystrenko with introgression of genetic material from synthetic hexaploid Triticum timopheevii zhuk. x Aegilops tauschii Coss].

    Science.gov (United States)

    Laikova, L I; Belan, I A; Badaeva, E D; Posseeva, L P; Shepelev, S S; Shumny, V K; Pershina, L A

    2013-01-01

    Synthetic hexaploids are bridges for transferring new genes that determine resistance to stress factors from wild-type species to bread wheat. In the present work, the method of developing the spring bread wheat variety Pamyati Maystrenko and the results of its study are described. This variety was obtained using one of the immune lines produced earlier via the hybridization of the spring bread wheat variety Saratovskaya 29 with the synthetic hexaploid T. timopheevii Zhuk. x Ae. tauschii Coss. The C-staining of chromosomes in the Pamyati Maystrenko variety revealed substitutions of 2B and 6B chromosomes by the homeologous chromosomes of the G genome of T. timopheevii and the substitution of chromosome 1D by an orthologous chromosome ofAe. tauschii. It was found that this variety is characterized by resistance to leaf and stem rust, powdery mildew, and loose smut as well as by high grain and bread-making qualities. The role of the alien genetic material introgressed into the bread-wheat genome in the expression of adaptive and economically valuable traits in the Pamyati Maystrenko variety is discussed.

  19. Development of an iron-enriched high-yieldings indica rice cultivar by introgression of a high-iron trait from transgenic iron-biofortified rice.

    Science.gov (United States)

    Paul, Soumitra; Ali, Nusrat; Datta, Swapan K; Datta, Karabi

    2014-09-01

    Low level of iron in staple food crops is one reason for the predominance of iron-deficiency anemia in developing countries. Most of the iron in rice grains accumulates in the outer aleurone layer and embryo, which are removed during milling, and the edible endosperm contains very low amounts of iron. In an effort to increase iron nutrition, we report here the transgene introgression of a high-iron trait into a high-yielding indica rice cultivar. The ferritin gene from soybean (soyfer1) was introduced into rice plants through interbreeding between soybean ferritin-overexpressing transgenic IR68144 and the high-yielding cultivar Swarna. The stable integration of the soyfer1 gene was confirmed in the BC2F4 generation, and the hybrid seeds showed 2.6-fold soybean ferritin gene expression over the recurrent parent Swarna. The hybrid milled seeds revealed a 2.54-fold increase in iron and 1.54-fold increase in zinc compared to Swarna. Agronomic data and an SSR marker analysis of the hybrid rice plants were taken into account for NIL character identification.

  20. Mitochondrial introgression via ancient hybridization, and systematics of the Australian endemic pygopodid gecko genus Delma.

    Science.gov (United States)

    Brennan, Ian G; Bauer, Aaron M; Jackman, Todd R

    2016-01-01

    Of the more than 1500 species of geckos found across six continents, few remain as unfamiliar as the pygopodids - Family Pygopodidae (Gray, 1845). These gekkotans are limited to Australia (44 species) and New Guinea (2 species), but have diverged extensively into the most ecologically diverse limbless radiation save Serpentes. Current phylogenetic understanding of the family has relied almost exclusively on two works, which have produced and synthesized an immense amount of morphological, geographical, and molecular data. However, current interspecific relationships within the largest genus Delma Gray 1831 are based chiefly upon data from two mitochondrial loci (16s, ND2). Here, we reevaluate the interspecific relationships within the genus Delma using two mitochondrial and four nuclear loci (RAG1, MXRA5, MOS, DYNLL1), and identify points of strong conflict between nuclear and mitochondrial genomic data. We address mito-nuclear discordance, and remedy this conflict by recognizing several points of mitochondrial introgression as the result of ancient hybridization events. Owing to the legacy value and intraspecific informativeness, we suggest the continued use of ND2 as a phylogenetic marker. Results identify strong support for species groups, but relationships among these clades, and the placement of several enigmatic taxa remain uncertain. We suggest a more careful review of Delma australis and the 'northwest Australia' clade. Accurately assessing and addressing species richness and relationships within this endemic Australian Gekkotan genus is relevant for understanding patterns of squamate speciation across the region. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. New insight into hybridization and unidirectional introgression between Ammodytes japonicus and Ammodytes heian (Trachiniformes, Ammodytidae).

    Science.gov (United States)

    Kim, Jin-Koo; Bae, Seung Eun; Lee, Soo Jeong; Yoon, Moon Geun

    2017-01-01

    Based on northern (NOL) and southern (SOL) mitochondrial lineages, recently, it proposed the new species Ammodytes heian and revived the species name Ammodytes japonicus to describe sand lances from the northwestern Pacific Ocean. This study used molecular methods to investigate genetic relationships between the two sand lance species in Korea and Japan. In total, 154 specimens were collected from four locations in Korea (Baengnyeongdo in the Yellow Sea, Tongyeong in the Korean Strait, and Jumunjin and Gijang in the East Sea), and 50 specimens were collected from a single location in Japan (Wakkanai in the Okhotsk Sea). Mitochondrial DNA analysis demonstrated that the individuals from Baengnyeongdo and Tongyeong all belonged to the SOL, whereas those from Gijang, Jumunjin, and Wakkanai included individuals from both the NOL and SOL (over 75% NOL). Population structure analyses were performed on the same individuals using seven microsatellite DNA markers. The population structure analysis based on 201 specimens identified two clusters (named as northern group and southern group), with the admixture proportion (q) of hybridization and unidirectional introgression from SOL to NOL occurs in southwestern margin of the East Sea. Our findings illustrate the speciation process based on different patterns of gene flow between Korean and Japanese sand lance, which is strongly influenced by both the paleo-climatic change and the contemporary local oceanic current pattern.

  2. Introgression of novel traits from a wild wheat relative improves drought adaptation in wheat.

    Science.gov (United States)

    Placido, Dante F; Campbell, Malachy T; Folsom, Jing J; Cui, Xinping; Kruger, Greg R; Baenziger, P Stephen; Walia, Harkamal

    2013-04-01

    Root architecture traits are an important component for improving water stress adaptation. However, selection for aboveground traits under favorable environments in modern cultivars may have led to an inadvertent loss of genes and novel alleles beneficial for adapting to environments with limited water. In this study, we elucidate the physiological and molecular consequences of introgressing an alien chromosome segment (7DL) from a wild wheat relative species (Agropyron elongatum) into cultivated wheat (Triticum aestivum). The wheat translocation line had improved water stress adaptation and higher root and shoot biomass compared with the control genotypes, which showed significant drops in root and shoot biomass during stress. Enhanced access to water due to higher root biomass enabled the translocation line to maintain more favorable gas-exchange and carbon assimilation levels relative to the wild-type wheat genotypes during water stress. Transcriptome analysis identified candidate genes associated with root development. Two of these candidate genes mapped to the site of translocation on chromosome 7DL based on single-feature polymorphism analysis. A brassinosteroid signaling pathway was predicted to be involved in the novel root responses observed in the A. elongatum translocation line, based on the coexpression-based gene network generated by seeding the network with the candidate genes. We present an effective and highly integrated approach that combines root phenotyping, whole-plant physiology, and functional genomics to discover novel root traits and the underlying genes from a wild related species to improve drought adaptation in cultivated wheat.

  3. Role of cytoplasm-specific introgression in the evolution of the polyploid wheats

    Science.gov (United States)

    Gill, Bikram S.; Chen, P. D.

    1987-01-01

    Studies of N-banded mitotic and meiotic karyotypes of Triticum turgidum L. (2n = 28; AABB) and Triticum timopheevii Zhuk. (2n = 28; AAGG) and hybrids between them, along with observations of meiotic pairing between telocentrics of the AB-genome chromosomes and their respective homologues and homeologues in T. timopheevii, showed that chromosome 4 (m4) of Triticum monococcum L. is present (as 4At) in T. timopheevii but is lacking in T. turgidum. Neither 4A nor 4B pairs with 4At, but 4A pairs with 4G and, for this reason and because of its banding pattern, must be considered a B-genome chromosome. T. timopheevii chromosomes 4At and 3At are involved in a reciprocal translocation, and 2At, 1G, 2G, and 5G are also involved in translocations. Chromosome arm 4BL occasionally pairs with 7G. The satellites are on the short arms of chromosomes 6At and 6G of T. timopheevii and 1B and 6B of T. turgidum. It is suggested that (i) T. timopheevii orginated as an allotetraploid of Aegilops speltoides Tausch/T. monococcum and (ii) T. turgidum was derived from T. timopheevii by introgressive hybridization with an unknown diploid species, which contributed its distinctive cytoplasm, chromosome 4B or a substantial portion of it, and additional chromosome segments. Rapid fixation of 4B in T. turgidum was ensured by cytoplasm-specific transmission. Images PMID:16578821

  4. Genetic Analysis of Kernel Traits in Maize-Teosinte Introgression Populations

    Directory of Open Access Journals (Sweden)

    Zhengbin Liu

    2016-08-01

    Full Text Available Seed traits have been targeted by human selection during the domestication of crop species as a way to increase the caloric and nutritional content of food during the transition from hunter-gather to early farming societies. The primary seed trait under selection was likely seed size/weight as it is most directly related to overall grain yield. Additional seed traits involved in seed shape may have also contributed to larger grain. Maize (Zea mays ssp. mays kernel weight has increased more than 10-fold in the 9000 years since domestication from its wild ancestor, teosinte (Z. mays ssp. parviglumis. In order to study how size and shape affect kernel weight, we analyzed kernel morphometric traits in a set of 10 maize-teosinte introgression populations using digital imaging software. We identified quantitative trait loci (QTL for kernel area and length with moderate allelic effects that colocalize with kernel weight QTL. Several genomic regions with strong effects during maize domestication were detected, and a genetic framework for kernel traits was characterized by complex pleiotropic interactions. Our results both confirm prior reports of kernel domestication loci and identify previously uncharacterized QTL with a range of allelic effects, enabling future research into the genetic basis of these traits.

  5. Genomics and introgression: discovery and mapping of thousands of species-diagnostic SNPs using RAD sequencing

    Science.gov (United States)

    Hand, Brian K.; Hether, Tyler D; Kovach, Ryan P.; Muhlfeld, Clint C.; Amish, Stephen J.; Boyer, Matthew C.; O’Rourke, Sean M.; Miller, Michael R.; Lowe, Winsor H.; Hohenlohe, Paul A.; Luikart, Gordon

    2015-01-01

    Invasive hybridization and introgression pose a serious threat to the persistence of many native species. Understanding the effects of hybridization on native populations (e.g., fitness consequences) requires numerous species-diagnostic loci distributed genome-wide. Here we used RAD sequencing to discover thousands of single-nucleotide polymorphisms (SNPs) that are diagnostic between rainbow trout (RBT, Oncorhynchus mykiss), the world’s most widely introduced fish, and native westslope cutthroat trout (WCT, O. clarkii lewisi) in the northern Rocky Mountains, USA. We advanced previous work that identified 4,914 species-diagnostic loci by using longer sequence reads (100 bp vs. 60 bp) and a larger set of individuals (n = 84). We sequenced RAD libraries for individuals from diverse sampling sources, including native populations of WCT and hatchery broodstocks of WCT and RBT. We also took advantage of a newly released reference genome assembly for RBT to align our RAD loci. In total, we discovered 16,788 putatively diagnostic SNPs, 10,267 of which we mapped to anchored chromosome locations on the RBT genome. A small portion of previously discovered putative diagnostic loci (325 of 4,914) were no longer diagnostic (i.e., fixed between species) based on our wider survey of non-hybridized RBT and WCT individuals. Our study suggests that RAD loci mapped to a draft genome assembly could provide the marker density required to identify genes and chromosomal regions influencing selection in admixed populations of conservation concern and evolutionary interest.

  6. Characterizing haploinsufficiency of SHELL gene to improve fruit form prediction in introgressive hybrids of oil palm.

    Science.gov (United States)

    Teh, Chee-Keng; Muaz, Siti Dalila; Tangaya, Praveena; Fong, Po-Yee; Ong, Ai-Ling; Mayes, Sean; Chew, Fook-Tim; Kulaveerasingam, Harikrishna; Appleton, David

    2017-06-08

    The fundamental trait in selective breeding of oil palm (Eleais guineensis Jacq.) is the shell thickness surrounding the kernel. The monogenic shell thickness is inversely correlated to mesocarp thickness, where the crude palm oil accumulates. Commercial thin-shelled tenera derived from thick-shelled dura × shell-less pisifera generally contain 30% higher oil per bunch. Two mutations, sh MPOB (M1) and sh AVROS (M2) in the SHELL gene - a type II MADS-box transcription factor mainly present in AVROS and Nigerian origins, were reported to be responsible for different fruit forms. In this study, we have tested 1,339 samples maintained in Sime Darby Plantation using both mutations. Five genotype-phenotype discrepancies and eight controls were then re-tested with all five reported mutations (sh AVROS , sh MPOB , sh MPOB2 , sh MPOB3 and sh MPOB4 ) within the same gene. The integration of genotypic data, pedigree records and shell formation model further explained the haploinsufficiency effect on the SHELL gene with different number of functional copies. Some rare mutations were also identified, suggesting a need to further confirm the existence of cis-compound mutations in the gene. With this, the prediction accuracy of fruit forms can be further improved, especially in introgressive hybrids of oil palm. Understanding causative variant segregation is extremely important, even for monogenic traits such as shell thickness in oil palm.

  7. Outcomes of extensive hybridization and introgression in Epidendrum (Orchidaceae: can we rely on species boundaries?

    Directory of Open Access Journals (Sweden)

    Yesenia Vega

    Full Text Available Hybridization has the potential to contribute to phenotypic and genetic variation and can be a major evolutionary mechanism. However, when hybridization is extensive it can also lead to the blurring of species boundaries and the emergence of cryptic species (i.e., two or more species not distinguishable morphologically. In this study, we address this hypothesis in Epidendrum, the largest Neotropical genus of orchids where hybridization is apparently so common that it may explain the high levels of morphological diversity found. Nonetheless, this hypothesis is mostly based on the intermediacy of morphological characters and intermediacy by itself is not a proof of hybridization. Therefore, in this study, we first assessed the existence of hybrids using cpDNA and AFLP data gathered from a large-scale sampling comprising 1038 plants of three species of Epidendrum (E. calanthum, E. cochlidium and E. schistochilum. Subsequently, a Bayesian assignment of individuals into different genetic classes (pure species, F1, F2 or backcross generations revealed that hybrid genotypes were prevalent in all sympatric populations. In most cases, parental species were not assigned as pure individuals, rather consisting in backcrossed genotypes or F1 hybrids. We also found that reproductive barriers are apparently very weak in Epidendrum because the three species largely overlapped in their flowering periods and interspecific crosses always produced viable seeds. Further, hybridization contributed to enhance floral variability, genome size and reproductive success since we found that these traits were always higher in hybrid classes (F1, F2 and backcrosses than in pure parental species, and offer an explanation for the blurring of species boundaries in this genus of orchids. We hypothesize that these natural hybrids possess an evolutionary advantage, which may explain the high rates of cryptic species observed in this genus.

  8. New insight into hybridization and unidirectional introgression between Ammodytes japonicus and Ammodytes heian (Trachiniformes, Ammodytidae.

    Directory of Open Access Journals (Sweden)

    Jin-Koo Kim

    Full Text Available Based on northern (NOL and southern (SOL mitochondrial lineages, recently, it proposed the new species Ammodytes heian and revived the species name Ammodytes japonicus to describe sand lances from the northwestern Pacific Ocean. This study used molecular methods to investigate genetic relationships between the two sand lance species in Korea and Japan. In total, 154 specimens were collected from four locations in Korea (Baengnyeongdo in the Yellow Sea, Tongyeong in the Korean Strait, and Jumunjin and Gijang in the East Sea, and 50 specimens were collected from a single location in Japan (Wakkanai in the Okhotsk Sea. Mitochondrial DNA analysis demonstrated that the individuals from Baengnyeongdo and Tongyeong all belonged to the SOL, whereas those from Gijang, Jumunjin, and Wakkanai included individuals from both the NOL and SOL (over 75% NOL. Population structure analyses were performed on the same individuals using seven microsatellite DNA markers. The population structure analysis based on 201 specimens identified two clusters (named as northern group and southern group, with the admixture proportion (q of < 0.1 for the northern group in the Backyeongdo and Tongyeong sand lances and < 0.1 for the southern group in the Wakkanai sand lances. The high heterogeneity indicated that the former was probably A. japonicus and the latter probably A. heian. However, the admixture proportion in the Jumunjin and Gijang sand lances was 0.71-0.75 for the southern group, indicating that hybridization and unidirectional introgression from SOL to NOL occurs in southwestern margin of the East Sea. Our findings illustrate the speciation process based on different patterns of gene flow between Korean and Japanese sand lance, which is strongly influenced by both the paleo-climatic change and the contemporary local oceanic current pattern.

  9. Evidence for hybridization and introgression within a species-rich oak (Quercus spp. community

    Directory of Open Access Journals (Sweden)

    Finkeldey Reiner

    2007-11-01

    Full Text Available Abstract Background Analysis of interspecific gene flow is crucial for the understanding of speciation processes and maintenance of species integrity. Oaks (genus Quercus, Fagaceae are among the model species for the study of hybridization. Natural co-occurrence of four closely related oak species is a very rare case in the temperate forests of Europe. We used both morphological characters and genetic markers to characterize hybridization in a natural community situated in west-central Romania and which consists of Quercus robur, Q. petraea, Q. pubescens, and Q. frainetto, respectively. Results On the basis of pubescence and leaf morphological characters ~94% of the sampled individuals were assigned to pure species. Only 16 (~6% individual trees exhibited intermediate morphologies or a combination of characters of different species. Four chloroplast DNA haplotypes were identified in the study area. The distribution of haplotypes within the white oak complex showed substantial differences among species. However, the most common haplotypes were present in all four species. Furthermore, based on a set of 7 isozyme and 6 microsatellite markers and using a Bayesian admixture analysis without any a priori information on morphology we found that four genetic clusters best fit the data. There was a very good correspondence of each species with one of the inferred genetic clusters. The estimated introgression level varied markedly between pairs of species ranging from 1.7% between Q. robur and Q. frainetto to 16.2% between Q. pubescens and Q. frainetto. Only nine individuals (3.4% appeared to be first-generation hybrids. Conclusion Our data indicate that natural hybridization has occurred at relatively low rates. The different levels of gene flow among species might be explained by differences in flowering time and spatial position within the stand. In addition, a partial congruence between phenotypically and genetically intermediate individuals was

  10. EPAS1 variants in high altitude Tibetan wolves were selectively introgressed into highland dogs

    Directory of Open Access Journals (Sweden)

    Bridgett vonHoldt

    2017-07-01

    Full Text Available Background Admixture can facilitate adaptation. For example, black wolves have obtained the variant causing black coat color through past hybridization with domestic dogs and have higher fitness than gray colored wolves. Another recent example of the transfer of adaptive variation between the two species has been suggested by the similarity between high altitude Tibetan mastiffs and wolves at the EPAS1 gene, a transcription factor induced in low oxygen environments. Methods Here, we investigate the directionality of admixture in EPAS1 between 28 reference highland gray wolves, 15 reference domestic dogs, and 21 putatively admixed highland wolves. This experimental design represents an expanded sample of Asian dogs and wolves from previous studies. Admixture was inferred using 17,709 publicly available SNP genotypes on canine chromosome 10. We additionally conducted a scan for positive selection in the highland dog genome. Results We find an excess of highland gray wolf ancestry at the EPAS1 locus in highland domestic dogs, suggesting adaptive introgression from wolves to dogs. The signal of admixture is limited in genomic extent to a small region on chromosome 10, indicating that it is the focus of selection in an oxygen-limited environment. Discussion Our results suggest that an adaptive variant of EPAS1 in highland wolves was transferred to highland dogs, carrying linked variants that potentially function in hypoxia response at high elevation. The intertwined history of dogs and wolves ensures a unique evolutionary dynamic where variants that have appeared in the history of either species can be tested for their effects on fitness under natural and artificial selection. Such coupled evolutionary histories may be key to the persistence of wild canines and their domesticated kin given the increasing anthropogenic modifications that characterize the future of both species.

  11. Reduced SNP panels for genetic identification and introgression analysis in the dark honey bee (Apis mellifera mellifera.

    Directory of Open Access Journals (Sweden)

    Irene Muñoz

    Full Text Available Beekeeping activities, especially queen trading, have shaped the distribution of honey bee (Apis mellifera subspecies in Europe, and have resulted in extensive introductions of two eastern European C-lineage subspecies (A. m. ligustica and A. m. carnica into the native range of the M-lineage A. m. mellifera subspecies in Western Europe. As a consequence, replacement and gene flow between native and commercial populations have occurred at varying levels across western European populations. Genetic identification and introgression analysis using molecular markers is an important tool for management and conservation of honey bee subspecies. Previous studies have monitored introgression by using microsatellite, PCR-RFLP markers and most recently, high density assays using single nucleotide polymorphism (SNP markers. While the latter are almost prohibitively expensive, the information gained to date can be exploited to create a reduced panel containing the most ancestry-informative markers (AIMs for those purposes with very little loss of information. The objective of this study was to design reduced panels of AIMs to verify the origin of A. m. mellifera individuals and to provide accurate estimates of the level of C-lineage introgression into their genome. The discriminant power of the SNPs using a variety of metrics and approaches including the Weir & Cockerham's FST, an FST-based outlier test, Delta, informativeness (In, and PCA was evaluated. This study shows that reduced AIMs panels assign individuals to the correct origin and calculates the admixture level with a high degree of accuracy. These panels provide an essential tool in Europe for genetic stock identification and estimation of admixture levels which can assist management strategies and monitor honey bee conservation programs.

  12. Enhanced Bacterial Wilt Resistance in Potato Through Expression of Arabidopsis EFR and Introgression of Quantitative Resistance from Solanum commersonii.

    Science.gov (United States)

    Boschi, Federico; Schvartzman, Claudia; Murchio, Sara; Ferreira, Virginia; Siri, Maria I; Galván, Guillermo A; Smoker, Matthew; Stransfeld, Lena; Zipfel, Cyril; Vilaró, Francisco L; Dalla-Rizza, Marco

    2017-01-01

    Bacterial wilt (BW) caused by Ralstonia solanacearum is responsible for substantial losses in cultivated potato ( Solanum tuberosum ) crops worldwide. Resistance genes have been identified in wild species; however, introduction of these through classical breeding has achieved only partial resistance, which has been linked to poor agronomic performance. The Arabidopsis thaliana (At) pattern recognition receptor elongation factor-Tu (EF-Tu) receptor (EFR) recognizes the bacterial pathogen-associated molecular pattern EF-Tu (and its derived peptide elf18) to confer anti-bacterial immunity. Previous work has shown that transfer of AtEFR into tomato confers increased resistance to R. solanacearum . Here, we evaluated whether the transgenic expression of AtEFR would similarly increase BW resistance in a commercial potato line (INIA Iporá), as well as in a breeding potato line (09509.6) in which quantitative resistance has been introgressed from the wild potato relative Solanum commersonii. Resistance to R. solanacearum was evaluated by damaged root inoculation under controlled conditions. Both INIA Iporá and 09509.6 potato lines expressing AtEFR showed greater resistance to R. solanacearum , with no detectable bacteria in tubers evaluated by multiplex-PCR and plate counting. Notably, AtEFR expression and the introgression of quantitative resistance from S. commersonii had a significant additive effect in 09509.6-AtEFR lines. These results show that the combination of heterologous expression of AtEFR with quantitative resistance introgressed from wild relatives is a promising strategy to develop BW resistance in potato.

  13. Enhanced Bacterial Wilt Resistance in Potato Through Expression of Arabidopsis EFR and Introgression of Quantitative Resistance from Solanum commersonii

    Directory of Open Access Journals (Sweden)

    Federico Boschi

    2017-09-01

    Full Text Available Bacterial wilt (BW caused by Ralstonia solanacearum is responsible for substantial losses in cultivated potato (Solanum tuberosum crops worldwide. Resistance genes have been identified in wild species; however, introduction of these through classical breeding has achieved only partial resistance, which has been linked to poor agronomic performance. The Arabidopsis thaliana (At pattern recognition receptor elongation factor-Tu (EF-Tu receptor (EFR recognizes the bacterial pathogen-associated molecular pattern EF-Tu (and its derived peptide elf18 to confer anti-bacterial immunity. Previous work has shown that transfer of AtEFR into tomato confers increased resistance to R. solanacearum. Here, we evaluated whether the transgenic expression of AtEFR would similarly increase BW resistance in a commercial potato line (INIA Iporá, as well as in a breeding potato line (09509.6 in which quantitative resistance has been introgressed from the wild potato relative Solanum commersonii. Resistance to R. solanacearum was evaluated by damaged root inoculation under controlled conditions. Both INIA Iporá and 09509.6 potato lines expressing AtEFR showed greater resistance to R. solanacearum, with no detectable bacteria in tubers evaluated by multiplex-PCR and plate counting. Notably, AtEFR expression and the introgression of quantitative resistance from S. commersonii had a significant additive effect in 09509.6-AtEFR lines. These results show that the combination of heterologous expression of AtEFR with quantitative resistance introgressed from wild relatives is a promising strategy to develop BW resistance in potato.

  14. Evidence that the adaptive allele of the brain size gene microcephalin introgressed into Homo sapiens from an archaic Homo lineage.

    Science.gov (United States)

    Evans, Patrick D; Mekel-Bobrov, Nitzan; Vallender, Eric J; Hudson, Richard R; Lahn, Bruce T

    2006-11-28

    At the center of the debate on the emergence of modern humans and their spread throughout the globe is the question of whether archaic Homo lineages contributed to the modern human gene pool, and more importantly, whether such contributions impacted the evolutionary adaptation of our species. A major obstacle to answering this question is that low levels of admixture with archaic lineages are not expected to leave extensive traces in the modern human gene pool because of genetic drift. Loci that have undergone strong positive selection, however, offer a unique opportunity to identify low-level admixture with archaic lineages, provided that the introgressed archaic allele has risen to high frequency under positive selection. The gene microcephalin (MCPH1) regulates brain size during development and has experienced positive selection in the lineage leading to Homo sapiens. Within modern humans, a group of closely related haplotypes at this locus, known as haplogroup D, rose from a single copy approximately 37,000 years ago and swept to exceptionally high frequency (approximately 70% worldwide today) because of positive selection. Here, we examine the origin of haplogroup D. By using the interhaplogroup divergence test, we show that haplogroup D likely originated from a lineage separated from modern humans approximately 1.1 million years ago and introgressed into humans by approximately 37,000 years ago. This finding supports the possibility of admixture between modern humans and archaic Homo populations (Neanderthals being one possibility). Furthermore, it buttresses the important notion that, through such adminture, our species has benefited evolutionarily by gaining new advantageous alleles. The interhaplogroup divergence test developed here may be broadly applicable to the detection of introgression at other loci in the human genome or in genomes of other species.

  15. Dissimilarity of contemporary and historical gene flow in a wild carrot (Daucus carota) metapopulation under contrasting levels of human disturbance: implications for risk assessment and management of transgene introgression

    NARCIS (Netherlands)

    Rong, J.; Xu, S.; Meirmans, P.G.; Vrieling, K

    2013-01-01

    Background and Aims Transgene introgression from crops into wild relatives may increase the resistance of wild plants to herbicides, insects, etc. The chance of transgene introgression depends not only on the rate of hybridization and the establishment of hybrids in local wild populations, but also

  16. Smart parking barrier

    KAUST Repository

    Alharbi, Abdulrazaq M.

    2016-05-06

    Various methods and systems are provided for smart parking barriers. In one example, among others, a smart parking barrier system includes a movable parking barrier located at one end of a parking space, a barrier drive configured to control positioning of the movable parking barrier, and a parking controller configured to initiate movement of the parking barrier, via the barrier drive. The movable parking barrier can be positioned between a first position that restricts access to the parking space and a second position that allows access to the parking space. The parking controller can initiate movement of the movable parking barrier in response to a positive identification of an individual allowed to use the parking space. The parking controller can identify the individual through, e.g., a RFID tag, a mobile device (e.g., a remote control, smartphone, tablet, etc.), an access card, biometric information, or other appropriate identifier.

  17. Introgression between oilseed rape (¤Brassica napus¤ L.) and its weedy relative B-rapa L. in a natural population

    DEFF Research Database (Denmark)

    Hansen, L.B.; Siegismund, H.R.; Bagger Jørgensen, Rikke

    2001-01-01

    We investigated introgression in a mixed weedy population ofoilseed rape (Brassica napus) and itsrelative B. rapa usingspecies-specific AFLP-markers. The population wassituated in a field relayed from conventional to organic cultivation11 years ago. One-hundred-and-twoB. napus orB. rapa-like plan...... history of the field, thissuggests that the introgression process in the weedy mixed populationhas been in progress for some time. This study is the first to showintrogression between B.napus and B.rapa under natural conditions....

  18. Introgression of genetic material from Zea mays ssp. Mexicana into cultivated maize was facilitated by tissue culture

    International Nuclear Information System (INIS)

    Wang, L.; Gu, X.; Qu, M.; Luan, J.; Zhang, J.

    2012-01-01

    Zea mays ssp. mexicana, a wild relative of cultivated maize (Z. mays ssp. mays), is a useful gene resource for maize breeding. In this study, two populations were generated by conventional breeding scheme (population I) or tissue culture regime (population II), respectively, to introgress genetic material of Z. mays ssp. mexicana into maize. Karyotype analysis showed that the arm ratios of 10 pairs of chromosomes in parent maize Ye515 and derivative lines from 2 different populations with 26% and 38% chromosome variation frequencies, respectively. Alien chromatin was detected in the root tip cells of progeny plants through genomic in situ hybridization (GISH). There were 3.3 chromosomes carrying alien chromatin on average in population I and 6.5 in population II. The hybridization signals were located mainly at the terminal or sub terminal regions of the chromosomes and the sizes were notably variant among lines. Based on those results, it is concluded that the introgression of genetic material from Z. mays ssp. mexicana into cultivated maize was facilitated by tissue culture, and subsequently some excellent materials for maize breeding were created. (author)

  19. Spread of introgressed insect-resistance genes in wild populations of Brassica juncea: a simulated in-vivo approach.

    Science.gov (United States)

    Liu, Yongbo; Wei, Wei; Ma, Keping; Darmency, Henri

    2013-08-01

    Introgression between transgenic, insect-resistant crops and their wild relatives could lead to a progressive increase of the frequency of resistant plants in wild populations. However, few studies help predict the impact on the population dynamics. To simulate the performance of introgressed insect-resistant plants of wild Brassica juncea, independently from the interspecific hybridization cost, healthy plants were cultivated in pure and mixed stands with damaged plants through cutting leaves in field experiments over two field seasons. As expected, resistant (healthy) plants held a competitive advantage when in competition with susceptible (damaged) plants. Individual biomass and seed production of both types of plants decreased as the percentage of resistant plants increased, so that the relative advantage of resistant plants increased. The combined effects of defoliation and competition on the individual performance of B. juncea were additive. Replacement series experiments confirmed this trend but did not show different seed output in pure stand of susceptible versus resistant plots. The total vegetative and reproductive production of mixed populations was not significantly different of that of pure populations. These results suggest that if a transgene for insect-resistance were to colonize wild populations, high herbivory of susceptible plant and low resource availability would facilitate the spread of resistant individuals. However, at the population level, the shift from an insect-susceptible to a predominantly resistant population would not result in exacerbated habitat colonization.

  20. Interspecific Hybridization in Pilot Whales and Asymmetric Genetic Introgression in Northern Globicephala melas under the Scenario of Global Warming.

    Science.gov (United States)

    Miralles, Laura; Oremus, Marc; Silva, Mónica A; Planes, Serge; Garcia-Vazquez, Eva

    2016-01-01

    Pilot whales are two cetacean species (Globicephala melas and G. macrorhynchus) whose distributions are correlated with water temperature and partially overlap in some areas like the North Atlantic Ocean. In the context of global warming, distribution range shifts are expected to occur in species affected by temperature. Consequently, a northward displacement of the tropical pilot whale G. macrorynchus is expected, eventually leading to increased secondary contact areas and opportunities for interspecific hybridization. Here, we describe genetic evidences of recurrent hybridization between pilot whales in northeast Atlantic Ocean. Based on mitochondrial DNA sequences and microsatellite loci, asymmetric introgression of G. macrorhynchus genes into G. melas was observed. For the latter species, a significant correlation was found between historical population growth rate estimates and paleotemperature oscillations. Introgressive hybridization, current temperature increases and lower genetic variation in G. melas suggest that this species could be at risk in its northern range. Under increasing environmental and human-mediated stressors in the North Atlantic Ocean, it seems recommendable to develop a conservation program for G. melas.

  1. Heritability and genetic advance studies for biochemical traits in F2-3 introgressed families of Brassica

    International Nuclear Information System (INIS)

    Farhatullah, N.K.; Khalil, I.H.; Nahed, H.

    2015-01-01

    Higher heritability estimates along with high genetic advance values are effective in envisaging gain under selection in developing genotypes. The objective of the present study was to evaluate variability, heritability and genetic advance in 10 interspecific F2-3 families of Brassica species (B. napus * B. juncea, B. napus * B. rapa). These families were studied for heterospecific introgression of biochemical traits. Low to high heritability estimates were recorded for seed quality traits. Considerable variations within F2-3 families were observed for biochemical traits. Most of the F2-3 families for oil content and erucic showed moderate to high heritability indicating the slightest influence of environment thus modification of trait by selection would be more effective. Among F2-3 introgressed families Bn-510 x Bj-109 produced high oil i.e., 49.5% while Bn-532 x Br-118 (24.4%), Bn-533 x Bj-109 (24.1%) and high protein percentage in terms of mean performance. In the present research, individual segregating progenies of interspecific cross populations i.e., which possessed combination of desirable traits, were identified which could be incorporated in the future Breeding programs and it may facilitate varietal development. (author)

  2. Uncovering tomato quantitative trait loci and candidate genes for fruit cuticular lipid composition using the Solanum pennellii introgression line population.

    Science.gov (United States)

    Fernandez-Moreno, Josefina-Patricia; Levy-Samoha, Dorit; Malitsky, Sergey; Monforte, Antonio J; Orzaez, Diego; Aharoni, Asaph; Granell, Antonio

    2017-05-17

    The cuticle is a specialized cell wall layer that covers the outermost surface of the epidermal cells and has important implications for fruit permeability and pathogen susceptibility. In order to decipher the genetic control of tomato fruit cuticle composition, an introgression line (IL) population derived from a biparental cross between Solanum pennellii (LA0716) and the Solanum lycopersicum cultivar M82 was used to build a first map of associated quantitative trait loci (QTLs). A total of 24 cuticular waxes and 26 cutin monomers were determined. They showed changes associated with 18 genomic regions distributed in nine chromosomes affecting 19 ILs. Out of the five main fruit cuticular components described for the wild species S. pennellii, three of them were associated with IL3.4, IL12.1, and IL7.4.1, causing an increase in n-alkanes (≥C30), a decrease in amyrin content, and a decrease in cuticle thickness of ~50%, respectively. Moreover, we also found a QTL associated with increased levels of amyrins in IL3.4. In addition, we propose some candidate genes on the basis of their differential gene expression and single nucleotide polymorphism variability between the introgressed and the recurrent alleles, which will be the subjects of further investigation. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  3. SNP-markers in Allium species to facilitate introgression breeding in onion.

    Science.gov (United States)

    Scholten, Olga E; van Kaauwen, Martijn P W; Shahin, Arwa; Hendrickx, Patrick M; Keizer, L C Paul; Burger, Karin; van Heusden, Adriaan W; van der Linden, C Gerard; Vosman, Ben

    2016-08-31

    Within onion, Allium cepa L., the availability of disease resistance is limited. The identification of sources of resistance in related species, such as Allium roylei and Allium fistulosum, was a first step towards the improvement of onion cultivars by breeding. SNP markers linked to resistance and polymorphic between these related species and onion cultivars are a valuable tool to efficiently introgress disease resistance genes. In this paper we describe the identification and validation of SNP markers valuable for onion breeding. Transcriptome sequencing resulted in 192 million RNA seq reads from the interspecific F1 hybrid between A. roylei and A. fistulosum (RF) and nine onion cultivars. After assembly, reliable SNPs were discovered in about 36 % of the contigs. For genotyping of the interspecific three-way cross population, derived from a cross between an onion cultivar and the RF (CCxRF), 1100 SNPs that are polymorphic in RF and monomorphic in the onion cultivars (RF SNPs) were selected for the development of KASP assays. A molecular linkage map based on 667 RF-SNP markers was constructed for CCxRF. In addition, KASP assays were developed for 1600 onion-SNPs (SNPs polymorphic among onion cultivars). A second linkage map was constructed for an F2 of onion x A. roylei (F2(CxR)) that consisted of 182 onion-SNPs and 119 RF-SNPs, and 76 previously mapped markers. Markers co-segregating in both the F2(CxR) and the CCxRF population were used to assign the linkage groups of RF to onion chromosomes. To validate usefulness of these SNP markers, QTL mapping was applied in the CCxRF population that segregates for resistance to Botrytis squamosa and resulted in a QTL for resistance on chromosome 6 of A. roylei. Our research has more than doubled the publicly available marker sequences of expressed onion genes and two onion-related species. It resulted in a detailed genetic map for the interspecific CCxRF population. This is the first paper that reports the detection of

  4. Toward a genome-wide approach for detecting hybrids: informative SNPs to detect introgression between domestic cats and European wildcats (Felis silvestris).

    Science.gov (United States)

    Oliveira, R; Randi, E; Mattucci, F; Kurushima, J D; Lyons, L A; Alves, P C

    2015-09-01

    Endemic gene pools have been severely endangered by human-mediated hybridization, which is posing new challenges in the conservation of several vertebrate species. The endangered European wildcat is an example of this problem, as several natural populations are suffering introgression of genes from the domestic cat. The implementation of molecular methods for detecting hybridization is crucial for supporting appropriate conservation programs on the wildcat. In this study, genetic variation at 158 single-nucleotide polymorphisms (SNPs) was analyzed in 139 domestic cats, 130 putative European wildcats and 5 captive-bred hybrids (N=274). These SNPs were variable both in wild (HE=0.107) and domestic cats (HE=0.340). Although we did not find any SNP that was private in any population, 22 SNPs were monomorphic in wildcats and pairwise FCT values revealed marked differences between domestic and wildcats, with the most divergent 35 loci providing an average FCT>0.74. The power of all the loci to accurately identify admixture events and discriminate the different hybrid categories was evaluated. Results from simulated and real genotypes show that the 158 SNPs provide successful estimates of admixture, with 100% hybrid individuals (two to three generations in the past) being correctly identified in STRUCTURE and over 92% using the NEWHYBRIDS' algorithm. None of the unclassified cats were wrongly allocated to another hybrid class. Thirty-five SNPs, showing the highest FCT values, provided the most parsimonious panel for robust inferences of parental and first generations of admixed ancestries. This approach may be used to further reconstruct the evolution of wildcat populations and, hopefully, to develop sound conservation guidelines for its legal protection in Europe.

  5. Cytological and morphological analysis of hybrids between Brassicoraphanus, and Brassica napus for introgression of clubroot resistant trait into Brassica napus L.

    Science.gov (United States)

    Zhan, Zongxiang; Nwafor, Chinedu Charles; Hou, Zhaoke; Gong, Jianfang; Zhu, Bin; Jiang, Yingfen; Zhou, Yongming; Wu, Jiangsheng; Piao, Zhongyun; Tong, Yue; Liu, Chao; Zhang, Chunyu

    2017-01-01

    Interspecific hybridization is a powerful tool for improvement of crop species, it has the potential to broaden the genetic base and create new plant forms for breeding programs. Synthetic allopolyploid is a widely-used model for the study of genetic recombination and fixed heterosis in Brassica. In Brassica napus breeding, identification and introgression of new sources of clubroot resistance trait from wild or related species into it by hybridization is a long-term crop management strategy for clubroot disease. Radish (Raphanus sativus L.) is a close relative of the Brassica and most radish accessions are immune to the clubroot disease. A synthesized allotetraploid Brassicoraphanus (RRCC, 2n = 36) between R. sativus cv. HQ-04 (2n = 18, RR) and Brassica oleracea var. alboglabra (L.H Bailey) (2n = 18, CC) proved resistant of multiple clubroot disease pathogen P. brassicae. To predict the possibility to transfer the clubroot resistance trait from the RR subgenome of allotetraploid Brassicoraphanus (RRCC, 2n = 36) into Brassica napus (AACC, 2n = 38), we analyzed the frequency of chromosome pairings in the F1 hybrids produced from a cross between B. napus cv. HS5 and the allotetraploid, characterize the genomic composition of some backcrossed progeny (BC1) using GISH, BAC-FISH and AFLP techniques. The level of intergenomic pairing between A and R genomes in the F1 hybrid was high, allosyndetic bivalents formed in 73.53% PMCs indicative of significant level of homeologous recombination between two genomes and high probability of incorporating chromosomal segments/genes from R-genome into A/C-genomes. The BC1 plants inherited variant extra R chromosomes or fragments from allotetraploid as revealed by GISH and AFLP analysis. 13.51% BC2 individuals were resistant to clubroot disease, and several resistance lines had high pollen fertility, Overall, the genetic material presented in this work represents a potential new genetic resource for practical use in breeding B. napus

  6. Safety-barrier diagrams

    DEFF Research Database (Denmark)

    Duijm, Nijs Jan

    2007-01-01

    are discussed. A simple method for quantification of safety-barrier diagrams is proposed, including situations where safety barriers depend on shared common elements. It is concluded that safety-barrier diagrams provide a useful framework for an electronic data structure that integrates information from risk...

  7. Skin barrier function

    DEFF Research Database (Denmark)

    2016-01-01

    barrier integrity, factors influencing the penetration of the skin, influence of wet work, and guidance for prevention and saving the barrier. Distinguished researchers have contributed to this book, providing a comprehensive and thorough overview of the skin barrier function. Researchers in the field...... on the subject. It covers new basic research on skin markers, including results on filaggrin and on methods for the assessment of the barrier function. Biological variation and aspects of skin barrier function restoration are discussed as well. Further sections are dedicated to clinical implications of skin...

  8. Safety- barrier diagrams

    DEFF Research Database (Denmark)

    Duijm, Nijs Jan

    2008-01-01

    trees and Bayesian networks is discussed. A simple method for quantification of safety-barrier diagrams is proposed. It is concluded that safety-barrier diagrams provide a useful framework for an electronic data structure that integrates information from risk analysis with operational safety management.......Safety-barrier diagrams and the related so-called 'bow-tie' diagrams have become popular methods in risk analysis. This paper describes the syntax and principles for constructing consistent and valid safety-barrier diagrams. The relation of safety-barrier diagrams to other methods such as fault...

  9. A genome-wide survey of hybrid incompatibility factors by the introgression of marked segments of Drosophila mauritiana chromosomes into Drosophila simulans

    Energy Technology Data Exchange (ETDEWEB)

    True, J.R.; Laurie, C.C. [Duke Univ., Durham, NC (United States); Weir, B.S. [North Carolina State Univ., Raleigh, NC (United States)

    1996-03-01

    In hybrids between Drosophila simulans and D. mauritiana, males are sterile and females are fertile, in compliance with HALDANE`s rule. The genetic basis of this phenomenon was investigated by introgression of segments of the mauritiana genome into a simulans background. A total of 87 positions throughout the mauritiana genome were marked with P-element insertions and replicate introgressions were made by repeated backcrossing to simulans for 15 generations. The fraction of hemizygous X chromosomal introgressions that are male sterile is {approximately}50% greater than the fraction of homozygous autosomal segments. This result suggests that male sterility factors have evolved at a higher rate on the X, but chromosomal differences in segment length cannot be ruled out. The fraction of homozygous autosomal introgressions that are male sterile is several times greater than the fraction that are either female sterile or inviable. This observation strongly indicates that male sterility factors have evolved more rapidly than either female sterility or inviability factors. These results, combined with previous work on these and other species, suggest that HALDANE`s rule has at least two causes: recessivity of incompatibility factors and differential accumulation of sterility factors affecting males and females. 50 refs., 4 figs., 3 tabs.

  10. Use of introgression lines to determine the ecophysiological basis for changes in water use efficiency and yield in California processing tomatoes

    Science.gov (United States)

    Felipe H. Barrios-Masias; Roger T. Chetelat; Nancy E. Grulke; Louise E. Jackson

    2014-01-01

    Field and greenhouse studies examined the effects of growth habit and chloroplast presence in leaf veins for their role in increasing agronomic water use efficiency and yields of California modern processing tomato (Solanum lycopersicum L.) cultivars. Five introgression lines (ILs), made with Solanum pennellii Cor. in the...

  11. Evidence for suppression of immunity as a driver for genomic introgressions and host range expansion in races of Albugo candida, a generalist parasite

    DEFF Research Database (Denmark)

    McMullan, Mark; Gardiner, Anastasia; Bailey, Kate

    2015-01-01

    How generalist parasites with wide host ranges can evolve is a central question in parasite evolution. Albugo candida is an obligate biotrophic parasite that consists of many physiological races that each specialize on distinct Brassicaceae host species. By analyzing genome sequence assemblies of......, Darwin's finches, sunflowers and cichlid fishes, and the implications of introgression for pathogen evolution in an agro-ecological environment....

  12. Effects of introgression on the genetic population structure of two ecologically and economically important conifer species: lodgepole pine (Pinus contorta var. latifolia) and jack pine (Pinus banksiana).

    Science.gov (United States)

    Cullingham, Catherine I; Cooke, Janice E K; Coltman, David W

    2013-10-01

    Forest trees exhibit a remarkable range of adaptations to their environment, but as a result of frequent and long-distance gene flow, populations are often only weakly differentiated. Lodgepole and jack pine hybridize in western Canada, which adds the opportunity for introgression through hybridization to contribute to population structure and (or) adaptive variation. Access to large sample size, high density SNP datasets for these species would improve our ability to resolve population structure, parameterize introgression, and separate the influence of demography from adaptation. To accomplish this, 454 transcriptome reads for lodgepole and jack pine were assembled using Newbler and MIRA, the assemblies mined for SNPs, and 1536 SNPs were selected for typing on lodgepole pine, jack pine, and their hybrids (N = 536). We identified population structure using both Bayesian clustering and discriminate analysis of principle components. Introgressed SNP loci were identified and their influence on observed population structure was assessed. We found that introgressed loci resulted in increased differentiation both within lodgepole and jack pine populations. These findings are timely given the recent mountain pine beetle population expansion in the hybrid zone, and will facilitate future studies of adaptive traits in these ecologically important species.

  13. Using chromosome introgression lines to map quantitative trait loci for photosynthesis parameters in rice (Oryza sativa L.) leaves under drought and well-watered field conditions

    NARCIS (Netherlands)

    Gu, J.; Yin, X.; Struik, P.C.; Stomph, T.J.; Wang, J.

    2012-01-01

    Photosynthesis is fundamental to biomass production, but sensitive to drought. To understand the genetics of leaf photosynthesis, especially under drought, upland rice cv. Haogelao, lowland rice cv. Shennong265, and 94 of their introgression lines (ILs) were studied at flowering and grain filling

  14. Identification, introgression, and molecular marker genetic analysis and selection of a highly effective novel oat crown rust resistance from diploid oat, Avena strigosa

    Science.gov (United States)

    A new highly effective resistance to oat crown rust (Puccinia coronata f. sp. avenae) was identified in the diploid oat Avena strigosa PI 258731 and introgressed into hexaploid cultivated oat. Young plants with this resistance show moderate susceptibility, whereas older plant tissues and adult plant...

  15. Safety-barrier diagrams

    DEFF Research Database (Denmark)

    Duijm, Nijs Jan

    2007-01-01

    Safety-barrier diagrams and the related so-called "bow-tie" diagrams have become popular methods in risk analysis. This paper describes the syntax and principles for constructing consistent and valid safety-barrier diagrams. The relation with other methods such as fault trees and Bayesian network...... analysis with operational safety management.......Safety-barrier diagrams and the related so-called "bow-tie" diagrams have become popular methods in risk analysis. This paper describes the syntax and principles for constructing consistent and valid safety-barrier diagrams. The relation with other methods such as fault trees and Bayesian networks...... are discussed. A simple method for quantification of safety-barrier diagrams is proposed, including situations where safety barriers depend on shared common elements. It is concluded that safety-barrier diagrams provide a useful framework for an electronic data structure that integrates information from risk...

  16. Molecular mapping of the novel powdery mildew resistance gene Pm36 introgressed from Triticum turgidum var. dicoccoides in durum wheat.

    Science.gov (United States)

    Blanco, Antonio; Gadaleta, A; Cenci, A; Carluccio, A V; Abdelbacki, A M M; Simeone, R

    2008-06-01

    Powdery mildew, caused by Blumeria graminis f.sp. tritici, is one of the most important wheat diseases in many regions of the world. Triticum turgidum var. dicoccoides (2n=4x=AABB), the progenitor of cultivated wheats, shows particular promises as a donor of useful genetic variation for several traits, including disease resistances. The wild emmer accession MG29896, resistant to powdery mildew, was backcrossed to the susceptible durum wheat cultivar Latino, and a set of backcross inbred lines (BC(5)F(5)) was produced. Genetic analysis of F(3) populations from two resistant introgression lines (5BIL-29 x Latino and 5BIL-42 x Latino) indicated that the powdery mildew resistance is controlled by a single dominant gene. Molecular markers and the bulked segregant analysis were used to characterize and map the powdery mildew resistance. Five AFLP markers (XP43M32((250)), XP46M31((410)), XP41M37((100)), XP41M39((250)), XP39M32((120))), three genomic SSR markers (Xcfd07, Xwmc75, Xgwm408) and one EST-derived SSR marker (BJ261635) were found to be linked to the resistance gene in 5BIL-29 and only the BJ261635 marker in 5BIL-42. By means of Chinese Spring nullisomic-tetrasomic, ditelosomic and deletion lines, the polymorphic markers and the resistance gene were assigned to chromosome bin 5BL6-0.29-0.76. These results indicated that the two lines had the same resistance gene and that the introgressed dicoccoides chromosome segment was longer (35.5 cM) in 5BIL-29 than that introgressed in 5BIL-42 (less than 1.5 cM). As no powdery mildew resistance gene has been reported on chromosome arm 5BL, the novel resistance gene derived from var. dicoccoides was designated Pm36. The 244 bp allele of BJ261635 in 5BIL-42 can be used for marker-assisted selection during the wheat resistance breeding process for facilitating gene pyramiding.

  17. Feasible introgression of an anti-pathogen transgene into an urban mosquito population without using gene-drive.

    Directory of Open Access Journals (Sweden)

    Kenichi W Okamoto

    2014-07-01

    Full Text Available Introgressing anti-pathogen constructs into wild vector populations could reduce disease transmission. It is generally assumed that such introgression would require linking an anti-pathogen gene with a selfish genetic element or similar technologies. Yet none of the proposed transgenic anti-pathogen gene-drive mechanisms are likely to be implemented as public health measures in the near future. Thus, much attention now focuses instead on transgenic strategies aimed at mosquito population suppression, an approach generally perceived to be practical. By contrast, aiming to replace vector competent mosquito populations with vector incompetent populations by releasing mosquitoes carrying a single anti-pathogen gene without a gene-drive mechanism is widely considered impractical.Here we use Skeeter Buster, a previously published stochastic, spatially explicit model of Aedes aegypti to investigate whether a number of approaches for releasing mosquitoes with only an anti-pathogen construct would be efficient and effective in the tropical city of Iquitos, Peru. To assess the performance of such releases using realistic release numbers, we compare the transient and long-term effects of this strategy with two other genetic control strategies that have been developed in Ae. aegypti: release of a strain with female-specific lethality, and a strain with both female-specific lethality and an anti-pathogen gene. We find that releasing mosquitoes carrying only an anti-pathogen construct can substantially decrease vector competence of a natural population, even at release ratios well below that required for the two currently feasible alternatives that rely on population reduction. Finally, although current genetic control strategies based on population reduction are compromised by immigration of wild-type mosquitoes, releasing mosquitoes carrying only an anti-pathogen gene is considerably more robust to such immigration.Contrary to the widely held view that

  18. Generation of a multi-locus chicken introgression line to study the effects of genetic interactions on metabolic phenotypes in chickens

    Directory of Open Access Journals (Sweden)

    Weronica eEk

    2012-03-01

    Full Text Available Most biological traits are regulated by a complex interplay between genetic and environmental factors. By intercrossing divergent lines, it is possible to identify individual and interacting QTL involved in the genetic architecture of these traits. When the loci have been mapped, alternative strategies are needed for fine-mapping and studying the individual and interactive effects of the QTL in detail. We have previously identified, replicated and fine-mapped a four-locus QTL network that determines nearly half of the eight-fold difference in body-weight at 56 days of age between two divergently selected chicken lines. Here, we describe, to our knowledge, the first generation of a three-locus QTL introgression line in chickens to further study the effect of three of the interacting loci in this network on metabolic phenotypes. Recurrent marker assisted backcrossing was used to simultaneously transfer QTL alleles from the low-weight selected line into the high-weight selected line. Three generations of backcrossing and one generation of intercrossing resulted in an introgression line where all three introgressed QTL and several unlinked and linked control-loci were segregating at nearly expected allele frequencies. We show that marker-based sexing is an efficient method for sexing breeding populations and how intensive selection can be applied using artificial insemination to generate large half-sib families. Based on our empirical observations, we provide recommendations for future introgression-line breeding experiments. In the future, use of this confirmed introgression line will facilitate detailed studies of the effects of genetic interactions on complex traits.

  19. Genetic susceptibility to infectious disease in East African Shorthorn Zebu: a genome-wide analysis of the effect of heterozygosity and exotic introgression.

    Science.gov (United States)

    Murray, Gemma G R; Woolhouse, Mark E J; Tapio, Miika; Mbole-Kariuki, Mary N; Sonstegard, Tad S; Thumbi, Samuel M; Jennings, Amy E; van Wyk, Ilana Conradie; Chase-Topping, Margo; Kiara, Henry; Toye, Phil; Coetzer, Koos; deC Bronsvoort, Barend M; Hanotte, Olivier

    2013-11-09

    Positive multi-locus heterozygosity-fitness correlations have been observed in a number of natural populations. They have been explained by the correlation between heterozygosity and inbreeding, and the negative effect of inbreeding on fitness (inbreeding depression). Exotic introgression in a locally adapted population has also been found to reduce fitness (outbreeding depression) through the breaking-up of co-adapted genes, or the introduction of non-locally adapted gene variants. In this study we examined the inter-relationships between genome-wide heterozygosity, introgression, and death or illness as a result of infectious disease in a sample of calves from an indigenous population of East African Shorthorn Zebu (crossbred Bos taurus x Bos indicus) in western Kenya. These calves were observed from birth to one year of age as part of the Infectious Disease in East African Livestock (IDEAL) project. Some of the calves were found to be genetic hybrids, resulting from the recent introgression of European cattle breed(s) into the indigenous population. European cattle are known to be less well adapted to the infectious diseases present in East Africa. If death and illness as a result of infectious disease have a genetic basis within the population, we would expect both a negative association of these outcomes with introgression and a positive association with heterozygosity. In this indigenous livestock population we observed negative associations between heterozygosity and both death and illness as a result of infectious disease and a positive association between European taurine introgression and episodes of clinical illness. We observe the effects of both inbreeding and outbreeding depression in the East African Shorthorn Zebu, and therefore find evidence of a genetic component to vulnerability to infectious disease. These results indicate that the significant burden of infectious disease in this population could, in principle, be reduced by altered breeding

  20. Reduced SNP Panels for Genetic Identification and Introgression Analysis in the Dark Honey Bee (Apis mellifera mellifera)

    DEFF Research Database (Denmark)

    Muñoz, Irene; Henriques, Dora; Johnston, J. Spencer

    2015-01-01

    Beekeeping activities, especially queen trading, have shaped the distribution of honey bee (Apis mellifera) subspecies in Europe, and have resulted in extensive introductions of two eastern European C-lineage subspecies (A. m. ligustica and A. m. carnica) into the native range of the M-lineage A. m....... mellifera subspecies in Western Europe. As a consequence, replacement and gene flow between native and commercial populations have occurred at varying levels across western European populations. Genetic identification and introgression analysis using molecular markers is an important tool for management...... be exploited to create a reduced panel containing the most ancestry-informative markers (AIMs) for those purposes with very little loss of information. The objective of this study was to design reduced panels of AIMs to verify the origin of A. m. mellifera individuals and to provide accurate estimates...

  1. Multilayer moisture barrier

    Science.gov (United States)

    Pankow, Joel W; Jorgensen, Gary J; Terwilliger, Kent M; Glick, Stephen H; Isomaki, Nora; Harkonen, Kari; Turkulainen, Tommy

    2015-04-21

    A moisture barrier, device or product having a moisture barrier or a method of fabricating a moisture barrier having at least a polymer layer, and interfacial layer, and a barrier layer. The polymer layer may be fabricated from any suitable polymer including, but not limited to, fluoropolymers such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), or ethylene-tetrafluoroethylene (ETFE). The interfacial layer may be formed by atomic layer deposition (ALD). In embodiments featuring an ALD interfacial layer, the deposited interfacial substance may be, but is not limited to, Al.sub.2O.sub.3, AlSiO.sub.x, TiO.sub.2, and an Al.sub.2O.sub.3/TiO.sub.2 laminate. The barrier layer associated with the interfacial layer may be deposited by plasma enhanced chemical vapor deposition (PECVD). The barrier layer may be a SiO.sub.xN.sub.y film.

  2. Thermal barriers for compartments

    Science.gov (United States)

    Kreutzer, Cory J.; Lustbader, Jason A.

    2017-10-17

    An aspect of the present disclosure is a thermal barrier that includes a core layer having a first surface, a second surface, and a first edge, and a first outer layer that includes a third surface and a second edge, where the third surface substantially contacts the first surface, the core layer is configured to minimize conductive heat transfer through the barrier, and the first outer layer is configured to maximize reflection of light away from the barrier.

  3. Tunnel barrier schottky

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Rongming; Cao, Yu; Li, Zijian; Williams, Adam J.

    2018-02-20

    A diode includes: a semiconductor substrate; a cathode metal layer contacting a bottom of the substrate; a semiconductor drift layer on the substrate; a graded aluminum gallium nitride (AlGaN) semiconductor barrier layer on the drift layer and having a larger bandgap than the drift layer, the barrier layer having a top surface and a bottom surface between the drift layer and the top surface, the barrier layer having an increasing aluminum composition from the bottom surface to the top surface; and an anode metal layer directly contacting the top surface of the barrier layer.

  4. Overcoming natural replication barriers: differential helicase requirements.

    Science.gov (United States)

    Anand, Ranjith P; Shah, Kartik A; Niu, Hengyao; Sung, Patrick; Mirkin, Sergei M; Freudenreich, Catherine H

    2012-02-01

    DNA sequences that form secondary structures or bind protein complexes are known barriers to replication and potential inducers of genome instability. In order to determine which helicases facilitate DNA replication across these barriers, we analyzed fork progression through them in wild-type and mutant yeast cells, using 2-dimensional gel-electrophoretic analysis of the replication intermediates. We show that the Srs2 protein facilitates replication of hairpin-forming CGG/CCG repeats and prevents chromosome fragility at the repeat, whereas it does not affect replication of G-quadruplex forming sequences or a protein-bound repeat. Srs2 helicase activity is required for hairpin unwinding and fork progression. Also, the PCNA binding domain of Srs2 is required for its in vivo role of replication through hairpins. In contrast, the absence of Sgs1 or Pif1 helicases did not inhibit replication through structural barriers, though Pif1 did facilitate replication of a telomeric protein barrier. Interestingly, replication through a protein barrier but not a DNA structure barrier was modulated by nucleotide pool levels, illuminating a different mechanism by which cells can regulate fork progression through protein-mediated stall sites. Our analyses reveal fundamental differences in the replication of DNA structural versus protein barriers, with Srs2 helicase activity exclusively required for fork progression through hairpin structures.

  5. Transforming Education: Overcoming Barriers.

    Science.gov (United States)

    David, Jane L.; Goren, Paul D.

    Barriers to progress in educational reform exist inside and outside the education system. Some arise where new practices encounter traditional expectations and boundaries, but others go much deeper than education, such as poverty, racism, local political conflicts, and human resistance to change. The following five categories of barriers are…

  6. Catalytic thermal barrier coatings

    Science.gov (United States)

    Kulkarni, Anand A.; Campbell, Christian X.; Subramanian, Ramesh

    2009-06-02

    A catalyst element (30) for high temperature applications such as a gas turbine engine. The catalyst element includes a metal substrate such as a tube (32) having a layer of ceramic thermal barrier coating material (34) disposed on the substrate for thermally insulating the metal substrate from a high temperature fuel/air mixture. The ceramic thermal barrier coating material is formed of a crystal structure populated with base elements but with selected sites of the crystal structure being populated by substitute ions selected to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a higher rate than would the base compound without the ionic substitutions. Precious metal crystallites may be disposed within the crystal structure to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a lower light-off temperature than would the ceramic thermal barrier coating material without the precious metal crystallites.

  7. Genetic Diversity and Phenotypic Variation in an Introgression Line Population Derived from an Interspecific Cross between Oryza glaberrima and Oryza sativa

    Science.gov (United States)

    Nassirou, Tondi Yacouba; Zhou, Wei; Yin, Yilong; Dong, Xilong; Rao, Quanqin; Shi, Han; Zhao, Wubin; Efisue, Andrew; Jin, Deming

    2016-01-01

    The introduction of closely related species genomic fragments is an effective way to enrich genetic diversity and creates new germplasms in crops. Here, we studied the genetic diversity of an introgression line (IL) population composed of 106 ILs derived from an interspecific tetra cross between O. glaberrima and O. sativa (RAM3/Jin23B//Jin23B///YuetaiB). The proportion of O. glaberrima genome (PGG) in the ILs ranged from 0.3% to 36.7%, with an average value of 12.32% which is close to the theoretically expected proportion. A total of 250 polymorphic alleles were amplified by 21 AFLP primer combinations with an average of 12 alleles per primer. Population structure analysis revealed that the IL population can be divided into four genetically distinct subpopulations. Both principal component analysis and neighbor-joining tree analysis showed that ILs with a higher PGG displayed greater genetic diversity. Canonical discriminant analysis identified six phenotypic traits (plant height, yield per plant, filled grain percentage, panicle length, panicle number and days to flowering) as the main discriminatory traits among the ILs and between the subpopulations and showed significant phenotypic distances between subpopulations. The effects of PGG on phenotypic traits in the ILs were estimated using a linear admixed model, which showed a significant positive effect on grain yield per plant (0.286±0.117), plant height (0.418 ± 0.132), panicle length (0.663 ± 0.107), and spikelet number per panicle (0.339 ± 0.128), and a significant negative effect on filled grain percentage (-0.267 ± 0.123) and days to flowering (-0.324 ± 0.075). We found that an intermediate range (10% − 20%) of PGG was more effective for producing ILs with favorable integrated agronomic traits. Our results confirm that construction of IL population carrying O. glaberrima genomic fragments could be an effective approach to increase the genetic diversity of O. sativa genome and an appropriate level

  8. Unified Model of Dynamic Forced Barrier Crossing in Single Molecules

    Energy Technology Data Exchange (ETDEWEB)

    Friddle, R W

    2007-06-21

    Thermally activated barrier crossing in the presence of an increasing load can reveal kinetic rate constants and energy barrier parameters when repeated over a range of loading rates. Here we derive a model of the mean escape force for all relevant loading rates--the complete force spectrum. Two well-known approximations emerge as limiting cases; one of which confirms predictions that single-barrier spectra should converge to a phenomenological description in the slow loading limit.

  9. Vehicle barrier systems

    International Nuclear Information System (INIS)

    Sena, P.A.

    1986-01-01

    The ground vehicle is one of the most effective tools available to an adversary force. Vehicles can be used to penetrate many types of perimeter barriers, transport equipment and personnel rapidly over long distances, and deliver large amounts of explosives directly to facilities in suicide missions. The function of a vehicle barrier system is to detain or disable a defined threat vehicle at a selected distance from a protected facility. Numerous facilities are installing, or planning to install, vehicle barrier systems and many of these facilities are requesting guidance to do so adequately. Therefore, vehicle barriers are being evaluated to determine their stopping capabilities so that systems can be designed that are both balanced and capable of providing a desired degree of protection. Equally important, many of the considerations that should be taken into account when establishing a vehicle barrier system have been identified. These considerations which pertain to site preparation, barrier selection, system integration and operation, and vehicle/barrier interaction, are discussed in this paper

  10. Do competitive conditions affect introgression of transgenes from oilseed rape (Brassica napus) to weedy Brassica rapa? AS case study with special reference to transplastomic oilseed rape

    DEFF Research Database (Denmark)

    Johannessen, Marina

    In species where chloroplast inheritance is exclusively or predominantly maternal, pollen-mediated flow of transgenes is reduced if transgenes are inserted in chloroplast DNA instead of nuclear DNA. However, transmission of chloroplast-encoded transgeneswill still occur if transgenic individuals...... affected the thousand-kernel weight significantly. It was concluded that further introgression of transgenes from transplastomic oilseed rape to B. rapa is mostlikely at current field densities of B. napus and when B. rapa is an abundant weed....

  11. QTL Mapping for Pest and Disease Resistance in Cassava and Coincidence of Some QTL with Introgression Regions Derived from Manihot glaziovii

    Directory of Open Access Journals (Sweden)

    Inosters Nzuki

    2017-07-01

    Full Text Available Genetic mapping of quantitative trait loci (QTL for resistance to cassava brown streak disease (CBSD, cassava mosaic disease (CMD, and cassava green mite (CGM was performed using an F1 cross developed between the Tanzanian landrace, Kiroba, and a breeding line, AR37-80. The population was evaluated for two consecutive years in two sites in Tanzania. A genetic linkage map was derived from 106 F1 progeny and 1,974 SNP markers and spanned 18 chromosomes covering a distance of 1,698 cM. Fifteen significant QTL were identified; two are associated with CBSD root necrosis only, and were detected on chromosomes V and XII, while seven were associated with CBSD foliar symptoms only and were detected on chromosomes IV, VI, XVII, and XVIII. QTL on chromosomes 11 and 15 were associated with both CBSD foliar and root necrosis symptoms. Two QTL were found to be associated with CMD and were detected on chromosomes XII and XIV, while two were associated with CGM and were identified on chromosomes V and X. There are large Manihot glaziovii introgression regions in Kiroba on chromosomes I, XVII, and XVIII. The introgression segments on chromosomes XVII and XVIII overlap with QTL associated with CBSD foliar symptoms. The introgression region on chromosome I is of a different haplotype to the characteristic “Amani haplotype” found in the landrace Namikonga and others, and unlike some other genotypes, Kiroba does not have a large introgression block on chromosome IV. Kiroba is closely related to a sampled Tanzanian “tree cassava.” This supports the observation that some of the QTL associated with CBSD resistance in Kiroba are different to those observed in another variety, Namikonga.

  12. Introgression of lineage c honey bees into black honey bee populations: a genome-wide estimation using single nucleotide polymorphisms (SNPS)

    OpenAIRE

    Henriques, Dora; Chavez-Galarza, Julio; Kryger, Per; Johnston, J. Spencer; De la Rúa, Pilar; Rufino, José; Dall'Olio, Raffaele; Garnery, Lionel; Pinto, M. Alice

    2012-01-01

    The black honey bee, Apis mellifera mellifera L., is probably the honey bee subspecies more threatened by introgression from foreign subspecies, specially lineage C A. m. carnica and A. m. ligustica. In fact, in some areas of its distributional range, intensive beekeeping with foreign subspecies has driven A. m. mellifera populations to nearly replacement. While massive and repeated introductions may lead to loss of native genetic patrimony, a low level of gene flow can also be detrimental be...

  13. Recycler barrier RF buckets

    Energy Technology Data Exchange (ETDEWEB)

    Bhat, C.M.; /Fermilab

    2011-03-01

    The Recycler Ring at Fermilab uses a barrier rf systems for all of its rf manipulations. In this paper, I will give an overview of historical perspective on barrier rf system, the longitudinal beam dynamics issues, aspects of rf linearization to produce long flat bunches and methods used for emittance measurements of the beam in the RR barrier rf buckets. Current rf manipulation schemes used for antiproton beam stacking and longitudinal momentum mining of the RR beam for the Tevatron collider operation are explained along with their importance in spectacular success of the Tevatron luminosity performance.

  14. Converse Barrier Certificate Theorem

    DEFF Research Database (Denmark)

    Wisniewski, Rafael; Sloth, Christoffer

    2013-01-01

    This paper presents a converse barrier certificate theorem for a generic dynamical system.We show that a barrier certificate exists for any safe dynamical system defined on a compact manifold. Other authors have developed a related result, by assuming that the dynamical system has no singular...... points in the considered subset of the state space. In this paper, we redefine the standard notion of safety to comply with generic dynamical systems with multiple singularities. Afterwards, we prove the converse barrier certificate theorem and illustrate the differences between ours and previous work...

  15. Converse Barrier Certificate Theorems

    DEFF Research Database (Denmark)

    Wisniewski, Rafael; Sloth, Christoffer

    2016-01-01

    This paper shows that a barrier certificate exists for any safe dynamical system. Specifically, we prove converse barrier certificate theorems for a class of structurally stable dynamical systems. Other authors have developed a related result by assuming that the dynamical system has neither...... singular points nor closed orbits. In this paper, we redefine the standard notion of safety to comply with dynamical systems with multiple singular elements. Hereafter, we prove the converse barrier certificate theorems and highlight the differences between our results and previous work by a number...

  16. The Barrier within: Relational Aggression among Women

    Science.gov (United States)

    Brock, Barbara L.

    2010-01-01

    Relational aggression among women presents an overlooked barrier to women's quest for advancement in the workplace. Although research on women's leadership extols their ability to collaborate and form lasting, supportive relationships, one cannot assume that all women are supportive of other women. Research reveals that relational aggression,…

  17. Photoelectric effect in surface-barrier structures

    International Nuclear Information System (INIS)

    Kononenko, V.K.; Tupenevich, P.A.

    1985-08-01

    Deviations from the Fowler law were observed when investigating photoelectric emission in p-type ZnTe surface-barrier structures. The revealed peculiarities of the structure photosensitivity spectrum are explained by the electron transitions involving surface states at the metal-semiconductor interface. (author)

  18. Mathematics revealed

    CERN Document Server

    Berman, Elizabeth

    1979-01-01

    Mathematics Revealed focuses on the principles, processes, operations, and exercises in mathematics.The book first offers information on whole numbers, fractions, and decimals and percents. Discussions focus on measuring length, percent, decimals, numbers as products, addition and subtraction of fractions, mixed numbers and ratios, division of fractions, addition, subtraction, multiplication, and division. The text then examines positive and negative numbers and powers and computation. Topics include division and averages, multiplication, ratios, and measurements, scientific notation and estim

  19. Source-sink estimates of genetic introgression show influence of hatchery strays on wild chum salmon populations in Prince William Sound, Alaska.

    Directory of Open Access Journals (Sweden)

    James R Jasper

    Full Text Available The extent to which stray, hatchery-reared salmon affect wild populations is much debated. Although experiments show that artificial breeding and culture influence the genetics of hatchery salmon, little is known about the interaction between hatchery and wild salmon in a natural setting. Here, we estimated historical and contemporary genetic population structures of chum salmon (Oncorhynchus keta in Prince William Sound (PWS, Alaska, with 135 single nucleotide polymorphism (SNP markers. Historical population structure was inferred from the analysis of DNA from fish scales, which had been archived since the late 1960's for several populations in PWS. Parallel analyses with microsatellites and a test based on Hardy-Weinberg proportions showed that about 50% of the fish-scale DNA was cross-contaminated with DNA from other fish. These samples were removed from the analysis. We used a novel application of the classical source-sink model to compare SNP allele frequencies in these archived fish-scales (1964-1982 with frequencies in contemporary samples (2008-2010 and found a temporal shift toward hatchery allele frequencies in some wild populations. Other populations showed markedly less introgression, despite moderate amounts of hatchery straying. The extent of introgression may reflect similarities in spawning time and life-history traits between hatchery and wild fish, or the degree that hybrids return to a natal spawning area. The source-sink model is a powerful means of detecting low levels of introgression over several generations.

  20. Development and Genetic Characterization of Advanced Backcross Materials and An Introgression Line Population of Solanum incanum in a S. melongena Background

    Directory of Open Access Journals (Sweden)

    Pietro Gramazio

    2017-08-01

    Full Text Available Advanced backcrosses (ABs and introgression lines (ILs of eggplant (Solanum melongena can speed up genetics and genomics studies and breeding in this crop. We have developed the first full set of ABs and ILs in eggplant using Solanum incanum, a wild eggplant that has a relatively high tolerance to drought, as a donor parent. The development of these ABs and IL eggplant populations had a low efficiency in the early stages, because of the lack of molecular markers and genomic tools. However, this dramatically improved after performing genotyping-by-sequencing in the first round of selfing, followed by high-resolution-melting single nucleotide polymorphism genotyping in subsequent selection steps. A set of 73 selected ABs covered 99% of the S. incanum genome, while 25 fixed immortal ILs, each carrying a single introgressed fragment in homozygosis, altogether spanned 61.7% of the S. incanum genome. The introgressed size fragment in the ILs contained between 0.1 and 10.9% of the S. incanum genome, with a mean value of 4.3%. Sixty-eight candidate genes involved in drought tolerance were identified in the set of ILs. This first set of ABs and ILs of eggplant will be extremely useful for the genetic dissection of traits of interest for eggplant, and represents an elite material for introduction into the breeding pipelines for developing new eggplant cultivars adapted to the challenges posed by the climate-change scenario.

  1. SNPs selected by information content outperform randomly selected microsatellite loci for delineating genetic identification and introgression in the endangered dark European honeybee (Apis mellifera mellifera).

    Science.gov (United States)

    Muñoz, Irene; Henriques, Dora; Jara, Laura; Johnston, J Spencer; Chávez-Galarza, Julio; De La Rúa, Pilar; Pinto, M Alice

    2017-07-01

    The honeybee (Apis mellifera) has been threatened by multiple factors including pests and pathogens, pesticides and loss of locally adapted gene complexes due to replacement and introgression. In western Europe, the genetic integrity of the native A. m. mellifera (M-lineage) is endangered due to trading and intensive queen breeding with commercial subspecies of eastern European ancestry (C-lineage). Effective conservation actions require reliable molecular tools to identify pure-bred A. m. mellifera colonies. Microsatellites have been preferred for identification of A. m. mellifera stocks across conservation centres. However, owing to high throughput, easy transferability between laboratories and low genotyping error, SNPs promise to become popular. Here, we compared the resolving power of a widely utilized microsatellite set to detect structure and introgression with that of different sets that combine a variable number of SNPs selected for their information content and genomic proximity to the microsatellite loci. Contrary to every SNP data set, microsatellites did not discriminate between the two lineages in the PCA space. Mean introgression proportions were identical across the two marker types, although at the individual level, microsatellites' performance was relatively poor at the upper range of Q-values, a result reflected by their lower precision. Our results suggest that SNPs are more accurate and powerful than microsatellites for identification of A. m. mellifera colonies, especially when they are selected by information content. © 2016 John Wiley & Sons Ltd.

  2. Development and Genetic Characterization of Advanced Backcross Materials and An Introgression Line Population of Solanum incanum in a S. melongena Background

    Science.gov (United States)

    Gramazio, Pietro; Prohens, Jaime; Plazas, Mariola; Mangino, Giulio; Herraiz, Francisco J.; Vilanova, Santiago

    2017-01-01

    Advanced backcrosses (ABs) and introgression lines (ILs) of eggplant (Solanum melongena) can speed up genetics and genomics studies and breeding in this crop. We have developed the first full set of ABs and ILs in eggplant using Solanum incanum, a wild eggplant that has a relatively high tolerance to drought, as a donor parent. The development of these ABs and IL eggplant populations had a low efficiency in the early stages, because of the lack of molecular markers and genomic tools. However, this dramatically improved after performing genotyping-by-sequencing in the first round of selfing, followed by high-resolution-melting single nucleotide polymorphism genotyping in subsequent selection steps. A set of 73 selected ABs covered 99% of the S. incanum genome, while 25 fixed immortal ILs, each carrying a single introgressed fragment in homozygosis, altogether spanned 61.7% of the S. incanum genome. The introgressed size fragment in the ILs contained between 0.1 and 10.9% of the S. incanum genome, with a mean value of 4.3%. Sixty-eight candidate genes involved in drought tolerance were identified in the set of ILs. This first set of ABs and ILs of eggplant will be extremely useful for the genetic dissection of traits of interest for eggplant, and represents an elite material for introduction into the breeding pipelines for developing new eggplant cultivars adapted to the challenges posed by the climate-change scenario. PMID:28912788

  3. A common genetic determinism for sensitivities to soil water deficit and evaporative demand: meta-analysis of quantitative trait Loci and introgression lines of maize.

    Science.gov (United States)

    Welcker, Claude; Sadok, Walid; Dignat, Grégoire; Renault, Morgan; Salvi, Silvio; Charcosset, Alain; Tardieu, François

    2011-10-01

    Evaporative demand and soil water deficit equally contribute to water stress and to its effect on plant growth. We have compared the genetic architectures of the sensitivities of maize (Zea mays) leaf elongation rate with evaporative demand and soil water deficit. The former was measured via the response to leaf-to-air vapor pressure deficit in well-watered plants, the latter via the response to soil water potential in the absence of evaporative demand. Genetic analyses of each sensitivity were performed over 21 independent experiments with (1) three mapping populations, with temperate or tropical materials, (2) one population resulting from the introgression of a tropical drought-tolerant line in a temperate line, and (3) two introgression libraries genetically independent from mapping populations. A very large genetic variability was observed for both sensitivities. Some lines maintained leaf elongation at very high evaporative demand or water deficit, while others stopped elongation in mild conditions. A complex architecture arose from analyses of mapping populations, with 19 major meta-quantitative trait loci involving strong effects and/or more than one mapping population. A total of 68% of those quantitative trait loci affected sensitivities to both evaporative demand and soil water deficit. In introgressed lines, 73% of the tested genomic regions affected both sensitivities. To our knowledge, this study is the first genetic demonstration that hydraulic processes, which drive the response to evaporative demand, also have a large contribution to the genetic variability of plant growth under water deficit in a large range of genetic material.

  4. Adaptive divergence in wine yeasts and their wild relatives suggests a prominent role for introgressions and rapid evolution at noncoding sites.

    Science.gov (United States)

    Almeida, Pedro; Barbosa, Raquel; Bensasson, Douda; Gonçalves, Paula; Sampaio, José Paulo

    2017-04-01

    In Saccharomyces cerevisiae, the main yeast in wine fermentation, the opportunity to examine divergence at the molecular level between a domesticated lineage and its wild counterpart arose recently due to the identification of the closest relatives of wine strains, a wild population associated with Mediterranean oaks. As genomic data are available for a considerable number of representatives belonging to both groups, we used population genomics to estimate the degree and distribution of nucleotide variation between wine yeasts and their closest wild relatives. We found widespread genomewide divergence, particularly at noncoding sites, which, together with above average divergence in trans-acting DNA binding proteins, may suggest an important role for divergence at the level of transcriptional regulation. Nine outlier regions putatively under strong divergent selection were highlighted by a genomewide scan under stringent conditions. Several cases of introgressions, originating in the sibling species Saccharomyces paradoxus, were also identified in the Mediterranean oak population. FZF1 and SSU1, mostly known for conferring sulphite resistance in wine yeasts, were among the introgressed genes, although not fixed. Because the introgressions detected in our study are not found in wine strains, we hypothesize that ongoing divergent ecological selection segregates the two forms between the different niches. Together, our results provide a first insight into the extent and kind of divergence between wine yeasts and their closest wild relatives. © 2017 John Wiley & Sons Ltd.

  5. Development and validation of cross-transferable and polymorphic DNA markers for detecting alien genome introgression in Oryza sativa from Oryza brachyantha.

    Science.gov (United States)

    Ray, Soham; Bose, Lotan K; Ray, Joshitha; Ngangkham, Umakanta; Katara, Jawahar L; Samantaray, Sanghamitra; Behera, Lambodar; Anumalla, Mahender; Singh, Onkar N; Chen, Meingsheng; Wing, Rod A; Mohapatra, Trilochan

    2016-08-01

    African wild rice Oryza brachyantha (FF), a distant relative of cultivated rice Oryza sativa (AA), carries genes for pests and disease resistance. Molecular marker assisted alien gene introgression from this wild species to its domesticated counterpart is largely impeded due to the scarce availability of cross-transferable and polymorphic molecular markers that can clearly distinguish these two species. Availability of the whole genome sequence (WGS) of both the species provides a unique opportunity to develop markers, which are cross-transferable. We observed poor cross-transferability (~0.75 %) of O. sativa specific sequence tagged microsatellite (STMS) markers to O. brachyantha. By utilizing the genome sequence information, we developed a set of 45 low cost PCR based co-dominant polymorphic markers (STS and CAPS). These markers were found cross-transferrable (84.78 %) between the two species and could distinguish them from each other and thus allowed tracing alien genome introgression. Finally, we validated a Monosomic Alien Addition Line (MAAL) carrying chromosome 1 of O. brachyantha in O. sativa background using these markers, as a proof of concept. Hence, in this study, we have identified a set molecular marker (comprising of STMS, STS and CAPS) that are capable of detecting alien genome introgression from O. brachyantha to O. sativa.

  6. Distinguishing between incomplete lineage sorting and genomic introgressions: complete fixation of allospecific mitochondrial DNA in a sexually reproducing fish (Cobitis; Teleostei, despite clonal reproduction of hybrids.

    Directory of Open Access Journals (Sweden)

    Lukas Choleva

    Full Text Available Distinguishing between hybrid introgression and incomplete lineage sorting causing incongruence among gene trees in that they exhibit topological differences requires application of statistical approaches that are based on biologically relevant models. Such study is especially challenging in hybrid systems, where usual vectors mediating interspecific gene transfers--hybrids with Mendelian heredity--are absent or unknown. Here we study a complex of hybridizing species, which are known to produce clonal hybrids, to discover how one of the species, Cobitis tanaitica, has achieved a pattern of mito-nuclear mosaic genome over the whole geographic range. We appplied three distinct methods, including the method using solely the information on gene tree topologies, and found that the contrasting mito-nuclear signal might not have resulted from the retention of ancestral polymorphism. Instead, we found two signs of hybridization events related to C. tanaitica; one concerning nuclear gene flow and the other suggested mitochondrial capture. Interestingly, clonal inheritance (gynogenesis of contemporary hybrids prevents genomic introgressions and non-clonal hybrids are either absent or too rare to be detected among European Cobitis. Our analyses therefore suggest that introgressive hybridizations are rather old episodes, mediated by previously existing hybrids whose inheritance was not entirely clonal. Cobitis complex thus supports the view that the type of resulting hybrids depends on a level of genomic divergence between sexual species.

  7. Barriers for administering primary health care services to battered ...

    African Journals Online (AJOL)

    Background: Violence against women is an important public-health problem that draws attention of a wide spectrum of clinicians. However, multiple barriers undermine the efforts of primary health care workers to properly manage and deal with battered women. Objectives: The aim of the present study was to reveal barriers ...

  8. Optimistic barrier synchronization

    Science.gov (United States)

    Nicol, David M.

    1992-01-01

    Barrier synchronization is fundamental operation in parallel computation. In many contexts, at the point a processor enters a barrier it knows that it has already processed all the work required of it prior to synchronization. The alternative case, when a processor cannot enter a barrier with the assurance that it has already performed all the necessary pre-synchronization computation, is treated. The problem arises when the number of pre-sychronization messages to be received by a processor is unkown, for example, in a parallel discrete simulation or any other computation that is largely driven by an unpredictable exchange of messages. We describe an optimistic O(log sup 2 P) barrier algorithm for such problems, study its performance on a large-scale parallel system, and consider extensions to general associative reductions as well as associative parallel prefix computations.

  9. Barrier Infrared Detector (BIRD)

    Data.gov (United States)

    National Aeronautics and Space Administration — A recent breakthrough in MWIR detector design, has resulted in a high operating temperature (HOT) barrier infrared detector (BIRD) that is capable of spectral...

  10. Protective barrier development: Overview

    International Nuclear Information System (INIS)

    Wing, N.R.; Gee, G.W.

    1990-01-01

    Protective barrier and warning marker systems are being developed to isolate wastes disposed of near the earth's surface at the Hanford Site. The barrier is designed to function in an arid to semiarid climate, to limit infiltration and percolation of water through the waste zone to near-zero, to be maintenance free, and to last up to 10,000 yr. Natural materials (e.g., fine soil, sand, gravel, riprap, clay, asphalt) have been selected to optimize barrier performance and longevity and to create an integrated structure with redundant features. These materials isolate wastes by limiting water drainage; reducing the likelihood of plant, animal, and human intrusion; controlling emission of noxious gases; and minimizing erosion. Westinghouse Hanford Company and Pacific Northwest Laboratory efforts to assess the performance of various barrier and marker designs will be discussed

  11. Genetic variation and risks of introgression in the wild Coffea arabica gene pool in south-western Ethiopian montane rainforests.

    Science.gov (United States)

    Aerts, Raf; Berecha, Gezahegn; Gijbels, Pieter; Hundera, Kitessa; Glabeke, Sabine; Vandepitte, Katrien; Muys, Bart; Roldán-Ruiz, Isabel; Honnay, Olivier

    2013-02-01

    The montane rainforests of SW Ethiopia are the primary centre of diversity of Coffea arabica and the origin of all Arabica coffee cultivated worldwide. This wild gene pool is potentially threatened by forest fragmentation and degradation, and by introgressive hybridization with locally improved coffee varieties. We genotyped 703 coffee shrubs from unmanaged and managed coffee populations, using 24 microsatellite loci. Additionally, we genotyped 90 individuals representing 23 Ethiopian cultivars resistant to coffee berry disease (CBD). We determined population genetic diversity, genetic structure, and admixture of cultivar alleles in the in situ gene pool. We found strong genetic differentiation between managed and unmanaged coffee populations, but without significant differences in within-population genetic diversity. The widespread planting of coffee seedlings including CBD-resistant cultivars most likely offsets losses of genetic variation attributable to genetic drift and inbreeding. Mixing cultivars with original coffee genotypes, however, leaves ample opportunity for hybridization and replacement of the original coffee gene pool, which already shows signs of admixture. In situ conservation of the wild gene pool of C. arabica must therefore focus on limiting coffee production in the remaining wild populations, as intensification threatens the genetic integrity of the gene pool by exposing wild genotypes to cultivars.

  12. Marker-assisted introgression of broad-spectrum blast resistance genes into the cultivated MR219 rice variety.

    Science.gov (United States)

    Miah, Gous; Rafii, Mohd Y; Ismail, Mohd R; Puteh, Adam B; Rahim, Harun A; Latif, Mohammad A

    2017-07-01

    The rice cultivar MR219 is famous for its better yield and long and fine grain quality; however, it is susceptible to blast disease. The main objective of this study was to introgress blast resistance genes into MR219 through marker-assisted selection (MAS). The rice cultivar MR219 was used as the recurrent parent, and Pongsu Seribu 1 was used as the donor. Marker-assisted foreground selection was performed using RM6836 and RM8225 to identify plants possessing blast resistance genes. Seventy microsatellite markers were used to estimate recurrent parent genome (RPG) recovery. Our analysis led to the development of 13 improved blast resistant lines with Piz, Pi2 and Pi9 broad-spectrum blast resistance genes and an MR219 genetic background. The RPG recovery of the selected improved lines was up to 97.70% with an average value of 95.98%. Selected improved lines showed a resistance response against the most virulent blast pathogen pathotype, P7.2. The selected improved lines did not express any negative effect on agronomic traits in comparison with MR219. The research findings of this study will be a conducive approach for the application of different molecular techniques that may result in accelerating the development of new disease-resistant rice varieties, which in turn will match rising demand and food security worldwide. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  13. A genome-wide assessment of stages of elevational parapatry in Bornean passerine birds reveals no introgression: implications for processes and patterns of speciation

    Directory of Open Access Journals (Sweden)

    Robert G. Moyle

    2017-05-01

    Full Text Available Topographically complex regions often contain the close juxtaposition of closely related species along elevational gradients. The evolutionary causes of these elevational replacements, and thus the origin and maintenance of a large portion of species diversity along elevational gradients, are usually unclear because ecological differentiation along a gradient or secondary contact following allopatric diversification can produce the same pattern. We used reduced representation genomic sequencing to assess genetic relationships and gene flow between three parapatric pairs of closely related songbird taxa (Arachnothera spiderhunters, Chloropsis leafbirds, and Enicurus forktails along an elevational gradient in Borneo. Each taxon pair presents a different elevational range distribution across the island, yet results were uniform: little or no gene flow was detected in any pairwise comparisons. These results are congruent with an allopatric “species-pump” model for generation of species diversity and elevational parapatry of congeners on Borneo, rather than in situ generation of species by “ecological speciation” along an elevational gradient.

  14. Effectiveness of cable barriers, guardrails, and concrete barrier walls in reducing the risk of injury.

    Science.gov (United States)

    Zou, Yaotian; Tarko, Andrew P; Chen, Erdong; Romero, Mario A

    2014-11-01

    Roadway departure crashes tend to be severe, especially when the roadside exposes the occupants of errant vehicles to excessive injury hazards. As a cost-effective method when the clear zone width is insufficient, road barriers are often installed to prevent errant vehicles from colliding with dangerous obstacles or traversing steep slopes. This paper focuses on the safety performance of road barriers in Indiana in reducing the risk of injury. The objective of the study presented here is to compare the risk of injury among different hazardous events faced by an occupant in a single-vehicle crash. The studied hazardous events include rolling over, striking three types of barriers (guardrails, concrete barrier walls, and cable barriers) with different barrier offsets to the edge of the travelled way, and striking various roadside objects. A total of 2124 single-vehicle crashes (3257 occupants) that occurred between 2008 and 2012 on 517 pair-matched homogeneous barrier and non-barrier segments were analyzed. A binary logistic regression model with mixed effects was estimated for vehicle occupants. The segment pairing process and the use of random effects were able to handle the commonality within the same segment pair as well as the heterogeneity across segment pairs. The modeling results revealed that hitting a barrier is associated with lower risk of injury than a high-hazard event (hitting a pole, rollover, etc.). The odds of injury are reduced by 39% for median concrete barrier walls offset 15-18ft from the travelled way, reduced by 65% for a guardrail face offset 5-55ft, reduced by 85% for near-side median cable barriers (offset between 10ft and 29ft), and reduced by 78% with far-side median cable barriers (offset at least 30ft). Comparing different types of barriers is useful where some types of barriers can be used alternatively. This study found that the odds of injury are 43% lower when striking a guardrail instead of a median concrete barrier offset 15-18ft

  15. Intestinal Barrier and Behavior.

    Science.gov (United States)

    Julio-Pieper, M; Bravo, J A

    2016-01-01

    The intestinal barrier function contributes to gut homeostasis by modulating absorption of water, electrolytes, and nutrients from the lumen into the circulation while restricting the passage of noxious luminal substances and microorganisms. Chronic conditions such as rheumatoid arthritis, inflammatory bowel disease, and celiac disease are associated to intestinal barrier dysfunction. Here, the hypothesis is that a leaky intestinal wall allowing for indiscriminate passage of intraluminal compounds to the vascular compartment could in turn lead to systemic inflammation. An increasing number of studies are now investigating the association between gut permeability and CNS disorders, under the premise that translocation of intestinal luminal contents could affect CNS function, either directly or indirectly. Still, it is unknown whether disruption of intestinal barrier is a causative agent or a consequence in these situations. Here, we discuss the latest evidence pointing to an association between increased gut permeability and disrupted behavioral responses. © 2016 Elsevier Inc. All rights reserved.

  16. Skin barrier in rosacea*

    Science.gov (United States)

    Addor, Flavia Alvim Sant'Anna

    2016-01-01

    Recent studies about the cutaneous barrier demonstrated consistent evidence that the stratum corneum is a metabolically active structure and also has adaptive functions, may play a regulatory role in the inflammatory response with activation of keratinocytes, angiogenesis and fibroplasia, whose intensity depends primarily on the intensity the stimulus. There are few studies investigating the abnormalities of the skin barrier in rosacea, but the existing data already show that there are changes resulting from inflammation, which can generate a vicious circle caused a prolongation of flare-ups and worsening of symptoms. This article aims to gather the most relevant literature data about the characteristics and effects of the state of the skin barrier in rosacea. PMID:26982780

  17. Health Barriers to Learning

    Directory of Open Access Journals (Sweden)

    Delaney Gracy

    2014-01-01

    Full Text Available This article summarizes the results from a 2013 online survey with 408 principals and assistant principals in New York City public elementary and middle schools. The survey assessed three primary areas: health issues in the school, health issues perceived as barriers to learning for affected students, and resources needed to address these barriers. Eighteen of the 22 health conditions listed in the survey were considered a moderate or serious issue within their schools by at least 10% of respondents. All 22 of the health issues were perceived as a barrier to learning by between 12% and 87% of the respondents. Representatives from schools that serve a higher percentage of low-income students reported significantly higher levels of concern about the extent of health issues and their impact on learning. Respondents most often said they need linkages with organizations that can provide additional services and resources at the school, especially for mental health.

  18. Barriers faced by Romanian SMEs in exporting

    Directory of Open Access Journals (Sweden)

    Dana BOŞCOR

    2017-07-01

    Full Text Available This study aims to identify the most important barriers faced by Romanians SMEs in the process of exporting. The research was based on a focus group including 12 managers from different exporting companies from Brasov. The most important barriers encountered by companies were linked to currency fluctuations, methods of payment, lack of specialized staff, lack of financial resources and a low level of government support. Results from the study revealed that companies should have access at financing in order to invest in new technologies and to create higher quality products that could meet the requirements of the foreign buyers. In order to reduce the export barriers, small and medium sized exporters should create partnerships for reducing the costs of promotion in foreign markets. The government should also increase its support by offering exporters access at financing and market information at lower costs.

  19. An extreme breaching of a barrier spit: insights on large breach formation and its impact on barrier dynamics

    Science.gov (United States)

    Iulian Zăinescu, Florin; Vespremeanu-Stroe, Alfred; Tătui, Florin

    2017-04-01

    sediment release through shoreface retreat, and resulted in widening the barrier to a maximum of 1 km. Since the newly-formed barrier shoreline got displaced backward up to 500 m, this reveals that barrier breaching is an important mechanism which significantly accelerates the landward migration of the barrier system and is a proof of the highly nonlinear morphodynamics involved in the barrier island translation. We demonstrate that the 2012-2015 event was an example of complex barrier breaching which has a substantial influence on the longer-term evolution of the spit. Studies of breaching help us understand the barrier evolution and will help coastal erosion risk management policy makers undertake better decisions on barrier management practice.

  20. Crossing the Salt Barrier

    Indian Academy of Sciences (India)

    Fry. RIVER. To cross the salt barrier is, therefore, an obligatory part of every amphihaline fish cycle. Figure 2a. Life Cycle of. Salmon. Adult salmon migrate from sea towards the river. After reaching their hatching ground, the eggs are laid in the gravel. The spawned fishes are called kelts. Alevin is a stage from hatching to fry.

  1. Great Barrier Reef

    Science.gov (United States)

    2002-01-01

    A better than average view of the Great Barrier Reef was captured by SeaWiFS on a recent overpass. There is sunglint northeast of the reef and there appears to be some sort of filamentous bloom in the Capricorn Channel.

  2. Flooding tolerance in interspecific introgression lines containing chromosome segments from teosinte (Zea nicaraguensis) in maize (Zea mays subsp. mays)

    Science.gov (United States)

    Mano, Y.; Omori, F.

    2013-01-01

    Background and Aims Nicaraguan teosinte (Zea nicaraguensis), a species found in frequently flooded areas, provides useful germplasm for breeding flooding-tolerant maize (Z. mays subsp. mays). The objective of this study was to select flooding-tolerant lines using a library of introgression lines (ILs), each containing a chromosome segment from Z. nicaraguensis in the maize inbred line Mi29. Methods To produce the ILs, a single F1 plant derived from a cross between maize Mi29 and Z. nicaraguensis was backcrossed to Mi29 three times, self-pollinated four times and genotyped using simple sequence repeat markers. Flooding tolerance was evaluated at the seedling stage under reducing soil conditions. Key Results By backcrossing and selfing, a series of 45 ILs were developed covering nearly the entire maize genome. Five flooding-tolerant lines were identified from among the ILs by evaluating leaf injury. Among these, line IL#18, containing a Z. nicaraguensis chromosome segment on the long arm of chromosome 4, showed the greatest tolerance to flooding, suggesting the presence of a major quantitative trait locus (QTL) in that region. The presence of the QTL was verified by examining flooding tolerance in a population segregating for the candidate region of chromosome 4. There was no significant relationship between the capacity to form constitutive aerenchyma and flooding tolerance in the ILs, indicating the presence of other factors related to flooding tolerance under reducing soil conditions. Conclusions A flooding-tolerant genotype, IL#18, was identified; this genotype should be useful for maize breeding. In addition, because the chromosome segments of Z. nicaraguensis in the ILs cover nearly the entire genome and Z. nicaraguensis possesses several unique traits related to flooding tolerance, the ILs should be valuable material for additional QTL detection and the development of flooding-tolerant maize lines. PMID:23877074

  3. Characterization of QTL for unique agronomic traits of new-plant-type rice varieties using introgression lines of IR64

    Directory of Open Access Journals (Sweden)

    Analiza G. Tagle

    2016-02-01

    Full Text Available To enhance the yield potential of an elite indica rice cultivar, an introgression (BC3-derived line of IR64, YTH288, was developed using a new-plant-type cultivar, IR66215-44-2-3, as a donor parent. YTH288 has agronomically valuable characteristics such as large panicles, few unproductive tillers, and large leaves inherited from NPT. To identify the genetic basis of these traits, we used 167 F2 plants derived from a cross between IR64 and YTH288 to conduct QTL analysis for five agronomic traits: days to heading (DTH, culm length (CL, flag leaf length (FLL, flag leaf width (FLW, and filled spikelet number per panicle (FSN. Six putative QTL were detected: four on chromosome 4 (for CL, FLL, FLW, and FSN and two on chromosome 2 (for DTH and FLL. All QTL with the IR66215-44-2-3 allele, except that for FLL on chromosome 2, had positive effects on each trait. To confirm the effects of these putative QTL, we developed NILs with the IR64 genetic background by marker-assisted selection. We observed significant differences in several agronomic traits between IR64 and NILs that carried these QTL on chromosomes 2 and 4. Additionally, four IR64-NILs carrying chromosomal segments derived from different NPT varieties on the long arm of chromosome 4 exhibited similar pleiotropic effects for unique agronomic traits. These NILs can be used as research materials for studying each trait and as breeding materials for yield improvement of indica rice cultivars.

  4. North African hybrid sparrows (Passer domesticus, P. hispaniolensis) back from oblivion - ecological segregation and asymmetric mitochondrial introgression between parental species.

    Science.gov (United States)

    Ait Belkacem, Abdelkrim; Gast, Oliver; Stuckas, Heiko; Canal, David; LoValvo, Mario; Giacalone, Gabriele; Päckert, Martin

    2016-08-01

    A stabilized hybrid form of the house sparrow (Passer domesticus) and the Spanish sparrow (P. hispaniolensis) is known as Passer italiae from the Italian Peninsula and a few Mediterranean islands. The growing attention for the Italian hybrid sparrow and increasing knowledge on its biology and genetic constitution greatly contrast the complete lack of knowledge of the long-known phenotypical hybrid sparrow populations from North Africa. Our study provides new data on the breeding biology and variation of mitochondrial DNA in three Algerian populations of house sparrows, Spanish sparrows, and phenotypical hybrids. In two field seasons, the two species occupied different breeding habitats: Spanish sparrows were only found in rural areas outside the cities and bred in open-cup nests built in large jujube bushes. In contrast, house sparrows bred only in the town centers and occupied nesting holes in walls of buildings. Phenotypical hybrids were always associated with house sparrow populations. House sparrows and phenotypical hybrids started breeding mid of March, and most pairs had three successive clutches, whereas Spanish sparrows started breeding almost one month later and had only two successive clutches. Mitochondrial introgression is strongly asymmetric because about 75% of the rural Spanish sparrow population carried house sparrow haplotypes. In contrast, populations of the Italian hybrid form, P. italiae, were genetically least diverse among all study populations and showed a near-fixation of house sparrow haplotypes that elsewhere were extremely rare or that were even unique for the Italian Peninsula. Such differences between mitochondrial gene pools of Italian and North African hybrid sparrow populations provide first evidence that different demographic histories have shaped the extant genetic diversity observed on both continents.

  5. Parallel genetic divergence among coastal-marine ecotype pairs of European anchovy explained by differential introgression after secondary contact.

    Science.gov (United States)

    Le Moan, A; Gagnaire, P-A; Bonhomme, F

    2016-07-01

    Ecophenotypic differentiation among replicate ecotype pairs within a species complex is often attributed to independent outcomes of parallel divergence driven by adaptation to similar environmental contrasts. However, the extent to which parallel phenotypic and genetic divergence patterns have emerged independently is increasingly questioned by population genomic studies. Here, we document the extent of genetic differentiation within and among two geographic replicates of the coastal and marine ecotypes of the European anchovy (Engraulis encrasicolus) gathered from Atlantic and Mediterranean locations. Using a genome-wide data set of RAD-derived SNPs, we show that habitat type (marine vs. coastal) is the most important component of genetic differentiation among populations of anchovy. By analysing the joint allele frequency spectrum of each coastal-marine ecotype pair, we show that genomic divergence patterns between ecotypes can be explained by a postglacial secondary contact following a long period of allopatric isolation (c. 300 kyrs). We found strong support for a model including heterogeneous migration among loci, suggesting that secondary gene flow has eroded past differentiation at different rates across the genome. Markers experiencing reduced introgression exhibited strongly correlated differentiation levels among Atlantic and Mediterranean regions. These results support that partial reproductive isolation and parallel genetic differentiation among replicate pairs of anchovy ecotypes are largely due to a common divergence history prior to secondary contact. They moreover provide comprehensive insights into the origin of a surprisingly strong fine-scale genetic structuring in a high gene flow marine fish, which should improve stock management and conservation actions. © 2016 John Wiley & Sons Ltd.

  6. Sound trapping and dredging barriers.

    Science.gov (United States)

    Wang, Xu; Wang, Xiaonan; Yu, Wuzhou; Jiang, Zaixiu; Mao, Dongxing

    2017-06-01

    When sound barriers are installed on both sides of a noise source, degradation in performance is observed. Barriers having negative-phase-gradient surfaces successfully eliminate this drawback by trapping sound energy in between the barriers. In contrast, barriers can also be designed to "dredge" the energy flux out. An extended model considering higher-order diffractions, which resulted from the interplay of the induced surface wave and barrier surface periodicity, is presented. It is found that the sound dredging barriers provide a remarkable enhancement over the trapping ones, and hence have the potential to be widely used in noise control engineering.

  7. A fifth major genetic group among honeybees revealed in Syria.

    Science.gov (United States)

    Alburaki, Mohamed; Bertrand, Bénédicte; Legout, Hélène; Moulin, Sibyle; Alburaki, Ali; Sheppard, Walter Steven; Garnery, Lionel

    2013-12-06

    Apiculture has been practiced in North Africa and the Middle-East from antiquity. Several thousand years of selective breeding have left a mosaic of Apis mellifera subspecies in the Middle-East, many uniquely adapted and survived to local environmental conditions. In this study we explore the genetic diversity of A. mellifera from Syria (n = 1258), Lebanon (n = 169) and Iraq (n = 35) based on 14 short tandem repeat (STR) loci in the context of reference populations from throughout the Old World (n = 732). Our data suggest that the Syrian honeybee Apis mellifera syriaca occurs in both Syrian and Lebanese territories, with no significant genetic variability between respective populations from Syria and Lebanon. All studied populations clustered within a new fifth independent nuclear cluster, congruent with an mtDNA Z haplotype identified in a previous study. Syrian honeybee populations are not associated with Oriental lineage O, except for sporadic introgression into some populations close to the Turkish and Iraqi borders. Southern Syrian and Lebanese populations demonstrated high levels of genetic diversity compared to the northern populations. This study revealed the effects of foreign queen importations on Syrian bee populations, especially for the region of Tartus, where extensive introgression of A. m. anatolica and/or A. m. caucasica alleles were identified. The policy of creating genetic conservation centers for the Syrian subspecies should take into consideration the influence of the oriental lineage O from the northern Syrian border and the large population of genetically divergent indigenous honeybees located in southern Syria.

  8. Genetic Diversity of Aromatic Rice Germplasm Revealed By SSR Markers

    Directory of Open Access Journals (Sweden)

    Saba Jasim Aljumaili

    2018-01-01

    Full Text Available Aromatic rice cultivars constitute a small but special group of rice and are considered the best in terms of quality and aroma. Aroma is one of the most significant quality traits of rice, and variety with aroma has a higher price in the market. This research was carried out to study the genetic diversity among the 50 aromatic rice accessions from three regions (Peninsular Malaysia, Sabah, and Sarawak with 3 released varieties as a control using the 32 simple sequence repeat (SSR markers. The objectives of this research were to quantify the genetic divergence of aromatic rice accessions using SSR markers and to identify the potential accessions for introgression into the existing rice breeding program. Genetic diversity index among the three populations such as Shannon information index (I ranged from 0.25 in control to 0.98 in Sabah population. The mean numbers of effective alleles and Shannon’s information index were 0.36 and 64.90%, respectively. Similarly, the allelic diversity was very high with mean expected heterozygosity (He of 0.60 and mean Nei’s gene diversity index of 0.36. The dendrogram based on UPGMA and Nei’s genetic distance classified the 53 rice accessions into 10 clusters. Analysis of molecular variance (AMOVA revealed that 89% of the total variation observed in this germplasm came from within the populations, while 11% of the variation emanated among the populations. These results reflect the high genetic differentiation existing in this aromatic rice germplasm. Using all these criteria and indices, seven accessions (Acc9993, Acc6288, Acc6893, Acc7580, Acc6009, Acc9956, and Acc11816 from three populations have been identified and selected for further evaluation before introgression into the existing breeding program and for future aromatic rice varietal development.

  9. Geophysical characterization of subsurface barriers

    International Nuclear Information System (INIS)

    Borns, D.J.

    1995-08-01

    An option for controlling contaminant migration from plumes and buried waste sites is to construct a subsurface barrier of a low-permeability material. The successful application of subsurface barriers requires processes to verify the emplacement and effectiveness of barrier and to monitor the performance of a barrier after emplacement. Non destructive and remote sensing techniques, such as geophysical methods, are possible technologies to address these needs. The changes in mechanical, hydrologic and chemical properties associated with the emplacement of an engineered barrier will affect geophysical properties such a seismic velocity, electrical conductivity, and dielectric constant. Also, the barrier, once emplaced and interacting with the in situ geologic system, may affect the paths along which electrical current flows in the subsurface. These changes in properties and processes facilitate the detection and monitoring of the barrier. The approaches to characterizing and monitoring engineered barriers can be divided between (1) methods that directly image the barrier using the contrasts in physical properties between the barrier and the host soil or rock and (2) methods that reflect flow processes around or through the barrier. For example, seismic methods that delineate the changes in density and stiffness associated with the barrier represents a direct imaging method. Electrical self potential methods and flow probes based on heat flow methods represent techniques that can delineate the flow path or flow processes around and through a barrier

  10. Reliability of modified tunneling barriers for high performance nonvolatile charge trap flash memory application

    Science.gov (United States)

    Park, Goon-Ho; Cho, Won-Ju

    2010-01-01

    Charge trap flash memory devices with modified tunneling barriers were fabricated using the tunneling barrier engineering technique. Variable oxide thickness (VARIOT) barrier and CRESTED barrier consisting of thin SiO2 and Si3N4 dielectric layers were used as engineered tunneling barriers. High-k dielectrics were used as charge trapping and blocking oxide layer to improve the program/erase speed. The VARIOT type tunneling barrier composed of oxide-nitride-oxide layers revealed reliable electrical characteristics; long retention time and superior endurance. On the other hand, the CRESTED tunneling barrier composed of nitride-oxide-nitride (NON) layers showed degraded retention and endurance characteristics. It is found that the degradation of NON barrier is associated with the increase in interface state density at tunneling barrier/silicon channel by programming and erasing (P/E) stress.

  11. Dissimilarity of contemporary and historical gene flow in a wild carrot (Daucus carota) metapopulation under contrasting levels of human disturbance: implications for risk assessment and management of transgene introgression.

    Science.gov (United States)

    Rong, Jun; Xu, Shuhua; Meirmans, Patrick G; Vrieling, Klaas

    2013-11-01

    Transgene introgression from crops into wild relatives may increase the resistance of wild plants to herbicides, insects, etc. The chance of transgene introgression depends not only on the rate of hybridization and the establishment of hybrids in local wild populations, but also on the metapopulation dynamics of the wild relative. The aim of the study was to estimate gene flow in a metapopulation for assessing and managing the risks of transgene introgression. Wild carrots (Daucus carota) were sampled from 12 patches in a metapopulation. Eleven microsatellites were used to genotype wild carrots. Genetic structure was estimated based on the FST statistic. Contemporary (over the last several generations) and historical (over many generations) gene flow was estimated with assignment and coalescent methods, respectively. The genetic structure in the wild carrot metapopulation was moderate (FST = 0·082) and most of the genetic variation resided within patches. A pattern of isolation by distance was detected, suggesting that most of the gene flow occurred between neighbouring patches (≤1 km). The mean contemporary gene flow was 5 times higher than the historical estimate, and the correlation between them was very low. Moreover, the contemporary gene flow in roadsides was twice that in a nature reserve, and the correlation between contemporary and historical estimates was much higher in the nature reserve. Mowing of roadsides may contribute to the increase in contemporary gene flow. Simulations demonstrated that the higher contemporary gene flow could accelerate the process of transgene introgression in the metapopulation. Human disturbance such as mowing may alter gene flow patterns in wild populations, affecting the metapopulation dynamics of wild plants and the processes of transgene introgression in the metapopulation. The risk assessment and management of transgene introgression and the control of weeds need to take metapopulation dynamics into consideration.

  12. Apoplastic Diffusion Barriers in Arabidopsis

    Science.gov (United States)

    Schreiber, Lukas; Franke, Rochus Benni; Geldner, Niko; Reina-Pinto, José J.; Kunst, Ljerka

    2013-01-01

    During the development of Arabidopsis and other land plants, diffusion barriers are formed in the apoplast of specialized tissues within a variety of plant organs. While the cuticle of the epidermis is the primary diffusion barrier in the shoot, the Casparian strips and suberin lamellae of the endodermis and the periderm represent the diffusion barriers in the root. Different classes of molecules contribute to the formation of extracellular diffusion barriers in an organ- and tissue-specific manner. Cutin and wax are the major components of the cuticle, lignin forms the early Casparian strip, and suberin is deposited in the stage II endodermis and the periderm. The current status of our understanding of the relationships between the chemical structure, ultrastructure and physiological functions of plant diffusion barriers is discussed. Specific aspects of the synthesis of diffusion barrier components and protocols that can be used for the assessment of barrier function and important barrier properties are also presented. PMID:24465172

  13. Performance of engineered barriers

    International Nuclear Information System (INIS)

    Rajaram, V.; Dean, P.V.; McLellan, S.A.

    1997-01-01

    Engineered barriers, both vertical and horizontal, have been used to isolate hazardous wastes from contact, precipitation, surface water and groundwater. The primary objective of this study was to determine the performance of subsurface barriers installed throughout the U.S. over the past 20 years to contain hazardous wastes. Evaluation of Resource Conservation and Recovery Act (RCRA) Subtitle C or equivalent caps was a secondary objective. A nationwide search was launched to select hazardous waste sites at which vertical barrier walls and/or caps had been used as the containment method. None of the sites selected had an engineered floor. From an initial list of 130 sites, 34 sites were selected on the basis of availability of monitoring data for detailed analysis of actual field performance. This paper will briefly discuss preliminary findings regarding the design, construction quality assurance/construction quality control (CQA/CQC), and monitoring at the 34 sites. In addition, the short-term performance of these sites (less than 5 years) is presented since very little long-term performance data was available

  14. Barriers to healthcare of homeless residents of three Honolulu shelters.

    Science.gov (United States)

    Hoshide, Reid R; Manog, Jenny D; Noh, Thomas; Omori, Jill

    2011-10-01

    In Honolulu, health insurance rates amongst the homeless are one of the highest in the nation, yet significant health care needs are still unmet. In a previous model, health care barriers have been divided into four domains: bureaucratic, personal, programmatic, and financial. This study aimed to determine the risk factors associated with the domains of health care barriers amongst the study's sample of 128 subjects across three Honolulu homeless shelters. Univariate models revealed health care barriers; but only the lack of health insurance was a significant financial barrier to health care in multivariate analyses (Odds ratio: 2.12; 95% Confidence Interval: 1.09-4.16). The identification of barriers should guide how health care programs approach Honolulu's homeless population to better serve their health care needs.

  15. Horizontal Acoustic Barriers for Protection from Seismic Waves

    Directory of Open Access Journals (Sweden)

    Sergey V. Kuznetsov

    2011-01-01

    Full Text Available The basic idea of a seismic barrier is to protect an area occupied by a building or a group of buildings from seismic waves. Depending on nature of seismic waves that are most probable in a specific region, different kinds of seismic barriers can be suggested. Herein, we consider a kind of a seismic barrier that represents a relatively thin surface layer that prevents surface seismic waves from propagating. The ideas for these barriers are based on one Chadwick's result concerning nonpropagation condition for Rayleigh waves in a clamped half-space, and Love's theorem that describes condition of nonexistence for Love waves. The numerical simulations reveal that to be effective the length of the horizontal barriers should be comparable to the typical wavelength.

  16. Trends and barriers to lateral gene transfer in prokaryotes.

    Science.gov (United States)

    Popa, Ovidiu; Dagan, Tal

    2011-10-01

    Gene acquisition by lateral gene transfer (LGT) is an important mechanism for natural variation among prokaryotes. Laboratory experiments show that protein-coding genes can be laterally transferred extremely fast among microbial cells, inherited to most of their descendants, and adapt to a new regulatory regime within a short time. Recent advance in the phylogenetic analysis of microbial genomes using networks approach reveals a substantial impact of LGT during microbial genome evolution. Phylogenomic networks of LGT among prokaryotes reconstructed from completely sequenced genomes uncover barriers to LGT in multiple levels. Here we discuss the kinds of barriers to gene acquisition in nature including physical barriers for gene transfer between cells, genomic barriers for the integration of acquired DNA, and functional barriers for the acquisition of new genes. Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. Weak population structure in European roe deer (Capreolus capreolus) and evidence of introgressive hybridization with Siberian roe deer (C. pygargus) in northeastern Poland.

    Science.gov (United States)

    Olano-Marin, Juanita; Plis, Kamila; Sönnichsen, Leif; Borowik, Tomasz; Niedziałkowska, Magdalena; Jędrzejewska, Bogumiła

    2014-01-01

    We investigated contemporary and historical influences on the pattern of genetic diversity of European roe deer (Capreolus capreolus). The study was conducted in northeastern Poland, a zone where vast areas of primeval forests are conserved and where the European roe deer was never driven to extinction. A total of 319 unique samples collected in three sampling areas were genotyped at 16 microsatellites and one fragment (610 bp) of mitochondrial DNA (mtDNA) control region. Genetic diversity was high, and a low degree of genetic differentiation among sampling areas was observed with both microsatellites and mtDNA. No evidence of genetic differentiation between roe deer inhabiting open fields and forested areas was found, indicating that the ability of the species to exploit these contrasting environments might be the result of its phenotypic plasticity. Half of the studied individuals carried an mtDNA haplotype that did not belong to C. capreolus, but to a related species that does not occur naturally in the area, the Siberian roe deer (C. pygargus). No differentiation between individuals with Siberian and European mtDNA haplotypes was detected at microsatellite loci. Introgression of mtDNA of Siberian roe deer into the genome of European roe deer has recently been detected in eastern Europe. Such introgression might be caused by human-mediated translocations of Siberian roe deer within the range of European roe deer or by natural hybridization between these species in the past.

  18. Weak population structure in European roe deer (Capreolus capreolus and evidence of introgressive hybridization with Siberian roe deer (C. pygargus in northeastern Poland.

    Directory of Open Access Journals (Sweden)

    Juanita Olano-Marin

    Full Text Available We investigated contemporary and historical influences on the pattern of genetic diversity of European roe deer (Capreolus capreolus. The study was conducted in northeastern Poland, a zone where vast areas of primeval forests are conserved and where the European roe deer was never driven to extinction. A total of 319 unique samples collected in three sampling areas were genotyped at 16 microsatellites and one fragment (610 bp of mitochondrial DNA (mtDNA control region. Genetic diversity was high, and a low degree of genetic differentiation among sampling areas was observed with both microsatellites and mtDNA. No evidence of genetic differentiation between roe deer inhabiting open fields and forested areas was found, indicating that the ability of the species to exploit these contrasting environments might be the result of its phenotypic plasticity. Half of the studied individuals carried an mtDNA haplotype that did not belong to C. capreolus, but to a related species that does not occur naturally in the area, the Siberian roe deer (C. pygargus. No differentiation between individuals with Siberian and European mtDNA haplotypes was detected at microsatellite loci. Introgression of mtDNA of Siberian roe deer into the genome of European roe deer has recently been detected in eastern Europe. Such introgression might be caused by human-mediated translocations of Siberian roe deer within the range of European roe deer or by natural hybridization between these species in the past.

  19. QTL Mapping of Grain Quality Traits Using Introgression Lines Carrying Oryza rufipogon Chromosome Segments in Japonica Rice.

    Science.gov (United States)

    Yun, Yeo-Tae; Chung, Chong-Tae; Lee, Young-Ju; Na, Han-Jung; Lee, Jae-Chul; Lee, Sun-Gye; Lee, Kwang-Won; Yoon, Young-Hwan; Kang, Ju-Won; Lee, Hyun-Sook; Lee, Jong-Yeol; Ahn, Sang-Nag

    2016-12-01

    Improved eating quality is a major breeding target in japonica rice due to market demand. Consequently, quantitative trait loci (QTL) for glossiness of cooked rice and amylose content associated with eating quality have received much research focus because of their importance in rice quality. In this study, QTL associated with 12 grain quality traits were identified using 96 introgression lines (IL) of rice developed from an interspecific cross between the Korean elite O. sativa japonica cultivar 'Hwaseong' and O. rufipogon over 7 years. QTL analyses indicated that QTL qDTH6 for heading date, detected on chromosome 6 is associated with variance in grain traits. Most QTLs detected in this study clustered near the qDTH6 locus on chromosome 6, suggesting the effect of qDTH6. O. rufipogon alleles negatively affected grain quality traits except for a few QTLs, including qGCR9 for glossiness of cooked rice on chromosome 9. To characterize the effect of the O. rufipogon locus harboring qGCR9, four lines with a single but different O. rufipogon segment near qGCR9 were compared to Hwaseong. Three lines (O. rufipopgon ILs) having O. rufipogon segment between RM242 and RM245 in common showed higher glossiness of cooked rice than Hwaseong and the other line (Hwaseong IL), indicating that qGCR9 is located in the 3.4-Mb region between RM242 and RM245. Higher glossiness of cooked rice conferred by the O. rufipogon allele might be associated with protein content considering that three lines had lower protein content than Hwaseong (P < 0.1). These three O. rufipogon ILs showed higher yield than Hwaseong and Hwaseong IL due to increase in spikelets per panicle and grain weight indicating the linkage of qGCR9 and yield component QTLs. The qGCR9 locus is of particular interest because of its independence from other undesirable grain quality traits in O. rufipogon. SSR markers linked to qGCR9 can be used to develop high-quality japonica lines and offer a starting point for map

  20. Adaptive consequences of human-mediated introgression for indigenous tree species: the case of a relict Pinus pinaster population.

    Science.gov (United States)

    Ramírez-Valiente, José Alberto; Robledo-Arnuncio, Juan José

    2014-12-01

    , a potential early selective advantage of exotic and hybrid genotypes would enhance initial steps of introgression of non-native genes into the study relict population of P. pinaster. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  1. Studying the Genetics of Resistance to CyHV-3 Disease Using Introgression from Feral to Cultured Common Carp Strains

    Science.gov (United States)

    Tadmor-Levi, Roni; Asoulin, Efrat; Hulata, Gideon; David, Lior

    2017-01-01

    Sustainability and further development of aquaculture production are constantly challenged by outbreaks of fish diseases, which are difficult to prevent or control. Developing fish strains that are genetically resistant to a disease is a cost-effective and a sustainable solution to address this challenge. To do so, heritable genetic variation in disease resistance should be identified and combined together with other desirable production traits. Aquaculture of common carp has suffered substantial losses from the infectious disease caused by the cyprinid herpes virus type 3 (CyHV-3) virus and the global spread of outbreaks indicates that many cultured strains are susceptible. In this research, CyHV-3 resistance from the feral strain “Amur Sassan” was successfully introgressed into two susceptible cultured strains up to the first backcross (BC1) generation. Variation in resistance of families from F1 and BC1 generations was significantly greater compared to that among families of any of the susceptible parental lines, a good starting point for a family selection program. Considerable additive genetic variation was found for CyHV-3 resistance. This phenotype was transferable between generations with contributions to resistance from both the resistant feral and the susceptible cultured strains. Reduced scale coverage (mirror phenotype) is desirable and common in cultured strains, but so far, cultured mirror carp strains were found to be susceptible. Here, using BC1 families ranging from susceptible to resistant, no differences in resistance levels between fully scaled and mirror full-sib groups were found, indicating that CyHV-3 resistance was successfully combined with the desirable mirror phenotype. In addition, the CyHV-3 viral load in tissues throughout the infection of susceptible and resistant fish was followed. Although resistant fish get infected, viral loads in tissues of these fish are significantly lesser than in those of susceptible fish, allowing them

  2. Evidence for the occurrence of two sympatric sibling species within the Anopheles (Kerteszia) cruzii complex in southeast Brazil and the detection of asymmetric introgression between them using a multilocus analysis.

    Science.gov (United States)

    Rona, Luísa D P; Carvalho-Pinto, Carlos J; Peixoto, Alexandre A

    2013-09-24

    Anopheles (Kerteszia) cruzii (Diptera: Culicidae) is a primary vector of human and simian malaria parasites in southern and southeastern Brazil. Earlier studies using chromosome inversions, isoenzymes and a number of molecular markers have suggested that An. cruzii is a species complex. In this study, a multilocus approach using six loci, three circadian clock genes and three encoding ribosomal proteins, was carried out to investigate in more detail the genetic differentiation between the An. cruzii populations from Florianópolis-Santa Catarina (southern Brazil) and Itatiaia-Rio de Janeiro States (southeastern Brazil). The analyses were performed first comparing Florianópolis and Itatiaia, and then comparing the two putative sympatric incipient species from Itatiaia (Itatiaia A and Itatiaia B). The analysis revealed high FST values between Florianópolis and Itatiaia (considering Itatiaia A and B together) and also between the sympatric Itatiaia A and Itatiaia B, irrespective of their function. Also, using the IM program, no strong indication of migration was found between Florianópolis and Itatiaia (considering Itatiaia A and B together) using all loci together, but between Itatiaia A and Itatiaia B, the results show evidence of migration only in the direction of Itatiaia B. The results of the multilocus analysis indicate that Florianópolis and Itatiaia represent different species of the An. cruzii complex that diverged around 0.6 Mya, and also that the Itatiaia sample is composed of two sympatric incipient species A and B, which diverged around 0.2 Mya. Asymmetric introgression was found between the latter two species despite strong divergence in some loci.

  3. Barrier mechanisms in the Drosophila blood-brain barrier

    Directory of Open Access Journals (Sweden)

    Samantha Jane Hindle

    2014-12-01

    Full Text Available The invertebrate blood-brain barrier field is growing at a rapid pace and, in recent years, studies have shown a physiologic and molecular complexity that has begun to rival its vertebrate counterpart. Novel mechanisms of paracellular barrier maintenance through GPCR signaling were the first demonstrations of the complex adaptive mechanisms of barrier physiology. Building upon this work, the integrity of the invertebrate blood-brain barrier has recently been shown to require coordinated function of all layers of the compound barrier structure, analogous to signaling between the layers of the vertebrate neurovascular unit. These findings strengthen the notion that many blood-brain barrier mechanisms are conserved between vertebrates and invertebrates, and suggest that novel findings in invertebrate model organisms will have a significant impact on the understanding of vertebrate BBB functions. In this vein, important roles in coordinating localized and systemic signaling to dictate organism development and growth are beginning to show how the blood-brain barrier can govern whole animal physiologies. This includes novel functions of blood-brain barrier gap junctions in orchestrating synchronized neuroblast proliferation, and of blood-brain barrier secreted antagonists of insulin receptor signaling. These advancements and others are pushing the field forward in exciting new directions. In this review, we provide a synopsis of invertebrate blood-brain barrier anatomy and physiology, with a focus on insights from the past 5 years, and highlight important areas for future study.

  4. Linguistic Barriers and Bridges

    DEFF Research Database (Denmark)

    Thuesen, Frederik

    2016-01-01

    The influence of language on social capital in low-skill and ethnically diverse workplaces has thus far received very limited attention within the sociology of work. As the ethnically diverse workplace is an important social space for the construction of social relations bridging different social...... and intercultural communication, this article analyses interviews with 31 employees from two highly ethnically diverse Danish workplaces. The article shows how linguistic barriers such as different levels of majority language competence and their consequent misunderstandings breed mistrust and hostility, whilst...... communication related to collaboration and ‘small talk’ may provide linguistic bridges to social capital formation....

  5. [Barrier methods of contraception].

    Science.gov (United States)

    Goldsmith, A; Edelman, D A

    1982-01-01

    Vaginal methods of contraception were the earliest types used and some references to them date back to antiquity. Most of the vaginal contraceptive agents identified by the ancient Greeks, Indians, Japanese, and Chinese have been found in modern laboratory tests to have spermicidal properties, but it is doubtful that the methods were fully reliable or were used by many people. During the 19th century the condom, vaginal spermicides, and diaphragm became available. The development of nonoxynol-9 and other nonirritating but effective spermicidal agents improved vaginal contraceptives greatly by the 1950s, but starting in the 1960s newer methods began to replace the vaginal methods. Interest in barrier methods has been reawakened somewhat by concern about the health effects of hormonal methods. At present all barrier methods leave something to be desired. Failure rates of 3-30% for barrier methods in general have been estimated, but the higher rates are believed due to incorrect or inconsistent use. Theoretical failure rates of condoms and diaphragms have been estimated at 3/100 women-years, but in actual use failure rates may reach 15 for condoms and 13 for diaphragms used with spermicides. Use-effectiveness rates are greatly influenced by motivation. For a variety of reasons, the acceptability of barrier methods is low, especially in developing countries. New developments in spermicidal agents include sperm inhibitors, which impede the fertilizing capacity of sperm rather than attempting a spermicidal effect; a number of such agents have been studied and have proven more effective in animal tests than conventional spermicides. Neosampoon, a new spermicidal foam, has attracted an increasing number of users, especially in developing countries. A new condom, made of thin polymers and containing a standard dose of nonoxynol-9, has been designed to dissolve in the vaginal fluid. Further studies are needed of its acceptability, efficacy, and side effects before it becomes

  6. Support or Barrier?

    DEFF Research Database (Denmark)

    Sanden, Guro Refsum; Lønsmann, Dorte

    employees use to cross language boundaries in their everyday work, and, secondly, how these practices relate to top-down language management in the case companies. Our findings show that employees are often dependent on ad hoc and informal solutions in cross- language situations, which leads us......This study offers a critical look at how corporate-level language management influences front-line language practices among employees in three multinational corporations (MNCs) headquartered in Scandinavia. Based on interview and document data, we examine, firstly, what front-line practices...... to a discussion of how a company’s language policy may be seen as both support and a barrier....

  7. Introgression of tomato chromosomes into the potato genome : an analysis through molecular marker and in situ hybridisation techniques = [Introgressie van tomatenchromosomen in het aardappelgenoom : een analyse met behulp van moleculaire merker en in situ hybridisatie technieken

    NARCIS (Netherlands)

    Garriga Caldere, F.

    1998-01-01

    Transfer of alien chromosomes and genes across intergeneric boundaries can be useful not only for the introgression of desirable characters but also for fundamental genetic studies. The successful demonstration of hybridisation of potato ( Solanum tuberosum ) and tomato

  8. Stem cell heterogeneity revealed

    DEFF Research Database (Denmark)

    Andersen, Marianne S; Jensen, Kim B

    2016-01-01

    The skin forms a protective, water-impermeable barrier consisting of heavily crosslinked epithelial cells. However, the specific role of stem cells in sustaining this barrier remains a contentious issue. A detailed analysis of the interfollicular epidermis now proposes a model for how a composite...... of cells with different properties are involved in its maintenance....

  9. Performing a local barrier operation

    Science.gov (United States)

    Archer, Charles J; Blocksome, Michael A; Ratterman, Joseph D; Smith, Brian E

    2014-03-04

    Performing a local barrier operation with parallel tasks executing on a compute node including, for each task: retrieving a present value of a counter; calculating, in dependence upon the present value of the counter and a total number of tasks performing the local barrier operation, a base value, the base value representing the counter's value prior to any task joining the local barrier; calculating, in dependence upon the base value and the total number of tasks performing the local barrier operation, a target value of the counter, the target value representing the counter's value when all tasks have joined the local barrier; joining the local barrier, including atomically incrementing the value of the counter; and repetitively, until the present value of the counter is no less than the target value of the counter: retrieving the present value of the counter and determining whether the present value equals the target value.

  10. Exposure, Uptake, and Barriers

    Science.gov (United States)

    Baeza-Squiban, Armelle; Lanone, Sophie

    The nanotechnologies market is booming, e.g., in the food industry (powder additives, etc.) and in medical applications (drug delivery, prosthetics, diagnostic imaging, etc.), but also in other industrial sectors, such as sports, construction, cosmetics, and so on. In this context, with an exponential increase in the number of current and future applications, it is particularly important to evaluate the problem of unintentional (i.e., non-medical) exposure to manufactured nanoparticles (so excluding nanoparticles found naturally in the environment). In this chapter, we begin by discussing the various parameters that must be taken into account in any serious assessment of exposure to man-made nanoparticles. We then list the potential routes by which nanoparticles might enter into the organism, and outline the mechanisms whereby they could get past the different biological barriers. Finally, we describe the biodistribution of nanoparticles in the organism and the way they are eliminated.

  11. Countermeasures and barriers

    International Nuclear Information System (INIS)

    Petersen, Johannes

    2005-10-01

    In 1973 Haddon proposed ten strategies for reducing and avoiding damages based on a model of potential harmful energy transfer (Haddon, 1973). The strategies apply to a large variety of unwanted phenomena. Haddon's pioneering work on countermeasures has had a major influence on later thinking about safety. Considering its impact it is remarkable that the literature offers almost no discussions related to the theoretical foundations of Haddon's countermeasure strategies. The present report addresses a number of theoretical issues related to Haddon's countermeasure strategies, which are: 1) A reformulation and formalization of Haddon's countermeasure strategies. 2) An identification and description of some of the problems associated with the term 'barrier'. 3) Suggestions for a more precise terminology based on the causal structure of countermeasures. 4) Extending the scope of countermeasures to include sign-based countermeasures. (au)

  12. Countermeasures and barriers

    Energy Technology Data Exchange (ETDEWEB)

    Petersen, Johannes [Oersted - DTU, Automation, Kgs. Lyngby (Denmark)

    2005-10-01

    In 1973 Haddon proposed ten strategies for reducing and avoiding damages based on a model of potential harmful energy transfer (Haddon, 1973). The strategies apply to a large variety of unwanted phenomena. Haddon's pioneering work on countermeasures has had a major influence on later thinking about safety. Considering its impact it is remarkable that the literature offers almost no discussions related to the theoretical foundations of Haddon's countermeasure strategies. The present report addresses a number of theoretical issues related to Haddon's countermeasure strategies, which are: 1) A reformulation and formalization of Haddon's countermeasure strategies. 2) An identification and description of some of the problems associated with the term 'barrier'. 3) Suggestions for a more precise terminology based on the causal structure of countermeasures. 4) Extending the scope of countermeasures to include sign-based countermeasures. (au)

  13. Multi-level barriers analysis to promote guideline based nursing care: a leadership strategy from home health care.

    Science.gov (United States)

    Gifford, Wendy A; Graham, Ian D; Davies, Barbara L

    2013-07-01

    Understanding the types of barriers that exist when implementing change can assist healthcare managers to tailor implementation strategies for optimal patient outcomes. The aim of this paper is to present an organising framework, the Barriers Assessment Taxonomy, for understanding barriers to nurses' use of clinical practice guideline recommendations. Barriers to recommendations are illustrated using the Barriers Assessment Taxonomy and insights discussed. As part of a pilot implementation study, semi-structured interviews (n = 26) were conducted to understand barriers to nurses' use of nine guideline recommendations for diabetic foot ulcers. Content analysis of verbatim transcripts included thematic coding and categorising barriers using the Barriers Assessment Taxonomy. Nineteen barriers were associated with nine recommendations, crossing five levels of the health care delivery system. The Barriers Assessment Taxonomy revealed that all recommendations had individual and organisational level barriers, with one recommendation having barriers at all levels. Individual level barriers were most frequent and lack of knowledge and skills was the only barrier that crossed all recommendations. The Barriers Assessment Taxonomy provides a framework for nursing managers to understand the complexity of barriers that exist, and can assist in choosing intervention strategies to support improved quality care and patient outcomes. © 2013 John Wiley & Sons Ltd.

  14. Thames barrier (flood protection barriers on the Thames)

    International Nuclear Information System (INIS)

    Ilkovic, J.

    2005-01-01

    In this paper the flood protection barriers on the Thames are presented. The flood protection system on the Thames in 1984 was commissioned. During two decades this barrier was used 54 times against to the high water and 34 times against storm-sewage. There is installed buttress type hydroelectric power plant

  15. Sex and Ethnic Differences in the Perception of Educational and Career-Related Barriers and Levels of Coping Efficacy.

    Science.gov (United States)

    Luzzo, Darrell Anthony; McWhirter, Ellen Hawley

    2001-01-01

    Evaluates sex and ethnic differences in perceived career-related and educational barriers and coping efficacy among college students (N=286). Results reveal that women and ethnic minorities anticipated significantly more career-related barriers. Ethnic minorities also exhibited more perceived educational barriers and lower self-efficacy for coping…

  16. Identification of Loci Affecting Accumulation of Secondary Metabolites in Tomato Fruit of a Solanum lycopersicum × Solanum chmielewskii Introgression Line Population.

    Science.gov (United States)

    Ballester, Ana-Rosa; Tikunov, Yury; Molthoff, Jos; Grandillo, Silvana; Viquez-Zamora, Marcela; de Vos, Ric; de Maagd, Ruud A; van Heusden, Sjaak; Bovy, Arnaud G

    2016-01-01

    Semi-polar metabolites such as flavonoids, phenolic acids, and alkaloids are very important health-related compounds in tomato. As a first step to identify genes responsible for the synthesis of semi-polar metabolites, quantitative trait loci (QTLs) that influence the semi-polar metabolite content in red-ripe tomato fruit were identified, by characterizing fruits of a population of introgression lines (ILs) derived from a cross between the cultivated tomato Solanum lycopersicum and the wild species Solanum chmielewskii . By analyzing fruits of plants grown at two different locations, we were able to identify robust metabolite QTLs for changes in phenylpropanoid glycoconjugation on chromosome 9, for accumulation of flavonol glycosides on chromosome 5, and for alkaloids on chromosome 7. To further characterize the QTLs we used a combination of genome sequencing, transcriptomics and targeted metabolomics to identify candidate key genes underlying the observed metabolic variation.

  17. Temporal change in genetic integrity suggests loss of local adaptation in a wild Atlantic salmon (Salmo salar) population following introgression by farmed escapees.

    Science.gov (United States)

    Bourret, V; O'Reilly, P T; Carr, J W; Berg, P R; Bernatchez, L

    2011-03-01

    In some wild Atlantic salmon populations, rapid declines in numbers of wild returning adults has been associated with an increase in the prevalence of farmed salmon. Studies of phenotypic variation have shown that interbreeding between farmed and wild salmon may lead to loss of local adaptation. Yet, few studies have attempted to assess the impact of interbreeding at the genome level, especially among North American populations. Here, we document temporal changes in the genetic makeup of the severely threatened Magaguadavic River salmon population (Bay of Fundy, Canada), a population that might have been impacted by interbreeding with farmed salmon for nearly 20 years. Wild and farmed individuals caught entering the river from 1980 to 2005 were genotyped at 112 single-nucleotide polymorphisms (SNPs), and/or eight microsatellite loci, to scan for potential shifts in adaptive genetic variation. No significant temporal change in microsatellite-based estimates of allele richness or gene diversity was detected in the wild population, despite its precipitous decline in numbers over the last two decades. This might reflect the effect of introgression from farmed salmon, which was corroborated by temporal change in linkage-disequilibrium. Moreover, SNP genome scans identified a temporal decrease in candidate loci potentially under directional selection. Of particular interest was a SNP previously shown to be strongly associated with an important quantitative trait locus for parr mark number, which retained its genetic distinctiveness between farmed and wild fish longer than other outliers. Overall, these results indicate that farmed escapees have introgressed with wild Magaguadavic salmon resulting in significant alteration of the genetic integrity of the native population, including possible loss of adaptation to wild conditions.

  18. Evidence for the introduction of the Asian red alga Neosiphonia japonica and its introgression with Neosiphonia harveyi (Ceramiales, Rhodophyta) in the Northwest Atlantic.

    Science.gov (United States)

    Savoie, Amanda M; Saunders, Gary W

    2015-12-01

    There is currently conflict in the literature on the taxonomic status of the reportedly cosmopolitan species Neosiphonia harveyi, a common red alga along the coast of Atlantic Canada and New England, USA. Neosiphonia harveyi sensu lato was assessed using three molecular markers: COI-5P, ITS and rbcL. All three markers clearly delimited three genetic species groups within N. harveyi sensu lato in this region, which we identified as N. harveyi, N. japonica and Polysiphonia akkeshiensis (here resurrected from synonymy with N. japonica). Although Neosiphonia harveyi is considered by some authors to be introduced to the Atlantic from the western Pacific, it was only confirmed from the North Atlantic suggesting it is native to this area. In contrast, Neosiphonia japonica was collected from only two sites in Rhode Island, USA, as well as from its reported native range in Asia (South Korea), which when combined with data in GenBank indicates that this species was introduced to the Northwest Atlantic. The GenBank data further indicate that N. japonica was also introduced to North Carolina, Spain, Australia and New Zealand. Despite the fact that all three markers clearly delimited N. harveyi and N. japonica as distinct genetic species groups, the ITS sequences for some N. harveyi individuals displayed mixed patterns and additivity indicating introgression of nuclear DNA from N. japonica into N. harveyi in the Northwest Atlantic. Introgression of DNA from an introduced species to a native species (i.e. 'genetic pollution') is one of the possible consequences of species introductions, and we believe this is the first documented evidence for this phenomenon in red algae. © 2015 John Wiley & Sons Ltd.

  19. The Inheritance of the Pheromone Sensory System in TwoHelicoverpaSpecies: Dominance ofH. armigeraand Possible Introgression fromH. assulta.

    Science.gov (United States)

    Xu, Meng; Dong, Jun-Feng; Wu, Han; Zhao, Xin-Cheng; Huang, Ling-Qiao; Wang, Chen-Zhu

    2016-01-01

    Hybridization of sympatric closely related species may sometimes lead to introgression and speciation. The sister species Helicoverpa armigera and Helicoverpa assulta both use (Z)-11-hexadecenal and (Z)-9-hexadecenal as sex pheromone components but in reversed ratios. Female H. armigera and male H. assulta could hybridize and produce fertile male hybrids, which can then backcross with females of the two parent species to get backcross lines in the laboratory. In this study, we compared the olfactory responses to pheromone compounds in the periphery and in the antennal lobes (ALs) of males of the two species, as well as of their hybrids and backcrosses. Single-sensillum recordings were carried out to explore characteristics of male-specific sensilla on the antennae, and in vivo calcium imaging combined with digital 3D-reconstruction was used to describe what happens in the macroglomerular complex (MGC) of the AL. The results show that the population ratio of the two male-specific types of olfactory sensory neurons responding to two sex pheromone components are controlled by a major gene, and that the allele of H. armigera is dominant. Consistently, the study of the representative areas activated by sex pheromone components in the ALs further support the dominance of H. armigera . However, the topological structure of the MGC in the hybrid was similar but not identical to that in H. armigera . All subtypes of male-specific sensilla identified in the two species were found in the male hybrids and backcrosses. Moreover, two new subtypes with broader response spectra (the expanded A subtype and the expanded C subtype) emerged in the hybrids. Based on the inheritance pattern of the pheromone sensory system, we predict that when hybridization of female H. armigera and male H. assulta occurs in the field, male hybrids would readily backcross with female H. armigera , and introgression might occur from H. assulta into H. armigera through repeated backcrossing.

  20. The construction of a Solanum habrochaites LYC4 introgression line population and the identification of QTLs for resistance to Botrytis cinerea

    Science.gov (United States)

    van Heusden, Adriaan W.; Meijer-Dekens, Fien; van Kan, Jan A. L.; Maris, Paul; Lindhout, Pim

    2007-01-01

    Tomato (Solanum lycopersicum) is susceptible to grey mold (Botrytis cinerea). Partial resistance to this fungus has been identified in accessions of wild relatives of tomato such as Solanum habrochaites LYC4. In a previous F2 mapping study, three QTLs conferring resistance to B. cinerea (Rbcq1, Rbcq2 and Rbcq4a) were identified. As it was probable that this study had not identified all QTLs involved in resistance we developed an introgression line (IL) population (n = 30), each containing a S. habrochaites introgression in the S. lycopersicum cv. Moneymaker genetic background. On average each IL contained 5.2% of the S. habrochaites genome and together the lines provide an estimated coverage of 95%. The level of susceptibility to B. cinerea for each of the ILs was assessed in a greenhouse trial and compared to the susceptible parent S. lycopersicum cv. Moneymaker. The effect of the three previously identified loci could be confirmed and seven additional loci were detected. Some ILs contains multiple QTLs and the increased resistance to B. cinerea in these ILs is in line with a completely additive model. We conclude that this set of QTLs offers good perspectives for breeding of B. cinerea resistant cultivars and that screening an IL population is more sensitive for detection of QTLs conferring resistance to B. cinerea than the analysis in an F2 population. Electronic supplementary material The online version of this article (doi:10.1007/s00122-006-0500-2) contains supplementary material, which is available to authorized users. PMID:17273845

  1. wMel limits zika and chikungunya virus infection in a Singapore Wolbachia-introgressed Ae. aegypti strain, wMel-Sg.

    Directory of Open Access Journals (Sweden)

    Cheong Huat Tan

    2017-05-01

    Full Text Available Zika (ZIKV and Chikungunya (CHIKV viruses are emerging Aedes-borne viruses that are spreading outside their known geographic range and causing wide-scale epidemics. It has been reported that these viruses can be transmitted efficiently by Ae. aegypti. Recent studies have shown that Ae. aegypti when transinfected with certain Wolbachia strains shows a reduced replication and dissemination of dengue (DENV, Chikungunya (CHIKV, and Yellow Fever (YFV viruses. The aim of this study was to determine whether the wMel strain of Wolbachia introgressed onto a Singapore Ae. aegypti genetic background was able to limit ZIKV and CHIKV infection in the mosquito.Five to seven-day old mosquitoes either infected or uninfected with wMel Wolbachia were orally infected with a Ugandan strain of ZIKV and several outbreak strains of CHIKV. The midgut and salivary glands of each mosquito were sampled at days 6, 9 and 13 days post infectious blood meal to determine midgut infection and salivary glands dissemination rates, respectively. In general, all wild type Ae. aegypti were found to have high ZIKV and CHIKV infections in their midguts and salivary glands, across all sampling days, compared to Wolbachia infected counterparts. Median viral titre for all viruses in Wolbachia infected mosquitoes were significantly lower across all time points when compared to wild type mosquitoes. Most significantly, all but two and one of the wMel infected mosquitoes had no detectable ZIKV and CHIKV, respectively, in their salivary glands at 14 days post-infectious blood meal.Our results showed that wMel limits both ZIKV and CHIKV infection when introgressed into a Singapore Ae. aegypti genetic background. These results also strongly suggest that female Aedes aegypti carrying Wolbachia will have a reduced capacity to transmit ZIKV and CHIKV.

  2. Simultaneous transfer, introgression, and genomic localization of genes for resistance to stem rust race TTKSK (Ug99) from Aegilops tauschii to wheat.

    Science.gov (United States)

    Olson, Eric L; Rouse, Matthew N; Pumphrey, Michael O; Bowden, Robert L; Gill, Bikram S; Poland, Jesse A

    2013-05-01

    Wheat production is currently threatened by widely virulent races of the wheat stem rust fungus, Puccinia graminis f. sp. tritici, that are part of the TTKSK (also known as 'Ug99') race group. The diploid D genome donor species Aegilops tauschii (2n = 2x = 14, DD) is a readily accessible source of resistance to TTKSK and its derivatives that can be transferred to hexaploid wheat, Triticum aestivum (2n = 6x = 42, AABBDD). To expedite transfer of TTKSK resistance from Ae. tauschii, a direct hybridization approach was undertaken that integrates gene transfer, mapping, and introgression into one process. Direct crossing of Ae. tauschii accessions with an elite wheat breeding line combines the steps of gene transfer and introgression while development of mapping populations during gene transfer enables the identification of closely linked markers. Direct crosses were made using TTKSK-resistant Ae. tauschii accessions TA1662 and PI 603225 as males and a stem rust-susceptible T. aestivum breeding line, KS05HW14, as a female. Embryo rescue enabled recovery of F1 (ABDD) plants that were backcrossed as females to the hexaploid recurrent parent. Stem rust-resistant BC1F1 plants from each Ae. tauschii donor source were used as males to generate BC2F1 mapping populations. Bulked segregant analysis of BC2F1 genotypes was performed using 70 SSR loci distributed across the D genome. Using this approach, stem rust resistance genes from both accessions were located on chromosome arm 1DS and mapped using SSR and EST-STS markers. An allelism test indicated the stem rust resistance gene transferred from PI 603225 is Sr33. Race specificity suggests the stem rust resistance gene transferred from TA1662 is unique and this gene has been temporarily designated SrTA1662. Stem rust resistance genes derived from TA1662 and PI 603225 have been made available with selectable molecular markers in genetic backgrounds suitable for stem rust resistance breeding.

  3. Physiological basis of genetic variation in leaf photosynthesis among rice (Oryza sativa L.) introgression lines under drought and well-watered conditions

    Science.gov (United States)

    Yin, Xinyou

    2012-01-01

    To understand the physiological basis of genetic variation and resulting quantitative trait loci (QTLs) for photosynthesis in a rice (Oryza sativa L.) introgression line population, 13 lines were studied under drought and well-watered conditions, at flowering and grain filling. Simultaneous gas exchange and chlorophyll fluorescence measurements were conducted at various levels of incident irradiance and ambient CO2 to estimate parameters of a model that dissects photosynthesis into stomatal conductance (g s), mesophyll conductance (g m), electron transport capacity (J max), and Rubisco carboxylation capacity (V cmax). Significant genetic variation in these parameters was found, although drought and leaf age accounted for larger proportions of the total variation. Genetic variation in light-saturated photosynthesis and transpiration efficiency (TE) were mainly associated with variation in g s and g m. One previously mapped major QTL of photosynthesis was associated with variation in g s and g m, but also in J max and V cmax at flowering. Thus, g s and g m, which were demonstrated in the literature to be responsible for environmental variation in photosynthesis, were found also to be associated with genetic variation in photosynthesis. Furthermore, relationships between these parameters and leaf nitrogen or dry matter per unit area, which were previously found across environmental treatments, were shown to be valid for variation across genotypes. Finally, the extent to which photosynthesis rate and TE can be improved was evaluated. Virtual ideotypes were estimated to have 17.0% higher photosynthesis and 25.1% higher TE compared with the best genotype investigated. This analysis using introgression lines highlights possibilities of improving both photosynthesis and TE within the same genetic background. PMID:22888131

  4. Informal export barriers and poverty

    OpenAIRE

    Porto, Guido G.

    2004-01-01

    The author investigates the poverty impacts of informal export barriers like transport costs, cumbersome customs practices, costly regulations, and bribes. He models these informal barriers as export taxes that distort the efficient allocation of resources. In low-income agricultural economies, this distortion lowers wages and household agricultural income, thereby leading to higher pover...

  5. Barriers to Women in Science

    Science.gov (United States)

    Butler, Rosemary

    2013-01-01

    The Presiding Officer of the National Assembly for Wales, Rosemary Butler AM, has put the issue of barriers to women in public life at the top of the political agenda in Wales. She has held sessions with women across Wales to find out what those barriers are and how they can be tackled. On International Women's Day in February, she invited…

  6. Structure information from fusion barriers

    Indian Academy of Sciences (India)

    It is shown that the analysis of fusion barrier distributions is not always an unambiguous test or a 'fingerprint' of the structure information of the colliding nuclei. Examples are presented with same fusion barrier distributions for nuclei having different structures. The fusion excitation functions for 16O+208Pb, using the coupled ...

  7. BARRIERS OF STRATEGIC ALLIANCES ORGANIZATION

    Directory of Open Access Journals (Sweden)

    Vladislav M. Sannikov

    2014-01-01

    Full Text Available General barriers of organization of different types of strategic alliances have beenconsidered in the article. There are several recommendations for overcoming themin cases of international alliances, and in case of work in one state. The article also identified goals and tasks of single coordination center of alliance to overcome organization barriers.

  8. Organizational Barriers to Transition: Summary.

    Science.gov (United States)

    Haynes, John; Justice, Thomas I., Ed.

    This study sought to identify the barriers that negatively impact the ability of disabled youth to successfully make a transition from school into employment and a quality adult life, and sought to specifically define organizational disincentives to successful transition. Current research is reviewed relating to organizational barriers to…

  9. Sub-barrier capture with quantum diffusion approach

    Directory of Open Access Journals (Sweden)

    Scheid W.

    2011-10-01

    Full Text Available With the quantum diffusion approach the behavior of capture cross sections and mean-square angular momenta of captured systems are revealed in the reactions with deformed and spherical nuclei at sub-barrier energies. With decreasing bombarding energy under the barrier the external turning point of the nucleus-nucleus potential leaves the region of short-range nuclear interaction and action of friction. Because of this change of the regime of interaction, an unexpected enhancement of the capture cross section is found at bombarding energies far below the Coulomb barrier. This effect is shown its worth in the dependence of mean-square angular momentum on the bombarding energy. From the comparison of calculated capture cross sections and experimental capture or fusion cross sections the importance of quasifission near the entrance channel is demonstrated for the actinidebased reactions and reactions with medium-heavy nuclei at extreme sub-barrier energies.

  10. Barriers to Asthma Management for School Nurses: An Integrative Review.

    Science.gov (United States)

    Hanley Nadeau, Ellen; Toronto, Coleen E

    2016-04-01

    Childhood asthma is a growing health concern. Asthma is the most common chronic illness of childhood and a leading cause of emergency room visits, hospitalizations, and school absenteeism. School nurses play a valuable role in asthma management. The purpose of this integrative review is to examine barriers to asthma management for school nurses in the school setting. Findings revealed multiple barriers school nurses encounter in managing asthma. Six themes emerged that included lack of resources and support, insufficient time, communication challenges, limited knowledge, and lack of awareness of school nurses' expertise. Students, parents, primary care physicians, school administration, staff, and school nurses themselves all play a role in constructing barriers to asthma management. There is a need for school nurses and school nurse leaders to focus efforts to develop strategies to overcome barriers to ensure evidence-based, best practice management of asthma in the school setting. © The Author(s) 2015.

  11. Epistemological barriers to radical behaviorism.

    Science.gov (United States)

    O'Donohue, W T; Callaghan, G M; Ruckstuhl, L E

    1998-01-01

    The historian and philosopher of science Gaston Bachelard proposed the concept of epistemological barriers to describe the intellectual challenges encountered by scientists in their work. In order to embrace novel ways of approaching a problem in science, scientists must overcome barriers or obstacles posed by their prior views. For example, Einsteinian physics presents scientists with claims that space is curved and that time and space are on the same continuum. We utilize Bachelard's concept of epistemological barriers to describe the differences between the intellectual journeys students pursuing advanced studies face when attempting to accept cognitive psychology or radical behaviorism. We contend that the folk psychological beliefs that students typically hold when entering these studies pose less challenge to cognitive psychology than to radical behaviorism. We also suggest that these barriers may also partly be involved in the problematic exegesis that has plagued radical behaviorism. In close, we offer some suggestions for dealing with these epistemological barriers.

  12. Epistemological barriers to radical behaviorism

    Science.gov (United States)

    O'Donohue, William T.; Callaghan, Glenn M.; Ruckstuhl, L. E.

    1998-01-01

    The historian and philosopher of science Gaston Bachelard proposed the concept of epistemological barriers to describe the intellectual challenges encountered by scientists in their work. In order to embrace novel ways of approaching a problem in science, scientists must overcome barriers or obstacles posed by their prior views. For example, Einsteinian physics presents scientists with claims that space is curved and that time and space are on the same continuum. We utilize Bachelard's concept of epistemological barriers to describe the differences between the intellectual journeys students pursuing advanced studies face when attempting to accept cognitive psychology or radical behaviorism. We contend that the folk psychological beliefs that students typically hold when entering these studies pose less challenge to cognitive psychology than to radical behaviorism. We also suggest that these barriers may also partly be involved in the problematic exegesis that has plagued radical behaviorism. In close, we offer some suggestions for dealing with these epistemological barriers. PMID:22478314

  13. Barriers for recess physical activity

    DEFF Research Database (Denmark)

    Pawlowski, Charlotte Skau; Tjørnhøj-Thomsen, Tine; Schipperijn, Jasper

    2014-01-01

    . This was verified by a thematic analysis of transcripts from the open discussions and go-along interviews. RESULTS: The most frequently identified barriers for both boys and girls were weather, conflicts, lack of space, lack of play facilities and a newly-found barrier, use of electronic devices. While boys......BACKGROUND: Many children, in particular girls, do not reach the recommended amount of daily physical activity. School recess provides an opportunity for both boys and girls to be physically active, but barriers to recess physical activity are not well understood. This study explores gender...... differences in children's perceptions of barriers to recess physical activity. Based on the socio-ecological model four types of environmental barriers were distinguished: natural, social, physical and organizational environment. METHODS: Data were collected through 17 focus groups (at 17 different schools...

  14. Hanford Protective Barriers Program asphalt barrier studies -- FY 1988

    International Nuclear Information System (INIS)

    Freeman, H.D.; Gee, G.W.

    1989-05-01

    The Hanford Protective Barrier (HPB) Program is evaluating alternative barriers to provide a means of meeting stringent water infiltration requirements. One type of alternative barrier being considered is an asphalt-based layer, 1.3 to 15 cm thick, which has been shown to be very effective as a barrier for radon gas and, hence, should be equally effective as a barrier for the larger molecules of water. Fiscal Year 1988 studies focused on the selection and formulation of the most promising asphalt materials for further testing in small-tube lysimeters. Results of laboratory-scale formulation and hydraulic conductivity tests led to the selection of a rubberized asphalt material and an admixture of 24 wt% asphalt emulsion and concrete sand as the two barriers for lysimeter testing. Eight lysimeters, four each containing the two asphalt treatments, were installed in the Small Tube Lysimeter Facility on the Hanford Site. The lysimeter tests allow the performance of these barrier formulations to be evaluated under more natural environmental conditions

  15. Development of engineered barrier

    Energy Technology Data Exchange (ETDEWEB)

    Chun, Kwan Sik; Cho, Won Jin; Lee, Jae Owan; Kim, Seung Soo; Kang, Mu Ja

    1999-03-01

    Engineered barrier development was carried out into the three research fields : waste form, disposal container, and buffer. The waste form field dealt with long-term leaching tests with borosilicate waste glasses surrounded by compacted bentonite. The leach rate decreased with increasing time, and was higher for the waste specimen rich in U and Na. In the container field, preliminary concepts of disposal containers were recommended by conducting structural analysis, thermal analysis, and shielding analysis, and major properties of stainless steel, copper, and titanium as a container material were surveyed. The sensitization degrees of SUS 316 and316L were lower than those of SUS 304 and 304L, respectively. The crevice corrosion of sensitized stainless steel was sensitive to the content of salt. Researches into the buffer included establishment of its performance criteria followed by investigating major properties of buffer using potential material in Korea. Experiments were made for measuring hydraulic conductivities, swelling properties, mechanical properties, thermal conductivities, pore-water chemistry properties, and adsorption properties was also investigated. (author)

  16. Alternative geochemical barrier materials

    International Nuclear Information System (INIS)

    1991-07-01

    Previous investigations of the effects of neutralization and reduction on uranium mill tailings pore fluids by the Technical Support Contractor indicated that arsenic, selenium, and molybdenum continue to remain in solution in all but reducing conditions. These hazardous constituents are present in groundwaters as oxyanions and, therefore, are not expected to be removed by adsorption into clays and most other soil constituents. It was decided to investigate the attenuation capacity of two commonly available crystalline iron oxides, taconite and scoria, and a zeolite, a network aluminosilicate with a cage structure. Columns of the candidate materials were exposed to solutions of individual constituents, including arsenic, molybdenum, selenium, and, uranium, and to the spiked tailings pore fluid from the Bodo Canyon disposal cell near Durango, Colorado. In addition to the single material columns, a homogeneous blend of the three materials and layers of the materials were exposed to spiked tailings pore fluids. The results of these experiments indicate that with the exception of molybdenum, the constituents of concern are attenuated by the taconite; however, they are not sufficiently attenuated to meet the groundwater protection standards applicable to the UMTRA Project. Therefore, the candidate barrier materials did not prove to be useful to the UMTRA Project for the cleanup of groundwaters

  17. Omnidirectional ventilated acoustic barrier

    Science.gov (United States)

    Zhang, Hai-long; Zhu, Yi-fan; Liang, Bin; Yang, Jing; Yang, Jun; Cheng, Jian-chun

    2017-11-01

    As an important problem in acoustics, sound insulation finds applications in a great variety of situations. In the existing schemes, however, there has always been a trade-off between the thinness of sound-insulating devices and their ventilating capabilities, limiting their potentials in the control of low-frequency sound in high ventilation environments. Here, we design and experimentally implement an omnidirectional acoustic barrier with a planar profile, subwavelength thickness ( 0.18 λ ), yet high ventilation. The proposed mechanism is based on the interference between the resonant scattering of discrete states and the background scattering of continuous states which induces a Fano-like asymmetric transmission profile. Benefitting from the binary-structured design of the coiled unit and hollow pipe, it maximally simplifies the design and fabrication while ensuring the ventilation for all the non-resonant units with open tubes. The simulated and measured results agree well, showing the effectiveness of our proposed mechanism to block low frequency sound coming from various directions while allowing 63% of the air flow to pass. We anticipate our design to open routes to design sound insulators and to enable applications in traditionally unattainable cases such as those calling for noise reduction and cooling simultaneously.

  18. INFLUENCE OF PERCEIVED EXPORT BARRIERS ON THE EXPORT INTENSITY OF THE CROATIAN MANUFACTURERS

    OpenAIRE

    Martinović, Marija; Matana, Elena

    2017-01-01

    This paper examines the influence of the perceived export barriers on export intensity. The survey was conducted on the sample of 100 Croatian manufacturers. Upon review of the literature 14 variables of the export barriers have been identified. The results reveal a negative relationship between the perceived export barriers on export intensity. Factor analyses were used to sort variables to 4 categories. This model introduced external environment factor, organization and commitment, governme...

  19. Fusion barrier characteristics of actinides

    Science.gov (United States)

    Manjunatha, H. C.; Sridhar, K. N.

    2018-03-01

    We have studied fusion barrier characteristics of actinide compound nuclei with atomic number range 89 ≤ Z ≤ 103 for all projectile target combinations. After the calculation of fusion barrier heights and positions, we have searched for their parameterization. We have achieved the empirical formula for fusion barrier heights (VB), positions (RB), curvature of the inverted parabola (ħω) of actinide compound nuclei with atomic number range 89 ≤ Z ≤ 103 for all projectile target combinations (6 actinides with the simple inputs of mass number (A) and atomic number (Z) of projectile-targets.

  20. Penetration through the Skin Barrier

    DEFF Research Database (Denmark)

    Nielsen, Jesper Bo; Benfeldt, Eva; Holmgaard, Rikke

    2016-01-01

    -through diffusion cells) as well as in vivo methods (microdialysis and microperfusion). Then follows a discussion with examples of how different characteristics of the skin (age, site and integrity) and of the penetrants (size, solubility, ionization, logPow and vehicles) affect the kinetics of percutaneous......The skin is a strong and flexible organ with barrier properties essential for maintaining homeostasis and thereby human life. Characterizing this barrier is the ability to prevent some chemicals from crossing the barrier while allowing others, including medicinal products, to pass at varying rates...

  1. Vehicle barrier with access delay

    Science.gov (United States)

    Swahlan, David J; Wilke, Jason

    2013-09-03

    An access delay vehicle barrier for stopping unauthorized entry into secure areas by a vehicle ramming attack includes access delay features for preventing and/or delaying an adversary from defeating or compromising the barrier. A horizontally deployed barrier member can include an exterior steel casing, an interior steel reinforcing member and access delay members disposed within the casing and between the casing and the interior reinforcing member. Access delay members can include wooden structural lumber, concrete and/or polymeric members that in combination with the exterior casing and interior reinforcing member act cooperatively to impair an adversarial attach by thermal, mechanical and/or explosive tools.

  2. A LOOK AT CULTURAL BARRIERS

    Directory of Open Access Journals (Sweden)

    Carmen A. VRÂNCEANU

    2015-06-01

    Full Text Available Nowadays the global market allows each individual to work in foreign countries. This fact is a great opportunity for business development, but also puts into light the problem of cultural barriers. Ineffective cross-cultural communication and collaboration can harm employees, customers, and other stakeholders. A company with employees from different cultures must acknowledge and understand these barriers in order to overcome them and to obtain the desired performance. The present study aims to expose the cultural barriers encountered by foreigners in a multinational company from Romania.

  3. INFLUENCE OF WORKPIECE SURFACE PREPARATION ON THERMAL BARRIER COATING DURABILITY

    Directory of Open Access Journals (Sweden)

    M. A. Petrova

    2014-01-01

    Full Text Available Article deals with the impact of workpiece surface quality on adhesive strength and durability of thermal barrier coating. The result revealed that the roughness of metal layer influences on the adhesion of ceramic coating and depends the thickness of ceramic crystals when using method of Electron beam deposition.

  4. Barriers and Perceptions of Natural Resource Careers by Minority Students

    Science.gov (United States)

    Haynes, Nia A.; Jacobson, Susan

    2015-01-01

    Using a framework based on social cognitive career theory, we conducted 38 interviews and four focus groups with college students to identify motivations and barriers faced by underrepresented groups to natural resource careers. Interviews revealed career satisfaction as the most important goal for both natural resource and a comparison of liberal…

  5. Numerical simulation of hole injection in high barrier metal ...

    African Journals Online (AJOL)

    , a comparison of the two-carrier model adopted in this work with the Schottky model reveals a discrepancy of 30% in the lnJ-V characteristics of a diode of 0.92 eV barrier height. Journal of the Nigerian Association of Mathematical Physics Vol.

  6. Barriers to maternal health service use in Chikhwawa, Southern ...

    African Journals Online (AJOL)

    Results: The discussions revealed the following as barriers to maternal health service utilization: walking long distances to access health facilities, lack of midwives, lack of or insufficient items to be used during delivery, long stay and rude health personnel. Seeking help from Traditional Birth Attendants (TBAs) during ...

  7. Time as a trade barrier

    Science.gov (United States)

    2001-07-01

    International trade occurs in physical space and moving goods requires time. This paper examines the importance of time as a trade barrier, estimates the magnitude of time costs, and relates these to patterns of trade and the international organizati...

  8. Coastal Structures and Barriers 2012

    Data.gov (United States)

    California Department of Resources — This dataset is a compilation of the UCSC Sand Retention Structures, MC Barriers, and USACE Coastal Structures. UCSC Sand Retention Structures originate from a...

  9. Coastal Structures and Barriers 2012

    Data.gov (United States)

    California Natural Resource Agency — This dataset is a compilation of the UCSC Sand Retention Structures, MC Barriers, and USACE Coastal Structures. UCSC Sand Retention Structures originate from a...

  10. Low Conductivity Thermal Barrier Coatings

    Science.gov (United States)

    Zhu, Dong-Ming

    2005-01-01

    Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and requirements will be discussed. An experimental approach is established to monitor in real time the thermal conductivity of the coating systems subjected to high-heat-flux, steady-state and cyclic temperature gradients. Advanced low conductivity thermal barrier coatings have also been developed using a multi-component defect clustering approach, and shown to have improved thermal stability. The durability and erosion resistance of low conductivity thermal barrier coatings have been improved utilizing advanced coating architecture design, composition optimization, in conjunction with more sophisticated modeling and design tools.

  11. Engineered barriers: current status 1989

    International Nuclear Information System (INIS)

    Atkinson, A.; Marsh, G.B.

    1989-06-01

    This report summarises the current state of research relevant to assessing the performance of engineered barriers made of steel and concrete in radioactive waste repositories. The objective of these barriers is to contain substantially the radionuclides within them by providing both physical and chemical impediment to their release. The physical barriers are of most value for highly soluble isotopes with relatively short half-lives (eg 137 Cs), since they can provide a measure of containment until a large fraction of the activity has decayed. In addition they can facilitate retrievability for some period after disposal. The chemical barriers operate by beneficial conditioning of the near field groundwater and providing sites for sorption of radionuclides. Both of these reduce the aqueous concentration of radionuclides in the near field. (author)

  12. Great Barrier Reef, Queensland, Australia

    Science.gov (United States)

    1990-01-01

    This detailed view of the Great Barrier Reef, Queensland, Australia (19.5S, 149.5E) shows several small patch reefs within the overall reef system. The Great Barrier Reef, largest in the world, comprises thousands of individual reefs of great variety and are closely monitored by marine ecologists. These reefs are about 6000 years old and sit on top of much older reefs. The most rapid coral growth occurs on the landward side of the reefs.

  13. Patient advocacy: barriers and facilitators

    OpenAIRE

    Nikravesh Mansoure; Ahmadi Fazlollah; Oskouie Fatemeh; Negarandeh Reza; Hallberg Ingalill

    2006-01-01

    Abstract Background During the two recent decades, advocacy has been a topic of much debate in the nursing profession. Although advocacy has embraced a crucial role for nurses, its extent is often limited in practice. While a variety of studies have been generated all over the world, barriers and facilitators in the patient advocacy have not been completely identified. This article presents the findings of a study exploring the barriers and facilitators influencing the role of advocacy among ...

  14. Barriers to Cyber Information Sharing

    Science.gov (United States)

    2014-12-01

    finding out relationships or no relationships. It is more equivalent with this study’s epistemology and methodology than free-mapping or pure...and industry remain educated on and sensitive to methods that can mitigate this concern and ensure antitrust compliance.151 4. Technology...legal scholars. One way to overcome the legal barriers is through education and clarity about the laws that are currently barriers such as anti-trust

  15. Barriers and Strategies in Guideline Implementation—A Scoping Review

    Directory of Open Access Journals (Sweden)

    Florian Fischer

    2016-06-01

    Full Text Available Research indicates that clinical guidelines are often not applied. The success of their implementation depends on the consideration of a variety of barriers and the use of adequate strategies to overcome them. Therefore, this scoping review aims to describe and categorize the most important barriers to guideline implementation. Furthermore, it provides an overview of different kinds of suitable strategies that are tailored to overcome these barriers. The search algorithm led to the identification of 1659 articles in PubMed. Overall, 69 articles were included in the data synthesis. The content of these articles was analysed by using a qualitative synthesis approach, to extract the most important information on barriers and strategies. The barriers to guideline implementation can be differentiated into personal factors, guideline-related factors, and external factors. The scoping review revealed the following aspects as central elements of successful strategies for guideline implementation: dissemination, education and training, social interaction, decision support systems and standing orders. Available evidence indicates that a structured implementation can improve adherence to guidelines. Therefore, the barriers to guideline implementation and adherence need to be analysed in advance so that strategies that are tailored to the specific setting and target groups can be developed.

  16. Erosion and foreign object damage of thermal barrier coatings

    International Nuclear Information System (INIS)

    Nicholls, J.R.; Jaslier, Y.; Rickerby, D.S.

    1997-01-01

    Thermal barrier coating technology is used in the hot sections of gas turbines to extend component life. To maximise these benefits, the thermal barrier coating has to remain intact throughout the life of the turbine. High velocity ballistic damage can lead to total thermal barrier removal, while erosion may lead to progressive loss of thickness during operation. This paper particularly addresses the erosion resistance and resistance to foreign object damage of thermal barrier coatings. It was found that EB-PVD thermal barriers are significantly more erosion resistant when impacted with alumina or silica, than the equivalent plasma spray coating, both at room temperature and 910 C. Examination of tested hardware, reveals that cracking occurs within the near surface region of the columns for EB-PVD ceramic and that erosion occurs by removal of these small blocks of material. In stark contrast, removal of material for plasma sprayed ceramic occurs through poorly bonded splat boundaries. Large particle impact results in severe damage to the EB-PVD thermal barrier, with cracks penetrating through the ceramic coating to the ceramic/bond coat interface. Material removal, per particle impact, increases with increased particle size. (orig.)

  17. Air barrier systems: Construction applications

    Energy Technology Data Exchange (ETDEWEB)

    Perrault, J.C

    1989-01-01

    An examination is presented of how ordinary building materials can be used in an innovative manner to design, detail, and construct effective air barrier systems for common types of walls. For residential construction, the air drywall approach uses the interior gypsum board as the main component of the wall air barrier system. Joints between the gypsum board and adjacent materials or assemblies are sealed by gaskets. In commercial construction, two different techniques are employed for using gypsum board as air barrier material: the accessible drywall and non-accessible drywall approaches. The former is similar to the air drywall approach except that high performance sealants are used instead of gaskets. In the latter approach, exterior drywall sheathing is the main component of the air barrier system; joints between boards are taped and joints between boards and other components are sealed using elastomeric membrane strips. For various types of commercial and institutional buildings, metal air barrier systems are widely used and include pre-engineered curtain walls or sheet metal walls. Masonry wall systems are regarded as still the most durable, fireproof, and soundproof wall type available but an effective air barrier system has typically been difficult to implement. Factory-made elastomeric membranes offer the potential to provide airtightness to masonry walls. These membranes are applied on the entire masonry wall surface and are used to make airtight connections with other building components. Two types of product are available: thermofusible and peel-and-stick membranes. 5 figs.

  18. Economic alternatives for containment barriers

    International Nuclear Information System (INIS)

    Nicholson, P.J.; Jasperse, B.H.; Fisher, M.J.

    1997-01-01

    Fixation, barriers, and containment of existing landfills and other disposal areas are often performed by insitu auger type soil mixing and jet grouting. Cement or other chemical reagents are mixed with soil to form both vertical and horizontal barriers. Immobilization of contaminants can be economically achieved by mixing soil and the contaminants with reagents that solidify or stabilize the contaminated area. Developed in Japan, and relatively new to the United States, the first large scale application was for a vertical barrier at the Jackson Lake Dam project in 1986. This technology has grown in both the civil and environmental field since. The paper describes current United States practice for Deep Soil Mixing (over 12 meters in depth), and Shallow Soil Mixing for vertical barriers and stabilization/solidification, and Jet Grouting for horizontal and vertical barriers. Creating very low permeability barriers at depth with minimal surface return often makes these techniques economical when compared to slurry trenches. The paper will discuss equipment, materials, soil and strength parameters, and quality control

  19. Marcadores moleculares na identificação de híbridos e introgressão genética em populações de Pseudoplatystoma corruscans e Pseudoplatystoma reticulatim

    OpenAIRE

    Prado, Fernanda Dotti do [UNESP

    2014-01-01

    Levels of genetic diversity and structure, as well as the investigation of interspecific and introgressive hybridization events in wild populations, are amongst the major analyzes to be considered in conservation projects. Hybridization between native fish species, especially when caused by human actions, has led to increasing rates of non natural crosses between different taxa, which may cause ecological and genetic impacts. The Neotropical catfish species, Pseudoplatystoma reticulatum and P...

  20. Evolutionary patterns of two major reproduction candidate genes (Zp2 and Zp3 reveal no contribution to reproductive isolation between bovine species

    Directory of Open Access Journals (Sweden)

    Beja-Pereira Albano

    2011-01-01

    Full Text Available Abstract Background It has been established that mammalian egg zona pellucida (ZP glycoproteins are responsible for species-restricted binding of sperm to unfertilized eggs, inducing the sperm acrosome reaction, and preventing polyspermy. In mammals, ZP apparently represents a barrier to heterospecific fertilization and thus probably contributes to reproductive isolation between species. The evolutionary relationships between some members of the tribe Bovini are complex and highly debatable, particularly, those involving Bos and Bison species for which interspecific hybridization is extensively documented. Because reproductive isolation is known to be a major precursor of species divergence, testing evolutionary patterns of ZP glycoproteins may shed some light into the speciation process of these species. To this end, we have examined intraspecific and interspecific genetic variation of two ZP genes (Zp2 and Zp3 for seven representative species (111 individuals from the Bovini tribe, including five species from Bos and Bison, and two species each from genera Bubalus and Syncerus. Results A pattern of low levels of intraspecific polymorphism and interspecific divergence was detected for the two sequenced fragments each for Zp2 and Zp3. At intraspecific level, none of neutrality tests detected deviations from neutral equilibrium expectations for the two genes. Several haplotypes in both genes were shared by multiple species from Bos and Bison. Conclusions Here we argue that neither ancestral polymorphism nor introgressive hybridization alone can fully account for haplotype sharing among species from Bos and Bison, and that both scenarios have contributed to such a pattern of haplotype sharing observed here. Additionally, codon-based tests revealed strong evidence for purifying selection in the Zp3 coding haplotype sequences and weak evidence for purifying selection in the Zp2 coding haplotype sequences. Contrary to a general genetic pattern that

  1. Speciation history and widespread introgression in the European short-call tree frogs (Hyla arborea sensu lato, H. intermedia and H. sarda).

    Science.gov (United States)

    Gvoždík, Václav; Canestrelli, Daniele; García-París, Mario; Moravec, Jiří; Nascetti, Giuseppe; Recuero, Ernesto; Teixeira, José; Kotlík, Petr

    2015-02-01

    European tree frogs (Hyla) characterized by short temporal parameters of the advertisement call form six genetically differentiated but morphologically cryptic taxa, H. arborea sensu stricto, H. orientalis and H. molleri from across Europe to western Asia (together referred to as H. arborea sensu lato), two putative taxa within H. intermedia (Northern and Southern) from the Italian Peninsula and Sicily, and H. sarda from Sardinia and Corsica. Here, we assess species limits and phylogenetic relationships within these 'short-call tree frogs' based on mitochondrial DNA and nuclear protein-coding markers. The mitochondrial and nuclear genes show partly incongruent phylogeographic patterns, which point to a complex history of gene flow across taxa, particularly in the Balkans. To test the species limits in the short-call tree frogs and to infer the species tree, we used coalescent-based approaches. The monophyly of H. arborea sensu lato is supported by the mtDNA as well as by the all-gene species tree. The Northern and Southern lineages of H. intermedia have been connected by nuclear gene flow (despite their deep mtDNA divergence) and should be treated as conspecific. On the contrary, the parapatric taxa within H. arborea sensu lato should be considered distinct species (H. arborea, H. orientalis, H. molleri) based on the coalescent analysis, although signs of hybridization were detected between them (H. arborea×H. orientalis; H. arborea×H. molleri). A mitochondrial capture upon secondary contact appears to explain the close mtDNA relationship between the geographically remote Iberian H. molleri and H. orientalis from around the Black Sea. Introgressive hybridization occurred also between the Balkan H. arborea and northern Italian H. intermedia, and between the Minor Asiatic H. orientalis and Arabian H. felix arabica (the latter belonging to a different acoustic group/clade). Our results shed light on the species limits in the European short-call tree frogs and show

  2. The critical role of the barrier thickness in spin filter tunneling

    International Nuclear Information System (INIS)

    Miller, Casey W.

    2009-01-01

    Spin filter tunneling is considered in the low bias limit as functions of the temperature dependent barrier parameters. We demonstrate the generation of spin polarized tunneling currents in relation to the magnetic order parameter, and discuss how an interfacially suppressed order parameter leads to a temperature dependent tunneling current asymmetry. Analyzing the full parameter space reveals that the often overlooked barrier thickness plays a critical role in spin filter tunneling. With all else fixed, thicker barriers yield higher spin polarization, and allow a given polarization to be achieved at higher temperatures. This insight may open the door for new materials to serve as spin filter barriers.

  3. Implementation of renewable technologies - Opportunities and barriers. Zimbabwe country study

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-07-01

    . The committee was tasked with the responsibility of coming up with recommendations to barrier removal and promotion of RETs. After interested stake holders had presented their candidate projects proposals, the committee started the process of identifying barriers to the projects and selecting feasible projects. A final workshop was then held in August 2000 where the findings of the whole process were presented to all stake holders for discussion and analysis. The problem of barriers was found to be very complex. A good number of RETs projects in the country were successfully implemented. The success of such projects was underpinned by the following factors, addressing the immediate and basic needs of the people, participatory approach, awareness creation and enabling income generation activities. Some projects were also not very successful as they faced a lot of barriers like poor institutional framework, limited financial resources, lack of appreciation of associated benefits and technology failure. A close analysis of barriers revealed that there are two classes of barrier namely primary barriers and secondary barriers. Primary barriers are the real barriers while secondary barriers are more of the effects of primary barriers. (BA)

  4. Barriers and Opportunities for Sustainable Food Systems in Northeastern Kansas

    Directory of Open Access Journals (Sweden)

    Rhonda Janke

    2010-01-01

    Full Text Available Survey responses of producers and institutional buyers in northeastern Kansas (United States were analyzed to understand barriers and opportunities for sustainable food systems in the region where their emergence has been limited. Producers and buyers identified barriers previously noted regarding mismatches of available quantities and prices. Producers’ enthusiasm to supply locally exceeded buyers’ interest to source locally. Transportation was identified as one of the major concerns by producers, and their responses to choice tasks revealed producers’ preferences to sell locally while pricing their products to secure sales revenue and to cover their logistics expenses at least partially.

  5. Barriers to health care access for Latino children: a review.

    Science.gov (United States)

    Flores, G; Vega, L R

    1998-03-01

    More than 9 million Latino children currently live in the United States. Latinos will soon be the largest minority group in the country, but little is known about access barriers to health care faced by Latino children. We reviewed the literature to define specific barriers to care for Latino children, identify methodologic problems, and highlight the clinical and research implications of the identified barriers. We did a MEDLINE search, using combinations of the key words Hispanic, children, and access. Study exclusion criteria included "not an original research article," "enrolled only adult subjects," "no separate data analysis for children," and "dental care focus." The search yielded 497 citations, of which 27 met the inclusion criteria. Of the 32 potential barriers identified, 21 had good supportive evidence. Lack of health insurance was a consistent barrier; recent data revealed that 26% of Latino children are uninsured, compared with 10% of white children and 14% of African-American children. Latino children also are at greater risk for episodic insurance coverage, low rates of private insurance, and loss of employee-based coverage. Parent beliefs about the etiology and treatment of their child's illness, use of home remedies, choice of sources of advice, and folk medicine practices may also influence how health care is obtained. Few data are available on differences in access among major Latino subpopulations, and no studies focused primarily on barriers as perceived by Latino parents. Evidence is equivocal or lacking that the following are barriers for Latino children: immigration status, duration of parent residency in the United States, and acculturation. Several barriers were identified that originate with practices and behaviors of health care providers, including reduced screening, missed vaccination opportunities, decreased likelihood of receiving prescriptions, and poor communication. Lack of health insurance and lack of a regular source of care

  6. Diabetes and diet : managing dietary barriers

    NARCIS (Netherlands)

    Friele, R.D.

    1989-01-01

    This thesis reports on the barriers diabetic patients experience with their diet, and the ways they cope with these barriers. A dietary barrier is a hinderance to a person's well-being, induced by being advised a diet. First inventories were made of possible dietary barriers and ways of

  7. Molecular characterization of a rice mutator-phenotype derived from an incompatible cross-pollination reveals transgenerational mobilization of multiple transposable elements and extensive epigenetic instability

    Directory of Open Access Journals (Sweden)

    Xu Chunming

    2009-05-01

    Full Text Available Abstract Background Inter-specific hybridization occurs frequently in plants, which may induce genetic and epigenetic instabilities in the resultant hybrids, allopolyploids and introgressants. It remains unclear however whether pollination by alien pollens of an incompatible species may impose a "biological stress" even in the absence of genome-merger or genetic introgression, whereby genetic and/or epigenetic instability of the maternal recipient genome might be provoked. Results We report here the identification of a rice mutator-phenotype from a set of rice plants derived from a crossing experiment involving two remote and apparently incompatible species, Oryza sativa L. and Oenothera biennis L. The mutator-phenotype (named Tong211-LP showed distinct alteration in several traits, with the most striking being substantially enlarged panicles. Expectably, gel-blotting by total genomic DNA of the pollen-donor showed no evidence for introgression. Characterization of Tong211-LP (S0 and its selfed progenies (S1 ruled out contamination (via seed or pollen or polyploidy as a cause for its dramatic phenotypic changes, but revealed transgenerational mobilization of several previously characterized transposable elements (TEs, including a MITE (mPing, and three LTR retrotransposons (Osr7, Osr23 and Tos17. AFLP and MSAP fingerprinting revealed extensive, transgenerational alterations in cytosine methylation and to a less extent also genetic variation in Tong211-LP and its immediate progenies. mPing mobility was found to correlate with cytosine methylation alteration detected by MSAP but not with genetic variation detected by AFLP. Assay by q-RT-PCR of the steady-state transcript abundance of a set of genes encoding for the various putative DNA methyltransferases, 5-methylcytosine DNA glycosylases, and small interference RNA (siRNA pathway-related proteins showed that, relative to the rice parental line, heritable perturbation in expression of 12 out of

  8. Communication barriers among Spanish-speaking women with pelvic floor disorders: lost in translation?

    Science.gov (United States)

    Khan, Aqsa A; Sevilla, Claudia; Wieslander, Cecilia K; Moran, Meghan B; Rashid, Rezoana; Mittal, Brita; Maliski, Sally L; Rogers, Rebecca G; Anger, Jennifer T

    2013-01-01

    The purpose of our study was to evaluate barriers in communication and disease understanding among office staff and interpreters when communicating with Spanish-speaking women with pelvic floor disorders. We conducted a qualitative study to evaluate barriers to communication with Spanish-speaking women with pelvic floor disorders among office staff and interpreters. Sixteen office staff and interpreters were interviewed; interview questions focused on experiences with Spanish-speaking patients with pelvic floor disorders in the clinic setting. Interview transcripts were analyzed qualitatively using grounded theory methodology. Analysis of the interview transcripts revealed several barriers in communication as identified by office staff and interpreters. Three major classes were predominant: patient, interpreter, and system-related barriers. Patient-related barriers included a lack of understanding of anatomy and medical terminology and inhibited discussions due to embarrassment. Provider-related barriers included poor interpreter knowledge of pelvic floor vocabulary and the use of office staff without interpreting credentials. System-related barriers included poor access to information. From these preliminary themes, an emergent concept was revealed: it is highly likely that Spanish-speaking women with pelvic floor disorders have poor understanding of their condition owing to multiple obstacles in communication. There are many levels of barriers to communications with Latin women treated for pelvic floor disorders, arising from the patient, interpreter, and the system itself. These barriers contribute to a low level of understanding of their diagnosis, treatment options, and administered therapies.

  9. Permeation barrier for lightweight liquid hydrogen tanks

    Energy Technology Data Exchange (ETDEWEB)

    Schultheiss, D.

    2007-04-16

    For the future usage of hydrogen as an automotive fuel, its on-board storage is crucial. One approach is the storage of liquid hydrogen (LH2, 20 K) in double-walled, vacuum insulated tanks. The introduction of carbon fiber reinforced plastics (CFRP) as structural material enables a high potential of reducing the weight in comparison to the state-of-the-art stainless steel tanks. The generally high permeability of hydrogen through plastics, however, can lead to long-term degradation of the insulating vacuum. The derived objective of this dissertation was to find and apply an adequate permeation barrier (liner) on CFRP. The investigated liners were either foils adhered on CFRP specimens or coatings deposited on CFRP specimens. The coatings were produced by means of thermal spraying, metal plating or physical vapor deposition (PVD). The materials of the liners included Al, Au, Cu, Ni and Sn as well as stainless steel and diamond-like carbon. The produced liners were tested for their permeation behavior, thermal shock resistance and adherence to the CFRP substrate. Additionally, SEM micrographs were used to characterize and qualify the liners. The foils, although being a good permeation barrier, adhered weakly to the substrate. Furthermore, leak-free joining of foil segments is a challenge still to be solved. The metal plating liners exhibited the best properties. For instance, no permeation could be detected through a 50 {mu}m thick Cu coating within the accuracy of the measuring apparatus. This corresponds to a reduction of the permeation gas flow by more than factor 7400 compared to uncoated CFRP. In addition, the metal platings revealed a high adherence and thermal shock resistance. The coatings produced by means of thermal spraying and PVD did not show a sufficient permeation barrier effect. After having investigated the specimens, a 170 liter CFRP tank was fully coated with 50 {mu}m Cu by means of metal plating. (orig.)

  10. Assessment of interbreeding and introgression of farm genes into a small Scottish Atlantic salmon Salmo salar stock: ad hoc samples - ad hoc results?

    Science.gov (United States)

    Verspoor, E; Knox, D; Marshall, S

    2016-12-01

    An eclectic set of tissues and existing data, including purposely collected samples, spanning 1997-2006, was used in an ad hoc assessment of hybridization and introgression of farmed wild Atlantic salmon Salmo salar in the small Loch na Thull (LnT) catchment in north-west Scotland. The catchment is in an area of marine farm production and contains freshwater smolt rearing cages. The LnT S. salar stock was found to be genetically distinctive from stocks in neighbouring rivers and, despite regular reports of feral farm S. salar, there was no evidence of physical or genetic mixing. This cannot be completely ruled out, however, and low level mixing with other local wild stocks has been suggested. The LnT population appeared underpinned by relatively smaller effective number of breeders (N eb ) and showed relatively low levels of genetic diversity, consistent with a small effective population size. Small sample sizes, an incomplete farm baseline and the use of non-diagnostic molecular markers, constrain the power of the analysis but the findings strongly support the LnT catchment having a genetically distinct wild S. salar population little affected by interbreeding with feral farm escapes. © 2016 The Fisheries Society of the British Isles.

  11. Identification for Heat Tolerance in Backcross Recombinant Lines and Screening of Backcross Introgression Lines with Heat Tolerance at Milky Stage in Rice

    Directory of Open Access Journals (Sweden)

    Jiang-lin LIAO

    2011-12-01

    Full Text Available The present study aimed at breeding new rice germplasms with similar genome but significantly differed in heat tolerance during the grain filling stage. A total of 791 BC1F8 backcross recombinant lines, derived from the cross of Xieqingzao B / N22 // Xieqingzao B, were used as materials. Each rice line was separated evenly into two groups, and the heat tolerance of all rice lines were evaluated at natural high temperature in fields. The rice lines with heat tolerant index higher than 90% or lower than 40% were selected to compare the phenotypic characters and further identify heat tolerance at the early milky stage in a phytotron. Rice lines with similar phenotypic characters but significantly differed in heat tolerance at the milky stage were analyzed by 887 simple sequence repeat markers that were evenly distributed on the 12 rice chromosomes. In the result, 12 (6 pairs rice lines with similar phenotypic characters but significantly differed in heat tolerance at the milky stage were obtained. Molecular marker analysis indicated that the genomic polymorphism between 703T and 704S was the smallest in the 6 pairs of rice lines, with only 16 polymorphic sites, including 22 different alleles. The application of these two backcross introgression rice lines for future study on the mechanisms of heat tolerance in rice at the milky stage will be theoretically beneficial in reducing the interference caused by genetic differences from experimental materials.

  12. Improvement of the agronomic traits of a wheat-barley centric fusion by introgressing the 3HS.3BL translocation into a modern wheat cultivar.

    Science.gov (United States)

    Türkösi, Edina; Farkas, András; Aranyi, Nikolett Réka; Hoffmann, Borbála; Tóth, Viola; Molnár-Láng, Márta

    2014-11-01

    The 3HS.3BL spontaneous Robertsonian translocation obtained from the progenies of wheat-barley (Chinese Spring × Betzes) hybrids backcrossed with wheat line Mv9kr1 was transferred into the modern Martonvásár wheat cultivar Mv Bodri. The translocation was identified with molecular cytogenetic methods. The inheritance of the translocation was traced using genomic in situ hybridization. Fluorescence in situ hybridization using barley subtelomeric (HvT01) and centromere-specific [(AGGGAG)4] repetitive DNA probes confirmed that the complete barley chromosome arm was involved in the Robertsonian translocation. The wheat-specific repetitive DNA probes identified the presence of the whole wheat genome, except the short arm of the 3B chromosome. Genotypes homozygous for the centric fusion were selected, after which morphological analysis was performed on the plants and the yield components were measured in the field during two consecutive vegetative seasons. The introgression of the 3HS.3BL translocation into the modern wheat cultivar Mv Bodri significantly reduced the plant height due to the incorporation of the dwarfing allele RhtD1b. The presence of the 3HS.3BL translocation in the Mv9kr1 and Mv Bodri wheat background improved tillering and seeds per plant productivity in field experiments carried out in Martonvásár and Keszthely, Hungary.

  13. Marker-free transgenic (MFT) near-isogenic introgression lines (NIILs) of 'golden' indica rice (cv. IR64) with accumulation of provitamin A in the endosperm tissue.

    Science.gov (United States)

    Baisakh, Niranjan; Rehana, Sayda; Rai, Mayank; Oliva, Norman; Tan, Jing; Mackill, David J; Khush, Gurdev S; Datta, Karabi; Datta, Swapan K

    2006-07-01

    We have developed near-isogenic introgression lines (NIILs) of an elite indica rice cultivar (IR64) with the genes for beta-carotene biosynthesis from dihaploid (DH) derivatives of golden japonica rice (cv. T309). A careful analysis of the DH lines indicated the integration of the genes of interest [phytoene synthase (psy) and phytoene desaturase (crtI)] and the selectable marker gene (hygromycin phosphotransferase, hph) in two unlinked loci. During subsequent crossing, progenies could be obtained carrying only the locus with psy and crtI, which was segregated independently from the locus containing the hph gene during meiotic segregation. The NIILs (BC(2)F(2)) showed maximum similarity with the recurrent parent cultivar IR64. Further, progenies of two NIILs were devoid of any fragments beyond the left or right border, including the chloramphenicol acetyltransferase (cat) antibiotic resistance gene of the transformation vector. Spectrophotometric readings showed the accumulation of up to 1.06 microg total carotenoids, including beta-carotene, in 1 g of the endosperm. The accumulation of beta-carotene was also evident from the clearly visible yellow colour of the polished seeds.

  14. Skin Barrier Function and Allergens

    DEFF Research Database (Denmark)

    Engebretsen, Kristiane Aasen; Thyssen, Jacob Pontoppidan

    2016-01-01

    and skin barrier status. Psoriasis has traditionally been regarded a Th1-dominated disease, but the discovery of Th17 cells and IL-17 provides new and interesting information regarding the pathogenesis of the disease. Research suggests an inverse relationship between psoriasis and CA, possibly due......The skin is an important barrier protecting us from mechanical insults, microorganisms, chemicals and allergens, but, importantly, also reducing water loss. A common hallmark for many dermatoses is a compromised skin barrier function, and one could suspect an elevated risk of contact sensitization...... to increased levels of Th17 cells and its associated cytokines. As for AD, a positive association to CS has been established in epidemiological studies, but is still unresolved. Experimental studies show, however, an inverse relationship between AD and CS. The opposing and antagonistic influences of Th1 (CS...

  15. Neutrophils Compromise Retinal Pigment Epithelial Barrier Integrity

    Directory of Open Access Journals (Sweden)

    Jiehao Zhou

    2010-01-01

    Full Text Available We hypothesized that neutrophils and their secreted factors mediate breakdown of the integrity of the outer blood-retina-barrier by degrading the apical tight junctions of the retinal pigment epithelium (RPE. The effect of activated neutrophils or neutrophil cell lysate on apparent permeability of bovine RPE-Choroid explants was evaluated by measuring [H] mannitol flux in a modified Ussing chamber. The expression of matrix metalloproteinase- (MMP- 9 in murine peritoneal neutrophils, and the effects of neutrophils on RPE tight-junction protein expression were assessed by confocal microscopy and western blot. Our results revealed that basolateral incubation of explants with neutrophils decreased occludin and ZO-1 expression at 1 and 3 hours and increased the permeability of bovine RPE-Choroid explants by >3-fold (P<.05. Similarly, basolateral incubation of explants with neutrophil lysate decreased ZO-1 expression at 1 and 3 hours (P<.05 and increased permeability of explants by 75%. Further, we found that neutrophils prominently express MMP-9 and that incubation of explants with neutrophils in the presence of anti-MMP-9 antibody inhibited the increase in permeability. These data suggest that neutrophil-derived MMP-9 may play an important role in disrupting the integrity of the outer blood-retina barrier.

  16. Barrier mechanisms in the Drosophila blood-brain barrier.

    Science.gov (United States)

    Hindle, Samantha J; Bainton, Roland J

    2014-01-01

    The invertebrate blood-brain barrier (BBB) field is growing at a rapid pace and, in recent years, studies have shown a physiologic and molecular complexity that has begun to rival its vertebrate counterpart. Novel mechanisms of paracellular barrier maintenance through G-protein coupled receptor signaling were the first demonstrations of the complex adaptive mechanisms of barrier physiology. Building upon this work, the integrity of the invertebrate BBB has recently been shown to require coordinated function of all layers of the compound barrier structure, analogous to signaling between the layers of the vertebrate neurovascular unit. These findings strengthen the notion that many BBB mechanisms are conserved between vertebrates and invertebrates, and suggest that novel findings in invertebrate model organisms will have a significant impact on the understanding of vertebrate BBB functions. In this vein, important roles in coordinating localized and systemic signaling to dictate organism development and growth are beginning to show how the BBB can govern whole animal physiologies. This includes novel functions of BBB gap junctions in orchestrating synchronized neuroblast proliferation, and of BBB secreted antagonists of insulin receptor signaling. These advancements and others are pushing the field forward in exciting new directions. In this review, we provide a synopsis of invertebrate BBB anatomy and physiology, with a focus on insights from the past 5 years, and highlight important areas for future study.

  17. Communication barriers in the family

    Directory of Open Access Journals (Sweden)

    BARBARA KOC-KOZŁOWIEC

    2017-10-01

    Full Text Available The art of communication – listening and speaking – is a major life skill, with a thorough influence on every human life. Remaining silent while the interlocutor speaks is not all that there is to the act of listening to messages. True listening is based on an intention to get involved in understanding of the other person, enjoying his or her presence, learning something from the conversation, giving assistance, or comforting the interlocutor. In the article the author describes obstacles (barriers, which render true listening impossible. These barriers have been identified by a group of young adults.

  18. Systems study on engineered barriers: barrier performance analysis

    International Nuclear Information System (INIS)

    Stula, R.T.; Albert, T.E.; Kirstein, B.E.; Lester, D.H.

    1980-09-01

    A performance assessment model for multiple barrier packages containing unreprocessed spent fuel has been modified and applied to several package designs. The objective of the study was to develop information to be used in programmatic decision making concerning engineered barrier package design and development. The assessment model, BARIER, was developed in previous tasks of the System Study on Engineered Barriers (SSEB). The new version discussed in this report contains a refined and expanded corrosion rate data base which includes pitting, crack growth, and graphitization as well as bulk corrosion. Corrosion rates for oxic and anoxic conditions at each of the two temperature ranges are supplied. Other improvements include a rigorous treatment of radionuclide release after package failure which includes resistance of damaged barriers and backfill, refined temperature calculations that account for convection and radiation, a subroutine to calculate nuclear gamma radiation field at each barrier surface, refined stress calculations with reduced conservatism and various coding improvements to improve running time and core usage. This report also contains discussion of alternative scenarios to the assumed flooded repository as well as the impact of water exclusion backfills. The model was used to assess post repository closure performance for several designs which were all variation of basic designs from the Spent Unreprocessed Fuel (SURF) program. Many designs were found to delay the onset of leaching by at least a few hundreds of years in all geologic media. Long delay times for radionuclide release were found for packages with a few inches of sorption backfill. Release of uranium, plutonium, and americium was assessed

  19. Systems study on engineered barriers: barrier performance analysis

    Energy Technology Data Exchange (ETDEWEB)

    Stula, R.T.; Albert, T.E.; Kirstein, B.E.; Lester, D.H.

    1980-09-01

    A performance assessment model for multiple barrier packages containing unreprocessed spent fuel has been modified and applied to several package designs. The objective of the study was to develop information to be used in programmatic decision making concerning engineered barrier package design and development. The assessment model, BARIER, was developed in previous tasks of the System Study on Engineered Barriers (SSEB). The new version discussed in this report contains a refined and expanded corrosion rate data base which includes pitting, crack growth, and graphitization as well as bulk corrosion. Corrosion rates for oxic and anoxic conditions at each of the two temperature ranges are supplied. Other improvements include a rigorous treatment of radionuclide release after package failure which includes resistance of damaged barriers and backfill, refined temperature calculations that account for convection and radiation, a subroutine to calculate nuclear gamma radiation field at each barrier surface, refined stress calculations with reduced conservatism and various coding improvements to improve running time and core usage. This report also contains discussion of alternative scenarios to the assumed flooded repository as well as the impact of water exclusion backfills. The model was used to assess post repository closure performance for several designs which were all variation of basic designs from the Spent Unreprocessed Fuel (SURF) program. Many designs were found to delay the onset of leaching by at least a few hundreds of years in all geologic media. Long delay times for radionuclide release were found for packages with a few inches of sorption backfill. Release of uranium, plutonium, and americium was assessed.

  20. BARRIER MARKET RESTRICTIONS, THEIR ECONOMIC NATURE AND CONSEQUENCES

    Directory of Open Access Journals (Sweden)

    Maksimova Ekaterina Yurievna

    2018-02-01

    Full Text Available Subject: indicators of modern economic growth in construction, published by the government agencies, reflect individual directions of growth. At the same time, the analysis of the reasons for the unachieved results is conducted by various researchers primarily from the standpoint of the inadequacy of economic and other resources. This article deals with the problem of ensuring the growth of construction enterprises from the viewpoint of systemic barriers, and in this regard, these barriers are defined as the subject of the present research. Research objectives: studying the concept of barrier market restrictions, their impact on the activities of construction companies. Materials and methods: statistical data in the field of housing construction, provided by the Ministry of Construction of the Russian Federation and Rosstat, is examined to solve the given tasks set. The content of state programs and activities of state institutions in the field of support and development of construction activities is considered. Based on investigations of sustainable economic development, an understanding of the constraints and incentives for development is revealed. Results: we have identified the content of barrier market restrictions, which are not possible to overcome only by involving additional economic resources in the turnover. The ways of confronting these restrictions are shown. Conclusions: it was shown that implementation of promising activities is impossible without overcoming various systemic constraints. Their structure is described in sufficient detail. Principles of economic sustainable development are proposed. It was proved that the reserve system can serve as an effective way to overcome market barriers.

  1. Barriers of lean construction implementation in the Moroccan construction industry

    Science.gov (United States)

    Bajjou, Mohamed Saad; Chafi, Anas

    2018-04-01

    Improving the production system performance has become a fundamental pillar that must be taken into consideration in the construction industry. Recent developments in the construction sector have led to renewed interest in new techniques of management. Lean Construction is a very effective approach that has gained a high popularity by its ability to eliminate waste and maximize the value for the customer. Although both developed and developing countries have gained large benefits by implementing Lean Construction approach, several experiences showed many barriers that are hindering its implementation especially in developing countries. This paper aims to assess the critical barriers to the successful implementation in the Moroccan construction industry. Based on a literature review, followed by an analysis of data collected from a questionnaire survey which targeted 330 practitioners in the Moroccan construction field, several barriers were identified as key barriers. The findings of this investigation revealed that there are significant barriers such as Lack of knowledge about Lean Construction concepts, Unskilled Human Resources, and insufficient financial resources.

  2. Prioritizing barriers to successful implementation of hospital information systems.

    Science.gov (United States)

    Ahmadian, Leila; Khajouei, Reza; Nejad, Simin Salehi; Ebrahimzadeh, Maryam; Nikkar, Somayeh Ezhari

    2014-12-01

    Hospital information systems (HIS) are often implemented to enhance the quality of care, as well as to improve the efficiency and safety of health care services. However, there are various barriers for their successful implementation. The aim of this paper is to prioritize these barriers. This research is a cross sectional analytic-descriptive study. The study populations were hospital managers, IT department administrators, and clinical supervisors at the academic and non-academic hospitals of two cities in Iran. The data was collected by a questionnaire that its content validity was confirmed by three specialists. Its reliability was confirmed using Cronbach's alpha (α = 0.78). Questionnaire contained five dimensions and 39 implementation barriers. The collected data was analyzed by descriptive and analytical statistics using the Kendall Rank Correlation Coefficient and Chi2 tests. The findings of the study revealed that lack of powerful information networks, error in data entry, technical problems related to system design, lack of organizational training, lack of users' knowledge about system and working with it, and negative attitudes of providers and patients toward systems are the most important barriers of HIS implementation. Prioritizing of these barriers helps policy makers to decide what to do when planning for HIS utilization.

  3. Health care barriers, racism, and intersectionality in Australia.

    Science.gov (United States)

    Bastos, João L; Harnois, Catherine E; Paradies, Yin C

    2018-02-01

    While racism has been shown to negatively affect health care quality, little is known about the extent to which racial discrimination works with and through gender, class, and sexuality to predict barriers to health care (e.g., perceived difficulty accessing health services). Additionally, most existing studies focus on racial disparities in the U.S. context, with few examining marginalized groups in other countries. To address these knowledge gaps, we analyze data from the 2014 Australian General Social Survey, a nationally representative survey of individuals aged 15 and older living in 12,932 private dwellings. Following an intersectional perspective, we estimate a series of multivariable logit regression models to assess three hypotheses: racial discrimination will be positively associated with perceived barriers to health care (H1); the effect of perceived racial discrimination will be particularly severe for women, sexual minorities, and low socio-economic status individuals (H2); and, in addition to racial discrimination, other forms of perceived discrimination will negatively impact perceived barriers to health care (H3). Findings show that perceptions of racial discrimination are significantly associated with perceived barriers to health care, though this relationship is not significantly stronger for low status groups. In addition, our analyses reveal that perceived racism and other forms of discrimination combine to predict perceived barriers to health care. Taken together, these results speak to the benefits of an intersectional approach for examining racial inequalities in perceived access to health care. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Barriers against psychosocial communication: oncologists' perceptions.

    Science.gov (United States)

    Fagerlind, Hanna; Kettis, Åsa; Glimelius, Bengt; Ring, Lena

    2013-10-20

    To explore oncologists' psychosocial attitudes and beliefs and their perceptions regarding barriers against psychosocial communication. A questionnaire was distributed to oncologists in Sweden (n = 537). Questions covered demography, the Physician Psychosocial Beliefs Scale (PPBS), and barriers against psychosocial communication. Stepwise multiple regression was used to determine what factors contribute the most to the PPBS score and the total number of barriers and barriers affecting clinical practice, respectively. Spearman rank-order correlation was used to determine correlation between PPBS score and number of barriers. Questionnaire response rate was 64%. Mean PPBS value was 85.5 (range, 49 to 123; SD, 13.0). Most oncologists (93%) perceived one or more barriers in communicating psychosocial aspects with patients. On average, five different communication barriers were perceived, of which most were perceived to affect clinical practice. These barriers included insufficient consultation time, lack of resources for taking care of problems discovered, and lack of methods to evaluate patients' psychosocial health in clinical practice. There was a positive correlation (rs = 0.490; P barriers (ie, less psychosocially oriented oncologists perceived more barriers). Oncologists with supplementary education with a psychosocial focus perceived fewer barriers/barriers affecting clinical practice (P barriers affecting psychosocial communication in clinical practice. Interventions aiming to improve psychosocial communication must therefore be multifaceted and individualized to clinics and individual oncologists. It is important to minimize barriers to facilitate optimal care and treatment of patients with cancer.

  5. Plastic Schottky barrier solar cells

    Science.gov (United States)

    Waldrop, James R.; Cohen, Marshall J.

    1984-01-24

    A photovoltaic cell structure is fabricated from an active medium including an undoped, intrinsically p-type organic semiconductor comprising polyacetylene. When a film of such material is in rectifying contact with a magnesium electrode, a Schottky-barrier junction is obtained within the body of the cell structure. Also, a gold overlayer passivates the magnesium layer on the undoped polyacetylene film.

  6. Structure information from fusion barriers

    Indian Academy of Sciences (India)

    test or a 'fingerprint' of the structure information of the colliding nuclei. Examples are presented with same fusion barrier distributions for nuclei having different structures. The fusion excitation functions for. ½. O+ ѕј. Pb, using the coupled reaction channel (CRC) method and correct structure information, have been analysed.

  7. Functional barriers: Properties and evaluation

    NARCIS (Netherlands)

    Feigenbaum, A.; Dole, P.; Aucejo, S.; Dainelli, D.; Cruz Garcia, C. de la; Hankemeier, T.; N'Gono, Y.; Papaspyrides, C.D.; Paseiro, P.; Pastorelli, S.; Pavlidou, S.; Pennarun, P.Y.; Saillard, P.; Vidal, L.; Vitrac, O.; Voulzatis, Y.

    2005-01-01

    Functional barriers are multilayer structures deemed to prevent migration of some chemicals released by food-contact materials into food. In the area of plastics packaging, different migration behaviours of mono- and multilayer structures are assessed in terms of lag time and of their influence of

  8. FX barriers with smile dynamics

    NARCIS (Netherlands)

    Baker, Glyn; Beneder, Reimer; Zilber, A.

    2004-01-01

    Our mandate in this work has been to isolate the features of smile consistent models that are most relevant to the pricing of barrier options. We consider the two classical approaches of stochastic and (parametric) local volatility. Although neither has been particularly successful in practice their

  9. Structure information from fusion barriers

    Indian Academy of Sciences (India)

    effects on the fusion excitation function. However, a simultaneous analysis of the fusion, elastic and quasi-elastic channels would fix the structure and the reaction unambiguously. Keywords. Heavy ion fusion; fusion barrier distributions; nuclear structure; coupled reaction chan- nel calculations. PACS Nos 25.70.Bc; 25.70.

  10. Results of falling barrier analyses

    International Nuclear Information System (INIS)

    Fox, G.L.

    1994-01-01

    This document assesses the consequences if the isolation barrier plate is dropped and falls over on the fuel stored in the water-filled K-East basin. The water slows the rate of fall and some canister bending is expected but only a few rods, if any, would get crushed. The basin criticality calculations will not be affected

  11. Seasonal breaching of coastal barriers

    NARCIS (Netherlands)

    Tuan, Thieu Quang

    2007-01-01

    Natural or unintended breaching can be catastrophic, causing loss of human lives and damage to infrastructures, buildings and natural habitats. Quantitative understand-ing of coastal barrier breaching is therefore of great importance to vulnerability as-sessment of protection works as well as to

  12. Reaction rates when barriers fluctuate

    OpenAIRE

    Reimann, Peter

    1999-01-01

    Reaction rates when barriers fluctuate : a path integral approach / P. Hänggi and P. Reimann. - In: International Conference on Path Integrals from peV to TeV : Proceedings of the ... / eds.: R. Casalbuoni ... - Singapore u.a. : World Scientific, 1999. - S. 407-409

  13. Nuclear species-diagnostic SNP markers mined from 454 amplicon sequencing reveal admixture genomic structure of modern citrus varieties.

    Directory of Open Access Journals (Sweden)

    Franck Curk

    Full Text Available Most cultivated Citrus species originated from interspecific hybridisation between four ancestral taxa (C. reticulata, C. maxima, C. medica, and C. micrantha with limited further interspecific recombination due to vegetative propagation. This evolution resulted in admixture genomes with frequent interspecific heterozygosity. Moreover, a major part of the phenotypic diversity of edible citrus results from the initial differentiation between these taxa. Deciphering the phylogenomic structure of citrus germplasm is therefore essential for an efficient utilization of citrus biodiversity in breeding schemes. The objective of this work was to develop a set of species-diagnostic single nucleotide polymorphism (SNP markers for the four Citrus ancestral taxa covering the nine chromosomes, and to use these markers to infer the phylogenomic structure of secondary species and modern cultivars. Species-diagnostic SNPs were mined from 454 amplicon sequencing of 57 gene fragments from 26 genotypes of the four basic taxa. Of the 1,053 SNPs mined from 28,507 kb sequence, 273 were found to be highly diagnostic for a single basic taxon. Species-diagnostic SNP markers (105 were used to analyse the admixture structure of varieties and rootstocks. This revealed C. maxima introgressions in most of the old and in all recent selections of mandarins, and suggested that C. reticulata × C. maxima reticulation and introgression processes were important in edible mandarin domestication. The large range of phylogenomic constitutions between C. reticulata and C. maxima revealed in mandarins, tangelos, tangors, sweet oranges, sour oranges, grapefruits, and orangelos is favourable for genetic association studies based on phylogenomic structures of the germplasm. Inferred admixture structures were in agreement with previous hypotheses regarding the origin of several secondary species and also revealed the probable origin of several acid citrus varieties. The developed species

  14. Barrier island facies models and recognition criteria

    Science.gov (United States)

    Mulhern, J.; Johnson, C. L.

    2017-12-01

    Barrier island outcrops record transgressive shoreline motion at geologic timescales, providing integral clues to understanding how coastlines respond to rising sea levels. However, barrier island deposits are difficult to recognize. While significant progress has been made in understanding the modern coastal morphodynamics, this insight is not fully leveraged in existing barrier island facies models. Excellent outcrop exposures of the paralic Upper Cretaceous Straight Cliffs Formation of southern Utah provide an opportunity to revise facies models and recognition criteria for barrier island deposits. Preserved barrier islands are composed of three main architectural elements (shorefaces, tidal inlets, and tidal channels) which occur independently or in combination to create larger-scale barrier island deposits. Barrier island shorefaces record progradation, while barrier island tidal inlets record lateral migration, and barrier island tidal channels record aggradation within the tidal inlet. Four facies associations are used to describe and characterize these barrier island architectural elements. Barrier islands occur in association with backarrier fill and internally contain lower and upper shoreface, high-energy upper shoreface, and tidal channel facies. Barrier islands bound lagoons or estuaries, and are distinguished from other shoreface deposits by their internal facies and geometry, association with backbarrier facies, and position within transgressive successions. Tidal processes, in particular tidal inlet migration and reworking of the upper shoreface, also distinguish barrier island deposits. Existing barrier island models highlight the short term heterogeneous and dynamic nature of barrier island systems, yet overlook processes tied to geologic time scales, such as multi-directional motion, erosion, and reworking, and their expressions in preserved barrier island strata. This study uses characteristic outcrop expressions of barrier island successions to

  15. Altered permeability barrier structure in cholesteatoma matrix

    DEFF Research Database (Denmark)

    Svane-Knudsen, Viggo; Halkier-Sørensen, Lars; Rasmussen, Gurli

    2002-01-01

    lipid structures filling the intercellular spaces mainly control the barrier function. The barrier in cholesteatoma epithelium is several times thicker than in unaffected skin but presents distinctive features of a defective barrier as seen in other scaling skin diseases. The intercellular spaces appear...... frequently occur. The corneocytes are shed in clusters, not as single cells. Further, lipid droplets and intracellular membranous material are occasionally seen. In spite of these clear signs of barrier dysfunction, it is unknown whether the thickness of the barrier compensates for the defect in barrier...

  16. Transcriptome Signatures of Selection, Drift, Introgression, and Gene Duplication in the Evolution of an Extremophile Endemic Plant.

    Science.gov (United States)

    Hawkins, Angela K; Garza, Elyssa R; Dietz, Valerie A; Hernandez, Oscar J; Hawkins, W Daryl; Burrell, A Millie; Pepper, Alan E

    2017-12-01

    Plants on serpentine soils provide extreme examples of adaptation to environment, and thus offer excellent models for the study of evolution at the molecular and genomic level. Serpentine outcrops are derived from ultramafic rock and have extremely low levels of essential plant nutrients (e.g., N, P, K, and Ca), as well as toxic levels of heavy metals (e.g., Ni, Cr, and Co) and low moisture availability. These outcrops provide habitat to a number of endemic plant species, including the annual mustard Caulanthus amplexicaulis var. barbarae (Cab) (Brassicaceae). Its sister taxon, C. amplexicaulis var. amplexicaulis (Caa), is intolerant to serpentine soils. Here, we assembled and annotated comprehensive reference transcriptomes of both Caa and Cab for use in protein coding sequence comparisons. A set of 29,443 reciprocal best Blast hit (RBH) orthologs between Caa and Cab was compared with identify coding sequence variants, revealing a high genome-wide dN/dS ratio between the two taxa (mean = 0.346). We show that elevated dN/dS likely results from the composite effects of genetic drift, positive selection, and the relaxation of negative selection. Further, analysis of paralogs within each taxon revealed the signature of a period of elevated gene duplication (∼10 Ma) that is shared with other species of the tribe Thelypodieae, and may have played a role in the striking morphological and ecological diversity of this tribe. In addition, distribution of the synonymous substitution rate, dS, is strongly bimodal, indicating a history of reticulate evolution that may have contributed to serpentine adaptation. © The Author(s) 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  17. Roadside vegetation barrier designs to mitigate near-road air pollution impacts.

    Science.gov (United States)

    Tong, Zheming; Baldauf, Richard W; Isakov, Vlad; Deshmukh, Parikshit; Max Zhang, K

    2016-01-15

    With increasing evidence that exposures to air pollution near large roadways increases risks of a number of adverse human health effects, identifying methods to reduce these exposures has become a public health priority. Roadside vegetation barriers have shown the potential to reduce near-road air pollution concentrations; however, the characteristics of these barriers needed to ensure pollution reductions are not well understood. Designing vegetation barriers to mitigate near-road air pollution requires a mechanistic understanding of how barrier configurations affect the transport of traffic-related air pollutants. We first evaluated the performance of the Comprehensive Turbulent Aerosol Dynamics and Gas Chemistry (CTAG) model with Large Eddy Simulation (LES) to capture the effects of vegetation barriers on near-road air quality, compared against field data. Next, CTAG with LES was employed to explore the effects of six conceptual roadside vegetation/solid barrier configurations on near-road size-resolved particle concentrations, governed by dispersion and deposition. Two potentially viable design options are revealed: a) a wide vegetation barrier with high Leaf Area Density (LAD), and b) vegetation-solid barrier combinations, i.e., planting trees next to a solid barrier. Both designs reduce downwind particle concentrations significantly. The findings presented in the study will assist urban planning and forestry organizations with evaluating different green infrastructure design options. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. The introgression of RNAi silencing of γ-gliadins into commercial lines of bread wheat changes the mixing and technological properties of the dough.

    Directory of Open Access Journals (Sweden)

    Javier Gil-Humanes

    Full Text Available In the present work the effects on dough quality by the down-regulation of γ-gliadins in different genetic backgrounds of bread wheat were investigated. RNAi-mediated silencing of γ-gliadins was introgressed by conventional crossing into three commercial bread wheat lines (namely 'Gazul', 'Podenco' and 'Arpain', and along with the transgenic line A1152 (cv. Bobwhite compared with their respective wild types. The protein fractions were quantified by RP-HPLC, whereas the technological and mixing properties were assessed by SDSS test and by the Mixograph instrument. Principal component analysis (PCA was carried out for both the wild types and the transgenic lines, showing differences in the factors affecting the technological and mixing properties of the dough as a consequence of the reduction of the γ-gliadins. In transgenic lines, the α- and ω-gliadins, and total gliadins negatively affected the dough strength and tolerance to over-mixing, whereas the L/H ratio showed the opposite effect, positively influencing the dough quality. The increase of the SDSS volume in the transgenic lines of 'Gazul', 'Podenco' and 'Arpain' indicates increased gluten strength and quality respect to the wild types. SDSS volume was found to be positively influenced by the amount of glutenins, which were also increased in the transgenic lines. In addition, a positive effect was observed in the MT, PR1 and RBD in some of the transgenic lines of 'Podenco' and 'Arpain'. In conclusion, the down-regulation of γ-gliadins resulted in stronger doughs and a better tolerance to over-mixing in some transgenic lines. Although the reduction of γ-gliadins seems not to have a direct effect on the mixing and bread-making properties, the compensatory effect on the synthesis of the other prolamins may result in stronger doughs with improved over-mixing resistance.

  19. The Genetic Integrity of the Ex Situ Population of the European Wildcat (Felis silvestris silvestris) Is Seriously Threatened by Introgression from Domestic Cats (Felis silvestris catus)

    Science.gov (United States)

    Witzenberger, Kathrin A.; Hochkirch, Axel

    2014-01-01

    Studies on the genetic diversity and relatedness of zoo populations are crucial for implementing successful breeding programmes. The European wildcat, Felis s. silvestris, is subject to intensive conservation measures, including captive breeding and reintroduction. We here present the first systematic genetic analysis of the captive population of Felis s. silvestris in comparison with a natural wild population. We used microsatellites and mtDNA sequencing to assess genetic diversity, structure and integrity of the ex situ population. Our results show that the ex situ population of the European wildcat is highly structured and that it has a higher genetic diversity than the studied wild population. Some genetic clusters matched the breeding lines of certain zoos or groups of zoos that often exchanged individuals. Two mitochondrial haplotype groups were detected in the in situ populations, one of which was closely related to the most common haplotype found in domestic cats, suggesting past introgression in the wild. Although native haplotypes were also found in the captive population, the majority (68%) of captive individuals shared a common mtDNA haplotype with the domestic cat (Felis s. catus). Only six captive individuals (7.7%) were assigned as wildcats in the STRUCTURE analysis (at K = 2), two of which had domestic cat mtDNA haplotypes and only two captive individuals were assigned as purebred wildcats by NewHybrids. These results suggest that the high genetic diversity of the captive population has been caused by admixture with domestic cats. Therefore, the captive population cannot be recommended for further breeding and reintroduction. PMID:25162450

  20. Genetics and mapping of a novel downy mildew resistance gene, Pl(18), introgressed from wild Helianthus argophyllus into cultivated sunflower (Helianthus annuus L.).

    Science.gov (United States)

    Qi, L L; Foley, M E; Cai, X W; Gulya, T J

    2016-04-01

    A novel downy mildew resistance gene, Pl(18), was introgressed from wild Helianthus argophyllus into cultivated sunflower and genetically mapped to linkage group 2 of the sunflower genome. The new germplasm, HA-DM1, carrying Pl(18) has been released to the public. Sunflower downy mildew (DM) is considered to be the most destructive foliar disease that has spread to every major sunflower-growing country of the world, except Australia. A new dominant downy mildew resistance gene (Pl 18) transferred from wild Helianthus argophyllus (PI 494573) into cultivated sunflower was mapped to linkage group (LG) 2 of the sunflower genome using bulked segregant analysis with 869 simple sequence repeat (SSR) markers. Phenotyping 142 BC1F2:3 families derived from the cross of HA 89 and H. argophyllus confirmed the single gene inheritance of resistance. Since no other Pl gene has been mapped to LG2, this gene was novel and designated as Pl (18). SSR markers CRT214 and ORS203 flanked Pl(18) at a genetic distance of 1.1 and 0.4 cM, respectively. Forty-six single nucleotide polymorphism (SNP) markers that cover the Pl(18) region were surveyed for saturation mapping of the region. Six co-segregating SNP markers were 1.2 cM distal to Pl(18), and another four co-segregating SNP markers were 0.9 cM proximal to Pl(18). The new BC2F4-derived germplasm, HA-DM1, carrying Pl(18) has been released to the public. This new line is highly resistant to all Plasmopara halstedii races identified in the USA providing breeders with an effective new source of resistance against downy mildew in sunflower. The molecular markers that were developed will be especially useful in marker-assisted selection and pyramiding of Pl resistance genes because of their close proximity to the gene and the availability of high-throughput SNP detection assays.

  1. Marker-Assisted Backcrossing to Introgress Resistance to Fusarium Wilt Race 1 and Ascochyta Blight in C 214, an Elite Cultivar of Chickpea

    Directory of Open Access Journals (Sweden)

    R. K. Varshney

    2014-03-01

    Full Text Available Fusarium wilt (FW and Ascochyta blight (AB are two major constraints to chickpea (Cicer arietinum production,Fusarium wilt (FW and Ascochyta blight (AB are two major constraints to chickpea (Cicer arietinum L. production. Therefore, two parallel marker-assisted backcrossing (MABC programs by targeting foc1 locus and two quantitative trait loci (QTL regions, ABQTL-I and ABQTL-II, were undertaken to introgress resistance to FW and AB, respectively, in C 214, an elite cultivar of chickpea. In the case of FW, foreground selection (FGS was conducted with six markers (TR19, TA194, TAA60, GA16, TA110, and TS82 linked to foc1 in the cross C 214 × WR 315 (FW-resistant. On the other hand, eight markers (TA194, TR58, TS82, GA16, SCY17, TA130, TA2, and GAA47 linked with ABQTL-I and ABQTL-II were used in the case of AB by deploying C 214 × ILC 3279 (AB-resistant cross. Background selection (BGS in both crosses was employed with evenly distributed 40 (C 214 × WR 315 to 43 (C 214 × ILC 3279 SSR markers in the chickpea genome to select plant(s with higher recurrent parent genome (RPG recovery. By using three backcrosses and three rounds of selfing, 22 BC3F4 lines were generated for C 214 × WR 315 cross and 14 MABC lines for C 214 × ILC 3279 cross. Phenotyping of these lines has identified three resistant lines (with 92.7–95.2% RPG to race 1 of FW, and seven resistant lines (with 81.7–85.40% RPG to AB that may be tested for yield and other agronomic traits under multilocation trials for possible release and cultivation.

  2. Using chromosome introgression lines to map quantitative trait loci for photosynthesis parameters in rice (Oryza sativa L.) leaves under drought and well-watered field conditions

    Science.gov (United States)

    Gu, Junfei; Yin, Xinyou; Struik, Paul C.; Stomph, Tjeerd Jan; Wang, Huaqi

    2012-01-01

    Photosynthesis is fundamental to biomass production, but sensitive to drought. To understand the genetics of leaf photosynthesis, especially under drought, upland rice cv. Haogelao, lowland rice cv. Shennong265, and 94 of their introgression lines (ILs) were studied at flowering and grain filling under drought and well-watered field conditions. Gas exchange and chlorophyll fluorescence measurements were conducted to evaluate eight photosynthetic traits. Since these traits are very sensitive to fluctuations in microclimate during measurements under field conditions, observations were adjusted for microclimatic differences through both a statistical covariant model and a physiological approach. Both approaches identified leaf-to-air vapour pressure difference as the variable influencing the traits most. Using the simple sequence repeat (SSR) linkage map for the IL population, 1–3 quantitative trait loci (QTLs) were detected per trait–stage–treatment combination, which explained between 7.0% and 30.4% of the phenotypic variance of each trait. The clustered QTLs near marker RM410 (the interval from 57.3 cM to 68.4 cM on chromosome 9) were consistent over both development stages and both drought and well-watered conditions. This QTL consistency was verified by a greenhouse experiment under a controlled environment. The alleles from the upland rice at this interval had positive effects on net photosynthetic rate, stomatal conductance, transpiration rate, quantum yield of photosystem II (PSII), and the maximum efficiency of light-adapted open PSII. However, the allele of another main QTL from upland rice was associated with increased drought sensitivity of photosynthesis. These results could potentially be used in breeding programmes through marker-assisted selection to improve drought tolerance and photosynthesis simultaneously. PMID:21984650

  3. Highway renewable energy : photovoltaic noise barriers

    Science.gov (United States)

    2017-07-01

    Highway photovoltaic noise barriers (PVNBs) represent the combination of noise barrier systems and photovoltaic systems in order to mitigate traffic noise while simultaneously producing renewable energy. First deployed in Switzerland in 1989, PVNBs a...

  4. Prototype Hanford Surface Barrier: Design basis document

    International Nuclear Information System (INIS)

    Myers, D.R.; Duranceau, D.A.

    1994-11-01

    The Hanford Site Surface Barrier Development Program (BDP) was organized in 1985 to develop the technology needed to provide a long-term surface barrier capability for the Hanford Site and other arid sites. This document provides the basis of the prototype barrier. Engineers and scientists have momentarily frozen evolving barrier designs and incorporated the latest findings from BDP tasks. The design and construction of the prototype barrier has required that all of the various components of the barrier be brought together into an integrated system. This integration is particularly important because some of the components of the protective barreir have been developed independently of other barreir components. This document serves as the baseline by which future modifications or other barrier designs can be compared. Also, this document contains the minutes of meeting convened during the definitive design process in which critical decisions affecting the prototype barrier's design were made and the construction drawings

  5. Numerical modelling of barrier discharge

    International Nuclear Information System (INIS)

    Kozlov, K.V.

    1990-01-01

    A survey is given of the theory of the barrier discharge in oxygen at atmospheric pressure. The discharge consists of a number of randomly distributed microdischarges of nanosecond duration. This complicated space-time structure must be taken into account in any numerical model of the barrier discharge. In a single discharge channel, three consequent phases can be distinguished; 1) electric breakdown and electron-time-scale processes; 2) ion drift and ion-time-scale processes; 3) slow chemical processes, diffusion of chemical products and heat transfer. The scheme of such a three-phase model is presented and the results of simulation are discussed and compared with experimental data. (J.U.) 9 figs., 15 refs

  6. Security barriers with automated reconnaissance

    Science.gov (United States)

    McLaughlin, James O; Baird, Adam D; Tullis, Barclay J; Nolte, Roger Allen

    2015-04-07

    An intrusion delaying barrier includes primary and secondary physical structures and can be instrumented with multiple sensors incorporated into an electronic monitoring and alarm system. Such an instrumented intrusion delaying barrier may be used as a perimeter intrusion defense and assessment system (PIDAS). Problems with not providing effective delay to breaches by intentional intruders and/or terrorists who would otherwise evade detection are solved by attaching the secondary structures to the primary structure, and attaching at least some of the sensors to the secondary structures. By having multiple sensors of various types physically interconnected serves to enable sensors on different parts of the overall structure to respond to common disturbances and thereby provide effective corroboration that a disturbance is not merely a nuisance or false alarm. Use of a machine learning network such as a neural network exploits such corroboration.

  7. Barriers to nursing advocacy: a concept analysis.

    Science.gov (United States)

    Hanks, Robert G

    2007-01-01

    Advocacy for clients is viewed as an essential function of nursing; however, to be effective advocates for patients, the nurse must often overcome barriers to being an effective advocate. This concept analysis of barriers to nursing advocacy uses the Walker and Avant method of concept analysis. By analyzing the barriers to effective nursing advocacy for clients, nursing can then find strategies to manage those barriers and maximize the nurse's advocacy efforts.

  8. Perceptions regarding strategic and structural entry barriers

    OpenAIRE

    Lutz, C.H.M.; Kemp, R.G.M.; Dijkstra, S.G.

    2010-01-01

    This article uses factor analysis to identify the underlying dimensions of strategic and structural entry barriers. We find that, in the perception of firms, both types of barriers are important and that the effectiveness of strategic barriers depends on attributes of the market structure. Based on the seven generic factors, a conjoint analysis is carried out to identify the most important factors perceived by firms. The conjoint analysis shows that in particular the barriers rooted in three ...

  9. A Common Genetic Determinism for Sensitivities to Soil Water Deficit and Evaporative Demand: Meta-Analysis of Quantitative Trait Loci and Introgression Lines of Maize1[W][OA

    Science.gov (United States)

    Welcker, Claude; Sadok, Walid; Dignat, Grégoire; Renault, Morgan; Salvi, Silvio; Charcosset, Alain; Tardieu, François

    2011-01-01

    Evaporative demand and soil water deficit equally contribute to water stress and to its effect on plant growth. We have compared the genetic architectures of the sensitivities of maize (Zea mays) leaf elongation rate with evaporative demand and soil water deficit. The former was measured via the response to leaf-to-air vapor pressure deficit in well-watered plants, the latter via the response to soil water potential in the absence of evaporative demand. Genetic analyses of each sensitivity were performed over 21 independent experiments with (1) three mapping populations, with temperate or tropical materials, (2) one population resulting from the introgression of a tropical drought-tolerant line in a temperate line, and (3) two introgression libraries genetically independent from mapping populations. A very large genetic variability was observed for both sensitivities. Some lines maintained leaf elongation at very high evaporative demand or water deficit, while others stopped elongation in mild conditions. A complex architecture arose from analyses of mapping populations, with 19 major meta-quantitative trait loci involving strong effects and/or more than one mapping population. A total of 68% of those quantitative trait loci affected sensitivities to both evaporative demand and soil water deficit. In introgressed lines, 73% of the tested genomic regions affected both sensitivities. To our knowledge, this study is the first genetic demonstration that hydraulic processes, which drive the response to evaporative demand, also have a large contribution to the genetic variability of plant growth under water deficit in a large range of genetic material. PMID:21795581

  10. Sea sand for reactive barriers

    International Nuclear Information System (INIS)

    Garcia R, G.; Ordonez R, E.; Ordonez R, En.

    2002-01-01

    Some phosphates have the property to suck in radioactive metals in solution, what it is taken in advance to make reactive barriers which are placed in the nuclear waste repositories. In an effort for contributing to the study of this type of materials, it has been obtained the zirconium silicate (ZrSiO 4 ) and the alpha zirconium hydrogen phosphate (Zr(HPO 4 ) 2H 2 O) starting from sea sand in an easy and economic way. (Author)

  11. Improved performance thermal barrier coatings

    International Nuclear Information System (INIS)

    Levine, S.R.; Miller, R.A.; Stecura, S.

    1983-01-01

    Thermal barrier coatings offer an attractive approach to improving the durability and efficiency of the hot section of heat engines. The coatings typically consist of an inner alloy bond coating about 0.01 cm thick resistant to oxidation and hot corrosion and an outer ceramic layer, usually a stabilized zirconia, 0.01-0.05 cm thick. Here, the materials, thermomechanical stress, and hot corrosion problems associated with thermal barrier coatings are reviewed along with the capabilities and limitations of current technology. The coatings discussed include ZrO2-Y2O3/NiCrAlY, ZrO2-Y2O3/NiCoCrAlY, ZrO2-MgO/NiCoCrAlY, CaO-SiO2/Co-Cr-Al-Y, and CaO-SiO2/NiCrAlY systems. It is emphasized that the performance of thermal barrier coatings is governed by many complex and interrelated factors, so that optimization of these coatings always involves certain tradeoffs. 27 references

  12. Addressing barriers to safe abortion.

    Science.gov (United States)

    Culwell, Kelly R; Hurwitz, Manuelle

    2013-05-01

    The latest World Health Organization data estimate that the total number of unsafe abortions globally has increased to 21.6 million in 2008. There is increasing recognition by the international community of the importance of the contribution of unsafe abortion to maternal mortality. However, the barriers to delivery of safe abortion services are many. In 68 countries, home to 26% of the world's population, abortion is prohibited altogether or only permitted to save a woman's life. Even in countries with more liberal abortion legal frameworks, additional social, economic, and health systems barriers and the stigma surrounding abortion prevent adequate access to safe abortion services and postabortion care. While much has been achieved to reduce the barriers to comprehensive abortion care, much remains to be done. Only through the concerted action of public, private, and civil society partners can we ensure that women have access to services that are safe, affordable, confidential, and stigma free. Copyright © 2013 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.

  13. Market barriers to welfare product innovations

    NARCIS (Netherlands)

    Binnekamp, M.H.A.; Ingenbleek, P.T.M.

    2006-01-01

    New products that are based on higher animal welfare standards encounter several barriers on the road to market acceptance. The authors focus on the Dutch poultry sector and distinguish between retailer and consumer barriers. Retailer barriers include the powerful position of retailers, the price

  14. Barriers to Mammography among Inadequately Screened Women

    Science.gov (United States)

    Stoll, Carolyn R. T.; Roberts, Summer; Cheng, Meng-Ru; Crayton, Eloise V.; Jackson, Sherrill; Politi, Mary C.

    2015-01-01

    Mammography use has increased over the past 20 years, yet more than 30% of women remain inadequately screened. Structural barriers can deter individuals from screening, however, cognitive, emotional, and communication barriers may also prevent mammography use. This study sought to identify the impact of number and type of barriers on mammography…

  15. Perceptions regarding strategic and structural entry barriers

    NARCIS (Netherlands)

    Lutz, C.H.M.; Kemp, R.G.M.; Dijkstra, S.G.

    2010-01-01

    This article uses factor analysis to identify the underlying dimensions of strategic and structural entry barriers. We find that, in the perception of firms, both types of barriers are important and that the effectiveness of strategic barriers depends on attributes of the market structure. Based on

  16. Perceptions regarding strategic and structural entry barriers

    NARCIS (Netherlands)

    Lutz, Clemens H. M.; Kemp, Ron G. M.; Dijkstra, S. Gerhard

    This article uses factor analysis to identify the underlying dimensions of strategic and structural entry barriers. We find that, in the perception of firms, both types of barriers are important and that the effectiveness of strategic barriers depends on attributes of the market structure. Based on

  17. Article Including Environmental Barrier Coating System

    Science.gov (United States)

    Lee, Kang N. (Inventor)

    2015-01-01

    An enhanced environmental barrier coating for a silicon containing substrate. The enhanced barrier coating may include a bond coat doped with at least one of an alkali metal oxide and an alkali earth metal oxide. The enhanced barrier coating may include a composite mullite bond coat including BSAS and another distinct second phase oxide applied over said surface.

  18. The Barriers and Needs of Online Learners

    Science.gov (United States)

    Srichanyachon, Napaporn

    2014-01-01

    This study investigated some specific barriers and needs that online students are facing when learning English through WebEx system. It compared students' barriers and needs with their background including gender, computer ownership, and monthly allowance. It also investigated the relationship among computer aptitude, barriers and needs of online…

  19. The Genetic Structure of Wild Orobanche cumana Wallr. (Orobanchaceae Populations in Eastern Bulgaria Reflects Introgressions from Weedy Populations

    Directory of Open Access Journals (Sweden)

    Rocío Pineda-Martos

    2014-01-01

    Full Text Available Orobanche cumana is a holoparasitic plant naturally distributed from central Asia to south-eastern Europe, where it parasitizes wild Asteraceae species. It is also an important parasitic weed of sunflower crops. The objective of this research was to investigate genetic diversity, population structure, and virulence on sunflower of O. cumana populations parasitizing wild plants in eastern Bulgaria. Fresh tissue of eight O. cumana populations and mature seeds of four of them were collected in situ on wild hosts. Genetic diversity and population structure were studied with SSR markers and compared to weedy populations. Two main gene pools were identified in Bulgarian populations, with most of the populations having intermediate characteristics. Cross-inoculation experiments revealed that O. cumana populations collected on wild species possessed similar ability to parasitize sunflower to those collected on sunflower. The results were explained on the basis of an effective genetic exchange between populations parasitizing sunflower crops and those parasitizing wild species. The occurrence of bidirectional gene flow may have an impact on wild populations, as new physiological races continuously emerge in weedy populations. Also, genetic variability of wild populations may favour the ability of weedy populations to overcome sunflower resistance mechanisms.

  20. The Genetic Structure of Wild Orobanche cumana Wallr. (Orobanchaceae) Populations in Eastern Bulgaria Reflects Introgressions from Weedy Populations

    Science.gov (United States)

    Pineda-Martos, Rocío; Pujadas-Salvà, Antonio J.; Fernández-Martínez, José M.; Stoyanov, Kiril; Pérez-Vich, Begoña

    2014-01-01

    Orobanche cumana is a holoparasitic plant naturally distributed from central Asia to south-eastern Europe, where it parasitizes wild Asteraceae species. It is also an important parasitic weed of sunflower crops. The objective of this research was to investigate genetic diversity, population structure, and virulence on sunflower of O. cumana populations parasitizing wild plants in eastern Bulgaria. Fresh tissue of eight O. cumana populations and mature seeds of four of them were collected in situ on wild hosts. Genetic diversity and population structure were studied with SSR markers and compared to weedy populations. Two main gene pools were identified in Bulgarian populations, with most of the populations having intermediate characteristics. Cross-inoculation experiments revealed that O. cumana populations collected on wild species possessed similar ability to parasitize sunflower to those collected on sunflower. The results were explained on the basis of an effective genetic exchange between populations parasitizing sunflower crops and those parasitizing wild species. The occurrence of bidirectional gene flow may have an impact on wild populations, as new physiological races continuously emerge in weedy populations. Also, genetic variability of wild populations may favour the ability of weedy populations to overcome sunflower resistance mechanisms. PMID:25143963

  1. Introgression of leaf rust and stripe rust resistance from Sharon goatgrass (Aegilops sharonensis Eig) into bread wheat (Triticum aestivum L.).

    Science.gov (United States)

    Millet, E; Manisterski, J; Ben-Yehuda, P; Distelfeld, A; Deek, J; Wan, A; Chen, X; Steffenson, B J

    2014-06-01

    Leaf rust and stripe rust are devastating wheat diseases, causing significant yield losses in many regions of the world. The use of resistant varieties is the most efficient way to protect wheat crops from these diseases. Sharon goatgrass (Aegilops sharonensis or AES), which is a diploid wild relative of wheat, exhibits a high frequency of leaf and stripe rust resistance. We used the resistant AES accession TH548 and induced homoeologous recombination by the ph1b allele to obtain resistant wheat recombinant lines carrying AES chromosome segments in the genetic background of the spring wheat cultivar Galil. The gametocidal effect from AES was overcome by using an "anti-gametocidal" wheat mutant. These recombinant lines were found resistant to highly virulent races of the leaf and stripe rust pathogens in Israel and the United States. Molecular DArT analysis of the different recombinant lines revealed different lengths of AES segments on wheat chromosome 6B, which indicates the location of both resistance genes.

  2. Gender Differences in College Students' Career Maturity and Perceived Barriers in Career Development.

    Science.gov (United States)

    Luzzo, Darrell Anthony

    1995-01-01

    Gender differences in 401 college students' career maturity were investigated with quantitative measures that included attitudes, decision-making skills, and vocational congruence. Analyses revealed that females scored significantly higher than males on each of the measures. Qualitative analyses revealed that the perception of barriers may serve…

  3. Atomistic modeling of the structural components of the blood-brain barrier

    Science.gov (United States)

    Glukhova, O. E.; Grishina, O. A.; Slepchenkov, M. M.

    2015-03-01

    Blood-brain barrier, which is a barrage system between the brain and blood vessels, plays a key role in the "isolation" of the brain of unnecessary information, and reduce the "noise" in the interneuron communication. It is known that the barrier function of the BBB strictly depends on the initial state of the organism and changes significantly with age and, especially in developing the "vascular accidents". Disclosure mechanisms of regulation of the barrier function will develop new ways to deliver neurotrophic drugs to the brain in the newborn. The aim of this work is the construction of atomistic models of structural components of the blood-brain barrier to reveal the mechanisms of regulation of the barrier function.

  4. Determination of the thickness of Al2O3 barriers in magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Buchanan, J.D.R.; Hase, T.P.A.; Tanner, B.K.; Hughes, N.D.; Hicken, R.J.

    2002-01-01

    The barrier thickness in magnetic spin-dependent tunnel junctions with Al 2 O 3 barriers has been measured using grazing incidence x-ray reflectivity and by fitting the tunneling current to the Simmons model. We have studied the effect of glow discharge oxidation time on the barrier structure, revealing a substantial increase in Al 2 O 3 thickness with oxidation. The greater thickness of barrier measured using grazing incidence x-ray reflectivity compared with that obtained by fitting current density-voltage to the Simmons electron tunneling model suggests that electron tunneling is localized to specific regions across the barrier, where the thickness is reduced by fluctuations due to nonconformal roughness

  5. Barriers to recovery in communities exposed to disasters: Sri Lankan voices speak.

    Science.gov (United States)

    Fernando, Gaithri A; Wilkins, Ashley

    2015-01-01

    Disasters experienced by a community place all members at risk for physical and psychological harm. While natural resilience may help many to recover, there may be barriers that hinder the recovery process. This qualitative study was conducted to examine barriers to recovery in a community impacted by both war and the tsunami. A group of 43 ethnically diverse Sri Lankans (F = 63%) participated in six focus groups and provided their perspectives on barriers they perceived to impede their recovery from traumatic events. Grounded-theory-based data analysis revealed culture-general and culture-specific socio-economic, environmental, sociocultural, and individual barriers that participants identified as impeding their recovery. Interventions and health policies targeting these groups could focus on helping communities to overcome these barriers as a means of facilitating recovery in these beleaguered communities.

  6. Marker-assisted breeding for introgression of opaque-2 allele into elite maize inbred line BML-7.

    Science.gov (United States)

    Krishna, M S R; Sokka Reddy, S; Satyanarayana, Sadam D V

    2017-07-01

    Improvement of quality protein maize (QPM) along with high content of lysine and tryptophan had foremost importance in maize breeding program. The efficient and easiest way of developing QPM hybrids was by backcross breeding in marker aided selection. Hence, the present investigation aimed at conversion of elite maize inbred line BML-7 into QPM line. CML-186 was identified to be a donor variety as it revealed high-quality polymorphism with BML-7 for opaque-2 gene specific marker umc1066. Non-QPM inbred line BML-7 was crossed with QPM donor CML-186 and produced F 1 followed by the development of BC 1 F 1 and BC 2 F 1 population. Foreground selection was carried out with umc1066 in F 1 , and selected plants were used for BC 1 F 1 and BC 2 F 1 populations. Two hundred plants were screened in both BC 1 F 1 and BC 2 F 1 population with umc1066 for foreground selection amino acid modifiers. Foreground selected plants for both opaque-2 and amino acid modifiers were screened for background selection for BML-7 genome. Recurrent parent genome (RPG) was calculated for BC 2 F 1 population plants. Two plants have shown with RPG 90-93% in two generation with back cross population. Two BC 2 F 2 populations resulted from marker recognized BC 2 F 1 individuals subjected toward foreground selection followed by tryptophan estimation. The tryptophan and lysine concentration was improved in all the plants. BC 2 F 2 lines developed from hard endosperm kernels were selfed for BC 2 F 2 lines and finest line was selected to illustrate the QPM version of BML-7, with 0.97% of tryptophan and 4.04% of lysine concentration in protein. Therefore, the QPM version of BML-7 line can be used for the development of single cross hybrid QPM maize version.

  7. From screening to postpartum follow-up - the determinants and barriers for gestational diabetes mellitus (GDM) services, a systematic review

    DEFF Research Database (Denmark)

    Nielsen, Karoline Kragelund; Kapur, Anil; Damm, Peter

    2014-01-01

    modifications seems even lower. Here too, health care provider, health system and client related determinants and barriers were identified. Studies reveal that sense of self-efficacy and social support are key determinants. CONCLUSIONS: The paper identifies and discusses determinants and barriers for GDM care...

  8. Nonallopatric and parallel origin of local reproductive barriers between two snail ecotypes.

    Science.gov (United States)

    Rolán-Alvarez, Emilio; Carballo, Monica; Galindo, Juan; Morán, Paloma; Fernández, Blanca; Caballero, Armando; Cruz, Raquel; Boulding, Elizabeth G; Johannesson, Kerstin

    2004-11-01

    Theory suggests that speciation is possible without physical isolation of populations (hereafter, nonallopatric speciation), but recent nonallopatric models need the support of irrefutable empirical examples. We collected snails (Littorina saxatilis) from three areas on the NW coast of Spain to investigate the population genetic structure of two ecotypes. Earlier studies suggest that these ecotypes may represent incipient species: a large, thick-shelled 'RB' ecotype living among the barnacles in the upper intertidal zone and a small, thin-shelled 'SU' ecotype living among the mussels in the lower intertidal zone only 10-30 m away. The two ecotypes overlap and hybridize in a midshore zone only 1-3 m wide. Three different types of molecular markers [allozymes, mitochondrial DNA (mtDNA) and microsatellites] consistently indicated partial reproductive isolation between the RB and the SU ecotypes at a particular site. However, each ecotype was related more closely to the other ecotype from the same site than to the same ecotype from another site further along the Galician coast (25-77 km away). These findings supported earlier results based solely on allozyme variation and we could now reject the possibility that selection produced these patterns. The patterns of genetic variation supported a nonallopatric model in which the ecotypes are formed independently at each site by parallel evolution and where the reproductive barriers are a byproduct of divergent selection for body size. We argue that neither our laboratory hybridization experiments nor our molecular data are compatible with a model based on allopatric ecotype formation, secondary overlap and introgression.

  9. Chemical barriers for controlling groundwater contamination

    International Nuclear Information System (INIS)

    Morrison, S.J.; Spangler, R.R.

    1993-01-01

    Chemical barriers are being explored as a low-cost means of controlling groundwater contamination. The barrier can intercept a contaminant plume and prevent migration by transferring contaminants from the groundwater to immobile solids. A chemical barrier can be emplaced in a landfill liner or in an aquifer cutoff wall or can be injected into a contaminant plume. Chemical barriers can be classified as either precipitation barriers or sorption barriers depending upon the dominant mode of contaminant extraction. In a precipitation barrier, contaminants are bound in the structures of newly formed phases; whereas, in a sorption barrier, contaminants attach to the surfaces of preexisting solids by adsorption or some other surface mechanism. Sorption of contaminants is pH dependent. A precipitation barrier can control the pH of the system, but alkaline groundwater may dominate the pH in a sorption barrier. A comparison is made of the characteristics of precipitation and sorption barriers. Experimental data on the extraction of uranium and molybdenum from simulated groundwater are used to demonstrate these concepts. 10 refs., 9 figs., 1 tab

  10. Mitochondrial Genome Analysis Reveals Historical Lineages in Yellowstone Bison.

    Directory of Open Access Journals (Sweden)

    David Forgacs

    Full Text Available Yellowstone National Park is home to one of the only plains bison populations that have continuously existed on their present landscape since prehistoric times without evidence of domestic cattle introgression. Previous studies characterized the relatively high levels of nuclear genetic diversity in these bison, but little is known about their mitochondrial haplotype diversity. This study assessed mitochondrial genomes from 25 randomly selected Yellowstone bison and found 10 different mitochondrial haplotypes with a haplotype diversity of 0.78 (± 0.06. Spatial analysis of these mitochondrial DNA (mtDNA haplotypes did not detect geographic population subdivision (FST = -0.06, p = 0.76. However, we identified two independent and historically important lineages in Yellowstone bison by combining data from 65 bison (defined by 120 polymorphic sites from across North America representing a total of 30 different mitochondrial DNA haplotypes. Mitochondrial DNA haplotypes from one of the Yellowstone lineages represent descendants of the 22 indigenous bison remaining in central Yellowstone in 1902. The other mitochondrial DNA lineage represents descendants of the 18 females introduced from northern Montana in 1902 to supplement the indigenous bison population and develop a new breeding herd in the northern region of the park. Comparing modern and historical mitochondrial DNA diversity in Yellowstone bison helps uncover a historical context of park restoration efforts during the early 1900s, provides evidence against a hypothesized mitochondrial disease in bison, and reveals the signature of recent hybridization between American plains bison (Bison bison bison and Canadian wood bison (B. b. athabascae. Our study demonstrates how mitochondrial DNA can be applied to delineate the history of wildlife species and inform future conservation actions.

  11. Ab initio transport across bismuth selenide surface barriers

    KAUST Repository

    Narayan, Awadhesh

    2014-11-24

    © 2014 American Physical Society. We investigate the effect of potential barriers in the form of step edges on the scattering properties of Bi2Se3(111) topological surface states by means of large-scale ab initio transport simulations. Our results demonstrate the suppression of perfect backscattering, while all other scattering processes, which do not entail a complete spin and momentum reversal, are allowed. Furthermore, we find that the spin of the surface state develops an out-of-plane component as it traverses the barrier. Our calculations reveal the existence of quasibound states in the vicinity of the surface barriers, which appear in the form of an enhanced density of states in the energy window corresponding to the topological state. For double barriers we demonstrate the formation of quantum well states. To complement our first-principles results we construct a two-dimensional low-energy effective model and illustrate its shortcomings. Our findings are discussed in the context of a number of recent experimental works.

  12. Food-associated stimuli enhance barrier properties of gastrointestinal mucus.

    Science.gov (United States)

    Yildiz, Hasan M; Speciner, Lauren; Ozdemir, Cafer; Cohen, David E; Carrier, Rebecca L

    2015-06-01

    Orally delivered drugs and nutrients must diffuse through mucus to enter the circulatory system, but the barrier properties of mucus and their modulation by physiological factors are generally poorly characterized. The main objective of this study was to examine the impact of physicochemical changes occurring upon food ingestion on gastrointestinal (GI) mucus barrier properties. Lipids representative of postprandial intestinal contents enhanced mucus barriers, as indicated by a 10-142-fold reduction in the transport rate of 200 nm microspheres through mucus, depending on surface chemistry. Physiologically relevant increases in [Ca(2+)] resulted in a 2-4-fold reduction of transport rates, likely due to enhanced cross-linking of the mucus gel network. Reduction of pH from 6.5 to 3.5 also affected mucus viscoelasticity, reducing particle transport rates approximately 5-10-fold. Macroscopic visual observation and micro-scale lectin staining revealed mucus gel structural changes, including clumping into regions into which particles did not penetrate. Histological examination indicated food ingestion can prevent microsphere contact with and endocytosis by intestinal epithelium. Taken together, these results demonstrate that GI mucus barriers are significantly altered by stimuli associated with eating and potentially dosing of lipid-based delivery systems; these stimuli represent broadly relevant variables to consider upon designing oral therapies. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. A high rotational barrier for physisorbed hydrogen in an fcu-metal-organic framework

    KAUST Repository

    Pham, Tony T.

    2014-01-01

    A combined inelastic neutron scattering (INS) and theoretical study of H2 sorption in Y-FTZB, a recently reported metal-organic framework (MOF) with fcu topology, reveals that the strongest binding site in the MOF causes a high barrier to rotation on the sorbed H2. This rotational barrier for H2 is the highest yet of reported MOF materials based on physisorption. This journal is

  14. Barriers Perceived by Teachers at Work, Coping Strategies, Self-efficacy and Burnout

    OpenAIRE

    Doménech Betoret, Fernando; Gómez Artiga, Amparo

    2010-01-01

    This study examines the relationships among stressors, coping strategies, self-efficacy and burnout in a sample of 724 Spanish primary and secondary teachers. We understood stressors as barriers perceived by teachers that interfere with their work meeting learning objectives and which cause them stress and burnout. An analysis of teacher responses using hierarchical regression revealed that pedagogical barriers had significant positive effects on the burnout dimensions. Furthermore, the resul...

  15. Surface barrier and bulk pinning in MgB$_2$ superconductor

    OpenAIRE

    Pissas, M.; Moraitakis, E.; Stamopoulos, D.; Papavassiliou, G.; Psycharis, V.; Koutandos, S.

    2001-01-01

    We present a modified method of preparation of the new superconductor MgB$_2$. The polycrystalline samples were characterized using x-ray and magnetic measurements. The surface barriers control the isothermal magnetization loops in powder samples. In bulk as prepared samples we always observed symmetric magnetization loops indicative of the presence of a bulk pinning mechanism. Magnetic relaxation measurements in the bulk sample reveal a crossover of surface barrier to bulk pinning.

  16. Examining empirical evidence of the effect of superfluidity on the fusion barrier

    Science.gov (United States)

    Scamps, Guillaume

    2018-04-01

    Background: Recent time-dependent Hartree-Fock-Bogoliubov (TDHFB) calculations predict that superfluidity enhances fluctuations of the fusion barrier. This effect is not fully understood and not yet experimentally revealed. Purpose: The goal of this study is to empirically investigate the effect of superfluidity on the distribution width of the fusion barrier. Method: Two new methods are proposed in the present study. First, the local regression method is introduced and used to determine the barrier distribution. The second method, which requires only the calculation of an integral of the cross section, is developed to determine accurately the fluctuations of the barrier. This integral method, showing the best performance, is systematically applied to 115 fusion reactions. Results: Fluctuations of the barrier for open-shell systems are, on average, larger than those for magic or semimagic nuclei. This is due to the deformation and the superfluidity. To disentangle these two effects, a comparison is made between the experimental width and the width estimated from a model that takes into account the tunneling, the deformation, and the vibration effect. This study reveals that superfluidity enhances the fusion barrier width. Conclusions: This analysis shows that the predicted effect of superfluidity on the width of the barrier is real and is of the order of 1 MeV.

  17. Barriers perceived by teachers at work, coping strategies, self-efficacy and burnout.

    Science.gov (United States)

    Doménech Betoret, Fernando; Gómez Artiga, Amparo

    2010-11-01

    This study examines the relationships among stressors, coping strategies, self-efficacy and burnout in a sample of 724 Spanish primary and secondary teachers. We understood stressors as barriers perceived by teachers that interfere with their work meeting learning objectives and which cause them stress and burnout. An analysis of teacher responses using hierarchical regression revealed that pedagogical barriers had significant positive effects on the burnout dimensions. Furthermore, the results show not only the moderator role played by coping strategies in the pedagogical barriers-burnout dimensions relationship, but also the association between self-efficacy and the coping strategies used by teachers. Practical implications are discussed.

  18. Regulatory Barriers for Flexible Coupling of the Nordic Power and District Heating Markets

    DEFF Research Database (Denmark)

    Skytte, Klaus; Olsen, Ole Jess

    2016-01-01

    can be generated. However, regulatory barriers and different energy taxes may hinder the potential benefits from systems integration and lower the realisable potentials. By a case study for Denmark we survey and discuss regulatory barriers and drivers for flexibility obtained from DH. We reveal...... that the choice of technologies for heat generation is mainly driven by outdated policies and tax conditions that create barriers for additional flexibility in the overall energy system. However, the balancing markets may be a main driver for introducing more electric boilers into DH and thereby increase its...

  19. Factors related to environmental barriers experienced by persons with and without disabilities in diverse African settings.

    Directory of Open Access Journals (Sweden)

    Surona Visagie

    Full Text Available This paper explores differences in experienced environmental barriers between individuals with and without disabilities and the impact of additional factors on experienced environmental barriers. Data was collected in 2011-2012 by means of a two-stage cluster sampling and comprised 400-500 households in different sites in South Africa, Sudan Malawi and Namibia. Data were collected through self-report survey questionnaires. In addition to descriptive statistics and simple statistical tests a structural equation model was developed and tested. The combined file comprised 9,307 participants. The Craig Hospital Inventory of Environmental Factors was used to assess the level of environmental barriers. Transportation, the natural environment and access to health care services created the biggest barriers. An exploratory factor analysis yielded support for a one component solution for environmental barriers. A scale was constructed by adding the items together and dividing by number of items, yielding a range from one to five with five representing the highest level of environmental barriers and one the lowest. An overall mean value of 1.51 was found. Persons with disabilities scored 1.66 and persons without disabilities 1.36 (F = 466.89, p < .001. Bivariate regression analyses revealed environmental barriers to be higher among rural respondents, increasing with age and severity of disability, and lower for those with a higher level of education and with better physical and mental health. Gender had an impact only among persons without disabilities, where women report more barriers than men. Structural equation model analysis showed that socioeconomic status was significantly and negatively associated with environmental barriers. Activity limitation is significantly associated with environmental barriers when controlling for a number of other individual characteristics. Reducing barriers for the general population would go some way to reduce the impact

  20. Demand and Financial Constraints in Eliminating Architectural and Technical Barriers for People with Disabilities in Poland

    Directory of Open Access Journals (Sweden)

    Maria Hełdak

    2018-01-01

    Full Text Available The purpose of the study is to analyse the availability of financial resources for people with disabilities and to assess the needs satisfaction level of the disabled in order to eliminate architectural and technical barriers in Poland. The research conducted among the disabled affected by physical disability indicates that mobility barriers and obstacles remain among the most important problems encountered by people with disabilities. The research has shown that the problem of barriers increases with age. The elimination of architectural barriers requires, each time, higher financial expenditure, whereas the elimination of technical barriers improves the life quality of people with disabilities at low financial outlays. The average funding in Poland amounted to PLN 827.53 in 2016, including the funding of EUR 1453.60 for the elimination of architectural barriers and approx. EUR 582 for the removal of technical barriers. The financial resources allocated for this purpose do not cover the actual needs of the people with disabilities. The analysis revealed that the demand for investment in the elimination of barriers is increasing with age, whereas the expenditure of the Polish state is decreasing.

  1. Understanding energy efficiency barriers in Ukraine: Insights from a survey of commercial and industrial firms

    International Nuclear Information System (INIS)

    Timilsina, Govinda R.; Hochman, Gal; Fedets, Iryna

    2016-01-01

    Improvement of energy efficiency is an important element of energy policy for a sustainable supply of energy in Ukraine. However, the country is facing several challenges to the large-scale deployment of energy efficient technologies. We conducted a two-stage quota sample survey of 509 commercial and industrial firms of all regions of Ukraine to understand the barriers to energy efficiency improvements. Our study finds that more than two-thirds of the commercial and industrial firms in the country view improvement of energy efficiency very important to their business. However, due to several barriers they are unable to realize the improvements of energy efficiency. Among the 19 potential barriers investigated in the study, the survey results show that high upfront investment requirement, lack of government policies to support energy efficiency improvements, higher cost of capital, and lack of information and awareness are the most critical barriers to the improvement of energy efficiency in the industrial and commercial sectors in Ukraine. - Highlights: • Despite attractiveness, large scale deployment of energy efficiency is lacking. • Several barriers are responsible for slow implementation of energy efficiency. • Understanding the barriers from the field is crucial to design effective policies. • A survey of commercial and industrial firms reveals the key barriers. • Financial barriers are the main hurdles to adopt energy efficient technologies.

  2. Reliability and Validity of a Treatment Barriers Scale for Individuals With Alcohol Use Disorder.

    Science.gov (United States)

    Possemato, Kyle; Funderburk, Jennifer; Spinola, Suzanne; Hutchison, Dezarie; Maisto, Stephen A; Lantinga, Larry J; Oslin, David W

    2016-01-01

    Few studies have measured addiction-specific barriers to treatment. A measurement of barriers with psychometric support that has been tested in diverse samples and that assesses multiple components of addiction treatment barriers is needed to inform providers and treatment programs. This paper aims to provide an initial psychometric investigation of a measure of barriers to seeking addictions treatment. Data were collected from 196 Veterans Affairs primary care patients with Alcohol Use Disorder that participated in a randomized clinical trial. A Principal Components Analysis revealed that the 32-item Treatment Barriers Scale (TBS) can be reduced to 14 items, measuring 4 factors: stigma, dislike of the treatment process, alcohol problem identification, and logistical concerns. Acceptable internal consistent reliability (α = .64-.76) and excellent precision of alpha (α = 0.001-0.009) was found for each subscale. Support for the measure's concurrent validity was found, for example, participants who reported more motivation to reduce their drinking perceived significantly fewer barriers to care. Support for the measure's predictive validity was also found, including that more barriers were related to future drinking among all participants and less mental health and addictions treatment visits among participants in one treatment condition. Conclusions/ Importance: Our results provide initial support for the utility of the TBS-14 among primary care patients with Alcohol Use Disorder. Use of the TBS-14 could enable healthcare providers to better understand patient-specific treatment barriers, provide corrective information on treatment misconceptions, and inform individualized treatment plans that increase patient engagement in addiction services.

  3. Mediated Intercultural Communication Barrier in No Drama Zone! Group

    OpenAIRE

    Lizal, Valentino

    2015-01-01

    This research study aimed to describe the mediated intercultural communication barriers in the No Drama Zone! group. This study is a qualitative descriptive type of research, with case study method. By doing in depth interview and observation, researcher found two barriers that generates other barriers in the group's mediated intercultural communication. The two big barriers were: language and physical barriers. Language barriers in this group generated two barriers, emotional barrier and pe...

  4. BREEDING AND GENETICS SYMPOSIUM:Breeding heat tolerant dairy cattle: the case for introgression of the "slick" prolactin receptor variant into dairy breeds.

    Science.gov (United States)

    Davis, S R; Spelman, R J; Littlejohn, M D

    2017-04-01

    Increasing environmental temperatures are a threat to the sustainability of livestock production and, because of the high metabolic demands of lactation, to dairy production in particular. Summer heat waves in temperate climates reduce feed intake, milk production, and cow comfort. In extreme heat events, there is an increase in cow mortality. In tropical climates, dairy cattle are mostly (zebu) type or zebu crossbred with temperate dairy breeds. Crossbreeding is undertaken to combine the heat tolerance and tick resistance of zebu with the productivity of temperate dairy breeds. In the absence of improved heat tolerance, milk production and fertility of temperate cattle is severely impaired. We have recently identified a key role for the prolactin pathway in regulating heat tolerance. A de novo mutation in prolactin that impairs prolactin activity was discovered in hairy and heat intolerant, New Zealand dairy cattle. The phenotypes produced were remarkably similar to those seen in fescue toxicosis, a syndrome seen in grazing cattle in the U.S. where ingestion of ergovaline, a fungal toxin from infected pasture, inhibits prolactin secretion. Recognition of the role of prolactin in hairy cattle led us to identify a deletion in exon 10 of the long-form of the prolactin receptor in Senepol cattle that causes truncation of the protein and determines the slick coat and heat tolerance traits found in this , beef breed. The short form of the prolactin receptor is predicted to be unaffected by the deletion. Knowledge of this dominant mutation has provided the impetus to begin a crossbreeding program to investigate performance and heat tolerance of temperate dairy cattle carrying the slick, prolactin receptor variant. The perceived opportunity is to introgress this variant into temperate dairy cattle to enable performance and welfare improvement in hot climates. Heat tolerance of cattle with slick coats appears to be mostly associated with coat type although sweating ability

  5. Fitness impact and stability of a transgene conferring resistance to dengue-2 virus following introgression into a genetically diverse Aedes aegypti strain.

    Directory of Open Access Journals (Sweden)

    Alexander W E Franz

    2014-05-01

    Full Text Available In 2006, we reported a mariner (Mos1-transformed Aedes aegypti line, Carb77, which was highly resistant to dengue-2 virus (DENV2. Carb77 mosquitoes expressed a DENV2-specific inverted-repeat (IR RNA in midgut epithelial cells after ingesting an infectious bloodmeal. The IR-RNA formed double-stranded DENV2-derived RNA, initiating an intracellular antiviral RNA interference (RNAi response. However, Carb77 mosquitoes stopped expressing the IR-RNA after 17 generations in culture and lost their DENV2-refractory phenotype. In the current study, we generated new transgenic lines having the identical transgene as Carb77. One of these lines, Carb109M, has been genetically stable and refractory to DENV2 for >33 generations. Southern blot analysis identified two transgene integration sites in Carb109M. Northern blot analysis detected abundant, transient expression of the IR-RNA 24 h after a bloodmeal. Carb109M mosquitoes were refractory to different DENV2 genotypes but not to other DENV serotypes. To further test fitness and stability, we introgressed the Carb109M transgene into a genetically diverse laboratory strain (GDLS by backcrossing for five generations and selecting individuals expressing the transgene's EGFP marker in each generation. Comparison of transgene stability in replicate backcross 5 (BC5 lines versus BC1 control lines demonstrated that backcrossing dramatically increased transgene stability. We subjected six BC5 lines to five generations of selection based on EGFP marker expression to increase the frequency of the transgene prior to final family selection. Comparison of the observed transgene frequencies in the six replicate lines relative to expectations from Fisher's selection model demonstrated lingering fitness costs associated with either the transgene or linked deleterious genes. Although minimal fitness loss (relative to GDLS was manifest in the final family selection stage, we were able to select homozygotes for the transgene in

  6. THE BARRIERS AND NEEDS OF ONLINE LEARNERS

    Directory of Open Access Journals (Sweden)

    Napaporn SRICHANYACHON

    2014-07-01

    Full Text Available This study investigated some specific barriers and needs that online students are facing when learning English through WebEx system. It compared students’ barriers and needs with their background including gender, computer ownership, and monthly allowance. It also investigated the relationship among computer aptitude, barriers and needs of online learners. The samples were 211 undergraduate students enrolled in Fundamental English course. The instrument in this study was a questionnaire. Results indicated that the levels of needs and barriers of online learners in general were moderate. There were no statistically significant differences at .05 level found in barriers and needs of online learners as classified by gender, computer ownership, and computer aptitude. As hypothesised, there was a negative relationship between computer aptitude and barriers of online learners at .01 level. Students with high computer aptitude had fewer barriers to learn online than those with low computer aptitude. In addition, there was a positive relationship between barriers and needs of online learners at .01 levels. Students with more barriers were found to have more needs to help them to learn online than those with few barriers. Teachers and institutions can take the results of this study into consideration when developing online courses.

  7. Subsurface barrier verification technologies, informal report

    International Nuclear Information System (INIS)

    Heiser, J.H.

    1994-06-01

    One of the more promising remediation options available to the DOE waste management community is subsurface barriers. Some of the uses of subsurface barriers include surrounding and/or containing buried waste, as secondary confinement of underground storage tanks, to direct or contain subsurface contaminant plumes and to restrict remediation methods, such as vacuum extraction, to a limited area. To be most effective the barriers should be continuous and depending on use, have few or no breaches. A breach may be formed through numerous pathways including: discontinuous grout application, from joints between panels and from cracking due to grout curing or wet-dry cycling. The ability to verify barrier integrity is valuable to the DOE, EPA, and commercial sector and will be required to gain full public acceptance of subsurface barriers as either primary or secondary confinement at waste sites. It is recognized that no suitable method exists for the verification of an emplaced barrier's integrity. The large size and deep placement of subsurface barriers makes detection of leaks challenging. This becomes magnified if the permissible leakage from the site is low. Detection of small cracks (fractions of an inch) at depths of 100 feet or more has not been possible using existing surface geophysical techniques. Compounding the problem of locating flaws in a barrier is the fact that no placement technology can guarantee the completeness or integrity of the emplaced barrier. This report summarizes several commonly used or promising technologies that have been or may be applied to in-situ barrier continuity verification

  8. Barriers to Medical Error Reporting.

    Science.gov (United States)

    Poorolajal, Jalal; Rezaie, Shirin; Aghighi, Negar

    2015-01-01

    This study was conducted to explore the prevalence of medical error underreporting and associated barriers. This cross-sectional study was performed from September to December 2012. Five hospitals, affiliated with Hamadan University of Medical Sciences, in Hamedan, Iran were investigated. A self-administered questionnaire was used for data collection. Participants consisted of physicians, nurses, midwives, residents, interns, and staffs of radiology and laboratory departments. Overall, 50.26% of subjects had committed but not reported medical errors. The main reasons mentioned for underreporting were lack of effective medical error reporting system (60.0%), lack of proper reporting form (51.8%), lack of peer supporting a person who has committed an error (56.0%), and lack of personal attention to the importance of medical errors (62.9%). The rate of committing medical errors was higher in men (71.4%), age of 50-40 years (67.6%), less-experienced personnel (58.7%), educational level of MSc (87.5%), and staff of radiology department (88.9%). This study outlined the main barriers to reporting medical errors and associated factors that may be helpful for healthcare organizations in improving medical error reporting as an essential component for patient safety enhancement.

  9. Antibiotic stewardship: overcoming implementation barriers.

    Science.gov (United States)

    Bal, Abhijit M; Gould, Ian M

    2011-08-01

    Antimicrobial stewardship is now recognized as a formal strategy for curbing the upward trend in antibiotic resistance. Literature on antimicrobial stewardship has focused on areas of strategic importance and operational delivery. A number of barriers have been recognized in the implementation of successful programs. These include lack of physician participation, lack of diagnostic facility, absence of formal mechanism of data collection, variation between countries, and lack of cooperative strategies. In this review, we suggest strategies to overcome these barriers. In the last few years, it has been recognized that an executive program is necessary for successful implementation of strategies to control the growing antibiotic resistance. Efforts have been made at higher levels of government through organizations such as the European Centre for Disease Prevention and Control. The need for community healthcare involvement has also been recognized. At a local level, strategies to promote cooperation between various committees (e.g. infection control and antimicrobial management teams) have been proposed and adopting antibiotic care bundles as part of patient safety and healthcare is being explored. We suggest that executive level planning, local cooperation, sustained education, emphasis on de-escalation, and use of care bundles could stem the tide of growing resistance.

  10. Barriers to medical error reporting

    Directory of Open Access Journals (Sweden)

    Jalal Poorolajal

    2015-01-01

    Full Text Available Background: This study was conducted to explore the prevalence of medical error underreporting and associated barriers. Methods: This cross-sectional study was performed from September to December 2012. Five hospitals, affiliated with Hamadan University of Medical Sciences, in Hamedan,Iran were investigated. A self-administered questionnaire was used for data collection. Participants consisted of physicians, nurses, midwives, residents, interns, and staffs of radiology and laboratory departments. Results: Overall, 50.26% of subjects had committed but not reported medical errors. The main reasons mentioned for underreporting were lack of effective medical error reporting system (60.0%, lack of proper reporting form (51.8%, lack of peer supporting a person who has committed an error (56.0%, and lack of personal attention to the importance of medical errors (62.9%. The rate of committing medical errors was higher in men (71.4%, age of 50-40 years (67.6%, less-experienced personnel (58.7%, educational level of MSc (87.5%, and staff of radiology department (88.9%. Conclusions: This study outlined the main barriers to reporting medical errors and associated factors that may be helpful for healthcare organizations in improving medical error reporting as an essential component for patient safety enhancement.

  11. Effects of barrier on creeping discharge characteristics in SF6 and N2 Gases under pulse voltages; SF6 oyobi N2 gas chu no pulse den`atsu ni yoru enmen hoden tokusei ni oyobosu barrier no koka

    Energy Technology Data Exchange (ETDEWEB)

    Watabe, K.; Kamatani, H.; Kobayashi, N.; Onoda, M.; Nakayama, H. [Himeji Inst. of Tech., Hyogo (Japan)

    1997-10-20

    This paper describes the effect of barrier upon creeping discharge characteristics in SF6, N2 and their mixture. The barrier height effect on the discharge voltage was investigated under the positive pulse voltage. The discharge voltage increased as increasing the barrier height in SF6 gas. On the other hand, the discharge voltage hardly changed with the barrier height in N2 gas. In order to make clear the mechanism of the initial creeping corona, it was observed with the optical technique such as ultra-high speed electronic imaging system (IMACON 468). As the result, creeping corona path revealed the difference in images under various barrier height. And the charge accumulated on the barrier induced with the initial corona in SF6 gas could suppress the development of the later creeping corona in contrast with N2 gas. 19 refs., 7 figs.

  12. Uncertainties as Barriers for Knowledge Sharing with Enterprise Social Media

    DEFF Research Database (Denmark)

    Trier, Matthias; Fung, Magdalene; Hansen, Abigail

    2017-01-01

    of the Enterprise Social Media tool Yammer for knowledge sharing in a large global organization. We identify and categorize nine uncertainties that were perceived as barriers by the respondents. The study revealed that the uncertainty types play an important role in affecting employees’ participation......Transferring knowledge has become a key challenge for global organizations and social media offers new opportunities to digitalize and support this process. However, the successful implementation of a social media based knowledge transfer environment is marked by several uncertainties that can...... become a barrier for the participants’ adoption. There is only limited existing research studying the types of uncertainties that employees perceive and their impact on knowledge transfer via social media. To address this gap, this article presents a qualitative interview-based study of the adoption...

  13. Fluorescence microscopy with diffraction resolution barrier broken by stimulated emission.

    Science.gov (United States)

    Klar, T A; Jakobs, S; Dyba, M; Egner, A; Hell, S W

    2000-07-18

    The diffraction barrier responsible for a finite focal spot size and limited resolution in far-field fluorescence microscopy has been fundamentally broken. This is accomplished by quenching excited organic molecules at the rim of the focal spot through stimulated emission. Along the optic axis, the spot size was reduced by up to 6 times beyond the diffraction barrier. The simultaneous 2-fold improvement in the radial direction rendered a nearly spherical fluorescence spot with a diameter of 90-110 nm. The spot volume of down to 0.67 attoliters is 18 times smaller than that of confocal microscopy, thus making our results also relevant to three-dimensional photochemistry and single molecule spectroscopy. Images of live cells reveal greater details.

  14. Measurement of Restricted Atmospheric Barrier Discharge in Nonwoven Fiber Pores

    Science.gov (United States)

    Kawabe, Masaaki

    The restricted dielectric barrier discharge in nonwoven pores has been investigated by observation of the current pulse, the Lissajous figure and light emissions. The current pulse measurement revealed that homogeneity of the discharge was relatively high and the amount of individual pulse was quite small on the order of 0.01nC. Such a small current pulse demonstrates that nonwoven fiber is effective as a dielectric barrier. Analysis of the Lissajous figure, indicates the calculated value of the gap voltage for the discharge starting point of nonwoven fiber layers is close to what was predicted using the Paschen curve. On the other hand, the measured value of the gap voltage in the Lissajous figure is larger than its calculated value, so the surface charge on the dielectrics dissipated relatively fast. The observations of light emissions also showed a high homogeneity.

  15. Elements modulating the prion species barrier and its passage consequences.

    Directory of Open Access Journals (Sweden)

    Juan-Maria Torres

    Full Text Available The specific characteristics of Transmissible Spongiform Encephalopathy (TSE strains may be altered during passage across a species barrier. In this study we investigated the biochemical and biological characteristics of Bovine Spongiform Encephalopathy (BSE after transmission in both natural host species (cattle, sheep, pigs and mice and in transgenic mice overexpressing the corresponding cellular prion protein (PrPC in comparison with other non-BSE related prions from the same species. After these passages, most features of the BSE agent remained unchanged. BSE-derived agents only showed slight modifications in the biochemical properties of the accumulated PrPSc, which were demonstrated to be reversible upon re-inoculation into transgenic mice expressing bovine-PrPC. Transmission experiments in transgenic mice expressing bovine, porcine or human-PrP revealed that all BSE-derived agents were transmitted with no or a weak transmission barrier. In contrast, a high species barrier was observed for the non-BSE related prions that harboured an identical PrP amino acid sequence, supporting the theory that the prion transmission barrier is modulated by strain properties (presumably conformation-dependent rather than by PrP amino acid sequence differences between host and donor. As identical results were observed with prions propagated either in natural hosts or in transgenic mouse models, we postulate that the species barrier and its passage consequences are uniquely governed by the host PrPC sequence and not influenced by other host genetic factors. The results presented herein reinforce the idea that the BSE agent is highly promiscuous, infecting other species, maintaining its properties in the new species, and even increasing its capabilities to jump to other species including humans. These data are essential for the development of an accurate risk assessment for BSE.

  16. Elements Modulating the Prion Species Barrier and Its Passage Consequences

    Science.gov (United States)

    Torres, Juan-Maria; Espinosa, Juan-Carlos; Aguilar-Calvo, Patricia; Herva, María-Eugenia; Relaño-Ginés, Aroa; Villa-Diaz, Ana; Morales, Mónica; Parra, Beatriz; Alamillo, Elia; Brun, Alejandro; Castilla, Joaquín; Molina, Susana; Hawkins, Steve A. C.; Andreoletti, Olivier

    2014-01-01

    The specific characteristics of Transmissible Spongiform Encephalopathy (TSE) strains may be altered during passage across a species barrier. In this study we investigated the biochemical and biological characteristics of Bovine Spongiform Encephalopathy (BSE) after transmission in both natural host species (cattle, sheep, pigs and mice) and in transgenic mice overexpressing the corresponding cellular prion protein (PrPC) in comparison with other non-BSE related prions from the same species. After these passages, most features of the BSE agent remained unchanged. BSE-derived agents only showed slight modifications in the biochemical properties of the accumulated PrPSc, which were demonstrated to be reversible upon re-inoculation into transgenic mice expressing bovine-PrPC. Transmission experiments in transgenic mice expressing bovine, porcine or human-PrP revealed that all BSE-derived agents were transmitted with no or a weak transmission barrier. In contrast, a high species barrier was observed for the non-BSE related prions that harboured an identical PrP amino acid sequence, supporting the theory that the prion transmission barrier is modulated by strain properties (presumably conformation-dependent) rather than by PrP amino acid sequence differences between host and donor. As identical results were observed with prions propagated either in natural hosts or in transgenic mouse models, we postulate that the species barrier and its passage consequences are uniquely governed by the host PrPC sequence and not influenced by other host genetic factors. The results presented herein reinforce the idea that the BSE agent is highly promiscuous, infecting other species, maintaining its properties in the new species, and even increasing its capabilities to jump to other species including humans. These data are essential for the development of an accurate risk assessment for BSE. PMID:24608126

  17. Experimental model for research on the blood-ocular barrier

    International Nuclear Information System (INIS)

    Kim, Hak Jin; Jea, Seung Youn; Park, Jae Sung; Jung, Yeon Joo; Kim, Yong Woo; Park, Byung Rae

    2006-01-01

    The eyeball has 2 blood-ocular barriers, i.e, the blood-retinal and blood-aqueous barriers. The purpose of this study was to evaluate if triolein emulsion could disrupt the barriers, and we wanted to suggest as an experimental model for future blood-ocular barrier studies. The triolein emulsion was made of 0.1 ml triolein and 20 ml normal saline, and this was infused into the carotid artery of ten cats (the experimental group). As a control group, only normal saline was infused in another ten cats. Precontrast and postcontrast T1-weighted MR images were obtained at 30 minutes and 3 hours after embolization in both groups. The signal intensities were evaluate qualitatively and quantitatively in the anterior and posterior chambers and also in the vitreus fluid. Statistical analysis was performed by employing the Kruskal Wallist test, Dunn's Multiple Comparison test and the wilcoxon signed rank test. In the control group, no contrast enhancement was demonstrated in the anterior or posterior chamber or in the vitreus fluid of the ipsilateral or contralateral eyeball on the 30 minutes MR images. The anterior chambers of the ipsilateral and contralateral eyeballs revealed delayed contrast enhancement on the 3 hour MR images. In the experimental group, the 30 minute-postembolization MR images were not different from those of the control group. The 30 minute-postembolization MR images demonstrated delayed contrast enhancement in the anterior chamber of the ipsilateral and contralateral eyeballs and in the posterior chamber of the ipsilateral eyeball. The delayed contrast enhancement of the posterior chamber of the ipsilateral eyeball was statistically significant (ρ < 0.05). The present study demonstrated significant contrast enhancement in the posterior chamber with infusion of the triolein emulsion, and this can serve as a model for blood-aqueous barrier studies

  18. Storm impacts on small barrier islands

    DEFF Research Database (Denmark)

    Kroon, Aart; Fruergaard, Mikkel

    The shorelines of the Baltic Sea and the inner coastal waters in Denmark consist of many barrier islands. These sandy barrier islands were mainly formed in the Holocene and are still very dynamic. The present day changes in the morphology are dominantly governed by storm waves and associated high...... water levels. These storms induce collision, overwash or inundation of the barrier crest and generate wash-over fans and barrier breaching. In this presentation, we focus on the present-day morphologic evolution of these barrier islands, couple these to extreme events, and we will predict the potential...... changes in this evolution due to changes in the climate and associated sea levels. We analyzed the morphologic evolution of a series of barrier islands over the last decades using maps, aerial photographs and satellite images. This decadal morphologic evolution was coupled to the frequency and intensity...

  19. Barrier experiment: Shock initiation under complex loading

    Energy Technology Data Exchange (ETDEWEB)

    Menikoff, Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-01-12

    The barrier experiments are a variant of the gap test; a detonation wave in a donor HE impacts a barrier and drives a shock wave into an acceptor HE. The question we ask is: What is the trade-off between the barrier material and threshold barrier thickness to prevent the acceptor from detonating. This can be viewed from the perspective of shock initiation of the acceptor subject to a complex pressure drive condition. Here we consider key factors which affect whether or not the acceptor undergoes a shock-to-detonation transition. These include the following: shock impedance matches for the donor detonation wave into the barrier and then the barrier shock into the acceptor, the pressure gradient behind the donor detonation wave, and the curvature of detonation front in the donor. Numerical simulations are used to illustrate how these factors affect the reaction in the acceptor.

  20. Internal Transport Barrier Physics in Helical Systems

    International Nuclear Information System (INIS)

    Yokoyama, M.; Maassberg, H.; Ida, K.; Estrada, T.; Castejon, F.; Minami, T.; Fujisawa, A.; Yamagishi, O.; Shats, M. G.; Dinklage, A.; Tribaldos, V.; Beidler, C. D.; Shimozuma, T.; Takeiri, Y.; Herranz, J.; Murakami, S.; Yamada, H.

    2005-01-01

    The characteristics of electron internal transport barriers (eITBs) in helical systems are reviewed. The common features are highly peaked Te profile with strongly positive Er in the core region. The transition nature of Er based on neoclassical (NC) ambipolarity, with the clear threshold feature such as ECH power and Ohmic current, is the common mechanism for the eITB formation. The electron heat confinement improvement has been revealed within the eITB region. The ECH power threshold can be lowered in the presence of ripple-trapped electrons-induced convective flux, and rational surfaces at the core region. The gyrokinetic calculations, for example eITB in LHD, have shown that the ETG mode is unstable in eITB region due to the large Te gradient. A larger zonal flow amplitude has been observed in eITB phase in CHS. The geodesic transfer of energy from stationary zonal flow to oscillatory modes (GAMs) recognized in H-1 implies that the stationary zonal flows can be maintained at a higher level by reducing the geodesic curvature in helical systems. This is the first report of the eITB branch in the framework of the International Stellarator Profile DataBase (ISPDB). (Author)

  1. Trade Barriers in a Global Perspective

    OpenAIRE

    Raihan, Selim

    2004-01-01

    This article develops an index of trade barrier for 119 countries by using the tariff and the import data from TRAINS database of UNCTAD at 6-digit level of HS classifications. Bivariate as well as multivariate econometric models have been estimated to explain cross-country variations in the constructed trade barrier indices. The results show that cross-country variations in trade barrier indices are much influenced by variations in per capita income, population and literacy rate. This articl...

  2. Barriers for realisation of energy savings in buildings; Barrierer for realisering af energibesparelser i bygninger

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, O.M.

    2004-07-01

    Many years' efforts within the energy labelling area have shown large saving potentials in heating and use of electricity in buildings. At the same time it has been proved that these saving potentials, even when economically advantageous, only are cashed to a limited extent. The reason to this is ascribed to barriers that meet the individual building owner who wants to start saving energy. Most barriers are known and a lot of these have been sought overcome for some time. The questions are how many barriers still exist, have new barriers arisen and the character of these barriers. On this background the objective of this survey has been to concretize and study the barriers, which are blocking reasonable energy savings. Focus has especially been on barriers for realisation of heating savings, but through a general evaluation of energy savings of barriers other forms of energy saving methods have been taken into consideration. Special interest has been directed towards houses, typically one family houses, which are affected by the Energy Labelling Scheme. The concept barriers include all kinds of barriers, also barriers that not are acknowledged as barriers by the individual house owner, or that on closer inspection turn out to be something else than actual barriers. This note suggests an alternative inertia model, in order to create an idea of the inertness characteristic of the many house owners who understand the message but fail to act on it. (BA)

  3. Barriers Approach to Innovation in Academic Libraries

    Directory of Open Access Journals (Sweden)

    Fu-Hsuan Chuang

    2016-11-01

    Full Text Available Innovation in academic libraries is not a brand new issue. Academic libraries can benefit from successful innovation, since innovation is a key contributor to gaining and sustaining competitive advantage for survival. Building on two case studies, 28 participants from leadership teams to practitioners are involved, the qualitative findings identified the specific two types of barriers that academic libraries face by applying a barriers approach to innovation, that’s, environmental and organizational barriers. Especially, seven dimensions of two types of barriers to innovation are found.

  4. Water and contaminant movement: migration barriers

    International Nuclear Information System (INIS)

    Lane, L.J.; Nyhan, J.W.

    1984-11-01

    Migration barriers are used in shallow land burial facilities to slow or stop the movement of water and contaminants and are discussed here as a single component embedded in a complex environmental system. Analytical solutions to solute transport equations are used to approximate the behavior of migration barriers and to derive design criteria for control of subsurface water and contaminant migration. Various types of migration barriers are compared and design recommendations are made for shallow land burial trench caps and liners. Needed improvements and suggested field experiments for future designs of migration barriers are then discussed relative to the management of low-level radioactive wastes

  5. Lattice QCD without topology barriers

    CERN Document Server

    Lüscher, Martin

    2011-01-01

    As the continuum limit is approached, lattice QCD simulations tend to get trapped in the topological charge sectors of field space and may consequently give biased results in practice. We propose to bypass this problem by imposing open (Neumann) boundary conditions on the gauge field in the time direction. The topological charge can then flow in and out of the lattice, while many properties of the theory (the hadron spectrum, for example) are not affected. Extensive simulations of the SU(3) gauge theory, using the HMC and the closely related SMD algorithm, confirm the absence of topology barriers if these boundary conditions are chosen. Moreover, the calculated autocorrelation times are found to scale approximately like the square of the inverse lattice spacing, thus supporting the conjecture that the HMC algorithm is in the universality class of the Langevin equation.

  6. Religious culture as a barrier?

    DEFF Research Database (Denmark)

    Agergaard, Sine

    2016-01-01

    Political interventions, media coverage and research often refer to the underrepresentation of ethnic minorities, particularly girls and women, participating in physical activity and organised sports. In both public and academic debates, reference is made to the religious culture as a particular...... barrier to participation in sports among Muslim girls and women. This article aims to provide a counter-narrative by focusing on young Muslim girls who simultaneously practice their religion and sports. The main research question was: How do young Danish Muslim girls align participation in sports...... religion as hegemonic, embodied and dynamic cultural phenomena, the analysis points to the diversity through which Muslim girls and women participate and engage in sports. Finally, the article discusses the extent to which counter-narratives may contribute to changing perspectives on so-called hard...

  7. Barriers over time to full implementation of health information exchange in the United States.

    Science.gov (United States)

    Kruse, Clemens Scott; Regier, Verna; Rheinboldt, Kurt T

    2014-09-30

    Although health information exchanges (HIE) have existed since their introduction by President Bush in his 2004 State of the Union Address, and despite monetary incentives earmarked in 2009 by the health information technology for economic and clinical health (HITECH) Act, adoption of HIE has been sparse in the United States. Research has been conducted to explore the concept of HIE and its benefit to patients, but viable business plans for their existence are rare, and so far, no research has been conducted on the dynamic nature of barriers over time. The aim of this study is to map the barriers mentioned in the literature to illustrate the effect, if any, of barriers discussed with respect to the HITECH Act from 2009 to the early months of 2014. We conducted a systematic literature review from CINAHL, PubMed, and Google Scholar. The search criteria primarily focused on studies. Each article was read by at least two of the authors, and a final set was established for evaluation (n=28). The 28 articles identified 16 barriers. Cost and efficiency/workflow were identified 15% and 13% of all instances of barriers mentioned in literature, respectively. The years 2010 and 2011 were the most plentiful years when barriers were discussed, with 75% and 69% of all barriers listed, respectively. The frequency of barriers mentioned in literature demonstrates the mindfulness of users, developers, and both local and national government. The broad conclusion is that public policy masks the effects of some barriers, while revealing others. However, a deleterious effect can be inferred when the public funds are exhausted. Public policy will need to lever incentives to overcome many of the barriers such as cost and impediments to competition. Process improvement managers need to optimize the efficiency of current practices at the point of care. Developers will need to work with users to ensure tools that use HIE resources work into existing workflows.

  8. Implementation of renewable energy technologies - Opportunities and barriers. Egypt country study

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-07-01

    The project used case studies of renewable energy implementation projects to analyse the reasons for success or failure of specific projects or technologies. In particular the study aimed to identify possibilities for 'removing' the main barriers and thus 'promoting' increased implementation of (RETs), and to 'generalise' the experiences from the case studies and produce results that can be disseminated and utilized further in a planned second phase. The specific objectives for Egypt Country Study were: 1) To determine, on the basis of analysis of the past experience, the barriers against implementation of RETs in Egypt, and to identify the favourable conditions and actions required for such implementation. 2) To apply the knowledge gained and results of the analysis of past projects for a detailed analysis of barriers to a chosen set of potential RETs implementation projects with view to success. 3) To identify specific RET projects for implementation including necessary actions to overcome identified barriers. The case study revealed that; for Domestic Solar Water Heating (DSWH) the main barriers are; the economic barriers followed by the awareness / information barriers, then the Technical and Institution barriers. For the PV rural electrification, the most important barriers are; the economic and financial barriers, the awareness and information barriers then the technical barriers. For the large-scale biogas systems, the main barriers are the institution and capacity, economic, policy and awareness / information respectively. According to the project results the main actions that could be taken to overcome the barriers and make use of the available opportunities are: Economic / Financial: 1) Creation of new financial schemes for the RETs applications components and systems. 2) Reducing the taxes and duties for the components and / or materials needed for Renewable Energy (RE) systems. 3) More government-supported market incentives

  9. Permeability Barrier Generation in the Martian Lithosphere

    Science.gov (United States)

    Schools, Joe; Montési, Laurent

    2015-11-01

    Permeability barriers develop when a magma produced in the interior of a planet rises into the cooler lithosphere and crystallizes more rapidly than the lithosphere can deform (Sparks and Parmentier, 1991). Crystallization products may then clog the porous network in which melt is propagating, reducing the permeability to almost zero, i.e., forming a permeability barrier. Subsequent melts cannot cross the barrier. Permeability barriers have been useful to explain variations in crustal thickness at mid-ocean ridges on Earth (Magde et al., 1997; Hebert and Montési, 2011; Montési et al., 2011). We explore here under what conditions permeability barriers may form on Mars.We use the MELTS thermodynamic calculator (Ghiorso and Sack, 1995; Ghiorso et al., 2002; Asimow et al., 2004) in conjunction with estimated Martian mantle compositions (Morgan and Anders, 1979; Wänke and Dreibus, 1994; Lodders and Fegley, 1997; Sanloup et al., 1999; Taylor 2013) to model the formation of permeability barriers in the lithosphere of Mars. In order to represent potential past and present conditions of Mars, we vary the lithospheric thickness, mantle potential temperature (heat flux), oxygen fugacity, and water content.Our results show that permeability layers can develop in the thermal boundary layer of the simulated Martian lithosphere if the mantle potential temperature is higher than ~1500°C. The various Martian mantle compositions yield barriers in the same locations, under matching variable conditions. There is no significant difference in barrier location over the range of accepted Martian oxygen fugacity values. Water content is the most significant influence on barrier development as it reduces the temperature of crystallization, allowing melt to rise further into the lithosphere. Our lower temperature and thicker lithosphere model runs, which are likely the most similar to modern Mars, show no permeability barrier generation. Losing the possibility of having a permeability

  10. Thermal Barrier Coatings Resistant to Glassy Deposits

    Science.gov (United States)

    Drexler, Julie Marie

    Engineering of alloys has for years allowed aircraft turbine engines to become more efficient and operate at higher temperatures. As advancements in these alloy systems have become more difficult, ceramic thermal barrier coatings (TBCs), often yttria (7 wt %) stabilized zirconia (7YSZ), have been utilized for thermal protection. TBCs have allowed for higher engine operating temperatures and better fuel efficiency but have also created new engineering problems. Specifically, silica based particles such as sand and volcanic ash that enter the engine during operation form glassy deposits on the TBCs. These deposits can cause the current industrial 7YSZ thermal barrier coatings to fail since the glass formed penetrates and chemically interacts with the TBC. When this occurs, coating failure may occur due to a loss of strain tolerance, which can lead to fracture, and phase changes of the TBC material. There have been several approaches used to stop calcium-magnesium aluminio-silcate (CMAS) glasses (molten sand) from destroying the entire TBC, but overall there is still limited knowledge. In this thesis, 7YSZ and new TBC materials will be examined for thermochemical and thermomechanical performance in the presence of molten CMAS and volcanic ash. Two air plasma sprayed TBCs will be shown to be resistant to volcanic ash and CMAS. The first type of coating is a modified 7YSZ coating with 20 mol% Al2O3 and 5 mol% TiO2 in solid solution (YSZ+20Al+5Ti). The second TBC is made of gadolinium zirconate. These novel TBCs impede CMAS and ash penetration by interacting with the molten CMAS or ash and drastically changing the chemistry. The chemically modified CMAS or ash will crystallize into an apatite or anorthite phase, blocking the CMAS or ash from further destroying the coating. A presented mechanism study will show these coatings are effective due to the large amount of solute (Gd, Al) in the zirconia structure, which is the key to creating the crystalline apatite or

  11. Barriers to Social Innovation and Ways of Overcoming them in Latvia

    Directory of Open Access Journals (Sweden)

    Karine Oganisjana

    2017-10-01

    Full Text Available The paper presents the findings of research conducted to determine the main barriers to social innovation in Latvia and explore the ways they are overcome. The analysis of the qualitative and quantitative data collected while interviewing social innovation projects revealed eight barriers to social innovation. Lack of financing, passivity in the society and administrative and bureaucratic barriers are most frequently faced here. The qualitative content analysis disclosed nine means for overcoming the barriers to social innovation. Three of them: promotional activities, external financial support and external support are most common. Each barrier to social innovation was analyzed also in regard with the means utilized for overcoming it. It showed that there is no universal way to overcome a certain barrier. There could be different combinations of means and actions undertaken. However, the most powerful mean in overcoming barriers to social innovation in Latvia turned out to be promotional activities defined as a set of activities aimed to: educate the society, encourage stakeholders to participate in the project, raise awareness about the topicality of the problem and share information about solutions with the project's target group.

  12. Opportunities and barriers for international bioenergy trade

    NARCIS (Netherlands)

    Junginger, H.M.|info:eu-repo/dai/nl/202130703; van Dam, J.M.C.; Zarrilli, S.; Mohamed, F.A.; Marchal, D.; Faaij, A.P.C.|info:eu-repo/dai/nl/10685903X

    2011-01-01

    Recently, the international trade of various bioenergy commodities has grown rapidly, yet this growth is also hampered by some barriers. The aim of this paper is to obtain an overview of what market actors currently perceive as major opportunities and barriers for the development of international

  13. Israel's Security Barrier: Effects On Operational Factors

    National Research Council Canada - National Science Library

    2004-01-01

    .... The route of the barrier is tinder intense discussion at this time and if implemented as planned by the Sharon government will negatively affect the factors of space and force. The barrier must be constructed along the correct route in order to maximize operational factors.

  14. Precast concrete barrier crash testing : final report.

    Science.gov (United States)

    2001-12-01

    The objectives of this project were to crash test the Oregon Standard (32-inch) F-shape precast concrete barrier and the Oregon Tall (42-inch) F-shape precast concrete barrier against the new NCHRP Report 350 standards, to ensure compliance of these ...

  15. Barriers to adherence in cystic fibrosis

    DEFF Research Database (Denmark)

    Bregnballe, Vibeke; Schiøtz, Peter Oluf

    2012-01-01

    Danish patients with cystic fibrosis aged 14 to 25 years and their parents. Conclusions: The present study showed that the majority of adolescents with CF and their parents experienced barriers to treatment adherence. Patients and parents agreed that the three most common barriers encountered lack...

  16. K-Basin isolation barrier seal

    International Nuclear Information System (INIS)

    Ruff, E.S.

    1994-10-01

    This report documents various aspects of the design, analysis, procurement, and fabrication of the hydraulic seal on the isolation barriers to be installed in the 100-K Area spent nuclear fuel basin. The isolation barrier is used to keep water in the basin in the event of an earthquake

  17. Origin of methyl torsional potential barrier

    Indian Academy of Sciences (India)

    Inadequacy of one dimensional description of internal rotation has been highlighted in small methyl conjugated molecules in the light of its multidimensional nature. The effect of skeletal flexing on the picture of barrier formation by dissecting the barrier energy into potential type, virial type and symmetry type is described.

  18. Attempting to be active: Self-efficacy and barrier limitation differentiate activity levels of working mothers.

    Science.gov (United States)

    Gierc, Madelaine; Locke, Sean; Jung, Mary; Brawley, Lawrence

    2016-07-01

    Working mothers are less physically active than working women without children and mothers who do not work. The purpose of this study was to examine concurrent self-regulatory efficacy and barriers to physical activity in a sample of working mothers. Women completed a mixed-methods survey which included measures of physical activity, concurrent self-regulatory efficacy, and barriers. Sufficiently active women experienced significantly greater concurrent self-regulatory efficacy and significantly less barrier limitation and frequency. No significant group differences were found for age, domestic duties performed, and children's extracurricular activities. Thematic analysis of barriers revealed six themes of common and unique factors, including limited time and family activities. © The Author(s) 2014.

  19. Charge transport mechanisms of graphene/semiconductor Schottky barriers: A theoretical and experimental study

    International Nuclear Information System (INIS)

    Zhong, Haijian; Liu, Zhenghui; Xu, Gengzhao; Shi, Lin; Fan, Yingmin; Yang, Hui; Xu, Ke; Wang, Jianfeng; Ren, Guoqiang

    2014-01-01

    Graphene has been proposed as a material for semiconductor electronic and optoelectronic devices. Understanding the charge transport mechanisms of graphene/semiconductor Schottky barriers will be crucial for future applications. Here, we report a theoretical model to describe the transport mechanisms at the interface of graphene and semiconductors based on conventional semiconductor Schottky theory and a floating Fermi level of graphene. The contact barrier heights can be estimated through this model and be close to the values obtained from the experiments, which are lower than those of the metal/semiconductor contacts. A detailed analysis reveals that the barrier heights are as the function of the interface separations and dielectric constants, and are influenced by the interfacial states of semiconductors. Our calculations show how this behavior of lowering barrier heights arises from the Fermi level shift of graphene induced by the charge transfer owing to the unique linear electronic structure

  20. Charge transport mechanisms of graphene/semiconductor Schottky barriers: A theoretical and experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Haijian; Liu, Zhenghui; Xu, Gengzhao; Shi, Lin; Fan, Yingmin; Yang, Hui [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Xu, Ke, E-mail: kxu2006@sinano.ac.cn; Wang, Jianfeng; Ren, Guoqiang [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Suzhou Nanowin Science and Technology Co., Ltd., Suzhou 215123 (China)

    2014-01-07

    Graphene has been proposed as a material for semiconductor electronic and optoelectronic devices. Understanding the charge transport mechanisms of graphene/semiconductor Schottky barriers will be crucial for future applications. Here, we report a theoretical model to describe the transport mechanisms at the interface of graphene and semiconductors based on conventional semiconductor Schottky theory and a floating Fermi level of graphene. The contact barrier heights can be estimated through this model and be close to the values obtained from the experiments, which are lower than those of the metal/semiconductor contacts. A detailed analysis reveals that the barrier heights are as the function of the interface separations and dielectric constants, and are influenced by the interfacial states of semiconductors. Our calculations show how this behavior of lowering barrier heights arises from the Fermi level shift of graphene induced by the charge transfer owing to the unique linear electronic structure.