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Sample records for weed biotypes resistant

  1. About the interplay of sensitive and resistant biotypes in weed populations - simulation exercises for Echinochloa crus-galli in maize crops

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    von Redwitz, Christoph

    2016-02-01

    Full Text Available Weed species easily establish in crops with a similar life cycle. Especially mono-cropping provides best conditions for such weeds. In maize this is true for Echinochloa crus-galli, which is a C4 plant and one of the worst weeds worldwide. In Germany E. crus-galli is one of the few typical weed species in maize. When recurrent herbicide treatments are applied, development of herbicide resistance is likely. Since maize is typically only treated once with herbicides, later germinating weeds can escape and produce seeds. These escaping weeds are not selected for herbicide resistance. Hence, they still have a more sensitive gene pool. E. crus-galli emerges with the highest density in spring and continues to germinate over the whole vegetative period of maize. In that way the early germinating biotypes are selected for herbicide resistance while the later germinating biotypes are not. To avoid the reproduction of E. crus-galli effort is made to suppress these later germinating weeds. Using undersown cover crops is one way to do that. We hypothesize that suppressing the later germinating biotypes enhances the development of herbicide resistance. We simulated the development of herbicide resistance in populations of E. crus-galli, composed of sensitive and resistant biotypes, in a continuous maize cropping system. We used the model PROSPER for our simulations. We assumed three levels of suppression of the later germinating weeds (0%, 30%, and 100%. The results show a faster development of herbicide resistance, when the later germinating individuals are suppressed. Nevertheless, the suppressive effect of undersown crops is able to lower the weed density even with high resistance level in the population.

  2. Análise do risco da ocorrência de biotipos de plantas daninhas resistentes aos herbicidas The risk of finding herbicide resistant weed biotypes

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    Ribas A. Vidal

    1997-01-01

    biotype depends on two aspects : the probability of selecting a herbicide resistant mutant, and the probability of spreading the resistance in the area. The objectives of this work were to study factors that control the probability of selecting a herbicide resista NT mutant, and to predict the risk of selecting a resistant plant. The factors that control the probability of selecting a herbicide resistant mutant are grouped in three categories: those related to the genetics of resistance, those related to the number of plants under selection, and thoserelated to the herbicide. The genetics of resistance is governed by the initial frequency of the resista nt allele, dominance of the gene, and type of species pollination. The number of plants under selection depend on size of the herbicide treated area and weed density. The factors related to the herbicide are its mechanism of action, and frequency of use of the same mechanism of action in the area. Computer simulations indicate great risk of occurrence of a resistant mutant in áreas with high weed density, mainly those sprayed with herbicides whose mechanisms of action present history of high initial frequency of the resistant trait on the weed populations.

  3. Comparative proteomic analysis of horseweed (Conyza canadensis) biotypes identifies candidate proteins for glyphosate resistance

    National Research Council Canada - National Science Library

    Fidel González-torralva; Adrian P Brown; Stephen Chivasa

    2017-01-01

    Emergence of glyphosate-resistant horseweed (Conyza canadensis) biotypes is an example of how unrelenting use of a single mode of action herbicide in agricultural weed control drives genetic adaptation in targeted species...

  4. Weed species shifts in glyphosate-resistant crops.

    Science.gov (United States)

    Owen, Micheal D K

    2008-04-01

    The adoption of glyphosate-based crop production systems has been one of the most important revolutions in the history of agriculture. Changes in weed communities owing to species that do not respond to current glyphosate-based management tactics are rapidly increasing. Clearly, glyphosate-resistant crops (GRCs) do not influence weeds any more than non-transgenic crops. For most crops, the trait itself is essentially benign in the environment. Rather, the weed control tactics imposed by growers create the ecological selection pressure that ultimately changes the weed communities. This is seen in the adoption of conservation tillage and weed management programs that focus on one herbicide mode of action and have hastened several important weed population shifts. Tillage (disturbance) is one of the primary factors that affect changes in weed communities. The intense selection pressure from herbicide use will result in the evolution of herbicide-resistant weed biotypes or shifts in the relative prominence of one weed species in the weed community. Changes in weed communities are inevitable and an intrinsic consequence of growing crops over time. The glyphosate-based weed management tactics used in GRCs impose the selection pressure that supports weed population shifts. Examples of weed population shifts in GRCs include common waterhemp [Amaranthus tuberculatus (Moq ex DC) JD Sauer], horseweed (Conyza canadensis L), giant ragweed (Ambrosia trifida L) and other relatively new weed problems. Growers have handled these weed population shifts with varying success depending on the crop. Copyright (c) 2008 Society of Chemical Industry.

  5. Activity of mesotrione on resistant weeds in maize.

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    Sutton, Peter; Richards, Claire; Buren, Larry; Glasgow, Les

    2002-09-01

    Mesotrione is a new callistemone herbicide that inhibits the HPPD enzyme (p-hydroxyphenylpyruvate dioxygenase) and introduces a new naturally selective tool into weed-management programmes for use in maize. Mesotrione provides control of the major broad-leaved weeds, and it can be used in integrated weed-management programmes depending on the grower's preferred weed-control strategy. At post-emergence rates of 150 g AI ha-1 or less, mesotrione provides naturally selective control of key species that may show triazine resistance (TR), e.g. Chenopodium album L, Amaranthus species, Solanum nigrum L, as well as species of weed that show resistance to acetolactase synthase (ALS) inhibitors e.g. Xanthium strumarium L, Amaranthus spp and Sonchus spp. The data presented show that resistant and susceptible biotypes of these species with resistance to triazine herbicides, such as atrazine, simazine, terbutylazine and metribuzin, or ALS-inhibitor herbicides, such as imazethepyr, remain susceptible to mesotrione. These results confirm that there is no cross-resistance in biotypes with target site resistance to triazine or ALS-inhibiting herbicides. It is important that herbicide choice and rotation becomes an integral part of planning weed management, so as to minimise the risks of crop losses from weed competition, build-up of weed seed in the soil and the further development of weed resistance across a range of herbicide modes of action.

  6. Impact of the safener Mefenpyr-diethyl on herbicide resistance evolution in Alopecurus myosuroides (Huds. biotypes

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    Rosenhauer, Maria

    2016-02-01

    Full Text Available The evolution of herbicide resistance is an important topic in plant protection and agricultural practice. Safeners are commonly used in herbicides to protect crops against herbicidal damage. Although no effect on the weed control is expected, it has been theorized that the rate of evolution of non-target site resistance (NTSR in weeds in cereals may be enhanced by use of herbicide products containing safeners. One of the most important safeners in cereals is mefenpyr-diethyl. Therefore, the possible influence of mefenpyr on herbicide resistance was studied in cooperative trials between Bayer CropScience (BCS, F-Höchst and FH Bingen. The trials tested in parallel different herbicide resistant black-grass (Alopecurus myosuroides (Huds. biotypes under greenhouse conditions. The biotypes where chosen due to known NTSR against Atlantis WG® (4 highly resistant and 5 moderately resistant as well as two susceptible biotypes. The populations were treated with the following three herbicide/safener regimes in six concentrations adjusted according to the anticipated biotype resistance levels. (1 mesosulfuron + iodosulfuron + without safener formulation, (2 mesosulfuron + iodosulfuron + constant mefenpyr concentration (45g/ha, (3 mesosulfuron + iodosulfuron + varying mefenpyr concentrations (ratio 5:1:15. The treatments were applied in post-emergence based on mesosulfuron to iodosulfuron ratios in Atlantis WG® (5:1. The trials were assessed visually (% effect and by fresh weight. Dose-response curves were performed and ED50 values for each treatment and biotype were calculated. Results showed a varying effect of safeners which was in the most cases negligible. Depending on the biotypes mostly no impact on the safener was found for herbicide resistance. In conclusion, the trials from Bingen and F-Höchst gave evidence, that there is no significant and consistent influence of the safener mefenpyr on evolution of NTSR black-grass.

  7. Biology, management and biochemical/genetic characterization of weed biotypes resistant to acetolactate synthase inhibitor herbicides Biologia, manejo e caracterização bioquímica e genética de biótipos resistentes aos herbicidas inibidores da acetolactato sintase

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    Patrícia Andrea Monquero

    2003-01-01

    Full Text Available Bidens pilosa and Amaranthus quitensis are major weeds infesting soybean [Glycine max L (Merrill] fields in Brazil and Argentina. The repetitive use of acetolactate synthase (ALS EC 4.1.3.18 inhibiting herbicides in São Gabriel do Oeste, MS, Brazil and in the provinces of Córdoba and Tucumã, Argentina, has selected for resistant (R biotypes of these weeds. Research work was developed to study the management, growth, biochemistry, and genetics of these R weed biotypes. In a field experiment it was found that chlorimuron-ethyl and imazethapyr at recommended rates (both ALS inhibitor herbicides, did not control R B. pilosa, but the alternative lactofen, fomesafen and bentazon were effective, either sprayed alone or mixed with the ALS inhibitor herbicides. Greenhouse studies confirmed the cross-resistance of both R biotypes to the imidazolinone and sulfonylurea herbicides, and these alternative herbicides, when sprayed alone or mixed with the ALS inhibitor, efficiently controlled both R and S populations. A growth analysis of the R and S biotypes of these weeds, under non-competitive conditions, indicated that there is no adaptive cost to the R biotypes (pleiotropic effect. A quick bioassay using ALS and ketoacid reductoisomerase (KARI inhibitors showed that the resistance of the R biotypes to herbicides is related to a lack of sensitivity of the ALS enzyme to the herbicides. On the other hand, the sequencing of the gene that codifies the ALS resistance in R A. quitensis did not present any mutation in the A Domain region, suggesting that other positions of the gene that confer insensitivity of the ALS to sulfonylurea and imidazolinone herbicides could have mutated.Bidens pilosa e Amaranthus quitensis são as principais plantas daninhas infestantes na cultura de soja [Glycine max L (Merrill] no Brasil e Argentina, respectivamente. O uso repetitivo de herbicidas inibidores da acetolactato sintase (ALS EC 4.1.3.18 em São Gabriel do Oeste (MS

  8. Herança da resistência aos herbicidas inibidores da ALS em biótipos da planta daninha Euphorbia heterophylla Inheritance of ALS inhibitor resistance in Euphorbia heterophylla weed biotypes

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    L. Vargas

    2001-12-01

    Full Text Available Os herbicidas inibidores da ALS são os principais produtos aplicados para o controle da planta daninha amendoim-bravo (Euphorbia herterophylla em lavouras de soja; no entanto, já foram identificados biótipos desta planta daninha resistentes a estes herbicidas no Brasil. O objetivo desta pesquisa foi estudar a herança, o número de genes que conferem a resistência e o grau de resistência dos biótipos homozigotos e heterozigotos resistentes. Foram realizados cruzamentos recíprocos entre os genitores suscetíveis e resistentes para obtenção de sementes F1 e, posteriormente, realizaram-se os retrocruzamentos (RC com os genitores resistente (R e suscetível (S. Plantas F1 foram autofecundadas artificialmente para obtenção da geração F2. As plantas F1, F2, RCr e RCs e dos genitores foram tratadas com o herbicida imazethapyr (150 g ha-1. Para avaliar o grau de resistência, plantas F1 e os genitores resistente e suscetível foram tratados com as doses de imazethapyr de 0, 100, 200, 400, 800 e 1.600 g ha-1. As plantas F1 mostraram-se totalmente resistentes ao herbicida, demonstrando que a resistência é nuclear e dominante. As plantas F2 apresentaram alta probabilidade para segregação 3:1, indicando que a resistência é codificada por um gene dominante. A aplicação de doses de imazethapyr sobre as plantas F1 demonstrou que os biótipos homozigotos resistentes e os heterozigotos apresentam o mesmo grau de resistência para doses de até 1.600 g ha-1 deste herbicida. A resistência é codificada por um gene dominante nuclear com dominância completa.The ALS inhibitor herbicides are the main products applied to control Euphorbia heterophylla in the soybean crop; however, resistant biotypes to these herbicides have been identified in Brazil. This research aimed to study the inheritance, number of genes involved in the resistance and the degree of resistance of the homozygous and heterozygous resistant biotypes. Reciprocal crossings (RSs

  9. Comparative proteomic analysis of horseweed (Conyza canadensis) biotypes identifies candidate proteins for glyphosate resistance.

    Science.gov (United States)

    González-Torralva, Fidel; Brown, Adrian P; Chivasa, Stephen

    2017-02-15

    Emergence of glyphosate-resistant horseweed (Conyza canadensis) biotypes is an example of how unrelenting use of a single mode of action herbicide in agricultural weed control drives genetic adaptation in targeted species. While in other weeds glyphosate resistance arose from target site mutation or target gene amplification, the resistance mechanism in horseweed uses neither of these, being instead linked to reduced herbicide uptake and/or translocation. The molecular components underpinning horseweed glyphosate-resistance remain unknown. Here, we used an in vitro leaf disc system for comparative analysis of proteins extracted from control and glyphosate-treated tissues of glyphosate-resistant and glyphosate-susceptible biotypes. Analysis of shikimic acid accumulation, ABC-transporter gene expression, and cell death were used to select a suitable glyphosate concentration and sampling time for enriching proteins pivotal to glyphosate resistance. Protein gel analysis and mass spectrometry identified mainly chloroplast proteins differentially expressed between the biotypes before and after glyphosate treatment. Chloroplasts are the organelles in which the shikimate pathway, which is targeted by glyphosate, is located. Calvin cycle enzymes and proteins of unknown function were among the proteins identified. Our study provides candidate proteins that could be pivotal in engendering resistance and implicates chloroplasts as the primary sites driving glyphosate-resistance in horseweed.

  10. Comparative proteomic analysis of horseweed (Conyza canadensis) biotypes identifies candidate proteins for glyphosate resistance

    Science.gov (United States)

    González-Torralva, Fidel; Brown, Adrian P.; Chivasa, Stephen

    2017-01-01

    Emergence of glyphosate-resistant horseweed (Conyza canadensis) biotypes is an example of how unrelenting use of a single mode of action herbicide in agricultural weed control drives genetic adaptation in targeted species. While in other weeds glyphosate resistance arose from target site mutation or target gene amplification, the resistance mechanism in horseweed uses neither of these, being instead linked to reduced herbicide uptake and/or translocation. The molecular components underpinning horseweed glyphosate-resistance remain unknown. Here, we used an in vitro leaf disc system for comparative analysis of proteins extracted from control and glyphosate-treated tissues of glyphosate-resistant and glyphosate-susceptible biotypes. Analysis of shikimic acid accumulation, ABC-transporter gene expression, and cell death were used to select a suitable glyphosate concentration and sampling time for enriching proteins pivotal to glyphosate resistance. Protein gel analysis and mass spectrometry identified mainly chloroplast proteins differentially expressed between the biotypes before and after glyphosate treatment. Chloroplasts are the organelles in which the shikimate pathway, which is targeted by glyphosate, is located. Calvin cycle enzymes and proteins of unknown function were among the proteins identified. Our study provides candidate proteins that could be pivotal in engendering resistance and implicates chloroplasts as the primary sites driving glyphosate-resistance in horseweed. PMID:28198407

  11. EPSPS variability, gene expression, and enzymatic activity in glyphosate-resistant biotypes of Digitaria insularis.

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    Galeano, E; Barroso, A A M; Vasconcelos, T S; López-Rubio, A; Albrecht, A J P; Victoria Filho, R; Carrer, H

    2016-08-12

    Weed resistance to herbicides is a natural phenomenon that exerts selection on individuals in a population. In Brazil, glyphosate resistance was recently detected in Digitaria insularis. The objective of this study was to elucidate mechanisms of weed resistance in this plant, including genetic variability, allelism, amino acid substitutions, gene expression, and enzymatic activity levels. Most of these have not previously been studied in this species. D. insularis DNA sequences were used to analyze genetic variability. cDNA from resistant and susceptible plants was used to identify mutations, alleles, and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) expression, using real-time quantitative reverse transcription-polymerase chain reaction. In addition, EPSPS activity was measured. We found a decrease in genetic variability between populations related to glyphosate application. Substitutions from proline to threonine and tyrosine to cysteine led to a decrease in EPSPS affinity for the glyphosate. In addition, the EPSPS enzymatic activity was slightly higher in resistant plants, whereas EPSPS gene expression was almost identical in both biotypes, suggesting feedback regulation at different levels. To conclude, our results suggest new molecular mechanisms used by D. insularis to increase glyphosate resistance.

  12. iMAR: An Interactive Web-Based Application for Mapping Herbicide Resistant Weeds.

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    Silvia Panozzo

    Full Text Available Herbicides are the major weed control tool in most cropping systems worldwide. However, the high reliance on herbicides has led to environmental issues as well as to the evolution of herbicide-resistant biotypes. Resistance is a major concern in modern agriculture and early detection of resistant biotypes is therefore crucial for its management and prevention. In this context, a timely update of resistance biotypes distribution is fundamental to devise and implement efficient resistance management strategies. Here we present an innovative web-based application called iMAR (interactive MApping of Resistance for the mapping of herbicide resistant biotypes. It is based on open source software tools and translates into maps the data reported in the GIRE (Italian herbicide resistance working group database of herbicide resistance at national level. iMAR allows an automatic, easy and cost-effective updating of the maps a nd provides two different systems, "static" and "dynamic". In the first one, the user choices are guided by a hierarchical tree menu, whereas the latter is more flexible and includes a multiple choice criteria (type of resistance, weed species, region, cropping systems that permits customized maps to be created. The generated information can be useful to various stakeholders who are involved in weed resistance management: farmers, advisors, national and local decision makers as well as the agrochemical industry. iMAR is freely available, and the system has the potential to handle large datasets and to be used for other purposes with geographical implications, such as the mapping of invasive plants or pests.

  13. iMAR: An Interactive Web-Based Application for Mapping Herbicide Resistant Weeds.

    Science.gov (United States)

    Panozzo, Silvia; Colauzzi, Michele; Scarabel, Laura; Collavo, Alberto; Rosan, Valentina; Sattin, Maurizio

    2015-01-01

    Herbicides are the major weed control tool in most cropping systems worldwide. However, the high reliance on herbicides has led to environmental issues as well as to the evolution of herbicide-resistant biotypes. Resistance is a major concern in modern agriculture and early detection of resistant biotypes is therefore crucial for its management and prevention. In this context, a timely update of resistance biotypes distribution is fundamental to devise and implement efficient resistance management strategies. Here we present an innovative web-based application called iMAR (interactive MApping of Resistance) for the mapping of herbicide resistant biotypes. It is based on open source software tools and translates into maps the data reported in the GIRE (Italian herbicide resistance working group) database of herbicide resistance at national level. iMAR allows an automatic, easy and cost-effective updating of the maps a nd provides two different systems, "static" and "dynamic". In the first one, the user choices are guided by a hierarchical tree menu, whereas the latter is more flexible and includes a multiple choice criteria (type of resistance, weed species, region, cropping systems) that permits customized maps to be created. The generated information can be useful to various stakeholders who are involved in weed resistance management: farmers, advisors, national and local decision makers as well as the agrochemical industry. iMAR is freely available, and the system has the potential to handle large datasets and to be used for other purposes with geographical implications, such as the mapping of invasive plants or pests.

  14. Identification and characterization of RAPD-SCAR markers linked to glyphosate-susceptible and -resistant biotypes of Eleusine indica (L.) Gaertn.

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    Cha, Thye San; Anne-Marie, Kaben; Chuah, Tse Seng

    2014-02-01

    Eleusine indica is one of the most common weed species found in agricultural land worldwide. Although herbicide-glyphosate provides good control of the weed, its frequent uses has led to abundant reported cases of resistance. Hence, the development of genetic markers for quick detection of glyphosate-resistance in E. indica population is imperative for the control and management of the weed. In this study, a total of 14 specific random amplified polymorphic DNA (RAPD) markers were identified and two of the markers, namely S4R727 and S26R6976 were further sequence characterized. Sequence alignment revealed that marker S4R727 showing a 12-bp nucleotides deletion in resistant biotypes, while marker S26R6976 contained a 167-bp nucleotides insertion in the resistant biotypes. Based on these sequence differences, three pairs of new sequence characterized amplified region (SCAR) primers were developed. The specificity of these primer pairs were further validated with genomic DNA extracted from ten individual plants of one glyphosate-susceptible and five glyphosate-resistant (R2, R4, R6, R8 and R11) populations. The resulting RAPD-SCAR markers provided the basis for assessing genetic diversity between glyphosate-susceptible and -resistant E. indica biotypes, as well for the identification of genetic locus link to glyphosate-resistance event in the species.

  15. Global perspective of herbicide-resistant weeds.

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    Heap, Ian

    2014-09-01

    Two hundred and twenty weed species have evolved resistance to one or more herbicides, and there are now 404 unique cases (species × site of action) of herbicide-resistant weeds globally. ALS inhibitor-resistant weeds account for about a third of all cases (133/404) and are particularly troublesome in rice and cereals. Although 71 weed species have been identified with triazine resistance, their importance has dwindled with the shift towards Roundup Ready® crops in the USA and the reduction of triazine usage in Europe. Forty-three grasses have evolved resistance to ACCase inhibitors, with the most serious cases being Avena spp., Lolium spp., Phalaris spp., Setaria spp. and Alopecurus myosuroides, infesting more than 25 million hectares of cereal production globally. Of the 24 weed species with glyphosate resistance, 16 have been found in Roundup Ready® cropping systems. Although Conyza canadensis is the most widespread glyphosate-resistant weed, Amaranthus palmeri and Amaranthus tuberculartus are the two most economically important glyphosate-resistant weeds because of the area they infest and the fact that these species have evolved resistance to numerous other herbicide sites of action, leaving growers with few herbicidal options for their control. The agricultural chemical industry has not brought any new herbicides with novel sites of action to market in over 30 years, making growers reliant on using existing herbicides in new ways. In addition, tougher registration and environmental regulations on herbicides have resulted in a loss of some herbicides, particularly in Europe. The lack of novel herbicide chemistries being brought to market combined with the rapid increase in multiple resistance in weeds threatens crop production worldwide. © 2013 Society of Chemical Industry.

  16. Evidence, Mechanism and Alternative Chemical Seedbank-Level Control of Glyphosate Resistance of a Rigid Ryegrass (Lolium rigidum) Biotype from Southern Spain.

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    Fernández-Moreno, Pablo T; Bastida, Fernando; De Prado, Rafael

    2017-01-01

    Rigid ryegrass (Lolium rigidum) is one of the most troublesome weeds in different crops in the Mediterranean region. A rigid ryegrass biotype from an olive grove in Jaén province (Andalusía, southern Spain), potentially resistant to glyphosate (RG), was tested for its resistance level through dose-response assays using a susceptible biotype (SG). To test the hypothesis of a non-target-site-based resistance, as point mutations are far less common mechanisms of glyphosate resistance, studies were also conducted to elucidate whether resistance was associated with biochemical, metabolism, molecular and/or physiological mechanisms. Alternative herbicide-based control options, including single-herbicide or herbicide mixtures with glyphosate, applied at seedling, tillering or full heading stages, were tested in field experiments for 2 years for their efficacy against rigid ryegrass plants and their effects on the soil seed bank. Resistance levels of the RG biotype were 23- (LD50) and 7-fold (GR50) higher compared to the SG biotype. The SG biotype exhibited a significantly greater shikimic acid accumulation than the RG one. At 96 HAT, 58 and 89% of applied (14)C-glyphosate was up taken by leaves of RG and SG biotype plants, respectively, and, at this time, a significantly higher proportion of the glyphosate taken up by the treated leaf remained in its tissue in RG plants compared to the SG ones. The RG biotype did not reveal any point mutation in the glyphosate target site EPSP synthase. Overall, results confirmed reduced glyphosate uptake and translocation as being the mechanism involved in glyphosate resistance in the RG biotype. RG biotype responses to the alternative treatments tested in situ indicated that herbicide applications at the later growth stage tended to be less effective in terms of immediate effects on population size than earlier applications, and that only in some cases, the removal of at least 85% of the RG biotype was achieved. However, with few

  17. Glyphosate, paraquat and ACCase multiple herbicide resistance evolved in a Lolium rigidum biotype.

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    Yu, Qin; Cairns, Andrew; Powles, Stephen

    2007-01-01

    Glyphosate is the world's most widely used herbicide. A potential substitute for glyphosate in some use patterns is the herbicide paraquat. Following many years of successful use, neither glyphosate nor paraquat could control a biotype of the widespread annual ryegrass (Lolium rigidum), and here the world's first case of multiple resistance to glyphosate and paraquat is confirmed. Dose-response experiments established that the glyphosate rate causing 50% mortality (LD(50)) for the resistant (R) biotype is 14 times greater than for the susceptible (S) biotype. Similarly, the paraquat LD(50 )for the R biotype is 32 times greater than for the S biotype. Thus, based on the LD(50 )R/S ratio, this R biotype of L. rigidum is 14-fold resistant to glyphosate and 32-fold resistant to paraquat. This R biotype also has evolved resistance to the acetyl-coenzyme A carboxylase (ACCase) inhibiting herbicides. The mechanism of paraquat resistance in this biotype was determined as restricted paraquat translocation. Resistance to ACCase-inhibiting herbicides was determined as due to an insensitive ACCase. Two mechanisms endowing glyphosate resistance were established: firstly, a point mutation in the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene, resulting in an amino acid substitution of proline to alanine at position 106; secondly, reduced glyphosate translocation was found in this R biotype, indicating a co-occurrence of two distinct glyphosate resistance mechanisms within the R population. In total, this R biotype displays at least four co-existing resistance mechanisms, endowing multiple resistance to glyphosate, paraquat and ACCase herbicides. This alarming case in the history of herbicide resistance evolution represents a serious challenge for the sustainable use of the precious agrochemical resources such as glyphosate and paraquat.

  18. Screening for detection of wild oat biotypes resistant to fenoxaprop-P-ethyl from Mexico

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    Fidel González-Torralva

    2012-03-01

    Full Text Available Avena is one of the world’s most important genera resistant to herbicides. Suspected resistant biotype and susceptible biotype of Avena fatua were tested by screening to confirm the resistance to fenoxaprop-P-ethyl from Mexico. Suspected-resistant population was collected in wheat fields after the herbicide failed to control wild oat and the susceptible one was collected from a field with no herbicide application. Petri dish experiments were performed using different fenoxaprop-P-ethyl concentrations (0, 1, 5, 10 and 40 mM. Experiments were arranged in a completely randomized design with ten replicates. Plumule length in both biotypes decreased as fenoxaprop-P-ethyl concentration increased. However, there was a different response between the R and S biotypes. The EC50 for the resistant biotype was 3.3 mM while for the susceptible biotype was 9.3 mM, showing that the resistant biotype tolerated herbicide concentration approximately three times higher than the susceptible biotype. The results confirm the presence of Avena fatua resistant to fenoxaprop-P-ethyl in Mexico.

  19. The Eco-Evolutionary Imperative: Revisiting Weed Management in the Midst of an Herbicide Resistance Crisis

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    Fabian D. Menalled

    2016-12-01

    Full Text Available Modern weed science is at a crossroads. Born out of advances in chemistry, it has focused on minimizing weed competition with genetically uniform crops and heavy reliance on herbicides. Paradoxically, the success obtained with such an approach and the reluctance to conduct integrated and multidisciplinary research has resulted in unintended, but predictable, consequences, including the selection of herbicide resistant biotypes. Advances in eco-evolutionary biology, a relatively recent discipline that seeks to understand how local population dynamics arise from phenotypic variation resulting from natural selection, habitat distribution, and propagule dispersal across the landscape are transforming our understanding of the processes that regulate agroecosystems. Within this framework, complementary tactics to develop alternative weed management programs include the following: (1 weed scientists must recognize that evolution occurs within crop fields at ecologically-relevant time scales and is rooted in the inherent variation that exists in all populations; (2 weed management should recognize that the probability of a resistant mutant is directly related to the population size; (3 farmers need to acknowledge that herbicide resistance transcends any one farm and should coordinate local practices with regional actions; (4 incentives should be developed and implemented to help the adoption of eco-evolutionary management programs; and (5 risk analysis can help incorporate an eco-evolutionary perspective into integrated weed management programs.

  20. Morpho-physiological characterization of glyphosate-resistant and -susceptible horseweed (Conyza canadensis) biotypes of US Midsouth

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    Growth chamber and greenhouse experiments were conducted to compare selected biological and physiological parameters of glyphosate-resistant (GR) and -susceptible (GS) horseweed biotypes from Mississippi with a broader goal of fitness characterization in these biotypes. Vegetative growth parameters ...

  1. Importance of herbicide resistance in weeds of natural areas

    OpenAIRE

    DiTomaso, Joseph

    2014-01-01

    Worldwide, the majority of the plant species that are developing herbicide resistance are those that occur as weeds in agricultural environments, on roadsides and in other rights-of-way. In contrast, herbicide resistance is not nearly so common in weeds of natural areas or rangelands. A search of the International Survey of Herbicide Resistant Weeds ( weedscience.com ) revealed no herbicide-resistant weeds (i.e., invasive nonnative species) listed for terrestrial natural areas anywhere in the...

  2. Herbicide-resistant crops and weed resistance to herbicides.

    Science.gov (United States)

    Owen, Micheal D K; Zelaya, Ian A

    2005-03-01

    The adoption of genetically modified (GM) crops has increased dramatically during the last 3 years, and currently over 52 million hectares of GM crops are planted world-wide. Approximately 41 million hectares of GM crops planted are herbicide-resistant crops, which includes an estimated 33.3 million hectares of herbicide-resistant soybean. Herbicide-resistant maize, canola, cotton and soybean accounted for 77% of the GM crop hectares in 2001. However, sugarbeet, wheat, and as many as 14 other crops have transgenic herbicide-resistant cultivars that may be commercially available in the near future. There are many risks associated with the production of GM and herbicide-resistant crops, including problems with grain contamination, segregation and introgression of herbicide-resistant traits, marketplace acceptance and an increased reliance on herbicides for weed control. The latter issue is represented in the occurrence of weed population shifts, the evolution of herbicide-resistant weed populations and herbicide-resistant crops becoming volunteer weeds. Another issue is the ecological impact that simple weed management programs based on herbicide-resistant crops have on weed communities. Asiatic dayflower (Commelina cumminus L) common lambsquarters (Chenopodium album L) and wild buckwheat (Polygonum convolvulus L) are reported to be increasing in prominence in some agroecosystems due to the simple and significant selection pressure brought to bear by herbicide-resistant crops and the concomitant use of the herbicide. Finally, evolution of herbicide-resistant weed populations attributable to the herbicide-resistant crop/herbicide program has been observed. Examples of herbicide-resistant weeds include populations of horseweed (Conyza canadensis (L) Cronq) resistant to N-(phosphonomethyl)glycine (glyphosate). An important question is whether or not these problems represent significant economic issues for future agriculture. Copyright 2005 Society of Chemical Industry

  3. Evolved glyphosate-resistant weeds around the world: lessons to be learnt.

    Science.gov (United States)

    Powles, Stephen B

    2008-04-01

    Glyphosate is the world's most important herbicide, with many uses that deliver effective and sustained control of a wide spectrum of unwanted (weedy) plant species. Until recently there were relatively few reports of weedy plant species evolving resistance to glyphosate. Since 1996, the advent and subsequent high adoption of transgenic glyphosate-resistant crops in the Americas has meant unprecedented and often exclusive use of glyphosate for weed control over very large areas. Consequently, in regions of the USA where transgenic glyphosate-resistant crops dominate, there are now evolved glyphosate-resistant populations of the economically damaging weed species Ambrosia artemissifolia L., Ambrosia trifida L., Amaranthus palmeri S Watson, Amaranthus rudis JD Sauer, Amaranthus tuberculatus (Moq) JD Sauer and various Conyza and Lolium spp. Likewise, in areas of transgenic glyphosate-resistant crops in Argentina and Brazil, there are now evolved glyphosate-resistant populations of Sorghum halepense (L.) Pers and Euphorbia heterophylla L. respectively. As transgenic glyphosate-resistant crops will remain very popular with producers, it is anticipated that glyphosate-resistant biotypes of other prominent weed species will evolve over the next few years. Therefore, evolved glyphosate-resistant weeds are a major risk for the continued success of glyphosate and transgenic glyphosate-resistant crops. However, glyphosate-resistant weeds are not yet a problem in many parts of the world, and lessons can be learnt and actions taken to achieve glyphosate sustainability. A major lesson is that maintenance of diversity in weed management systems is crucial for glyphosate to be sustainable. Glyphosate is essential for present and future world food production, and action to secure its sustainability for future generations is a global imperative.

  4. Different cross-resistance patterns to AHAS herbicides of two tribenuron-methyl resistant flixweed (Descurainiasophia L.) biotypes in China.

    Science.gov (United States)

    Deng, Wei; Cao, Yuan; Yang, Qian; Liu, Ming Jie; Mei, Yu; Zheng, Ming Qi

    2014-06-01

    Flixweed (Descurainiasophia L.) is a troublesome weed in winter wheat fields in China. Two flixweed accessions, HB08 and HB16 with a Pro-197-Leu and Pro-197-Ser AHAS-mutation respectively, have evolved very high levels resistance to sulfonylurea (SU) herbicide, tribenuron-methyl. Cross resistance of HB08 and HB16 to AHAS herbicides of SU, imidazolinone (IMI), triazolopyrimidine (TP) and pyrimidinyl-thiobenozoate (PTB) families was investigated by dose-response experiments. In addition, the effects of AHAS herbicides on the activity of AHAS extracted from HB08 and HB16 plants were evaluated. HB16 exhibited cross resistance to SU herbicides halosulfuron-methyl and triasulfuron, TP herbicides flumetsulam and penoxsulam, but displayed more sensitivity to IMI herbicide imazethapyr. By contrast, HB08 only showed cross resistance to SU herbicides halosulfuron-methyl and triasulfuron. The in vitro sensitivity of AHAS to AHAS herbicides is consistent with the results of dose-response experiments and the estimated Pearson's r values for HB08 and HB16 are 0.996 and 0.912 respectively. These indicated that altered AHAS sensitivity was responsible mainly for cross resistance patterns observed in the two resistant biotypes.

  5. Target site mutation and reduced translocation are present in a glyphosate-resistant Lolium multiflorum Lam. biotype from Spain.

    Science.gov (United States)

    González-Torralva, Fidel; Gil-Humanes, Javier; Barro, Francisco; Brants, Ivo; De Prado, Rafael

    2012-09-01

    The resistance mechanism of a glyphosate-resistant Lolium multiflorum Lam. biotype collected in Córdoba (Southern Spain) was examined. Resistance Factor values at three different growth stages ranged between 4.77 and 4.91. At 96 hours after treatment (HAT) the S biotype had accumulated seven times more shikimic acid than the R biotype. There were significant differences in translocation of (14)C-glyphosate between biotypes, i.e. at 96 HAT, the R biotype accumulated in the treated leaf more than 70% of the absorbed herbicide, in comparison with 59.21% of the S biotype; the R biotype translocated only 14.79% of the absorbed (14)C-glyphosate to roots, while in the S population this value was 24.79%. Visualization of (14)C-glyphosate by phosphor imaging showed a reduced distribution in the R biotype compared with the S. Glyphosate metabolism was not involved in the resistance mechanism due to both biotypes showing similar values of glyphosate at 96 HAT. Comparison of the EPSPS gene sequences between biotypes indicated that the R biotype has a proline 182 to serine amino acid substitution. In short, the resistance mechanism of the L. multiflorum Lam. biotype is due to an impaired translocation of the herbicide and an altered target site.

  6. Herbicide-resistant weeds: Management strategies and upcoming technologies

    Science.gov (United States)

    Herbicides have contributed to substantial increase in crop yields over the past seven decades. Over reliance on herbicides for weed control has led to rapid evolution of herbicide-resistant (HR) weeds. Increased awareness of herbicide resistance and adoption of diversified weed control tactics by f...

  7. Parthenium weed (Parthenium hysterophorus L.) and climate change: the effect of CO2 concentration, temperature, and water deficit on growth and reproduction of two biotypes.

    Science.gov (United States)

    Nguyen, Thi; Bajwa, Ali Ahsan; Navie, Sheldon; O'Donnell, Chris; Adkins, Steve

    2017-04-01

    Climate change will have a considerable impact upon the processes that moderate weed invasion, in particular to that of parthenium weed (Parthenium hysterophorus L.). This study evaluated the performance of two Australian biotypes of parthenium weed under a range of environmental conditions including soil moisture (100 and 50% of field capacity), atmospheric carbon dioxide (CO2) concentration (390 and 550 ppm), and temperature (35/20 and 30/15 °C/day/night). Measurements were taken upon growth, reproductive output, seed biology (fill, viability and dormancy) and soil seed longevity. Parthenium weed growth and seed output were significantly increased under the elevated CO2 concentration (550 ppm) and in the cooler (30/15 °C) and wetter (field capacity) conditions. However, elevated CO2 concentration could not promote growth or seed output when the plants were grown under the warmer (35/20 °C) and wetter conditions. Warm temperatures accelerated the growth of parthenium weed, producing plants with greater height biomass but with a shorter life span. Warm temperatures also affected the reproductive output by promoting both seed production and fill, and promoting seed longevity. Dryer soil conditions (50% of field capacity) also promoted the reproductive output, but did not retain high seed fill or promote seed longevity. Therefore, the rising temperatures, the increased atmospheric CO2 concentration and the longer periods of drought predicted under climate change scenarios are likely to substantially enhance the growth and reproductive output of these two Australian parthenium weed biotypes. This may facilitate the further invasion of this noxious weed in tropical and sub-tropical natural and agro-ecosystems.

  8. Use of resistant ACCase mutants to screen for novel inhibitors against resistant and susceptible forms of ACCase from grass weeds.

    Science.gov (United States)

    Shukla, Amit; Nycholat, Corwin; Subramanian, Mani V; Anderson, Richard J; Devine, Malcolm D

    2004-08-11

    The aryloxyphenoxypropionic acid (AOPP) and cyclohexanedione (CHD) herbicides inhibit the first committed enzyme in fatty acid biosynthesis, acetyl CoA carboxylase (ACCase). The frequent use of AOPP and CHD herbicides has resulted in the development of resistance to these herbicides in many grass weed species. New herbicides that inhibit both the susceptible and resistant forms of ACCase in grass weeds would have obvious commercial appeal. In the present study, an attempt was made to identify molecules that target both the herbicide-sensitive and -resistant forms of ACCase. Seven experimental compounds, either CHD-like or AOPP-CHD hybrids, were synthesized and assayed against previously characterized susceptible and resistant forms of ACCase. All seven compounds inhibited ACCase from sensitive biotypes of Setaria viridis and Eleusine indica (I50 values from 6.4 to >100 microM) but were not particularly potent compared to some commercialized herbicides (I50 values of 0.08-5.6 microM). In almost all cases, the I50 values for each compound assayed against the resistant ACCases were higher than those against the corresponding sensitive ACCase, indicating reduced binding to the resistant ACCases. One compound, a CHD analogue, was almost equally effective against the resistant and susceptible ACCases, although it was not a very potent ACCase inhibitor per se (I50 of 51 and 76 microM against susceptible ACCase from S. viridis and E. indica, respectively). The AOPP-CHD hybrid molecules also inhibited some of the resistant ACCases, with I50 values ranging from 6.4 to 50 microM. These compounds may be good leads for developing ACCase inhibitors that target a wider range of ACCase isoforms, including those found in AOPP- and CHD-resistant weed biotypes.

  9. Inheritance of Evolved Glyphosate Resistance in a North Carolina Palmer Amaranth (Amaranthus palmeri Biotype

    Directory of Open Access Journals (Sweden)

    Aman Chandi

    2012-01-01

    Full Text Available Inheritance of glyphosate resistance in a Palmer amaranth biotype from North Carolina was studied. Glyphosate rates for 50% survival of glyphosate-resistant (GR and glyphosate-susceptible (GS biotypes were 1288 and 58 g ha−1, respectively. These values for F1 progenies obtained from reciprocal crosses (GR×GS and GS×GR were 794 and 501 g ha−1, respectively. Dose response of F1 progenies indicated that resistance was not fully dominant over susceptibility. Lack of significant differences between dose responses for reciprocal F1 families suggested that genetic control of glyphosate resistance was governed by nuclear genome. Analysis of F1 backcross (BC1F1 families showed that 10 and 8 BC1F1 families out of 15 fitted monogenic inheritance at 2000 and 3000 g ha−1 glyphosate, respectively. These results indicate that inheritance of glyphosate resistance in this biotype is incompletely dominant, nuclear inherited, and might not be consistent with a single gene mechanism of inheritance. Relative 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS copy number varied from 22 to 63 across 10 individuals from resistant biotype. This suggested that variable EPSPS copy number in the parents might be influential in determining if inheritance of glyphosate resistance is monogenic or polygenic in this biotype.

  10. Dynamics of Bemisia tabaci biotypes and insecticide resistance in Fujian province in China during 2005–2014

    Science.gov (United States)

    Yao, Feng-Luan; Zheng, Yu; Huang, Xiao-Yan; Ding, Xue-Ling; Zhao, Jian-Wei; Desneux, Nicolas; He, Yu-Xian; Weng, Qi-Yong

    2017-01-01

    The whitefly Bemisia tabaci (Gennadius) is an important agricultural insect pest worldwide. The B and Q biotypes are the two most predominant and devastating biotypes prevalent across China. However, there are few studies regarding the occurrence of the Q biotype in Fujian Province, China, where high insecticide resistance has been reported in the B biotype. Differences in some biological characteristics between the B and Q biotypes, especially insecticide resistance, are considered to affect the outcome of their competition. Extensive surveys in Fujian revealed that the B biotype was predominant during 2005–2014, whereas the Q biotype was first detected in some locations in 2013 and widely detected throughout the province in 2014. Resistance to neonicotinoids (that have been used for more than 10 years) exhibited fluctuations in open fields, but showed a continual increasing trend in protected areas. Resistance to lambda-cyhalothrin, chlorpyrifos, and abamectin exhibited a declining trend. Resistance to novel insecticides, such as nitenpyram, pymetrozine, sulfoxaflor, and cyantraniliprole, in 2014 was generally below a moderate level. A decline in insecticide resistance in the B biotype and the rapid buildup of protected crops under global temperature increase may have promoted the establishment of the Q biotype in Fujian. PMID:28112233

  11. Characterization and genetics of multiple soybean aphid biotype resistance in five soybean plant introductions

    Science.gov (United States)

    Soybean aphid (Aphis glycines Matsumura) is the most important soybean [Glycine max (L.) Merr.] insect pest in the USA. The objectives of this study were to characterize the resistance expressed in the five plant introductions (PIs) to four soybean aphid biotypes, determine the mode of resistance in...

  12. Two non-target mechanisms are involved in glyphosate-resistant horseweed (Conyza canadensis L. Cronq.) biotypes.

    Science.gov (United States)

    González-Torralva, Fidel; Rojano-Delgado, Antonia M; Luque de Castro, María D; Mülleder, Norbert; De Prado, Rafael

    2012-11-15

    The physiological and biochemical bases for glyphosate resistance and susceptibility in horseweed (Conyza canadensis L. Cronq.) populations collected from Córdoba, Huelva, Málaga, Jaén and Seville in southern Spain were investigated. Screening 25 populations treated with glyphosate (238gacidequivalentha(-1)) at the rosette stage (BBCH 14-15) revealed reductions in fresh weight (fw) of 9-99%. The resistant biotype (R C004) was 6.1 times more resistant than the susceptible biotype (S). Shikimate accumulation in both biotypes increased until 72h after treatment (HAT), and then continued to increase (to 61.2%) in the S biotype, but decreased by 40% in the R (C004) biotype. Differential glyphosate spray retention and foliar uptake of applied (14)C-glyphosate between the R (C004) and S biotype had no effect on resistance to this herbicide. Quantitative and qualitative tests showed greater (14)C-glyphosate mobility in the S biotype than in the R (C004) biotype. Glyphosate was metabolized faster in the R (C004) biotype than in the S biotype. The herbicide disappeared completely from the R (C004) biotype by conversion into glyoxylate, sarcosine and aminomethylphosphonic acid within 96 HAT. On the other hand, 41.43nmolg(-1)fw of all glyphosate applied remained in the S biotype and glyoxylate was its only non-toxic metabolite. These results suggest that glyphosate resistance in horseweed is due to two different non-target mechanisms, namely: (a) impaired glyphosate translocation and (b) glyphosate metabolism to other compounds.

  13. Dynamics of biotypes B and Q of the whitefly Bemisia tabaci and its impact on insecticide resistance.

    Science.gov (United States)

    Horowitz, Abraham Rami; Ishaaya, Isaac

    2014-10-01

    The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a key pest in many agricultural crops, including vegetables, ornamentals and field crops. B. tabaci is known for its genetic diversity, which is expressed in a complex of biotypes or, as recently suggested, a complex of distinct cryptic species. The biotypes are largely differentiated on the basis of biochemical or molecular polymorphism and differ in characteristics such as host plant range, attraction by natural enemies, secondary symbionts and expression of insecticide resistance. An extensive survey of B. tabaci biotypes and their impact on insecticide resistance was conducted from 2003 to 2012 in cotton fields and other crops from several locations in Israel. Two biotypes of B. tabaci, B and Q, were identified, and some differences in the biotype dynamics were recorded from different areas. In northern Israel from 2003 to 2007, a higher proportion of the B biotype was consistently found in early season. However, by the end of the season a definite rise of the Q biotype was sampled, ranging from 60 to 100%, along with high resistance to the insect growth regulator (IGR) pyriproxyfen and to a lesser extent to the neonicotinoid insecticides. In fields located in the central part of Israel, the Q biotype was predominant throughout the seasons, with high resistance to pyriproxyfen. Since 2009, a significant shift in the biotype ratios has been observed: the B biotype has come to predominate over the Q biotype ranging up to 90% or more in most fields. At the same time, resistance to the IGR pyriproxyfen was reduced considerably. The possible reasons for the change in the dynamics of B. tabaci biotypes, and its implications for resistance management, are discussed. Strong B. tabaci resistance to pyriproxyfen in Israel has been associated with the Q rather than with the B biotype. The B biotype is more competitive than the Q biotype under untreated conditions. Reduction in the acreage of cotton fields

  14. Herbicide-resistant weed management: focus on glyphosate.

    Science.gov (United States)

    Beckie, Hugh J

    2011-09-01

    This review focuses on proactive and reactive management of glyphosate-resistant (GR) weeds. Glyphosate resistance in weeds has evolved under recurrent glyphosate usage, with little or no diversity in weed management practices. The main herbicide strategy for proactively or reactively managing GR weeds is to supplement glyphosate with herbicides of alternative modes of action and with soil-residual activity. These herbicides can be applied in sequences or mixtures. Proactive or reactive GR weed management can be aided by crop cultivars with alternative single or stacked herbicide-resistance traits, which will become increasingly available to growers in the future. Many growers with GR weeds continue to use glyphosate because of its economical broad-spectrum weed control. Government farm policies, pesticide regulatory policies and industry actions should encourage growers to adopt a more proactive approach to GR weed management by providing the best information and training on management practices, information on the benefits of proactive management and voluntary incentives, as appropriate. Results from recent surveys in the United States indicate that such a change in grower attitudes may be occurring because of enhanced awareness of the benefits of proactive management and the relative cost of the reactive management of GR weeds.

  15. Evaluation and reselection of wheat resistance to Russian wheat aphid biotype 2

    Science.gov (United States)

    Russian wheat aphid (RWA, Diuraphis noxia, Mordvilko) biotype 2 (RWA2) is virulent to most known RWA resistance genes and severely threatens wheat production in the hard winter wheat area of the US western Great Plains. We determined RWA2 reactions of 386 cultivars from China, 227 advanced breeding...

  16. Physiology of Glyphosate-Resistant and Glyphosate-Susceptible Palmer Amaranth (Amaranthus palmeri Biotypes Collected from North Carolina

    Directory of Open Access Journals (Sweden)

    Jared R. Whitaker

    2013-01-01

    Full Text Available Glyphosate-resistant (GR biotypes of Palmer amaranth are now commonly found across the southern United States. Experiments were conducted to characterize physiological differences between a GR biotype and a glyphosate-susceptible (GS biotype from North Carolina. The GR biotype had an 18-fold level of resistance based upon rates necessary to reduce shoot fresh weight 50%. Shikimate accumulated in both biotypes following glyphosate application, but greater concentrations were found in GS plants. Absorption and translocation of 14C-glyphosate were studied in both biotypes with and without an overspray with commercial glyphosate potassium salt (840 g ae ha−1 immediately prior to 14C-glyphosate application. Greater absorption was noted 6 h after treatment (HAT in GS compared with GR plants, but no differences were observed at 12 to 72 HAT. Oversprayed plants absorbed 33 and 61% more 14C by 48 and 72 HAT, respectively, than plants not oversprayed. 14C distribution (above treated leaf, below treated leaf, roots was similar in both biotypes. Together, these results suggest that resistance in this biotype is not due to an altered target enzyme or translocation but may be in part due to the rate of glyphosate absorption. These results also are consistent with resistance being due to increased gene copy number for the target enzyme.

  17. Herbicide Resistant Weeds: Do Economic Thresholds Still Have a Role in Weed Management?

    Science.gov (United States)

    Concern over the development of herbicide resistant weeds has prompted a closer look at the validity of using economic thresholds (ET) as a basis for making treatment decisions. In situations where herbicide resistance is suspected, growers are often advised to employ control measures to completely ...

  18. Reduced Fitness of Virulent Aphis glycines (Hemiptera: Aphididae) Biotypes May Influence the Longevity of Resistance Genes in Soybean.

    Science.gov (United States)

    Varenhorst, Adam J; McCarville, Michael T; O'Neal, Matthew E

    2015-01-01

    Sustainable use of insect resistance in crops require insect resistance management plans that may include a refuge to limit the spread of virulence to this resistance. However, without a loss of fitness associated with virulence, a refuge may not prevent virulence from becoming fixed within a population of parthenogenetically reproducing insects like aphids. Aphid-resistance in soybeans (i.e., Rag genes) prevent outbreaks of soybean aphid (Aphis glycines), yet four biotypes defined by their capacity to survive on aphid-resistant soybeans (e.g., biotype-2 survives on Rag1 soybean) are found in North America. Although fitness costs are reported for biotype-3 on aphid susceptible and Rag1 soybean, it is not clear if virulence to aphid resistance in general is associated with a decrease in fitness on aphid susceptible soybeans. In laboratory assays, we measured fitness costs for biotype 2, 3 and 4 on an aphid-susceptible soybean cultivar. In addition, we also observed negative cross-resistance for biotype-2 on Rag3, and biotype-3 on Rag1 soybean. We utilized a simple deterministic, single-locus, four compartment genetic model to account for the impact of these findings on the frequency of virulence alleles. When a refuge of aphid susceptible was included within this model, fitness costs and negative cross-resistance delayed the increase of virulence alleles when virulence was inherited recessively or additively. If virulence were inherited additively, fitness costs decreased the frequency of virulence. Combined, these results suggest that a refuge may prevent virulent A. glycines biotypes from overcoming Rag genes if this aphid-resistance were used commercially in North America.

  19. Resistance of soybean genotypes to Bemisia tabaci (Genn.) Biotype B (Hemiptera: Aleyrodidae).

    Science.gov (United States)

    Vieira, S S; Bueno, A F; Boff, M I C; Bueno, R C O F; Hoffman-Campo, C B

    2011-01-01

    The silverleaf whitefly Bemisia tabaci (Genn.) biotype B has become a serious problem for soybean cultivation because it can significantly reduce soybean productivity. The use of soybean cultivars resistant to whitefly attack is an important strategy in an integrated pest management (IPM) program. This study evaluated the preference for oviposition and colonization by B. tabaci biotype B on different soybean genotypes. In the free-choice test, the genotypes studied were 'IAC 17' and 'IAC 19' as the standards for resistance and 'IAC Holambra Stwart' as the standard for susceptibility, as well as BABR01-0492, BABR01-0173, BABR01-1259, BABR01-1576, BABR99-4021HC, BABR99-4021HP, 'Barreiras', 'Conquista', 'Corisco', 'BRS Gralha', PI274454, PI227687, and PI171451. In the no-choice test, the four best genotypes selected in the free-choice test, in addition to the susceptible and resistant standards were evaluated. Our data indicated 'Barreiras' as the most resistant genotype against B. tabaci biotype B. 'BRS Gralha', which was the least attractive to whitefly adults in the free-choice test, did not show resistance to insect attack when they were confined in cages in the no-choice test. Despite the high number of eggs observed, BABR01-1576 and BABR99-4021HC showed a reduced number of nymphs, indicating antibiosis. The genotypes with a high level of resistance can be used as a tool against B. tabaci in IPM or as a source of resistance in plant-breeding programs.

  20. Herbicide-resistant crops: utilities and limitations for herbicide-resistant weed management.

    Science.gov (United States)

    Green, Jerry M; Owen, Micheal D K

    2011-06-08

    Since 1996, genetically modified herbicide-resistant (HR) crops, particularly glyphosate-resistant (GR) crops, have transformed the tactics that corn, soybean, and cotton growers use to manage weeds. The use of GR crops continues to grow, but weeds are adapting to the common practice of using only glyphosate to control weeds. Growers using only a single mode of action to manage weeds need to change to a more diverse array of herbicidal, mechanical, and cultural practices to maintain the effectiveness of glyphosate. Unfortunately, the introduction of GR crops and the high initial efficacy of glyphosate often lead to a decline in the use of other herbicide options and less investment by industry to discover new herbicide active ingredients. With some exceptions, most growers can still manage their weed problems with currently available selective and HR crop-enabled herbicides. However, current crop management systems are in jeopardy given the pace at which weed populations are evolving glyphosate resistance. New HR crop technologies will expand the utility of currently available herbicides and enable new interim solutions for growers to manage HR weeds, but will not replace the long-term need to diversify weed management tactics and discover herbicides with new modes of action. This paper reviews the strengths and weaknesses of anticipated weed management options and the best management practices that growers need to implement in HR crops to maximize the long-term benefits of current technologies and reduce weed shifts to difficult-to-control and HR weeds.

  1. Herbicide resistance in weeds: Survey, characterization, and mechanisms

    Science.gov (United States)

    The goal of this paper is to present a systematic diagnostic approach towards the characterization of herbicide resistance in a given weed population with regards to profile (single, multiple, cross resistance), magnitude (fold level), mechanism, and related bio-physiological aspects. Diagnosing her...

  2. Underlying resistance mechanisms in the Cynosurus echinatus biotype to acetyl CoA carboxylase-inhibiting herbicides

    Directory of Open Access Journals (Sweden)

    Pablo eFernández

    2016-04-01

    Full Text Available Hedgehog dogtail (Cynosurus echinatus is an annual grass, native to Europe, but also widely distributed in North and South America, South Africa and Australia. Two hedgehog dogtail biotypes, one diclofop-methyl (DM-resistant and one DM-susceptible were studied in detail for experimental dose-response resistance mechanisms. Herbicide rates that inhibited shoot growth by 50% (GR50 were determined for DM, being the resistance factor (GR50R/GR50S of 43.81. When amitrole (Cyt. P450 inhibitor was applied before treatment with DM, the R biotype growth was significantly inhibited (GR50 of 1019.9 g ai ha-1 compared with the GR50 (1484.6 g ai ha-1 found for the R biotype without pretreatment with amitrole. However, GR50 values for S biotype do not vary with or without amitrole pretreatment. Dose-response experiments carried out to evaluate cross-resistance, showed resistance to aryloxyphenoxypropionate (APP, cyclohexanodione (CHD and phenylpyrazoline (PPZ inhibiting herbicides. Both R and S biotypes had a similar 14C-DM uptake and translocation. The herbicide was poorly distributed among leaves, the rest of the shoot and roots with unappreciable acropetal and/or basipetal DM translocation at 96 HAT. The metabolism of 14C-DM, D-acid and D-conjugate metabolites were identified by thin-layer chromatography. The results showed that DM resistance in C. echinatus is likely due to enhanced herbicide metabolism, involving Cyt. P450 as was demonstrated by indirect assays (amitrole pretreatment. The ACCase in vitro assays showed that the target site was very sensitive to APP, CHD and PPZ herbicides in the C. echinatus S biotype, while the R biotype was insensitive to the previously mentioned herbicides. DNA sequencing studies confirmed that C. echinatus cross-resistance to ACCase inhibitors has been conferred by specific ACCase double point mutations Ile-2041-Asn and Cys-2088-Arg.

  3. Deciphering the evolution of herbicide resistance in weeds.

    Science.gov (United States)

    Délye, Christophe; Jasieniuk, Marie; Le Corre, Valérie

    2013-11-01

    Resistance to herbicides in arable weeds is increasing rapidly worldwide and threatening global food security. Resistance has now been reported to all major herbicide modes of action despite the development of resistance management strategies in the 1990s. We review here recent advances in understanding the genetic bases and evolutionary drivers of herbicide resistance that highlight the complex nature of selection for this adaptive trait. Whereas early studied cases of resistance were highly herbicide-specific and largely under monogenic control, cases of greatest concern today generally involve resistance to multiple modes of action, are under polygenic control, and are derived from pre-existing stress response pathways. Although 'omics' approaches should enable unraveling the genetic bases of complex resistances, the appearance, selection, and spread of herbicide resistance in weed populations can only be fully elucidated by focusing on evolutionary dynamics and implementing integrative modeling efforts. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Resistance to a new biotype of the lettuce aphid Nasonovia ribisnigri in Lactuca virosa accession IVT280

    NARCIS (Netherlands)

    Broeke, ten C.J.M.; Dicke, M.; Loon, van J.J.A.

    2013-01-01

    Host plant resistance is an effective protection strategy to control aphids in many crops. However, the evolution of insensitive aphid biotypes necessitates the search for new resistance sources. Wild relatives of crop plants can be important sources for resistance genes to be introgressed into new

  5. Resistance to a new biotype of the lettuce aphid Nasonovia ribisnigri in Lactuca virosa accession IVT280

    NARCIS (Netherlands)

    Broeke, ten C.J.M.; Dicke, M.; Loon, van J.J.A.

    2013-01-01

    Host plant resistance is an effective protection strategy to control aphids in many crops. However, the evolution of insensitive aphid biotypes necessitates the search for new resistance sources. Wild relatives of crop plants can be important sources for resistance genes to be introgressed into new

  6. Taxonomic and life history bias in herbicide resistant weeds: implications for deployment of resistant crops.

    Directory of Open Access Journals (Sweden)

    Jodie S Holt

    Full Text Available Evolved herbicide resistance (EHR is an important agronomic problem and consequently a food security problem, as it jeopardizes herbicide effectiveness and increases the difficulty and cost of weed management. EHR in weeds was first reported in 1970 and the number of cases has accelerated dramatically over the last two decades. Despite 40 years of research on EHR, why some weeds evolve resistance and others do not is poorly understood. Here we ask whether weed species that have EHR are different from weeds in general. Comparing taxonomic and life history traits of weeds with EHR to a control group ("the world's worst weeds", we found weeds with EHR significantly over-represented in certain plant families and having certain life history biases. In particular, resistance is overrepresented in Amaranthaceae, Brassicaceae and Poaceae relative to all weeds, and annuality is ca. 1.5 times as frequent in weeds with EHR as in the control group. Also, for perennial EHR weeds, vegetative reproduction is only 60% as frequent as in the control group. We found the same trends for subsets of weeds with EHR to acetolactate synthase (ALS, photosystem II (PSII, and 5-enolpyruvylshikimate-3-phosphate (EPSP synthase-inhibitor herbicides and with multiple resistance. As herbicide resistant crops (transgenic or not are increasingly deployed in developing countries, the problems of EHR could increase in those countries as it has in the USA if the selecting herbicides are heavily applied and appropriate management strategies are not employed. Given our analysis, we make some predictions about additional species that might evolve resistance.

  7. Taxonomic and life history bias in herbicide resistant weeds: implications for deployment of resistant crops.

    Science.gov (United States)

    Holt, Jodie S; Welles, Shana R; Silvera, Katia; Heap, Ian M; Heredia, Sylvia M; Martinez-Berdeja, Alejandra; Palenscar, Kai T; Sweet, Lynn C; Ellstrand, Norman C

    2013-01-01

    Evolved herbicide resistance (EHR) is an important agronomic problem and consequently a food security problem, as it jeopardizes herbicide effectiveness and increases the difficulty and cost of weed management. EHR in weeds was first reported in 1970 and the number of cases has accelerated dramatically over the last two decades. Despite 40 years of research on EHR, why some weeds evolve resistance and others do not is poorly understood. Here we ask whether weed species that have EHR are different from weeds in general. Comparing taxonomic and life history traits of weeds with EHR to a control group ("the world's worst weeds"), we found weeds with EHR significantly over-represented in certain plant families and having certain life history biases. In particular, resistance is overrepresented in Amaranthaceae, Brassicaceae and Poaceae relative to all weeds, and annuality is ca. 1.5 times as frequent in weeds with EHR as in the control group. Also, for perennial EHR weeds, vegetative reproduction is only 60% as frequent as in the control group. We found the same trends for subsets of weeds with EHR to acetolactate synthase (ALS), photosystem II (PSII), and 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase-inhibitor herbicides and with multiple resistance. As herbicide resistant crops (transgenic or not) are increasingly deployed in developing countries, the problems of EHR could increase in those countries as it has in the USA if the selecting herbicides are heavily applied and appropriate management strategies are not employed. Given our analysis, we make some predictions about additional species that might evolve resistance.

  8. Diagnóstico da resistência aos herbicidas em plantas daninhas Diagnosis of herbicide resistance in weeds

    Directory of Open Access Journals (Sweden)

    R.A. Vidal

    2006-09-01

    Full Text Available A resistência de plantas daninhas aos herbicidas caracteriza-se como um fenômeno evolutivo, decorrente da seleção imposta por estes. Esse é um problema grave que vem aumentando nos últimos anos nas áreas agrícolas em todo o mundo. A prevenção por meio de métodos alternativos de manejo atrasa o aparecimento de plantas resistentes, porém o monitoramento periódico das lavouras é a melhor forma de evitar a disseminação quando do surgimento da resistência. Métodos diagnósticos rápidos, eficazes e precisos são úteis na confirmação dos casos de resistência, evitando a disseminação de sementes na área. Diversos métodos têm sido desenvolvidos nos últimos anos, buscando agilizar o diagnóstico da resistência. Recentemente, métodos desenvolvidos através do uso da biotecnologia têm sido aprimorados e mostram uma tendência para o futuro na detecção da resistência aos herbicidas pelas plantas daninhas. No presente trabalho, objetivou-se discutir os métodos para diagnóstico da resistência em plantas daninhas aos herbicidas relatados pela literatura, apresentando suas vantagens e desvantagens, bem como abordando suas possibilidades de aplicação.Weed resistance to herbicides is an evolutive phenomenon caused by the selection imposed by the herbicides. This serious problem has been increasing in the last years in agricultural areas. Prevention through alternative management methods delays the appearance of resistant weeds. However, periodic monitoring of farmlands is the best way to avoid the spreading of the selected resistance biotypes. Fast, efficient and precise diagnosis methods are useful in the confirmation of resistance cases avoiding seed dissemination. Different methods have been developed in the last years seeking to improve resistance diagnosis. Recent methods developed through biotechnology have been improved and are promising methods for herbicide resistant weed detection.

  9. Glyphosate resistant weeds - a threat to conservation agriculture

    Science.gov (United States)

    Glyphosate-resistant weeds are now present throughout the Southeast. Hundreds of thousands of conservation tillage cotton acres, some currently under USDA Natural Resources Conservation Service (NRCS) conservation program contracts, are at risk of being converted to higher-intensity tillage systems....

  10. 杂草对ACCase抑制剂的抗性%Resistance of Weed to ACCase-Inhibiting Herbicides

    Institute of Scientific and Technical Information of China (English)

    郭峰; 张朝贤; 黄红娟; 魏守辉; 张猛; 房峰

    2011-01-01

    以乙酰辅酶A羧化酶(ACCase)为作用靶标的除草剂是高效、选择性的禾本科杂草除草剂,其在全球范围内的广泛、重复使用,导致了抗药性杂草的发生和发展.到目前为止,已经在30个国家有37种抗此类除草剂的杂草生物型.抗药性杂草严重威胁杂草治理和农业生产,由此引发的生态问题及粮食安全问题引起了广泛的关注.文章概述了ACCase抑制剂抗药性杂草的发生现状,从杂草ACCase突变、代谢解毒等几个方面综述了杂草抗ACCase抑制剂的抗性机制,以期为ACCase抑制剂抗性研究提供参考.最后讨论了阻止或延缓抗药性发生的杂草管理措施.%Hebicides targeting acetyl - CoA carboxylase(ACCase) are effective and selective graminicides. Their widespread and repeated application in worldwide resulted in occurrence and evolution of resistant weed species. There have been 37 weed biotypes resistant to ACCase herbicides in 30 countries by now. The herbicide resistant weeds threatted to weed management and crop production, and the consequences leading to biological damage and food safety caused extensive concern in the world. This review summarized the current status of ACCase - inhibiting herbicide resistant weeds and the major mechanisms of resistance involed in the ACCase mutations, metabolic detoxification and so on. In order to provide useful information and references for researches of ACCase - inhibiting herbicide resistance. Potential management strategy for preventing and delaying the herbicide resistance evolution of weeds was discussed in the end.

  11. Protocols for Robust Herbicide Resistance Testing in Different Weed Species.

    Science.gov (United States)

    Panozzo, Silvia; Scarabel, Laura; Collavo, Alberto; Sattin, Maurizio

    2015-07-02

    Robust protocols to test putative herbicide resistant weed populations at whole plant level are essential to confirm the resistance status. The presented protocols, based on whole-plant bioassays performed in a greenhouse, can be readily adapted to a wide range of weed species and herbicides through appropriate variants. Seed samples from plants that survived a field herbicide treatment are collected and stored dry at low temperature until used. Germination methods differ according to weed species and seed dormancy type. Seedlings at similar growth stage are transplanted and maintained in the greenhouse under appropriate conditions until plants have reached the right growth stage for herbicide treatment. Accuracy is required to prepare the herbicide solution to avoid unverifiable mistakes. Other critical steps such as the application volume and spray speed are also evaluated. The advantages of this protocol, compared to others based on whole plant bioassays using one herbicide dose, are related to the higher reliability and the possibility of inferring the resistance level. Quicker and less expensive in vivo or in vitro diagnostic screening tests have been proposed (Petri dish bioassays, spectrophotometric tests), but they provide only qualitative information and their widespread use is hindered by the laborious set-up that some species may require. For routine resistance testing, the proposed whole plant bioassay can be applied at only one herbicide dose, so reducing the costs.

  12. Evolution of herbicide resistance mechanisms in grass weeds.

    Science.gov (United States)

    Matzrafi, Maor; Gadri, Yaron; Frenkel, Eyal; Rubin, Baruch; Peleg, Zvi

    2014-12-01

    Herbicide resistant weeds are becoming increasingly common, threatening global food security. Here, we present BrIFAR: a new model system for the functional study of mechanisms of herbicide resistance in grass weeds. We have developed a large collection of Brachypodium accessions, the BrI collection, representing a wide range of habitats. Wide screening of the responses of the accessions to four major herbicide groups (PSII, ACCase, ALS/AHAS and EPSPS inhibitors) identified 28 herbicide-resistance candidate accessions. Target-site resistance to PSII inhibitors was found in accessions collected from habitats with a known history of herbicide applications. An amino acid substitution in the psbA gene (serine264 to glycine) conferred resistance and also significantly affected the flowering and shoot dry weight of the resistant accession, as compared to the sensitive accession. Non-target site resistance to ACCase inhibitors was found in accessions collected from habitats with a history of herbicide application and from a nature reserve. In-vitro enzyme activity tests and responses following pre-treatment with malathion (a cytochrome-P450 inhibitor) indicated sensitivity at the enzyme level, and give strong support to diclofop-methyl and pinoxaden enhanced detoxification as NTS resistance mechanism. BrIFAR can promote better understanding of the evolution of mechanisms of herbicide resistance and aid the implementation of integrative management approaches for sustainable agriculture. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  13. About the value of species diversity in arable weeds for weed management

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    Gerowitt, Bärbel

    2016-02-01

    Full Text Available Arable weeds accompany arable land use – we define them based on their affiliation to ar able systems. They are adapted to such a degree that most of them cannot exist without arable land use. Weeds are part of the total biodiversity on arable fields, as primary producers they are basic for important functions within the ecosystem. This paper elaborates the relevance of species diversity in arable weeds for their management. Arable systems can be regarded for the number of different methods for preventive and direct weed control which are realized. Historical arable land use is roughly divided into three periods, which differ concerning the diversity of weed management and the occurring diversity in weed species. Obviously divers weed management in arable systems and diversity in weed species depend on each other, this is illustrated with a simple abstract picture. Arable systems, which are characterised by simpleness, favor the domination of few species which ensure an effective use of the resources within the ecosystem. One consequence under continuous pressure of an overused tool in weed management is that the genetic diversity within a dominating weed population is exploited to ensure this resource use. Current herbicides represent this tool – the results are herbicide resistant biotypes within the weed populations. Species diversity in arable weeds as a rationale within arable production can assist to prevent this development.

  14. Buva (Conyza bonariensis resistente ao glyphosate na região sul do Brasil Conyza bonariensis biotypes resistant to the glyphosate in southern Brazil

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    L. Vargas

    2007-09-01

    com mecanismo de ação distinto daquele do glyphosate. Entretanto, o biótipo resistente mostra baixa resposta ao herbicida glyphosate, mesmo se este for empregado em doses elevadas, evidenciando ter adquirido resistência a esse produto.Glyphosate is a non-selective herbicide used for over 20 years to control weeds in Rio Grande do Sul. Horseweed (Conyza bonariensis is a common weed in Rio Grande do Sul and traditionally sensitive to glyphosate. However, during the last years, some horseweed plants have not shown significant injury symptoms after treatment with glyphosate, suggesting that they are resistant to this herbicide. Aiming to evaluate the response of a population of horseweed plants to glyphosate, one field and two greenhouse experiments were carried out. The field experiment treatment had increasing rates of glyphosate (0, 360, 720, 1,440, 2,880 and 5,760 g ha-1, and also the herbicides paraquat and 2,4-D as standards. The greenhouse experiments had increasing rates of glyphosate (0, 360, 720, 1,440, 2,880 and 5,760 g ha-1 plus the above listed check herbicides sprayed on biotypes considered resistant and on plants of one susceptible biotype. In the second greenhouse experiment, the treatments were increasing rates of glyphosate (720, 1,440 and 2,880 g ha-1 and herbicides chlorimuron-ethyl, metsulfuron-methyl, 2,4-D, paraquat and diuron + paraquat sprayed on plants of resistant and susceptible biotypes. Horseweed control was accessed at 7, 15 and 30 DAT (days after treatment. Overall results of the field and greenhouse experiments provided evidence that the susceptible biotype is easily controlled by glyphosate and the other tested herbicides. In addition, the results demonstrated that the resistant biotype, as the susceptible biotype, is highly sensitive to herbicides with mode of action that differs from glyphosate. However, the resistant biotype showed low response to glyphosate, even at very high rates, confirming resistance of this horseweed

  15. Resistência de plantas daninhas aos herbicidas Weed resistance to herbicides

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    Pedro J. Christoffoleti

    1994-01-01

    Full Text Available A resistência de plantas daninhas aos herbicidas ocorre em função de um processo evolutivo. O desenvolvimento de biótipos de plantas daninhas resistentes é imposto pela agricultura moderna, através da pressão de seleção causada pelo uso intensivo dos herbicidas. O conhecimento dos mecanismos e fatores que favorecem o aparecimento de biótipos de plantas daninhas resistentes é fundamental para que técnicas de manejo sejam utilizadas no sentido de evitar ou retardar o aparecimento de plantas resistentes em uma área. São poucos os relatos ou citações de literatura no Brasil. Sendo assim, este trabalho de revisão procura relatar os principais avanços e descobertas na área de plantas daninhas resistentes aos herbicidas.Weed herbicide resistance has evolved from weed evolution. The modern agriculture is responsible for this evolution because of the intensive use of herbicides. The knowledge of mechanisms and factors that influence the weed herbicide resistance play an important role in the weed manegement techniques used to avoid or delay herbicide resistance appearence. There are not many report or scientific papers about herbi cide resistance in Brasil. Therefore, this literature review aims to provide information about the main advances and discoveries in the field of weed herbicide resistance.

  16. Competitiveness of ALS inhibitors resistant and susceptible biotypes of Greater Beggarticks (Bidens subalternans Competitividade de biótipos de Picão-Preto (Bidens subalternans Resistente e euscetível aos inibidores da ALS

    Directory of Open Access Journals (Sweden)

    F.P. Lamego

    2011-06-01

    Full Text Available The continuous use of ALS-inhibiting herbicides has led to the evolution of herbicide-resistant weeds worldwide. Greater beggarticks is one of the most troublesome weeds found in the soybean production system in Brazil. Recently, a greater beggarticks biotype that is resistant (R to ALS inhibitors due to Trp574Leu mutation in the ALS gene was identified. Also, the adaptive traits between susceptible (S and R to ALS inhibitors biotypes of greater beggarticks were compared. Specifically, we aimed to: (1 evaluate and compare the relative growth rates (RGR between the biotypes; (2 analyze the seed germination characteristics of R and S biotypes under different temperature conditions; and (3 evaluate their competitive ability in a replacement series study. The experiments were conducted at the University of Arkansas, USA, in 2007 and at Universidade Federal do Rio Grande do Sul (Federal University of Rio Grande do Sul, Brazil, in 2008. Plant proportions for replacement series studies were respectively 100:0, 75:25, 50:50, 25:75 and 0:100, with a total population of 150 plants m-2. There was no difference in RGR between R and S biotypes. The R-biotype germination rate was lower than that of the S biotype. However, at low temperature conditions (15 ºC, the reverse was observed. In general, there is no difference in the competitive ability between R and S greater beggarticks biotypes.O uso contínuo de herbicidas inibidores da ALS tem levado à evolução de plantas daninhas resistentes mundialmente. Picão-preto é uma das mais importantes plantas daninhas no sistema de produção de soja no Brasil. Recentemente, foi identificado um biótipo de picao-preto resistente (R aos inibidores da ALS devido à mutação Trp574Leu no gene ALS. Também, foram comparadas características adaptativas entre biótipos de picao-preto suscetível (S e R aos inibidores da ALS. Especificamente, os objetivos deste trabalho foram: (1 avaliar e comparar o crescimento

  17. Allelopathy—A Tool to Improve the Weed Competitive Ability of Wheat with Herbicide-Resistant Black-Grass (Alopecurus myosuroides Huds.

    Directory of Open Access Journals (Sweden)

    Nils-Ove Bertholdsson

    2012-10-01

    Full Text Available Controlling black-grass in winter wheat production in northern Europe is an increasing problem because of more frequent winter crops and development of herbicide resistance in weeds. Alternative weed management strategies are needed, e.g., use of more competitive cultivars. Factors that increase cultivar competitiveness include early vigor and straw length, but also allelopathy. Therefore, the allelopathic properties of wheat cultivars included in the Swedish national list or in the release pipeline were investigated using a bioassay with herbicide-resistant and herbicide-sensitive black-grass as receiver plants. Wheat-rye translocation lines were also included in this screening to identify possible sources of high allelopathic activity. The bioassay results were followed up in two-year field trials. The results revealed large variations in allelopathic activity between cultivars. Most cultivars showed interference with both herbicide-sensitive and herbicide-resistant black-grass, although the allelopathic effect was lower on the herbicide-resistant biotype. Cultivars with high allelopathic activity gave only half the black-grass biomass of low allelopathic cultivars. Dinaro, a triticale (wheat-rye hybrid cultivar and the new wheat cultivar Nimbus showed the highest allelopathy and inhibition of black-grass growth. Only a few wheat lines with rye chromatin, all or part of a rye chromosome, showed high allelopathy. Use of cultivars with high allelopathic activity can thus be important in integrated weed management of black-grass.

  18. Study on the Efficacy of Some Current Herbicides for Control of Resistant and Susceptible Canarygrass (Phalaris spp. Biotypes to Acetyl CoA Carboxylase (ACCase Inhibitors

    Directory of Open Access Journals (Sweden)

    e Zand

    2011-02-01

    Full Text Available Abstract Two separate greenhouse experiments were conducted in the greenhouse facilities of the Iranian Plant Protection Research Institute, Tehran, to study the efficacy of some herbicides to control of resistant and susceptible P. minor and P. paradoxa biotypes. In each experiment, resistant and susceptible biotypes were treated separately by 19 herbicide treatments. Treatments included 10 ACCase inhibitors, 6 Acetolactate Synthase (ALS inhibitors, prosulfocarb, flamprop-M-isopropyl, isoproturon plus diflufenican and a non-sprayed control. To evaluate the effects of treatments, different characteristics including percent damage based on EWRC scores at 15 and 30 days after spraying, percentage of survived plants after spraying relative to before spraying, and percentage of dry weight and wet weight of individual plants relative to control were studied. Results showed that the susceptible biotypes of P. minor were best controlled by clodinafop propargyl and pinoxaden at 450 ml/ha while pinoxaden at 450 ml/ha and cycloxydim were best options for control of the resistant biotype. Among ALS inhibitors, iodosulfuron plus mesosulfuron could control susceptible and resistant biotypes of P. minor very effectively and semi-satisfactory, respectively. Iodosulfuron plus mesosulfuron and sulfosulfuron plus metsulfuron could remarkably reduce the wet weight of individual plants compared to control so that the plants were not damaging any more. Among other herbicides, isoproturon plus diflufenican could control the susceptible and resistant biotypes semi-satisfactory and very effectively, respectively. Keywords: Herbicide resistance, ACCase inhibitors, ALS inhibitors

  19. Gene expression profiling in the thiamethoxam resistant and susceptible B-biotype sweetpotato whitefly, Bemisia tabaci.

    Science.gov (United States)

    Xie, Wen; Yang, Xin; Wang, Shao-Ii; Wu, Qing-jun; Yang, Ni-na; Li, Ru-mei; Jiao, Xiao-guo; Pan, Hui-peng; Liu, Bai-ming; Feng, Yun-tao; Xu, Bao-yun; Zhou, Xu-guo; Zhang, You-jun

    2012-01-01

    Thiamethoxam has been used as a major insecticide to control the B-biotype sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Due to its excessive use, a high level of resistance to thiamethoxam has developed worldwide over the past several years. To better understand the molecular mechanisms underlying this resistance in B. tabaci, gene profiles between the thiamethoxam-resistant and thiamethoxam-susceptible strains were investigated using the suppression subtractive hybridization (SSH) library approach. A total of 72 and 52 upand down-regulated genes were obtained from the forward and reverse SSH libraries, respectively. These expressed sequence tags (ESTs) belong to several functional categories based on their gene ontology annotation. Some categories such as cell communication, response to abiotic stimulus, lipid particle, and nuclear envelope were identified only in the forward library of thiamethoxam-resistant strains. In contrast, categories such as behavior, cell proliferation, nutrient reservoir activity, sequence-specific DNA binding transcription factor activity, and signal transducer activity were identified solely in the reverse library. To study the validity of the SSH method, 16 differentially expressed genes from both forward and reverse SSH libraries were selected randomly for further analyses using quantitative realtime PCR (qRT-PCR). The qRT-PCR results were fairly consistent with the SSH results; however, only 50% of the genes showed significantly different expression profiles between the thiamethoxam-resistant and thiamethoxam-susceptible whiteflies. Among these genes, a putative NAD-dependent methanol dehydrogenase was substantially over-expressed in the thiamethoxamresistant adults compared to their susceptible counterparts. The distributed profiles show that it was highly expressed during the egg stage, and was most abundant in the abdomen of adult females.

  20. Host plant resistance to parasitic weeds; recent progress and bottlenecks.

    Science.gov (United States)

    Yoder, John I; Scholes, Julie D

    2010-08-01

    Parasitic witchweeds (Striga spp.) and broomrapes (Orobanche and Phelipanche spp.) directly invade the roots of crop plants connecting to the vascular system and abstracting nutrients and water. As a consequence they cause devastating losses in crop yield. Genetic resistance to parasitic weeds is a highly desirable component of any control strategy. Resistance to parasitic plants can occur at different stages of the parasite lifecycle: before attachment to the host, during penetration of the root or after establishment of vascular connections. New studies are beginning to shed light on the molecular mechanisms and signaling pathways involved in plant-plant resistance. The first resistance gene to Striga, encoding a CC-NBS-LRR Resistance protein (R) has been identified and cloned suggesting that host plants resist attack from parasitic plants using similar surveillance mechanisms as those used against fungal and bacterial pathogens. It is becoming clear that the salicylic acid (SA) signaling pathway plays an important role in resistance to parasitic plants and genes encoding pathogenesis-related (PR) proteins are upregulated in a number of the resistant interactions. New strategies for engineering resistance to parasitic plants are also being explored, including the expression of parasite-specific toxins in host roots and RNAi to silence parasite genes crucial for development.

  1. Modeling "habitat suitability" for a herbicide resistant weed using a species distribution model and presence-only data

    Science.gov (United States)

    Herbicide resistant weeds are like invasive weeds: prompt management is needed to prevent their spread. For invasive weeds, first reports of a weed's occurrence are often analyzed with species distribution models (SDM) to prioritize detection and treatment. Suitability of other areas as habitat for ...

  2. Controlling herbicide-resistant weeds: consider incorporating alfalfa in a corn/soybean rotation

    Science.gov (United States)

    Herbicide resistant weeds (HRW) are a serious problem in the U.S. In 1968, the first confirmed case of herbicide resistance in weeds was reported in Washington state. In the 46 years since, the number of HRW in the U.S. has increased dramatically. A major reason for the recent increase in HRW has be...

  3. Mechanism of sulfonylurea herbicide resistance in the broadleaf weed, Kochia scoparia

    Energy Technology Data Exchange (ETDEWEB)

    Saari, L.L.; Cotterman, J.C.; Primiani, M.M. (E.I. duPont de Nemours Co., Inc., Wilmington, DE (USA))

    1990-05-01

    Selection of kochia (Kochia scoparia) biotypes resistant to the sulfonylurea herbicide chlorsulfuron has occurred through the continued use of this herbicide in monoculture cereal-growing areas in the United States. The apparent sulfonylurea resistance observed in kochia was confirmed in greenhouse tests. Fresh and dry weight accumulation in the resistance kochia was 2- to >350-fold higher in the presence of four sulfonylurea herbicides as compared to the susceptible biotype. Acetolactate synthase (ALS) activity isolated from sulfonylurea-resistant kochia was less sensitive to inhibition by three classes of ALS-inhibiting herbicides, sulfonylureas, imidazolinones, and sulfonanilides. The decrease in ALS sensitivity to inhibition (as measured by the ratio of resistant I{sub 50} to susceptible I{sub 50}) was 5- to 28-fold, 2- to 6-fold, and 20-fold for sulfonylurea herbicides, imidazolinone herbicides, and a sulfonanilide herbicide, respectively. No differences were observed in the ALS-specific activities or the rates of ({sup 14}C)chlorsulfuron uptake, translocation, and metabolism between susceptible and resistant kochia biotypes. The K{sub m} values for pyruvate using ALS from susceptible and resistant kochia were 2.13 and 1.74 mM, respectively. Based on these results, the mechanism of sulfonylurea resistance in this kochia biotype is due solely to a less sulfonylurea-sensitive ALS enzyme.

  4. Transgenic glyphosate-resistant oilseed rape (Brassica napus) as an invasive weed in Argentina: detection, characterization, and control alternatives.

    Science.gov (United States)

    Pandolfo, Claudio E; Presotto, Alejandro; Carbonell, Francisco Torres; Ureta, Soledad; Poverene, Mónica; Cantamutto, Miguel

    2016-12-01

    The presence of glyphosate-resistant oilseed rape populations in Argentina was detected and characterized. The resistant plants were found as weeds in RR soybeans and other fields. The immunological and molecular analysis showed that the accessions presented the GT73 transgenic event. The origin of this event was uncertain, as the cultivation of transgenic oilseed rape cultivars is prohibited in Argentina. This finding might suggest that glyphosate resistance could come from unauthorized transgenic oilseed rape crops cultivated in the country or as seed contaminants in imported oilseed rape cultivars or other seed imports. Experimentation showed that there are alternative herbicides for controlling resistant Brassica napus populations in various situations and crops. AHAS-inhibiting herbicides (imazethapyr, chlorimuron and diclosulam), glufosinate, 2,4-D, fluroxypyr and saflufenacil proved to be very effective in controlling these plants. Herbicides evaluated in this research were employed by farmers in one of the fields invaded with this biotype and monitoring of this field showed no evidence of its presence in the following years.

  5. Investigating the Mechanism of Glyphosate Resistance in Rigid Ryegrass (Lolium rigidum)

    Science.gov (United States)

    Glyphosate is a broad-spectrum herbicide that has been used extensively for more than 20 yr. The first glyphosate-resistant weed biotype appeared in 1996; it involved a rigid ryegrass population from Australia that exhibited an LD50 value approximately 10-fold higher than that of sensitive biotypes....

  6. Resistência de plantas daninhas aos herbicidas inibidores da ALS na cultura da soja (Glycine max Weed resistance to ALS - inhibiting herbicides in soybean (Glycine max crop

    Directory of Open Access Journals (Sweden)

    P.A. Monqueiro

    2000-01-01

    .a. ha-1. As curvas de dose-resposta da porcentagem de controle das plantas daninhas aos 14 dias após o tratamento dos biotipos resistentes apresentaram valores inferiores aos das curvas de dose-resposta dos biotipos suscetíveis, mesmo nas doses extremas utilizadas. As taxas de resistência (GR50(resistente/GR50(suscetível para picão-preto foram de 9,90 para chlorimuron-ethyl, 9,07 para nicosulfuron e 27,03 para imazethapyr, enquanto para caruru elas foram de 45,03 para o chlorimuron-ethyl, 181 para o nicosulfuron e 24,55 para o imazethapyr.In the soybean crop, the weeds Bidens pilosa/Bidens subalternans and Amaranthus quitensis are controlled by several herbicides, with the acetolactate synthase (ALS inhibitors being the ones most sprayed by growers. The intensive and repetitive use of these herbicides in soybean areas of São Gabriel do Oeste (Mato Grosso do Sul - Brazil and in the provinces of Córdoba and Tucumã (Argentina have imposed a great selection pressure on the resistant population of these weeds. In order to determine the cross resistance of these biotypes to ALS - inhibiting herbicides (sulfonylureas and imidazolinones, an experiment was conducted under greenhouse conditions at the Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Piracicaba, São Paulo, Brazil. The weeds Bidens pilosa/Bidens subalternans and Amaranthus quitensis, whose seeds were collected from suspected sites of herbicide resistance, were treated by the herbicides chlorimuron-ethyl, imazethapyr and nicosulfuron at several rates, and compared to plants whose seeds were obtained from susceptible populations. The treatments were established considering rates giving, at least, 50% of control (GR50, using multiples of the recommended rates. Chlorimuron-ethyl was sprayed at 1500, 750, 150, 75, 15, 7.5, 1.5 g a.i. ha-1, imazethapyr at 8000, 4000, 800, 400, 80, 40, 8 g a.i. ha-1 and nicosulfuron at 1.200, 600, 120, 60, 12, 6, 1.2 g a.i. ha-1. The resistant biotype

  7. Metabolic Profiling and Enzyme Analyses Indicate a Potential Role of Antioxidant Systems in Complementing Glyphosate Resistance in an Amaranthus palmeri Biotype.

    Science.gov (United States)

    Maroli, Amith S; Nandula, Vijay K; Dayan, Franck E; Duke, Stephen O; Gerard, Patrick; Tharayil, Nishanth

    2015-10-21

    Metabolomics and biochemical assays were employed to identify physiological perturbations induced by a commercial formulation of glyphosate in susceptible (S) and resistant (R) biotypes of Amaranthus palmeri. At 8 h after treatment (HAT), compared to the respective water-treated control, cellular metabolism of both biotypes were similarly perturbed by glyphosate, resulting in abundance of most metabolites including shikimic acid, amino acids, organic acids and sugars. However, by 80 HAT the metabolite pool of glyphosate-treated R-biotype was similar to that of the control S- and R-biotypes, indicating a potential physiological recovery. Furthermore, the glyphosate-treated R-biotype had lower reactive oxygen species (ROS) damage, higher ROS scavenging activity, and higher levels of potential antioxidant compounds derived from the phenylpropanoid pathway. Thus, metabolomics, in conjunction with biochemical assays, indicate that glyphosate-induced metabolic perturbations are not limited to the shikimate pathway, and the oxidant quenching efficiency could potentially complement the glyphosate resistance in this R-biotype.

  8. New weed control strategies in maize considering narrow crop rotations with maize, greater ALSresistance in common weeds and application restrictions with regard to active substance

    Directory of Open Access Journals (Sweden)

    Ewert, Katrin

    2014-02-01

    Full Text Available Many herbicides with different HRAC-groups are available for weed control in maize. Because of narrow maize crop rotation summer weeds and warmth loving weeds are encouraged. On the other hand the new confirmed cases of an ALS target site resistance in the weed species Echinochloa crus-galli and Amaranthus retroflexus in Brandenburg, Stellaria media in Saxony and Matricaria recutita and Tripleurospermum perforatum in Brandenburg and Thuringia, warn that in the future the sulfonylureas must be used only according to the management of herbicide resistance. In this way the selection of resistant weed biotypes will be prevented. Moreover in protected water areas it may be a requirement to reduce and to substitute the input of some active substances, for example terbuthylazine and bentazon. The control of E. crus-galli and P. convolvulus with non-sulfonylurea or/and non-terbuthylazine herbicides according to management of herbicide resistance will be discussed.

  9. Resistência de amendoim - bravo aos herbicidas inibidores da enzima ALS Resistance of the weed wild poinsettia to ALS inhibitor herbicides

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    Dionisio L. P. Gazziero

    1998-12-01

    lactofen, que apresentam mecanismo de ação diferente da inibição da enzima ALS, ocorreu alto índice de controle de ambos os biótipos de amendoim-bravo avaliados, principalmente, nas maiores doses, provando a não existência de resistência múltipla nesse biótipo de amendoim-bravo estudado.One of the most efficient methods of weed control in agriculture is the use of selective herbicides. However, repetitive use of the same herbicide or herbicides having the same mechanism of action, has led to the appearance of weed biotypes which have developed resistance. Thus, an experiment was carried out at Embrapa Soja, in Londrina, Paraná State, Brazil, in order to confirm whether or not there has been resistance of the weed E. heterophylla to the ALS inhibitor herbicides which had been sprayed for several years in a soybean field where the grower has observed failure of the weed control by the ALS inhibitor herbicides. The suspected resistant plants (E-298 from Cafelândia county, Paraná, Brazil, were treated with various doses of several herbicides, compared to a known susceptible biotype. The herbicides and its doses were cloransulan 0,0; 0,015; 0,03; 0,06; 0,12; 0,24 kg a.i./ha, plus Agral 0,2% v/v, imazetaphapyr 0,0; 0,05; 0,1; 0,2; 0,4 e 0,8 kg a.i./ha, imazaquin 0,0; 0,075; 0,15; 0,3; 0,6; 1,2 kg a.i./ha, plus Assist 0,3% v/v, sulfentrazone 0,0; 0,3; 0,6; 1,2; 2,4; 4,8 kg a.i./ha, plus Assist 0,3% v/v and lactofen 0,0; 0,082; 0,165; 0,33; 0,664; 1,329 kg a.i./ha.The results indicated different patterns of cross resistance to cloransulan, imazethapyr and imazaquin; and the GR50 ratios were 97.74; 11.90 and 10.86, respectively. The dose response curves of the resistant biotype presented lower values than the susceptible biotype in all the studied rates for the herbicides cloransulan, imazethapyr and imazaquin. On the other hand, there was no difference in the control between the resistant and susceptible biotypes when sulfentrazone and lactofen were sprayed. It was

  10. Management Options and Factors Affecting Control of a Common Waterhemp (Amaranthus rudis Biotype Resistant to Protoporphyrinogen Oxidase-Inhibiting Herbicides

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    Dana B. Harder

    2012-01-01

    Full Text Available Repeated use of protox-inhibiting herbicides has resulted in a common waterhemp (Amaranthus rudis Sauer biotype that survived lactofen applied up to 10 times the labeled rate. Field and greenhouse research evaluated control options for this biotype of common waterhemp. In the field, PRE applications of flumioxazin at 72 g ai ha−1, sulfentrazone at 240 g ai ha−1, and isoxaflutole at 70 g ai ha−1 controlled common waterhemp >90% up to 6 weeks after treatment. POST applications of fomesafen at 330 g ai ha−1, lactofen at 220 g ai ha−1, and acifluorfen at 420 g ai ha−1 resulted in <60% visual control of common waterhemp, but differences were detected among herbicides. In the greenhouse, glyphosate was the only herbicide that controlled protox resistant waterhemp. The majority of herbicide activity from POST flumioxazin, fomesafen, acifluorfen, and lactofen was from foliar placement, but control was less than 40% regardless of placement. Control of common waterhemp seeded at weekly intervals after herbicide treatment with flumioxazin, fomesafen, sulfentrazone, atrazine, and isoxaflutole exceeded 85% at 0 weeks after herbicide application (WAHA, while control with isoxaflutole was greater than 60% 6 WAHA. PRE and POST options for protox-resistant common waterhemp are available to manage herbicide resistance.

  11. Herbicide-resistant weeds: from research and knowledge to future needs.

    Science.gov (United States)

    Busi, Roberto; Vila-Aiub, Martin M; Beckie, Hugh J; Gaines, Todd A; Goggin, Danica E; Kaundun, Shiv S; Lacoste, Myrtille; Neve, Paul; Nissen, Scott J; Norsworthy, Jason K; Renton, Michael; Shaner, Dale L; Tranel, Patrick J; Wright, Terry; Yu, Qin; Powles, Stephen B

    2013-12-01

    Synthetic herbicides have been used globally to control weeds in major field crops. This has imposed a strong selection for any trait that enables plant populations to survive and reproduce in the presence of the herbicide. Herbicide resistance in weeds must be minimized because it is a major limiting factor to food security in global agriculture. This represents a huge challenge that will require great research efforts to develop control strategies as alternatives to the dominant and almost exclusive practice of weed control by herbicides. Weed scientists, plant ecologists and evolutionary biologists should join forces and work towards an improved and more integrated understanding of resistance across all scales. This approach will likely facilitate the design of innovative solutions to the global herbicide resistance challenge.

  12. Glyphosate-resistant weeds of South American cropping systems: an overview.

    Science.gov (United States)

    Vila-Aiub, Martin M; Vidal, Ribas A; Balbi, Maria C; Gundel, Pedro E; Trucco, Frederico; Ghersa, Claudio M

    2008-04-01

    Herbicide resistance is an evolutionary event resulting from intense herbicide selection over genetically diverse weed populations. In South America, orchard, cereal and legume cropping systems show a strong dependence on glyphosate to control weeds. The goal of this report is to review the current knowledge on cases of evolved glyphosate-resistant weeds in South American agriculture. The first reports of glyphosate resistance include populations of highly diverse taxa (Lolium multiflorum Lam., Conyza bonariensis L., C. canadensis L.). In all instances, resistance evolution followed intense glyphosate use in fruit fields of Chile and Brazil. In fruit orchards from Colombia, Parthenium hysterophorus L. has shown the ability to withstand high glyphosate rates. The recent appearance of glyphosate-resistant Sorghum halepense L. and Euphorbia heterophylla L. in glyphosate-resistant soybean fields of Argentina and Brazil, respectively, is of major concern. The evolution of glyphosate resistance has clearly taken place in those agroecosystems where glyphosate exerts a strong and continuous selection pressure on weeds. The massive adoption of no-till practices together with the utilization of glyphosate-resistant soybean crops are factors encouraging increase in glyphosate use. This phenomenon has been more evident in Argentina and Brazil. The exclusive reliance on glyphosate as the main tool for weed management results in agroecosystems biologically more prone to glyphosate resistance evolution.

  13. Weed response to herbicides: regional-scale distribution of herbicide resistance alleles in the grass weed Alopecurus myosuroides.

    Science.gov (United States)

    Menchari, Yosra; Camilleri, Christine; Michel, Séverine; Brunel, Dominique; Dessaint, Fabrice; Le Corre, Valérie; Délye, Christophe

    2006-01-01

    Effective herbicide resistance management requires an assessment of the range of spatial dispersion of resistance genes among weed populations and identification of the vectors of this dispersion. In the grass weed Alopecurus myosuroides (black-grass), seven alleles of the acetyl-CoA carboxylase (ACCase) gene are known to confer herbicide resistance. Here, we assessed their respective frequencies and spatial distribution on two nested geographical scales (the whole of France and the French administrative district of Côte d'Or) by genotyping 13 151 plants originating from 243 fields. Genetic variation in ACCase was structured in local populations at both geographical scales. No spatial structure in the distribution of resistant ACCase alleles and no isolation by distance were detected at either geographical scale investigated. These data, together with ACCase sequencing and data from the literature, suggest that evolution of A. myosuroides resistance to herbicides occurred at the level of the field or group of adjacent fields by multiple, independent appearances of mutant ACCase alleles that seem to have rather restricted spatial propagation. Seed transportation by farm machinery seems the most likely vector for resistance gene dispersal in A. myosuroides.

  14. Emerging Challenges and Opportunities for Education and Research in Weed Science.

    Science.gov (United States)

    Chauhan, Bhagirath S; Matloob, Amar; Mahajan, Gulshan; Aslam, Farhena; Florentine, Singarayer K; Jha, Prashant

    2017-01-01

    In modern agriculture, with more emphasis on high input systems, weed problems are likely to increase and become more complex. With heightened awareness of adverse effects of herbicide residues on human health and environment and the evolution of herbicide-resistant weed biotypes, a significant focus within weed science has now shifted to the development of eco-friendly technologies with reduced reliance on herbicides. Further, with the large-scale adoption of herbicide-resistant crops, and uncertain climatic optima under climate change, the problems for weed science have become multi-faceted. To handle these complex weed problems, a holistic line of action with multi-disciplinary approaches is required, including adjustments to technology, management practices, and legislation. Improved knowledge of weed ecology, biology, genetics, and molecular biology is essential for developing sustainable weed control practices. Additionally, judicious use of advanced technologies, such as site-specific weed management systems and decision support modeling, will play a significant role in reducing costs associated with weed control. Further, effective linkages between farmers and weed researchers will be necessary to facilitate the adoption of technological developments. To meet these challenges, priorities in research need to be determined and the education system for weed science needs to be reoriented. In respect of the latter imperative, closer collaboration between weed scientists and other disciplines can help in defining and solving the complex weed management challenges of the 21st century. This consensus will provide more versatile and diverse approaches to innovative teaching and training practices, which will be needed to prepare future weed science graduates who are capable of handling the anticipated challenges of weed science facing in contemporary agriculture. To build this capacity, mobilizing additional funding for both weed research and weed management

  15. Complete sequence of three different biotypes of tomato spotted wilt virus (wild type, tomato Sw-5 resistance-breaking and pepper Tsw resistance-breaking) from Spain.

    Science.gov (United States)

    Debreczeni, Diana E; López, Carmelo; Aramburu, José; Darós, José Antonio; Soler, Salvador; Galipienso, Luis; Falk, Bryce W; Rubio, Luis

    2015-08-01

    Tomato spotted wilt virus (TSWV) occurs worldwide and causes production losses in many important horticultural crops such as tomato and pepper. Breeding resistant cultivars has been the most successful method so far for TSWV disease control, but only two genes have been found to confer resistance against a wide spectrum of TSWV isolates: Sw-5 in tomato and Tsw in pepper. However, TSWV resistance-breaking isolates have emerged in different countries a few years after using resistant cultivars. In this paper, we report the first complete nucleotide sequences of three Spanish TSWV isolates with different biotypes according to their abilities to overcome resistance: LL-N.05 (wild type, WT), Pujol1TL3 (Sw-5 resistance breaking, SBR) and PVR (Tsw resistance-breaking, TBR). The genome of these TSWV isolates consisted of three segments: L (8913-8914 nt), M (4752-4825 nt) and (S 2924-2961 nt). Variations in nucleotide sequences and genomic RNA lengths among the different virus biotypes are reported here. Phylogenetic analysis of the five TSWV open reading frames showed evidence of reassortment between genomic segments of LL-N.05 and Pujol1TL3, which was supported by analysis with different recombination-detecting algorithms.

  16. Herbicidas alternativos para controle de biótipos de Conyza bonariensis e C. canadensis resistentes ao glyphosate Alternative herbicides to control glyphosate-resistant biotypes of Conyza bonariensis and C. canadensis

    Directory of Open Access Journals (Sweden)

    M.S. Moreira

    2010-01-01

    Full Text Available Após sucessivos anos, aplicações do herbicida glyphosate em pomares de citros no Estado de São Paulo selecionaram biótipos resistentes de Conyza bonariensis e C. canadensis. Na ocorrência de plantas daninhas resistentes em uma área agrícola, tornam-se necessárias mudanças nas práticas de manejo para obtenção de adequado controle das populações resistentes, bem como para a redução da pressão de seleção sobre outras espécies. Assim, este trabalho foi realizado com o objetivo de identificar herbicidas alternativos para controle de biótipos de Conyza spp. resistentes ao herbicida glyphosate, com aplicações em diferentes estádios fenológicos da planta daninha. Três experimentos foram conduzidos em campo, em pomares de citros em formação, sobre plantas de buva em estádio fenológico de dez folhas e no pré-florescimento. Para plantas no estádio de dez folhas, controle satisfatório foi obtido com aplicações de glyphosate + bromacil + diuron (1.440 + 1.200 + 1.200 g ha-1, glyphosate + atrazina (1.440 + 1.500 g ha-1 e glyphosate + diuron (1.440 + 1.500 g ha-1. Quando em estádio de pré-florescimento de Conyza spp., a aplicação do herbicida amônio-glufosinato, na dose de 400 g ha-1, isolado ou associado a MSMA, bromacil+diuron, metsulfuron, carfentrazone e paraquat, foi a alternativa viável para controle dos biótipos resistentes ao glyphosate.After successive years, glyphosate applications on São Paulo-Brazil citrus orchards selected resistant biotypes of Conyza bonariensis and C. canadensis. The occurrence of herbicide-resistant weed biotypes at some agricultural area makes it necessary to change the management practices to reach effective control of the selected resistant populations, as well as to reduce selection pressure on the other species. Thus, this work aimed to identify the alternative herbicides to control glyphosate-resistant biotypes of Conyza spp., with applications at different weed phenological

  17. Metabolic profiling and enzyme analyses indicate a potential role of antioxidant systems in complementing glyphosate resistance in an Amaranthus palmeri biotype

    Science.gov (United States)

    Targeted metabolomic profiling and biochemical assays were employed to identify metabolite-level perturbations induced by glyphosate in susceptible (S) and resistant (R) biotypes of Amaranthus palmeri. Plants were treated with 0.4 kg ae ha-1 glyphosate and tissues were harvested at 8 and 72 hours af...

  18. What do farmers' weed control decisions imply about glyphosate resistance? Evidence from surveys of US corn fields.

    Science.gov (United States)

    Wechsler, Seth J; McFadden, Jonathan R; Smith, David J

    2017-04-26

    The first case of glyphosate-resistant weeds in the United States was documented in 1998, 2 years after the commercialization of genetically engineered herbicide-resistant (HR) corn and soybeans. Currently, over 15 glyphosate-resistant weed species affect US crop production areas. These weeds have the potential to reduce yields, increase costs, and lower farm profitability. The objective of our study is to develop a behavioral model of farmers' weed management decisions and use it to analyze weed resistance to glyphosate in US corn farms. On average, we find that weed control increased US corn yields by 3700 kg ha(-1) (worth approximately $US 255 ha(-1) ) in 2005 and 3500 kg ha(-1) (worth approximately $US 575 ha(-1) ) in 2010. If glyphosate resistant weeds were absent, glyphosate killed approximately 99% of weeds, on average, when applied at the label rate in HR production systems. Average control was dramatically lower in states where glyphosate resistance was widespread. We find that glyphosate resistance had a significant impact on weed control costs and corn yields of US farmers in 2005 and 2010. Published 2017. This article is a U.S. Government work and is in the public domain in the USA. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

  19. Identificação de biótipos de azevém (Lolium multiflorum resistentes ao herbicida glyphosate em pomares de maçã Identification of glyphosate-resistant ryegrass (Lolium multiflorum biotypes in apple orchards

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    L. Vargas

    2004-12-01

    geral, evidenciam que o biótipo sensível é facilmente controlado com o herbicida glyphosate e pelos demais herbicidas pós-emergentes avaliados, independentemente do estádio vegetativo. Demonstram, ainda, que o biótipo resistente apresenta-se, igualmente ao biótipo sensível, altamente suscetível aos herbicidas com mecanismo de ação distinto daquele do glyphosate. No entanto, o biótipo resistente apresenta baixa resposta ao herbicida glyphosate, mesmo se este for empregado em altas doses, evidenciando ter adquirido resistência a esse produto.Glyphosate is a wide spectrum herbicide used for over 15 years in apple orchards in Vacaria-RS for weed control in rows of trees. Usually, 3 to 4 applications per year are made at a rate of 720 to 1080 g a.e. glyphosate ha-1 (2 to 3 L ha-1 of commercial product. Ryegrass (Lolium multiflorum is a common weed in orchards and traditionally sensitive to glyphosate. However, in the last years, some ryegrass plants have not been found to show significant toxicity symptoms after treatment with glyphosate, suggesting that they acquired resistance to this product. To evaluate the response of a ryegrass plant population to glyphosate, one field and two greenhouse experiments were carried out. The field experiment treatments had increasing rates of glyphosate (0; 360; 720; 1,440; 2,880; 5,760 and 11,520 g a.e. ha-1, in addition to the herbicides paraquat, glufosinate-ammonium, haloxyfop and diclofop-methyl as standards, sprayed at two different vegetative growth stages of ryegrass. The greenhouse experiments had increasing rates of glyphosate (0; 360; 720; 1,440; 2,880 and 5,760 g a.e. ha-1 plus the above listed check herbicides sprayed on biotypes considered resistant and on plants of one susceptible biotype. In the second greenhouse experiment, glyphosate rates (720; 1,440; 2,880; 720 + 720 and 720 + 1,440 g a.e. ha-1 were sprayed in single and sequential applications, in addition to the herbicides paraquat, glufosinate

  20. Resistência de biótipos de Euphorbia heterophylla l. Aos herbicidas inibidores da enzima ALS utilizados na cultura de soja Resistance of Euphorbia heterophylla l. Biotypes to ALS enzyme inhibitor herbicides used in soybean crop

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    GERSON AUGUSTO GELMINI

    2001-01-01

    Full Text Available Os herbicidas constituem-se na principal medida de controle de plantas daninhas na cultura de soja; no entanto, a pressão de seleção causada pelo uso contínuo de produtos com o mesmo mecanismo de ação pode provocar a seleção de biótipos resistentes, como ocorreu com Euphorbia heterophylla L., que se mostrou resistente aos herbicidas inibidores da enzima acetolactato sintase (ALS em áreas dos Estados do Paraná e Rio Grande do Sul. Para comprovar possíveis novos casos, bem como alternativas para prevenção e manejo, coletaram-se sementes de plantas de E. heterophylla L., na região de Assis (SP, que sobreviveram a tratamentos, em que esses herbicidas foram sistematicamente aplicados nos últimos anos. Desenvolveu-se o experimento em casa de vegetação, comparando-se o biótipo resistente ao suscetível, quando submetido aos diversos herbicidas aplicados em pós-emergência. Aplicaram-se quando as plantas encontravam-se no estádio de duas a quatro folhas verdadeiras, nas doses zero, uma, duas, quatro e oito vezes a recomendada. Aos 20 dias após a aplicação, avaliaram-se os parâmetros relativos ao controle e produção de fitomassa epígea visando ao estabelecimento de curvas de doses-resposta, à obtenção dos fatores de resistência com base nos valores da DL50 e GR50, e à verificação da ocorrência de resistência múltipla. O biótipo resistente apresentou diferentes níveis de resistência aos herbicidas chlorimuron-ethyl e imazethapyr, demonstrando resistência cruzada aos inibidores da ALS dos grupos das sulfoniluréias e imidazolinonas. No entanto, foi eficientemente controlado nos tratamentos com fomesafen (250 g.ha-1, lactofen (120 g.ha-1, flumiclorac-pentil (40 g.ha-1, glufosinato de amônio (150 g.ha-1 e glyphosate (360 g.ha-1.Herbicides are the main tool for weed control in soybean crop, but the selection pressure attributed to the repeated application of the same herbicides and the same mechanism of action can

  1. Changing trends in the prevalence of Shigella species: emergence of multi-drug resistant Shigella sonnei biotype g in Bangladesh.

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    Abu I M S Ud-Din

    Full Text Available Shigellosis, caused by Shigella species, is a major public health problem in Bangladesh. To determine the prevalence and distribution of different Shigella species, we analyzed 10,827 Shigella isolates from patients between 2001 and 2011. S. flexneri was the predominant species isolated throughout the period. However, the prevalence of S. flexneri decreased from 65.7% in 2001 to 47% in 2011, whereas the prevalence of S. sonnei increased from 7.2% in 2001 to 25% in 2011. S. boydii and S. dysenteriae accounted for 17.3% and 7.7% of the isolates respectively throughout the period. Of 200 randomly selected S. sonnei isolates for extensive characterization, biotype g strains were predominant (95% followed by biotype a (5%. Resistance to commonly used antibiotics including trimethoprim-sulfamethoxazole, nalidixic acid, ciprofloxacin, mecillinam and ampicillin was 89.5%, 86.5%, 17%, 10.5%, and 9.5%, respectively. All isolates were susceptible to ceftriaxone, cefotaxime, ceftazidime and imipenem. Ninety-eight percent of the strains had integrons belonging to class 1, 2 or both. The class 1 integron contained only dfrA5 gene, whereas among class 2 integron, 16% contained dhfrAI-sat1-aadA1-orfX gene cassettes and 84% harbored dhfrA1-sat2 gene cassettes. Plasmids of ∼5, ∼1.8 and ∼1.4 MDa in size were found in 92% of the strains, whereas only 33% of the strains carried the 120 MDa plasmid. PFGE analysis showed that strains having different integron patterns belonged to different clusters. These results show a changing trend in the prevalence of Shigella species with the emergence of multidrug resistant S. sonnei. Although S. flexneri continues to be the predominant species albeit with reduced prevalence, S. sonnei has emerged as the second most prevalent species replacing the earlier dominance by S. boydii and S. dysenteriae in Bangladesh.

  2. Changing Trends in the Prevalence of Shigella Species: Emergence of Multi-Drug Resistant Shigella sonnei Biotype g in Bangladesh

    Science.gov (United States)

    Ud-Din, Abu I. M. S.; Wahid, Syeda U. H.; Latif, Hasan A.; Shahnaij, Mohammad; Akter, Mahmuda; Azmi, Ishrat J.; Hasan, Trisheeta N.; Ahmed, Dilruba; Hossain, Mohammad A.; Faruque, Abu S. G.; Faruque, Shah M.; Talukder, Kaisar A.

    2013-01-01

    Shigellosis, caused by Shigella species, is a major public health problem in Bangladesh. To determine the prevalence and distribution of different Shigella species, we analyzed 10,827 Shigella isolates from patients between 2001 and 2011. S. flexneri was the predominant species isolated throughout the period. However, the prevalence of S. flexneri decreased from 65.7% in 2001 to 47% in 2011, whereas the prevalence of S. sonnei increased from 7.2% in 2001 to 25% in 2011. S. boydii and S. dysenteriae accounted for 17.3% and 7.7% of the isolates respectively throughout the period. Of 200 randomly selected S. sonnei isolates for extensive characterization, biotype g strains were predominant (95%) followed by biotype a (5%). Resistance to commonly used antibiotics including trimethoprim-sulfamethoxazole, nalidixic acid, ciprofloxacin, mecillinam and ampicillin was 89.5%, 86.5%, 17%, 10.5%, and 9.5%, respectively. All isolates were susceptible to ceftriaxone, cefotaxime, ceftazidime and imipenem. Ninety-eight percent of the strains had integrons belonging to class 1, 2 or both. The class 1 integron contained only dfrA5 gene, whereas among class 2 integron, 16% contained dhfrAI-sat1-aadA1-orfX gene cassettes and 84% harbored dhfrA1-sat2 gene cassettes. Plasmids of ∼5, ∼1.8 and ∼1.4 MDa in size were found in 92% of the strains, whereas only 33% of the strains carried the 120 MDa plasmid. PFGE analysis showed that strains having different integron patterns belonged to different clusters. These results show a changing trend in the prevalence of Shigella species with the emergence of multidrug resistant S. sonnei. Although S. flexneri continues to be the predominant species albeit with reduced prevalence, S. sonnei has emerged as the second most prevalent species replacing the earlier dominance by S. boydii and S. dysenteriae in Bangladesh. PMID:24367527

  3. Benchmark study on glyphosate-resistant cropping systems in the United States. Part 7: Effects of weed management strategy (grower practices versus academic recommendations) on the weed soil seedbank over 6 years.

    Science.gov (United States)

    Gibson, David J; Young, Bryan G; Owen, Micheal D K; Gage, Karla L; Matthews, Joseph L; Jordan, David L; Shaw, David R; Weller, Stephen C; Wilson, Robert G

    2016-04-01

    Shifts in weed species composition and richness resulting from near-exclusive reliance on herbicides in glyphosate-resistant (GR) cropping systems has necessitated the implementation of alternative weed management tactics to reduce selection pressures of herbicides. We contrasted the response of the weed soil seedbank to effects of weed management strategy, comparing grower practices with academic recommendations for best management practices (BMPs) over 6 years and across five weed hardiness zones in the US Midwest at sites subject to GR cropping systems. Total weed population density and species richness varied according to cropping system, location and prior year's crop, but less so to weed management strategy. The seedbank population density for 11 of the 14 most frequent weed species was affected by weed management strategy either alone or in an interaction with hardiness zone or year, or both. In only 29% of comparisons was weed population density lower following academic recommendations, and this depended upon prior crop and cropping system. The population density of high-risk weed species was reduced by academic recommendations, but only in two of six years and under continuous GR maize. Overall, the weed population density was decreasing in field halves subject to the BMPs in the academic recommendations relative to grower practices. The soil seedbank is slow to respond to academic recommendations to mitigate glyphosate-resistant weeds, but represents a biological legacy that growers need to keep in mind even when management practices reduce emerged field weed population densities. © 2015 Society of Chemical Industry.

  4. Benchmark study on glyphosate-resistant cropping systems in the United States. Part 6: Timeliness of economic decision-making in implementing weed resistance management strategies.

    Science.gov (United States)

    Weirich, Jason W; Shaw, David R; Coble, Keith H; Owen, Micheal D K; Dixon, Philip M; Weller, Stephen C; Young, Bryan G; Wilson, Robert G; Jordan, David L

    2011-07-01

    The introduction of glyphosate-resistant (GR) crops in the late 1990s made weed control in maize, cotton and soybean simple. With the rapid adoption of GR crops, many growers began to rely solely on glyphosate for weed control. This eventually led to the evolution of GR weeds. Growers are often reluctant to adopt a weed resistance best management practice (BMP) because of the added cost of additional herbicides to weed control programs which would reduce short-term revenue. This study was designed to evaluate when a grower that is risk neutral (profit maximizing) or risk averse should adopt a weed resistance BMP. Whether a grower is risk neutral or risk averse, the optimal decision would be to adopt a weed resistance BMP when the expected loss in revenue is greater than 30% and the probability of resistance evolution is 0.1 or greater. However, if the probability of developing resistance increases to 0.3, then the best decision would be to adopt a weed resistance BMP when the expected loss is 10% or greater. Given the scenarios analyzed, risk-neutral or risk-averse growers should implement a weed resistance BMP with confidence that they have made the right decision economically and avoided the risk of lost revenue from resistance. If the grower wants to continue to see the same level of return, adoption of BMP is required. Copyright © 2011 Society of Chemical Industry.

  5. Climate change increases the risk of herbicide-resistant weeds due to enhanced detoxification.

    Science.gov (United States)

    Matzrafi, Maor; Seiwert, Bettina; Reemtsma, Thorsten; Rubin, Baruch; Peleg, Zvi

    2016-12-01

    Global warming will increase the incidence of metabolism-based reduced herbicide efficacy on weeds and, therefore, the risk for evolution of non-target site herbicide resistance. Climate changes affect food security both directly and indirectly. Weeds are the major biotic factor limiting crop production worldwide, and herbicides are the most cost-effective way for weed management. Processes associated with climatic changes, such as elevated temperatures, can strongly affect weed control efficiency. Responses of several grass weed populations to herbicides that inhibit acetyl-CoA carboxylase (ACCase) were examined under different temperature regimes. We characterized the mechanism of temperature-dependent sensitivity and the kinetics of pinoxaden detoxification. The products of pinoxaden detoxification were quantified. Decreased sensitivity to ACCase inhibitors was observed under elevated temperatures. Pre-treatment with the cytochrome-P450 inhibitor malathion supports a non-target site metabolism-based mechanism of herbicide resistance. The first 48 h after herbicide application were crucial for pinoxaden detoxification. The levels of the inactive glucose-conjugated pinoxaden product (M5) were found significantly higher under high- than low-temperature regime. Under high temperature, a rapid elevation in the level of the intermediate metabolite (M4) was found only in pinoxaden-resistant plants. Our results highlight the quantitative nature of non-target-site resistance. To the best of our knowledge, this is the first experimental evidence for temperature-dependent herbicide sensitivity based on metabolic detoxification. These findings suggest an increased risk for the evolution of herbicide-resistant weeds under predicted climatic conditions.

  6. Curvas de dose-resposta de biótipos resistente e suscetível de Bidens pilosa L. aos herbicidas inibidores da ALS Rate-response curves of resistant and susceptible Bidens pilosa L. biotypes to ALS-inhibitor herbicides

    Directory of Open Access Journals (Sweden)

    Pedro Jacob Christoffoleti

    2002-09-01

    phenomenon. In this regard, experiments aiming to build rate-response curves comparing a resistant (R and a susceptible (S biotype of the weed Bidens pilosa L., to ALS inhibitor herbicides, were set up. At the stage of three to four leaves, biotypes R and S of B. pilosa were sprayed with the herbicides chlorymuron-ethyl, metsulfuron-methyl, nicosulfuron and imazethapyr, at multiples of 0.0; 0.001, 0.01, 0.1; 1.0; 10; 100 and 1,000 of the recommended field rates. Results lead to the building of percentage control rate-response curves. The ratio between the C50 of the resistant biotype, divided by the C50 of the susceptible biotype, were 40.92; 173.84; 57.47 and 57.16 for the herbicides chlorymuron-ethyl, nicosulfuron, metsulfuron-methyl and imazethapyr, respectively. The R biotype of B. pilosa had a high degree of resistance in relation to all ALS inhibitor herbicides studied, being also cross resistant to imidazolinone and sulfonylurea.

  7. Resistência ao glyphosate em biótipos de Conyza bonariensis e Conyza canadensis no Estado do Rio Grande do Sul, Brasil Resistance to glyphosate in Conyza bonariensis and Conyza canadensis biotypes in Rio Grande do Sul, Brazil

    Directory of Open Access Journals (Sweden)

    F.P. Lamego

    2008-06-01

    Full Text Available Experimentos de curva de dose-resposta foram conduzidos para avaliar a ocorrência de resistência ao glyphosate em biótipos de Conyza canadensis e Conyza bonariensis oriundos de municípios do Rio Grande do Sul. Para cada espécie foi realizado um experimento com dois biótipos um suscetível e outro com suspeita de resistência. Glyphosate nas doses de 0, 100, 200, 300, 400, 800 e 1.200 g ha-1 foi aplicado em plantas no estádio de 8-10 folhas. Curvas sigmoidais foram ajustadas para todos os biótipos testados. Confirmou-se a resistência ao glyphosate em biótipos de ambas as espécies, com fator de resistência em torno de 2,3.Dose-response experiments were conducted to evaluate the occurrence of resistance to glyphosate in Conyza canadensis and Conyza bonariensis biotypes originated from Rio Grande do Sul counties. For each species, one experiment was conducted with two biotypes, one susceptible and one suspected of resistance. Glyphosate rates of 0, 100, 200, 300, 400, 800 and 1200 g ha-1 were sprayed on the plants after reaching the 8-10 leaf growth stage. Sigmoidal curves were adjusted to each biotype tested. Resistance to glyphosate was confirmed for biotypes of both species with resistance factor of 2.3.

  8. Glyphosate Resistance of C3 and C4 Weeds under Rising Atmospheric CO2.

    Science.gov (United States)

    Fernando, Nimesha; Manalil, Sudheesh; Florentine, Singarayer K; Chauhan, Bhagirath S; Seneweera, Saman

    2016-01-01

    The present paper reviews current knowledge on how changes of plant metabolism under elevated CO2 concentrations (e[CO2]) can affect the development of the glyphosate resistance of C3 and C4 weeds. Among the chemical herbicides, glyphosate, which is a non-selective and post-emergence herbicide, is currently the most widely used herbicide in global agriculture. As a consequence, glyphosate resistant weeds, particularly in major field crops, are a widespread problem and are becoming a significant challenge to future global food production. Of particular interest here it is known that the biochemical processes involved in photosynthetic pathways of C3 and C4 plants are different, which may have relevance to their competitive development under changing environmental conditions. It has already been shown that plant anatomical, morphological, and physiological changes under e[CO2] can be different, based on (i) the plant's functional group, (ii) the available soil nutrients, and (iii) the governing water status. In this respect, C3 species are likely to have a major developmental advantage under a CO2 rich atmosphere, by being able to capitalize on the overall stimulatory effect of e[CO2]. For example, many tropical weed grass species fix CO2 from the atmosphere via the C4 photosynthetic pathway, which is a complex anatomical and biochemical variant of the C3 pathway. Thus, based on our current knowledge of CO2 fixing, it would appear obvious that the development of a glyphosate-resistant mechanism would be easier under an e[CO2] in C3 weeds which have a simpler photosynthetic pathway, than for C4 weeds. However, notwithstanding this logical argument, a better understanding of the biochemical, genetic, and molecular measures by which plants develop glyphosate resistance and how e[CO2] affects these measures will be important before attempting to innovate sustainable technology to manage the glyphosate-resistant evolution of weeds under e[CO2]. Such information will be of

  9. Resistance induction in chrysanthemum due to silicon application in the management of whitefly Bemisia tabaci Biotype B (Hemiptera: Aleyrodidae

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    Bruno Almeida Melo

    2015-12-01

    Full Text Available Whitefly Bemisia tabaci biotype B (Hemiptera: Aleyrodidae is a key pest in many cultures worldwide, among them chrysanthemum. The aim of this study was to evaluate whether silicon application in chrysanthemum plants can induce resistance to whitefly. The experiments were conducted in chrysanthemum cv. Rage in a greenhouse at EPAMIG in São João Del Rei, MG. The treatments were: 1 silicon applied as soil drench (dosage of 2t SiO2/ha on the 4th day after planting, 2 two silicon applied as foliar spray on the 4th and 12th days after planting, 3 control, with 10 replications each. The plants were infested with 100 whitefly adults/pot, released 16 days after planting. The number and viability of whitefly eggs and number of nymphs and adults were evaluated. The production of fresh and dry matter of shoots and the silicon content in plants were also evaluated. Silicon did not affect the whitefly oviposition preference; however, it affected the development of nymphs in free-choice test. Foliar silicon applications reduced the viability of whitefly eggs. There was no difference of fresh and dry weight and silicon content in plants with the application of silicon. Therefore, foliar silicon application on chrysanthemum can reduce the viability of eggs and delay the development of nymphs and thus contribute to the integrated whitefly management in commercial crops.

  10. Drug resistance, plasmids, biotypes and susceptibility to bacteriophages of Salmonella isolated from poultry in Canada.

    Science.gov (United States)

    Poppe, C; McFadden, K A; Demczuk, W H

    1996-07-01

    Salmonella isolates from 295 layer and 294 broiler flocks in Canada were examined to determine resistance to antimicrobial agents, plasmid profiles, biochemical properties, and susceptibility to polyvalent bacteriophages. Except for the high number of strains resistant to spectinomycin (97.8%), the frequency of drug resistance of Salmonella isolates from layer flocks was low. None of 457 isolates from layer flocks was resistant to amikacin or ciprofloxacin, and less than 2% of the strains were resistant to cephalothin, chloramphenicol, cotrimoxazole, gentamicin, kanamycin, neomycin, nitrofurantoin, and/or polymyxin B. About 3% of the strains were resistant to ampicillin, carbenicillin and/or tetracycline, whereas 8% of the strains were resistant to sulfisoxazole. Salmonella anatum var. O15+ and S. typhimurium var. copenhagen strains were resistant to multiple antimicrobial agents. None of 1159 Salmonella strains from broiler flocks was resistant to amikacin, cephalothin, ciprofloxacin or polymyxin B, less than 1% of the strains were resistant to chloramphenicol, 2% were resistant to ampicillin, carbenicillin and/or chloramphenicol; 5-7% were resistant to the aminoglycosides gentamicin, kanamycin and/or neomycin; 6% were resistant to nitrofurantoin; 10% to tetracycline; 14% to sulfisoxazole; and 99% to spectinomycin. A high percentage of S. binza, S. anatum var. O15+, S. schwarzengrund and S. heidelberg strains were resistant to antimicrobial agents. Some of the single or multiple resistances were encoded by conjugative plasmids or by plasmids that were thermosensitive for transfer. Eight percent of S. heidelberg strains did not produce hydrogen sulfide. Ninety-seven percent of the Salmonella strains were susceptible to the lytic effect of polyvalent bacteriophages.

  11. RESISTANCE TO ALS-INHIBITING HERBICIDES IN WEED POPULATIONS FROM BELGIAN WHEAT FIELDS.

    Science.gov (United States)

    S, Claerhout; B, De Cauwer

    2015-01-01

    In modern agriculture, most farmers rely on herbicides for weed control. The intensive use of herbicides in crops has led to the development of herbicide resistance in numerous weeds worldwide. In Belgium, farmers have encountered problems with controlling populations of Alopecurus myosuroides, Matricaria recutita, Stellaria media and Popover rhoeas in some wheat fields with the conventionally used acetolactate synthase (ALS)-inhibiting herbicides. Dose response assays were conducted in the greenhouse to test the sensitivity of these populations to the key ALS-inhibiting herbicides mesosulfuron-methyl + iodosulfuron-methyl for A. myosuroides and metsulfuron-methyl and florasulam for M. recutita, S. media and P. rhoeas. The ED₉₀- and ED₅₀-values (effective dose for resp. 90% and 50% biomass reduction) were compared with those of sensitive reference populations and the resistance index (RI) was calculated. High levels of resistance were detected forA. myosuroides (RI: 24.3) after treatment with mesosulfuron-methyl and for M. recutita (RI: 36.4 to 49.5), S. media (RI > 20) and P. rhoeas (RI: 23.6) after treatment with metsulfuron-methyl. However, the metsulfuron-methyl resistant populations of M. recutita and S. media were sufficiently controlled with florasulam at the maximum authorised field dose. This was not the case for P. rhoeas. The metsulfuron-methyl resistant P. rhoeas population were also high-level resistant against florasulam (RI: 29.5). Integrated weed management practices (crop rotation, herbicide mixing, ...) should be applied to reduce the selection pressure for resistant weeds.

  12. Glyphosate degradation in glyphosate-resistant and -susceptible crops and weeds.

    Science.gov (United States)

    Duke, Stephen O

    2011-06-08

    High levels of aminomethylphosphonic acid (AMPA), the main glyphosate metabolite, have been found in glyphosate-treated, glyphosate-resistant (GR) soybean, apparently due to plant glyphosate oxidoreductase (GOX)-like activity. AMPA is mildly phytotoxic, and under some conditions the AMPA accumulating in GR soybean correlates with glyphosate-caused phytotoxicity. A bacterial GOX is used in GR canola, and an altered bacterial glyphosate N-acetyltransferase is planned for a new generation of GR crops. In some weed species, glyphosate degradation could contribute to natural resistance. Neither an isolated plant GOX enzyme nor a gene for it has yet been reported in plants. Gene mutation or amplification of plant genes for GOX-like enzyme activity or horizontal transfer of microbial genes from glyphosate-degrading enzymes could produce GR weeds. Yet, there is no evidence that metabolic degradation plays a significant role in evolved resistance to glyphosate. This is unexpected, considering the extreme selection pressure for evolution of glyphosate resistance in weeds and the difficulty in plants of evolving glyphosate resistance via other mechanisms.

  13. Alteração das características biológicas dos biótipos de azevém (Lolium multiflorum ocasionada pela resistência ao herbicida glyphosate Change in the biological characteristics of ryegrass (Lolium multiflorum biotypes caused by resistance to the herbicide glyphosate

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    L. Vargas

    2005-03-01

    Full Text Available A resistência de biótipos de azevém ao herbicida glyphosate está alterando o manejo da vegetação de cobertura do solo em pomares de maçã. O objetivo deste trabalho foi determinar a dose de glyphosate necessária para reduzir 50% do acúmulo de matéria seca (GR50, a resposta do biótipo resistente e sensível a herbicidas graminicidas e o acúmulo de matéria seca destes biótipos durante o ciclo. Para isso, foram conduzidos três experimentos. No primeiro, os tratamentos constaram de doses crescentes de glyphosate aplicadas sobre plantas dos biótipos resistente e sensível para determinar o GR50. No segundo experimento, os tratamentos constaram de doses dos herbicidas glyphosate, haloxyfop-r, diclofop, fluazifop-p, fenoxaprop-p e paraquat. No terceiro experimento, sementes dos biótipos resistente e sensível foram semeadas em recipientes com capacidade para 10 L e as plantas originadas delas foram colhidas quinzenalmente, para determinação da matéria seca da parte aérea, radicular e total. Como resultados, foi obtido GR50 de 287,5 e de 4.833,5 g e.a. ha-1 de glyphosate para os biótipos sensível e resistente, respectivamente, e verificou-se que existem diferenças significativas na resposta dos biótipos aos herbicidas graminicidas, dependendo da dose utilizada. Além disso, o biótipo sensível evidenciou maior capacidade de acúmulo de matéria seca e produção de sementes. Constatouse, assim, fator de resistência (FR de 16,8 e que o mecanismo de resistência provoca alterações nas características biológicas do biótipo resistente e afeta a sensibilidade deste aos herbicidas graminicidas.The identification of ryegrass biotypes resistant to glyphosate is causing changes in weed management in apple orchards. Three experiments were carried out to determine the GR50 of the biotypes, to grass herbicides and dry matter accumulation. The first experiment tested different rates of glyphosate. Their effects on GR50 dry matter

  14. Silicon influence on resistance induction against Bemisia tabaci biotype B (Genn.) (Hemiptera: Aleyrodidae) and on vegetative development in two soybean cultivars.

    Science.gov (United States)

    Ferreira, R S; Moraes, J C; Antunes, C S

    2011-01-01

    The potential of populations of Bemisia tabaci (Genn.) to become resistant to insecticides has stimulated research into alternative tactics of integrated pest management such as the induction of host-plant resistance. Recent data have shown that silicon can increase the degree of resistance of host plants to insect pests. Therefore the aim of our work was to study the effects of silicon application on the vegetative development of soybean plants and on the induction of resistance to the silverleaf whitefly, B. tabaci biotype B. We performed choice and no-choice tests of oviposition preference on two soybean cultivars, IAC-19 (moderately resistant to B. tabaci biotype B) and MONSOY-8001 (susceptible), with and without application of silicon. Silicon did not affect silverleaf whitefly oviposition preferences, but caused significant mortality in nymphs. Thus, silicon increased the degree of resistance to silverleaf whitefly. Silicon decreased the production of phenolic compounds, but did not affect lignin production. However, when applied to cultivar IAC-19, it increased the production of non-protein organic nitrogen. Silicon had no effect on the vegetative development of soybean plants, but it increased the degree of resistance to the silverleaf whitefly. We conclude that silicon applications combined with cultivar IAC-19 can significantly decrease silverleaf whitefly populations, having a positive impact both on the soybean plant and on the environment.

  15. Multiple-herbicide resistance in Echinochloa crus-galli var. formosensis, an allohexaploid weed species, in dry-seeded rice.

    Science.gov (United States)

    Iwakami, Satoshi; Hashimoto, Masato; Matsushima, Ken-ichi; Watanabe, Hiroaki; Hamamura, Kenshiro; Uchino, Akira

    2015-03-01

    Biotypes of Echinochloa crus-galli var. formosensis with resistance to cyhalofop-butyl, an acetyl-CoA carboxylase (ACCase) inhibitor, have been found in dry-seeded rice fields in Okayama, Japan. We collected two lines with suspected resistance (Ecf27 and Ecf108) from dry-seeded rice fields and investigated their sensitivity to cyhalofop-butyl and other herbicides. Both lines exhibited approximately 7-fold higher resistance to cyhalofop-butyl than a susceptible line. Ecf108 was susceptible to penoxsulam, an acetolactate synthase (ALS) inhibitor. On the other hand, Ecf27 showed resistance to penoxsulam and two other ALS inhibitors: propyrisulfuron and pyriminobac-methyl. The alternative herbicides butachlor, thiobencarb, and bispyribac-sodium effectively controlled both lines. To examine the molecular mechanisms of resistance, we amplified and sequenced the target-site encoding genes in Ecf27, Ecf108, and susceptible lines. Partial sequences of six ACCase genes and full-length sequences of three ALS genes were examined. One of the ACCase gene sequences encodes a truncated aberrant protein due to a frameshift mutation in both lines. Comparisons of the genes among Ecf27, Ecf108, and the susceptible lines revealed that none of the ACCases and ALSs in Ecf27 and Ecf108 have amino acid substitutions that are known to confer herbicide resistance, although a single amino acid substitution was found in each of three ACCases in Ecf108. Our study reveals the existence of a multiple-herbicide resistant biotype of E. crus-galli var. formosensis at Okayama, Japan that shows resistance to cyhalofop-butyl and several ALS inhibitors. We also found a biotype that is resistant only to cyhalofop-butyl among the tested herbicides. The resistance mechanisms are likely to be non-target-site based, at least in the multiple-herbicide resistant biotype.

  16. Differential susceptibility and resistance to glyphosate in annual ryegrass and wavy-leaved fleabane

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    Flávia Regina da Costa

    2014-09-01

    Full Text Available Annual ryegrass (Lolium multiflorum and wavy-leaved fleabane (Conyza bonariensis were tested, aiming to investigate the dose-response of biotypes of both species to glyphosate. Glyphosate herbicide at doses varying from 0 up to 1.440 g e.a. ha-1 was sprayed onto annual ryegrass plants showed four leaves and wavy-leaved fleabane showed three pair of leaves. The fresh weight of shoot was obtained at 21 days after herbicide application. The response of biotypes of L. multiflorum and C. bonariensis to glyphosate was clearly different. For L. multiflorum, the S2, R1, and R3 biotypes supported glyphosate doses 1.5, 3.0, and 8.3 times higher than the biotype S1. For C. bonariensis, the S2 and R biotypes supported glyphosate doses 2.0 and 15.5 times higher than the biotype S1. We found a low glyphosate-resistant (R1 and a high glyphosate-resistant (R2 biotypes of L. multiflorum, in agricultural regions where other biotypes had been found. In addition, a high glyphosate-resistant (R biotype of C. bonariensis was identified in an agricultural area of Santa Catarina State, Brazil, where weed resistant was not previously found.

  17. Key role for a glutathione transferase in multiple-herbicide resistance in grass weeds.

    Science.gov (United States)

    Cummins, Ian; Wortley, David J; Sabbadin, Federico; He, Zhesi; Coxon, Christopher R; Straker, Hannah E; Sellars, Jonathan D; Knight, Kathryn; Edwards, Lesley; Hughes, David; Kaundun, Shiv Shankhar; Hutchings, Sarah-Jane; Steel, Patrick G; Edwards, Robert

    2013-04-09

    Multiple-herbicide resistance (MHR) in black-grass (Alopecurus myosuroides) and annual rye-grass (Lolium rigidum) is a global problem leading to a loss of chemical weed control in cereal crops. Although poorly understood, in common with multiple-drug resistance (MDR) in tumors, MHR is associated with an enhanced ability to detoxify xenobiotics. In humans, MDR is linked to the overexpression of a pi class glutathione transferase (GSTP1), which has both detoxification and signaling functions in promoting drug resistance. In both annual rye-grass and black-grass, MHR was also associated with the increased expression of an evolutionarily distinct plant phi (F) GSTF1 that had a restricted ability to detoxify herbicides. When the black-grass A. myosuroides (Am) AmGSTF1 was expressed in Arabidopsis thaliana, the transgenic plants acquired resistance to multiple herbicides and showed similar changes in their secondary, xenobiotic, and antioxidant metabolism to those determined in MHR weeds. Transcriptome array experiments showed that these changes in biochemistry were not due to changes in gene expression. Rather, AmGSTF1 exerted a direct regulatory control on metabolism that led to an accumulation of protective flavonoids. Further evidence for a key role for this protein in MHR was obtained by showing that the GSTP1- and MDR-inhibiting pharmacophore 4-chloro-7-nitro-benzoxadiazole was also active toward AmGSTF1 and helped restore herbicide control in MHR black-grass. These studies demonstrate a central role for specific GSTFs in MHR in weeds that has parallels with similar roles for unrelated GSTs in MDR in humans and shows their potential as targets for chemical intervention in resistant weed management.

  18. Prospección de las combinaciones de herbicidas para prevenir malezas tolerantes y resistentes al glifosato Exploration of herbicide associations to prevent glyphosate tolerant and resistant weeds

    Directory of Open Access Journals (Sweden)

    R.A. VIDAL

    2010-01-01

    inhibitors were documented in Argentina with Amaranthus quitensis. Likewise, in Brazil, it has increased weed resistance to glyphosate in weeds such as Lolium multiflorum and Euphorbia heterophylla. The objective of this research was to assess antagonism or synergism to control of the mentioned weeds for all possible combinations between two of the following herbicides: glyphosate, imazethapyr, clomazone, and lactofen. Biotypes susceptible to all herbicides were used in the research. Seedlings of A. hybridus with two cm and of the others with seven cm, were treated with the herbicides glyphosate, imazethapyr, clomazone and lactofen at 108, 10, 160 y 30 g ha-1 a.i. respectively, applied alone. Six additional treatments were included in all possible combinations between two of the herbicides and doses as described above. An untreated control was also used. A non-ionic adjuvant at a ratio of 0.2% was added to all treatments, except for the treatment of glyphosate alone and the untreated. The effect of the herbicide mixtures depended on the species tested and also on the herbicides used. Synergism was obtained only in the mixture glyphosate + imazethapyr. Clomazone resulted predominantly in antagonism, and lactofen had a neutral effect in most of the evaluated herbicide mixtures. Herbicide combinations are considered potentially useful in controlling weeds resistant or tolerant to glyphosate.

  19. Bioherbicidal effects of Myrothecium verrucaria on Glyphosate-resistant and -susceptible Palmer amaranth biotypes

    Science.gov (United States)

    Bioherbicidal effects of the fungus Myrothecium verrucaria (MV) on glyphosate-resistant and -susceptible Palmer amaranth were examined on whole plants and in leaf bioassays of young and mature plants. Leaf bioassays using mycelia from the fermentation product of MV indicated that excised leaves of ...

  20. Comparative growth of triazine-susceptible and -resistant biotypes of Solanum nigrum at different light levels

    NARCIS (Netherlands)

    Kremer, E.; Kropff, M.J.

    1999-01-01

    Effects of variation in light intensity on growth of plants from five different populations of triazine-susceptible and -resistantSolanum nigrumwere studied in growth chambers at three light levels. Plants were grown without intraspecific competition and with optimal mineral nutrition. After 29 d, t

  1. Don’t Farm So Close to Me: Testing Whether Spatial Externalities Contributed to the Emergence of Glyphosate-Resistant Weed Populations

    OpenAIRE

    Wood, Dallas

    2014-01-01

    The emergence of glyphosate-resistant weed populations threatens the economic viability of genetically modified, glyphosate-resistant crop varieties. This could not only have serious consequences for the welfare of U.S. farmers, but also for environmental quality as farmers turn to more toxic herbicides. The purpose of this paper is to better understand what economic factors have contributed to the rise of resistant weeds. Specifically, I investigate whether externalities associated with weed...

  2. A generalised individual-based algorithm for modelling the evolution of quantitative herbicide resistance in arable weed populations.

    Science.gov (United States)

    Liu, Chun; Bridges, Melissa E; Kaundun, Shiv S; Glasgow, Les; Owen, Micheal Dk; Neve, Paul

    2017-02-01

    Simulation models are useful tools for predicting and comparing the risk of herbicide resistance in weed populations under different management strategies. Most existing models assume a monogenic mechanism governing herbicide resistance evolution. However, growing evidence suggests that herbicide resistance is often inherited in a polygenic or quantitative fashion. Therefore, we constructed a generalised modelling framework to simulate the evolution of quantitative herbicide resistance in summer annual weeds. Real-field management parameters based on Amaranthus tuberculatus (Moq.) Sauer (syn. rudis) control with glyphosate and mesotrione in Midwestern US maize-soybean agroecosystems demonstrated that the model can represent evolved herbicide resistance in realistic timescales. Sensitivity analyses showed that genetic and management parameters were impactful on the rate of quantitative herbicide resistance evolution, whilst biological parameters such as emergence and seed bank mortality were less important. The simulation model provides a robust and widely applicable framework for predicting the evolution of quantitative herbicide resistance in summer annual weed populations. The sensitivity analyses identified weed characteristics that would favour herbicide resistance evolution, including high annual fecundity, large resistance phenotypic variance and pre-existing herbicide resistance. Implications for herbicide resistance management and potential use of the model are discussed. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  3. Emergence of Tetracycline Resistant Vibrio cholerae O1 Biotype El Tor Serotype Ogawa with Classical ctxB Gene from a Cholera Outbreak in Odisha, Eastern India

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    M. Jain

    2016-01-01

    Full Text Available In September 2010, a cholera outbreak was reported from Odisha, Eastern India. V. cholerae isolated from the clinical samples were biochemically and serologically confirmed as serogroup O1, biotype El Tor, and serotype Ogawa. Multiplex PCR screening revealed the presence of various genes, namely, ompW, ctxB, zot, rfbO1, tcp, ace, hlyA, ompU, rtx, and toxR, in all of the isolates. The isolates were resistant to co-trimoxazole, nalidixic acid, polymyxin B, spectinomycin, streptomycin, sulfamethoxazole, tetracycline, trimethoprim, and vibriostatic agent 2,4-diamino-6,7-diisopropylpteridine (O/129. Minimum inhibitory concentration of tetracycline decreased in the presence of carbonyl cyanide m-chlorophenylhydrazone (CCCP, suggesting the involvement of efflux pumps. PCR analysis confirmed the presence of class I integrons as well as SXT elements harbouring antibiotic resistance genes in all isolates. Sequencing revealed the presence of ctxB gene of classical biotype in all the isolates. The isolates harboured an RS1-CTX prophage array with El Tor type rstR and classical ctxB on the large chromosome. The study indicated that the V. cholerae El Tor variants are evolving in the area with better antibiotic resistance and virulence potential.

  4. Emergence of Tetracycline Resistant Vibrio cholerae O1 Biotype El Tor Serotype Ogawa with Classical ctxB Gene from a Cholera Outbreak in Odisha, Eastern India.

    Science.gov (United States)

    Jain, M; Kumar, P; Goel, A K

    2016-01-01

    In September 2010, a cholera outbreak was reported from Odisha, Eastern India. V. cholerae isolated from the clinical samples were biochemically and serologically confirmed as serogroup O1, biotype El Tor, and serotype Ogawa. Multiplex PCR screening revealed the presence of various genes, namely, ompW, ctxB, zot, rfbO1, tcp, ace, hlyA, ompU, rtx, and toxR, in all of the isolates. The isolates were resistant to co-trimoxazole, nalidixic acid, polymyxin B, spectinomycin, streptomycin, sulfamethoxazole, tetracycline, trimethoprim, and vibriostatic agent 2,4-diamino-6,7-diisopropylpteridine (O/129). Minimum inhibitory concentration of tetracycline decreased in the presence of carbonyl cyanide m-chlorophenylhydrazone (CCCP), suggesting the involvement of efflux pumps. PCR analysis confirmed the presence of class I integrons as well as SXT elements harbouring antibiotic resistance genes in all isolates. Sequencing revealed the presence of ctxB gene of classical biotype in all the isolates. The isolates harboured an RS1-CTX prophage array with El Tor type rstR and classical ctxB on the large chromosome. The study indicated that the V. cholerae El Tor variants are evolving in the area with better antibiotic resistance and virulence potential.

  5. Cholera outbreak caused by drug resistant Vibrio cholerae serogroup O1 biotype ElTor serotype Ogawa in Nepal; a cross-sectional study

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    Pappu Kumar Gupta

    2016-06-01

    Full Text Available Abstract Background Cholera is a major cause of mortality and morbidity in underdeveloped countries including Nepal. Recently drug resistance in Vibrio cholerae has become a serious problem mainly in developing countries. The main objectives of our study were to investigate the occurrence of Vibrio cholerae in stool samples from patients with watery diarrhea and to determine the antimicrobial susceptibility patterns of V. cholerae isolates. Methods A total of 116 stool samples from patients suffering from watery diarrhea during July to December 2012 were obtained from outbreak areas from all over Nepal. Alkaline peptone water and thiosulphate citrate bile salt sucrose agar (TCBS were used to isolate the Vibrio cholerae. The isolates were identified with the help of colony morphology, Gram’s staining, conventional biochemical testing, serotyping and biotyping. Antimicrobial susceptibility testing was performed by determining the minimum inhibitory concentration (MIC by agar dilution method. Results Vibrio cholerae was isolated from 26.72 % of total samples. All isolated Vibrio cholerae were confirmed to be Vibrio cholerae serogoup O1 biotype El Tor and serotype Ogawa. All isolates were resistant to ampicillin and cotrimoxazole. Twenty nine isolates were resistant toward two different classes of antibiotics, one strain was resistant to three different classes of antibiotics and one strain was resistant to four different classes of antibiotics. According to the definition of the multidrug resistant bacteria; 6.45 % of the strains of Vibrio cholerae were found to be multidrug resistant. Conclusions Cholera due to multidrug resistant Vibrio cholerae is also possible in Nepal. According to the antimicrobial susceptibility pattern of Vibrio cholerae in our study we recommend to use any antibiotics among tetracycline, doxycycline, levofloxacin, azithromycin, chloramphenicol and ciprofloxacin for preliminary treatment of cholera in Nepal.

  6. Cholera outbreak caused by drug resistant Vibrio cholerae serogroup O1 biotype ElTor serotype Ogawa in Nepal; a cross-sectional study.

    Science.gov (United States)

    Gupta, Pappu Kumar; Pant, Narayan Dutt; Bhandari, Ramkrishna; Shrestha, Padma

    2016-01-01

    Cholera is a major cause of mortality and morbidity in underdeveloped countries including Nepal. Recently drug resistance in Vibrio cholerae has become a serious problem mainly in developing countries. The main objectives of our study were to investigate the occurrence of Vibrio cholerae in stool samples from patients with watery diarrhea and to determine the antimicrobial susceptibility patterns of V. cholerae isolates. A total of 116 stool samples from patients suffering from watery diarrhea during July to December 2012 were obtained from outbreak areas from all over Nepal. Alkaline peptone water and thiosulphate citrate bile salt sucrose agar (TCBS) were used to isolate the Vibrio cholerae. The isolates were identified with the help of colony morphology, Gram's staining, conventional biochemical testing, serotyping and biotyping. Antimicrobial susceptibility testing was performed by determining the minimum inhibitory concentration (MIC) by agar dilution method. Vibrio cholerae was isolated from 26.72 % of total samples. All isolated Vibrio cholerae were confirmed to be Vibrio cholerae serogoup O1 biotype El Tor and serotype Ogawa. All isolates were resistant to ampicillin and cotrimoxazole. Twenty nine isolates were resistant toward two different classes of antibiotics, one strain was resistant to three different classes of antibiotics and one strain was resistant to four different classes of antibiotics. According to the definition of the multidrug resistant bacteria; 6.45 % of the strains of Vibrio cholerae were found to be multidrug resistant. Cholera due to multidrug resistant Vibrio cholerae is also possible in Nepal. According to the antimicrobial susceptibility pattern of Vibrio cholerae in our study we recommend to use any antibiotics among tetracycline, doxycycline, levofloxacin, azithromycin, chloramphenicol and ciprofloxacin for preliminary treatment of cholera in Nepal.

  7. Resistência ao glyphosate em biótipos de buva (Conyza spp. das regiões oeste e sudoeste do Paraná Resistance to glyphosate in Conyza spp. biotypes in western and southwestern Parana, Brazil

    Directory of Open Access Journals (Sweden)

    M.M Trezzi

    2011-01-01

    Full Text Available A resistência ao glyphosate em biótipos de Conyza spp. em áreas de lavoura das regiões oeste e sudoeste do Paraná causa grandes dificuldades ao manejo e, consequentemente, problemas econômicos e ambientais. Este experimento objetivou determinar a existência de resistência ao herbicida glyphosate em biótipos de buva (Conyza spp. suspeitos, coletados em lavouras das regiões oeste e sudoeste do Paraná, comparando-os com biótipos suscetíveis. O delineamento experimental utilizado foi inteiramente casualizado, em esquema fatorial 12 x 8 x 3. Os fatores consistiram de 12 biótipos de buva, doses de glyphosate (0, 100, 180, 324, 583, 1.050, 1.888 e 3.345 g ha-1 e épocas de avaliação para a variável controle (7, 14 e 21 dias após a aplicação. Para as variáveis matéria verde e matéria seca, o esquema fatorial utilizado foi o 12 x 8. As variáveis avaliadas foram controle visual, matéria verde, matéria seca, C50, GR50 e fator de resistência. A dose de 3.345 g glyphosate ha-1 foi a que apresentou maior nível de controle dos biótipos, porém o controle dos biótipos suspeitos não foi efetivo, necessitando de doses mais altas. Todos os biótipos de buva suspeitos de resistência ao glyphosate tiveram essa característica confirmada. Entretanto, constatou-se grande amplitude de fatores de resistência, o que caracteriza a variabilidade entre os biótipos resistentes. Essas informações poderão ser utilizadas no planejamento de estratégias de manejo das populações resistentes e na prevenção da ocorrência de novas áreas com buva resistente ao glyphosate.Glyphosate-resistant biotypes of Conyza spp. (hairy fleabane, horseweed in crop areas in the western and southwestern regions of the state of Paraná, Brazil, cause great management, economic, and environmental problems. This experiment aimed to determine the existence of horseweed biotypes resistant to glyphosate in the suspected populations collected from farms in western

  8. DNA analysis of herbarium Specimens of the grass weed Alopecurus myosuroides reveals herbicide resistance pre-dated herbicides.

    Science.gov (United States)

    Délye, Christophe; Deulvot, Chrystel; Chauvel, Bruno

    2013-01-01

    Acetyl-CoA carboxylase (ACCase) alleles carrying one point mutation that confers resistance to herbicides have been identified in arable grass weed populations where resistance has evolved under the selective pressure of herbicides. In an effort to determine whether herbicide resistance evolves from newly arisen mutations or from standing genetic variation in weed populations, we used herbarium specimens of the grass weed Alopecurus myosuroides to seek mutant ACCase alleles carrying an isoleucine-to-leucine substitution at codon 1781 that endows herbicide resistance. These specimens had been collected between 1788 and 1975, i.e., prior to the commercial release of herbicides inhibiting ACCase. Among the 734 specimens investigated, 685 yielded DNA suitable for PCR. Genotyping the ACCase locus using the derived Cleaved Amplified Polymorphic Sequence (dCAPS) technique identified one heterozygous mutant specimen that had been collected in 1888. Occurrence of a mutant codon encoding a leucine residue at codon 1781 at the heterozygous state was confirmed in this specimen by sequencing, clearly demonstrating that resistance to herbicides can pre-date herbicides in weeds. We conclude that point mutations endowing resistance to herbicides without having associated deleterious pleiotropic effects can be present in weed populations as part of their standing genetic variation, in frequencies higher than the mutation frequency, thereby facilitating their subsequent selection by herbicide applications.

  9. DNA analysis of herbarium Specimens of the grass weed Alopecurus myosuroides reveals herbicide resistance pre-dated herbicides.

    Directory of Open Access Journals (Sweden)

    Christophe Délye

    Full Text Available Acetyl-CoA carboxylase (ACCase alleles carrying one point mutation that confers resistance to herbicides have been identified in arable grass weed populations where resistance has evolved under the selective pressure of herbicides. In an effort to determine whether herbicide resistance evolves from newly arisen mutations or from standing genetic variation in weed populations, we used herbarium specimens of the grass weed Alopecurus myosuroides to seek mutant ACCase alleles carrying an isoleucine-to-leucine substitution at codon 1781 that endows herbicide resistance. These specimens had been collected between 1788 and 1975, i.e., prior to the commercial release of herbicides inhibiting ACCase. Among the 734 specimens investigated, 685 yielded DNA suitable for PCR. Genotyping the ACCase locus using the derived Cleaved Amplified Polymorphic Sequence (dCAPS technique identified one heterozygous mutant specimen that had been collected in 1888. Occurrence of a mutant codon encoding a leucine residue at codon 1781 at the heterozygous state was confirmed in this specimen by sequencing, clearly demonstrating that resistance to herbicides can pre-date herbicides in weeds. We conclude that point mutations endowing resistance to herbicides without having associated deleterious pleiotropic effects can be present in weed populations as part of their standing genetic variation, in frequencies higher than the mutation frequency, thereby facilitating their subsequent selection by herbicide applications.

  10. Ecologically sustainable weed management

    DEFF Research Database (Denmark)

    Liebman, Matt; Baraibar, Bàrbara; Buckley, Yvonne

    2016-01-01

    will be effective in various locations. Implementing new approaches for weed management will require multidisciplinary teams comprised of scientists, engineers, economists, sociologists, educators, farmers, land managers, industry personnel, policy makers, and others willing to focus on weeds within whole farming......Weed management is a critically important activity on both agricultural and non-agricultural lands, but it is faced with a daunting set of challenges: environmental damage caused by control practices, weed resistance to herbicides, accelerated rates of weed dispersal through global trade......, and greater weed impacts due to changes in climate and land use. Broad-scale use of new approaches is needed if weed management is to be successful in the coming era. We examine three approaches likely to prove useful for addressing current and future challenges from weeds: diversifying weed management...

  11. Resistência de meloeiro a Bemisia Tabaci biótipo B Resistance of melon to Bemisia Tabaci biotype B

    Directory of Open Access Journals (Sweden)

    Sérgio Alexandre Mottola Pereira Coelho

    2009-01-01

    Full Text Available Em âmbito mundial, a mosca-branca Bemisia tabaci (Genn. biótipo B é praga-chave em diversas culturas. O uso de resistência varietal se destaca entre os métodos de controle, sendo considerado o método ideal. O objetivo do presente trabalho foi avaliar, em casa de vegetação, a resistência de 32 cultivares de meloeiro em relação a essa mosca-branca. Para atratividade, em 'Neve' observou-se o menor número de adultos na face abaxial das folhas (0,6 adulto/10 cm², enquanto 'Nilo' foi a mais preferida (5,6 adultos/10 cm². A oviposição foi avaliada em testes com e sem chance de escolha; em ambos, 'Neve' proporcionou o menor número de ovos, contrastando com 'Nilo', a cultivar com a maior média. A colonização da mosca-branca durante o ciclo das plantas foi avaliada por meio de uma escala de notas variando de 0 (ausência de colonização até 6 (folha totalmente colonizada; 'Neve' destacou-se por sua reduzida colonização, sendo as mais altas médias obtidas em 'Imperial', 'Jangada', 'Vereda', 'Deneb' e 'Nilo'. Na duração do ciclo ovo-adulto da mosca-branca, que variou de 24,0 ('Neve' a 25,4 dias ('Jangada', as cultivares não diferiram entre si. Quanto à emergência de adultos, as menores médias foram induzidas por Vereda' (68,2% e 'Nilo' (69,3%, indicando a possível ocorrência de resistência do tipo antibiose nessas duas cultivares, enquanto as maiores médias ocorreram em 'Imperial' (90,9 % e 'Deneb' (89,6%. Considerando-se os parâmetros avaliados, infere-se que 'Neve' é a cultivar mais resistente a B. tabaci biótipo B, podendo ser indicada para plantio em regiões onde essa praga ocorra de forma acentuada ou para uso em programas de melhoramento.Silverleaf whitefly B. tabaci biotype B is an important worldwide pest of many crops. Use of resistant cultivars is considered the ideal method of control. In this research, 32 cultivars of melon were evaluated under greenhouse conditions reganding resistance to silverleaf

  12. Discovering the mechanism of enhanced metabolism in flufenacet resistant grass weeds

    Directory of Open Access Journals (Sweden)

    Dücker, Rebecca

    2016-02-01

    Full Text Available Inhibitors of very long chain fatty acid synthesis (VLCFAs, HRAC group K3 including flufenacet-based products are key herbicides in weed management strategies in particular of Western European cereal growing areas. They offer an alternative mode of action to those of frequently applied post-emergence active ingredients e.g. ACCase and ALS chemistries. In comparison, herbicide resistance to VLCFAs inhibitors develops considerably slower. Yet, resistance to the ‘low-risk’ herbicide flufenacet was documented in multi-resistant ryegrass (Lolium spp. in the northwestern United States. A 46-fold resistance shift in a population from Washington State was observed in a dose-response bioassay. The resistance levels described in black-grass (Alopecurus myosuroides Huds. field populations are lower and generally within the range of environmentally caused inconsistency in efficacy. An artificial selection of two UK multi-resistant black-grass populations with flufenacet applied annually for eight successive years resulted in resistant progeny surviving the field rate. Besides characterizing the degree of resistance in black-grass and ryegrass populations, we demonstrated that flufenacet resistance in these populations was caused by enhanced metabolism. No cross-resistance between flufenacet and pyroxasulfone, the newest VLCFAs-inhibiting herbicide, occurred in the ryegrass population. A good understanding of the resistance mechanism and early diagnostics can help preserve the efficacy of flufenacet.

  13. Simulating changes in cropping practices in conventional and glyphosate-resistant maize. II. Weed impacts on crop production and biodiversity.

    Science.gov (United States)

    Colbach, Nathalie; Darmency, Henri; Fernier, Alice; Granger, Sylvie; Le Corre, Valérie; Messéan, Antoine

    2017-05-01

    Overreliance on the same herbicide mode of action leads to the spread of resistant weeds, which cancels the advantages of herbicide-tolerant (HT) crops. Here, the objective was to quantify, with simulations, the impact of glyphosate-resistant (GR) weeds on crop production and weed-related wild biodiversity in HT maize-based cropping systems differing in terms of management practices. We (1) simulated current conventional and probable HT cropping systems in two European regions, Aquitaine and Catalonia, with the weed dynamics model FLORSYS; (2) quantified how much the presence of GR weeds contributed to weed impacts on crop production and biodiversity; (3) determined the effect of cultural practices on the impact of GR weeds and (4) identified which species traits most influence weed-impact indicators. The simulation study showed that during the analysed 28 years, the advent of glyphosate resistance had little effect on plant biodiversity. Glyphosate-susceptible populations and species were replaced by GR ones. Including GR weeds only affected functional biodiversity (food offer for birds, bees and carabids) and weed harmfulness when weed effect was initially low; when weed effect was initially high, including GR weeds had little effect. The GR effect also depended on cultural practices, e.g. GR weeds were most detrimental for species equitability when maize was sown late. Species traits most harmful for crop production and most beneficial for biodiversity were identified, using RLQ analyses. None of the species presenting these traits belonged to a family for which glyphosate resistance was reported. An advice table was built; the effects of cultural practices on crop production and biodiversity were synthesized, explained, quantified and ranked, and the optimal choices for each management technique were identified.

  14. Ecologically sustainable weed management

    NARCIS (Netherlands)

    Liebman, Matt; Baraibar, Bàrbara; Buckley, Yvonne; Childs, Dylan; Christensen, Svend; Cousens, Roger; Eizenberg, Hanan; Heijting, Sanne; Loddo, Donato; Merotto, Aldo; Renton, Michael; Riemens, Marleen

    2016-01-01

    Weed management is a critically important activity on both agricultural and non-agricultural lands, but it is faced with a daunting set of challenges: environmental damage caused by control practices, weed resistance to herbicides, accelerated rates of weed dispersal through global trade, and

  15. Performance and feeding behaviour of two biotypes of the black currant-lettuce aphid, Nasonovia ribisnigri, on resistant and susceptible Lactuca sativa near-isogenic lines.

    Science.gov (United States)

    ten Broeke, Cindy J M; Dicke, Marcel; van Loon, Joop J A

    2013-10-01

    The black currant-lettuce aphid, Nasonovia ribisnigri, is an important pest of cultivated lettuce, Lactuca sativa. Since 1982, the control of this aphid on lettuce is largely based on host plant resistance, conferred by the Nr gene, introgressed from Lactuca virosa. The resistance mechanism remains to be identified. N. ribisnigri populations virulent on the Nr-based resistance in lettuce have emerged in several locations in Europe since 2007. The objective of this study was to investigate the resistance mechanism mediated by the Nr gene in lettuce by detailed studies of aphid feeding behaviour and performance. Both avirulent (Nr:0) and virulent (Nr:1)biotypes of N. ribisnigri were studied on five resistant and two susceptible near isogenic lines (NILs). In addition, survival and colony development were quantified.Nr:0 aphids showed a strong decrease in sieve element ingestion and took longer to accept a sieve element on resistant NILs compared with susceptible NILs, and no aphids survived on the resistant NIL. Nr:1 aphids fed and performed equally well on the resistant and susceptible NILs. The resistance mechanism against Nr:0 aphids encoded by the Nr gene seems to be located in the phloem, although we also observed differences in feeding behaviour during the pathway phase to the phloem. Nr:1 aphids were highly virulent to the resistance conferred by the Nr gene. The consequences of the appearance of Nr:1 aphids for control of N. ribisnigri are discussed.

  16. Effect of new auxin herbicide formulations on control of herbicide resistant weeds and on microbial activities in the rhizosphere

    Science.gov (United States)

    Widespread distribution of glyphosate-resistant weeds in soybean-growing areas across Mississippi has economically affected soybean planting and follow-up crop management operations. New multiple herbicide-resistant crop (including soybean) technologies with associated formulations will soon be comm...

  17. Competitividade de biótipos de capim-arroz resistente e suscetível ao quinclorac Competitiveness of echinochloa biotypes resistant and susceptible to quinclorac

    Directory of Open Access Journals (Sweden)

    G. Concenço

    2008-03-01

    Full Text Available Objetivou-se com este trabalho avaliar a competitividade de dois biótipos de capim-arroz, resistente e suscetível ao quinclorac, coletados em regiões orizícolas do Estado de Santa Catarina. O experimento foi instalado em ambiente protegido, e os tratamentos constaram de diferentes densidades de plantas dos biótipos de capim-arroz comprovadamente resistente (ITJ-13 e suscetível (ITJ-17 ao quinclorac, oriundos da região arrozeira de Itajaí/SC. No centro da unidade experimental, foram semeadas três sementes do biótipo de capim-arroz, considerado como o tratamento da unidade experimental. Na periferia foram semeadas dez sementes do biótipo oposto ao do tratamento (central. Dez dias após a germinação foi efetuado o desbaste, deixando-se apenas uma planta no centro da unidade experimental e um número variável de plantas do biótipo oposto, de acordo com o tratamento (0, 1, 2, 3, 4 ou 5 plantas por vaso. O delineamento experimental utilizado foi o completamente casualizado, em esquema fatorial 2 x 6, com quatro repetições. Aos 40 dias após a emergência, foram avaliados altura de plantas, número de afilhos e de folhas, área foliar, massa fresca e seca e conteúdo de água de colmos e folhas. Os dados foram analisados pelo teste F, sendo efetuado teste de Duncan para comparar o efeito de densidade de plantas e teste da Diferença Mínima Significativa (DMS para avaliar diferenças entre os biótipos resistente e suscetível, além de correlação linear simples entre as variáveis avaliadas. Nas análises, utilizou-se o nível de 5% de probabilidade. Os biótipos estudados de capim-arroz resistente e suscetível ao quinclorac são similares quando sob alta intensidade de competição, com vantagem em algumas variáveis para o biótipo suscetível sob baixa ou moderada intensidade competitiva.The objective of this research was to evaluate the competitive potential of two Echinochloa sp. biotypes, resistant and susceptible to

  18. IMI resistance associated to crop-weed hybridization in a natural Brassica rapa population: characterization and fate.

    Science.gov (United States)

    Ureta, M S; Torres Carbonell, F; Pandolfo, C; Presotto, A D; Cantamutto, M A; Poverene, M

    2017-03-01

    Wild turnip (Brassica rapa) is a common weed and a close relative to oilseed rape (Brassica napus). The Clearfield® production system is a highly adopted tool which provides an alternative solution for weed management, but its efficiency is threatened by gene transfer from crop to weed relatives. Crop-weed hybrids with herbicide resistance were found in the progeny of a B. rapa population gathered from a weedy stand on the borders of an oilseed rape (B. napus) imidazolinone (IMI)-resistant crop. Interspecific hybrids were confirmed by morphological traits in the greenhouse and experimental field, survival after imazethapyr applications, DNA content through flow cytometry, and pollen viability. The transference of herbicide resistance was demonstrated even in a particular situation of pollen competition between both an herbicide-resistant crop and a non-resistant crop. However, IMI resistance was not found in further generations collected at the same location. These results verify gene transmission from oilseed rape to B. rapa in the main crop area in Argentina where resistant and susceptible varieties are found and seed loss and crop volunteers are common. Hybridization, introgression, and herbicide selection would be associated with the loss of effectiveness of IMI technology.

  19. Análise comparativa do crescimento de biótipos de picão-preto (Bidens pilosa resistente e suscetível aos herbicidas inibidores da ALS Growth analysis of Bidens pilosa biotypes resistant and susceptible to ALS inhibitor herbicides

    Directory of Open Access Journals (Sweden)

    P.J. Christoffoleti

    2001-04-01

    , TCA, TCR e TAL maiores que o suscetível. Dessa forma, concluiu-se que o biótipo de Bidens pilosa resistente aos herbicidas inibidores da ALS apresenta a mesma eficiência de produção de biomassa no final do ciclo. É provável que, quando em competição entre si e com as culturas, possua a mesma competitividade, sendo a dominância numérica de um biótipo sobre o outro decorrente apenas da pressão de seleção causada pelo herbicida.The resistance of weed biotypes to acetolactate synthase (ALS inhibitor herbicides is due to this enzyme's lack of sensitivity to ALS inhibitor herbicides, which inhibit its catalytic activity. ALS insensitivity results from a structural change in the aminoacid sequence, exactly in the site of action of these herbicides. Eventually this modification in the enzyme may result in a reduced plant growth rate. Such reduction was also observed in biotypes resistant to Photosystem II inhibitor herbicides. The possibility of a lower growth rate of the resistant plant may directly affect biotype competitiveness, its population dynamics and, as a consequence, resistance management strategies. The objective of this research was to compare the growth rates of both resistant and susceptible Bidens pilosa biotypes to ALS inhibitor herbicides. The experiment was conducted in a greenhouse, using one plant per pot of 5 L capacity. Four plants per biotype were harvested weekly, starting 14 days after planting, and the leaf area and dry biomass were measured. The Richards function fitted to the data enabled the derivation of absolute growth rate, relative growth rate and net assimilation rate. The susceptible biotype had a higher biomass accumulation during the early stages, with both biotypes having the same size, afterwards. The higher net assimilation rate of the resistant biotype during the early stages of growth was balanced by its lower size during the first four weeks of growth. It was concluded that both biotypes have the same size, being very

  20. Epidemiologic and Drug Resistance Pattern of Vibrio cholerae O1 Biotype El Tor, Serotype Ogawa, in the 2011 Cholera Outbreak, in Alborz Province, Iran

    Science.gov (United States)

    Barati, Hojatolah; Moradi, Ghobad; Rasouli, Mohammad Aziz; Mohammadi, Parvin

    2015-01-01

    Background: Although the national guidelines recommend special antibiotics, based on the antibiogram of National Reference Laboratory, it seems that, because of uncontrolled usage of antibiotics in the society and due to the changes in the serotypes causing the disease, it is essential to monitor the status of drug resistance, permanently, and to revise the current prescriptions guidelines. Objectives: This study aimed to assess the epidemiological aspects and drug resistance pattern of Vibrio cholerae O1, biotype El Tor, serotype Ogawa, in cholera outbreak, in Alborz province in Iran, during 2011. Materials and Methods: This is a cross-sectional study, which reviews a cholera epidemic that occurred in Iran. A total of 9844 specimens were taken from suspected cases, among diarrheal patients, via rectal swabs. The specimens were placed in Cary-Blair transport medium and sent to laboratory. Samples were enriched, in alkaline peptone water, and isolated on thiosulphate-citrate-bile salt-sucrose agar. From the 244 confirmed cases, 239 cases underwent antibiogram test, via disk diffusion method and based on national committee for clinical laboratory standards (NCCLS) instructions. The standard Escherichia coli ATCC 25922 was used for antibiogram quality control and, eventually, all results were interpreted and reported using NCCLS standard table. Results: In total, until October 22, 2011, which was announced as the end of outbreak, 9844 samples were taken from diarrheal patients. Regarding the type of V. cholerae, 244 El Tor biotype positive cases were reported. The case fatality rate was 1.3%. The mean age of patients was 37.8 years and the highest incidence rate occurred in the age group 21 - 30 years. After conducting antibiotic susceptibility test in the 244 V. cholerae, biotype El Tor, serotype Ogawa, it was found that ciprofloxacin had the highest level of antibiotic susceptibility (99.6%) and the highest level of antibiotic resistance was observed in co

  1. The origin and evolution of weed beets: consequences for the breeding and release of herbicide-resistant transgenic sugar beets.

    Science.gov (United States)

    Boudry, P; Mörchen, M; Saumitou-Laprade, P; Vernet, P; Van Dijk, H

    1993-12-01

    Populations of weed beets have expanded into European sugar beet production areas since the 1970s, thereby forming a serious new weed problem for this crop. We sampled seeds in different French populations and studied mitochondrial DNA, chloroplast DNA and life-cycle variability. Given the maternal inheritance of the mitochondrial and chloroplastic genomes and the nuclear determinism of the annual habit, we were able to determine the maternal origin and evolution of these weed beet populations. Our study shows that they carry the dominant allele "B" for annual habit at high frequency. The main cytoplasmic DNA type found in northern weed beet populations is the cytoplasmic male-sterile type characteristic of sugar beets. We were able to determine that these populations arise from seeds originating from the accidental pollinations of cultivated beets by adventitious beets in the seed production area, which have been transported to the regions where sugar beets are cultivated. These seeds are supposedly the origin of the weed forms and a frequently disturbed cultivated environment has selected for annual habit and early flowering genotypes. We discuss the consequences of the weed beet populations for the breeding, seed production and release of herbicide-resistant transgenic sugar beets.

  2. Safener responsiveness and multiple herbicide resistance in the weed black-grass (Alopecurus myosuroides).

    Science.gov (United States)

    Cummins, Ian; Bryant, David N; Edwards, Robert

    2009-10-01

    Safeners enhance the selectivity of graminicidal herbicides such as fenoxaprop ethyl in cereals, by increasing their rates of detoxification in the crop. While studying the selectivity of fenoxaprop ethyl in wheat, we determined that the safeners mefenpyr diethyl and fenchlorazole ethyl also enhanced herbicide tolerance in the competing weed black-grass (Alopecurus myosuroides). Fenoxaprop ethyl was detoxified by conjugation with glutathione in both wheat and black-grass, with the resulting metabolites processed to the respective cysteine derivatives, which were then N-glycosylated. In black-grass, these detoxification pathways were only slightly enhanced by safeners, suggesting that metabolism alone was unlikely to account for increased herbicide tolerance. Instead, it was determined that safening was associated with an accumulation of glutathione and hydroxymethylglutathione and enzymes with antioxidant functions including phi and lambda glutathione transferases, active as glutathione peroxidases and thiol transferases respectively. These safener-induced changes closely mirrored those determined in two independent black-grass populations that had acquired multiple herbicide resistance (MHR) in the field. In addition to enhanced glutathione metabolism, both safener treatment and MHR resulted in elevated levels of flavonoids in the foliage of black-grass plants, notably flavone-C-glycosides and anthocyanins. Our results demonstrate that safening in a grass weed is associated with an inducible activation in antioxidant and secondary metabolism which mirrors the biochemical phenotype exhibited in plants that are resistant to multiple classes of herbicides.

  3. Gene flow from genetically modified herbicide-resistant rapeseed to cruciferous weeds

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xiangxiang; XIA Qiuxia; LU Dalei; LU Weiping; QI Cunkou; PU Huiming; LIU Geshan; ZHAO Jian; WANG Youping

    2006-01-01

    The sexual compatibility between genetically modified (GM) glyphosate-resistant rapeseed variety Q3 (Brassica napus L. ) and 5 cruciferous weeds is studied through the observation of fluorescence microscopy and cross-fertility after manual pollination. The results indicated that Q3 (as male) was highly incompatible with Thlaspi arvense L., Capsella bursa-pastoris (L.) Medic, Cardamine hirsuta L. and Rorippa palustris (L.) Besser (as female). Fluorescence microscopic observation showed that growing of pollen tubes terminated on the stigma surface or at the upper 1/3 part of the style. However, B. juncea×Q3 was compatible, and the compatibility index was 1.65. Under the neighboring growth and natural pollination conditions, the rates of gene flow from Q3 to T. arvense, C.bursa-pastoris, C. hirsute and R. palustris were all 0, while it was 0.86 % for B. juncea. These results indicate that there is difference in the rate of gene flow between GM rapeseed and cruciferous wild weeds, and frequency of gene flow is highly correlated with sexual compatibility.

  4. Resistência de genótipos de feijoeiro a Bemisia tabaci biótipo B Resistance of bean genotypes to Bemisia tabaci biotype B

    Directory of Open Access Journals (Sweden)

    Lucas Castro Torres

    2012-01-01

    Full Text Available O estudo de genótipos de feijoeiro resistentes à mosca-branca Bemisia tabaci (Genn. biótipo B (Hemiptera: Aleyrodidae é de grande importância devido aos danos ocasionados por essa praga à cultura. Neste trabalho, foram estudados a atratividade para adultos, a preferência para oviposição em testes com e sem chance de escolha, o ciclo ovo-adulto e o tipo e número de tricomas presentes nos folíolos. Os experimentos foram realizados em casa de vegetação avaliando-se, inicialmente, cem genótipos de feijoeiro. A resistência do tipo não-preferência para alimentação e/ou antibiose foi observada nos genótipos ARC-3, IAC-Alvorada e Canário 101, sendo a emergência de adultos fortemente influenciada pelos genótipos. Também se observou correlação negativa moderada entre o número de ovos e o número de tricomas glandulares, e correlação positiva muito forte entre o número de ovos e o número de tricomas tectores unciformes.The study of bean genotypes resistant to the whitefly Bemisia tabaci (Genn. B biotype (Hemiptera: Aleyrodidae has been of great importance due to the damage caused by this pest. In this research, bean genotypes were evaluated regarding attractiveness to whitefly adults, the preference for oviposition in free-choice and non choice tests, egg-to-adult development time and characterized for the presence, type and number of trichomes. The experiments were carried out under greenhouse conditions initially evaluating 100 bean genotypes. The non-preference type of resistance for feeding and/or antibiosis was observed in the genotypes ARC-3, IAC-Alvorada and Canário 101, and the emergence of adults was strongly influenced by the genotypes. It was also observed a moderate negative correlation between the number of eggs and the number of glandular trichomes, as well as a very strong positive correlation between the number of eggs and the number of unciform non-glandular trichomes.

  5. Validation of the chlorophyll fluorescence imaging method (CFI for early detection of herbicide resistance in weeds

    Directory of Open Access Journals (Sweden)

    Menegat, Alexander

    2014-02-01

    Full Text Available The increasing number of herbicide tolerant weed populations is illustrating the increasing demand for reliable methods for an accelerated detection of herbicide tolerance compared to greenhouse studies. Several methods for resistance quick detection have been published in previous years. One of the recent methods is the Chlorophyll Fluorescence Imaging Method (CFI. For this method changes in photosynthetic activity of the target organisms, caused by herbicides, are determined. General assumption of this method in terms of herbicide resistance detection is that each herbicidal compound, independent of the mode of action, will cause changes within the photosynthetic apparatus of the target organisms. This effect already could be confirmed for several modes of action (PSII, ALS, ACCase, EPSPS, synth. Auxins. Aim of this study is to validate this novel method on the basis of greenhouse experiments and single nucleotide polymorphisms (SNP analysis. The resistance profiles of 10 black-grass populations (Alopecurus myosuroides Huds. have been determined in greenhouse herbicide efficacy trials and constitutive SNP analyses of the survivors. With the CFI-method it was possible to detect the resistance profile as well as the resistance frequency within the populations. The results from the greenhouse experiments could be reproduced with conformity of 94%. This result is valid for the tested herbicides mesosulfuron, pyroxsulam as well as clodinafop and pinoxaden.

  6. Resistência de clones de batata a Bemisia tabaci biótipo B Resistance of potato clones to Bemisia tabaci biotype B

    Directory of Open Access Journals (Sweden)

    Artur BO Rocha

    2012-03-01

    resistentes a B. tabaci biótipo B.The resistance of 30 potato genotypes to B. tabaci (Genn. biotype B (Hemiptera: Aleyrodidae was evaluated in three greenhouse experiments. In the first experiment we evaluated the attractiveness, the preference for oviposition and the trichome density in a free-choice test in randomized blocks design with 30 treatments and three replications. In other experiment, no-choice preference for oviposition was evaluated (randomized blocks, nine treatments and five replications. The whitefly egg-adult cycle was monitored using a statistical design in randomized blocks with five replications. In the free-choice test, the genotypes NYL 235-4 and MAC 2 were the most attractive to adults, whereas HPC 5B and BAP 82 presented the lowest number of adults. The genotypes HPC 6R, BACH 4, clone APTA 2135, HPC 9B, BAP 82, 'Baraka' and HPC 5B presented the lowest number of eggs. Clone NYL 235-4 had the greatest number of simple (ST and glandular (GT trichomes, whereas clone CH 2 had the lowest number of ST, and HPC 5B, 'Radosa', 'Cupido', 'Caesar', 'Saginaw Gold', BACH 3 and HPC 1B of GT. There was significant correlation between adult attractiveness and oviposition preference. In the no-choice test, only the genotypes BACH 4, HPC 9B, 'Baraka and 'Achat' remained resistant. Consequently, for these four genotypes non-preference is the oviposition resistance mechanism. The egg adult cycle varied from 34.4 to 36.6 days. For the adult emergence, genotypes BAP 82, 'Baraka' and BACH 4 showed the lowest number of adults emerged, suggesting the presence of antibiosis. Genotypes BAP82, 'Baraka' and BACH 4 were resistant to B. tabaci biotype B.

  7. Biotypes of Gardnerella vaginalis.

    Science.gov (United States)

    Piot, P; Van Dyck, E; Peeters, M; Hale, J; Totten, P A; Holmes, K K

    1984-10-01

    A simple and reproducible scheme for identifying biotypes of Gardnerella vaginalis has been developed, based on reactions for lipase, hippurate hydrolysis, and beta-galactosidase. Among a total of 359 strains tested, eight biotypes were observed, the most common ones being types 1 (beta-galactosidase positive, lipase positive, hippurate positive), 2 (beta-galactosidase negative, lipase positive, hippurate positive), and 5 (beta-galactosidase negative, lipase negative, hippurate positive). The distribution in biotypes was similar among isolates from Antwerp, Seattle, and Nairobi. There were no differences in biotypes between strains isolated from patients with and without bacterial vaginosis (nonspecific vaginitis). Up to 14% of women with bacterial vaginosis harbored at least two different biotypes of G. vaginalis in the vagina. G. vaginalis strains isolated before and after treatment for bacterial vaginosis belonged to identical biotypes when the time interval between two specimens was less than 1 week. Similarly, G. vaginalis isolates from the vaginas of women with bacterial vaginosis and from the urethras of their male sex partners belonged to identical biotypes when strains were isolated within the same 24-h period from both partners (P less than 0.005).

  8. GWN-3189 B – A new selective herbicide based on Triallate for control of herbicide resistant grass weed in cereals

    Directory of Open Access Journals (Sweden)

    Mühlschlegel, Friedrich

    2014-02-01

    Full Text Available With substantial work on the formulation, Gowan offers a new herbicide (GWN-3189 B based on Triallate for use on winter wheat, winter barley, winter rye, winter triticale and spring barley. GWN-3189B will be applied from pre-emergence to early post-emergence of the crop and offers a broad spectrum against grass-weeds. GWN-3189 B is selective on all cereal species. As soil herbicide GWN-3189 B offers interesting alternatives in grass-weed resistance management. The efficacy on grass weed, especially on Alopecurus myosuroides (blackgrass, Apera spica venti (silky bentgrass and Lolium multiflorum (italian ryegrass is demonstrated with results of field trials performed in France, Great Britain and Germany.

  9. Novos acessos de tomateiro resistentes à mosca-branca biótipo B New accessions of tomato resistant to whitefly biotype B

    Directory of Open Access Journals (Sweden)

    Maria Elisa de Sena Fernandes

    2009-11-01

    Full Text Available O objetivo deste trabalho foi selecionar novas fontes de resistência a Bemisia tabaci biótipo B, entre 34 acessos de tomateiro (Lycopersicon esculentum, do Banco de Germoplasma de Hortaliças da UFV. Avaliaram-se os números de adultos, ovos e ninfas por planta, além da densidade de tricomas. Detectaram-se diferenças entre os acessos nas variáveis avaliadas. Os acessos BGH-166, BGH-616, BGH-850, BGH-990, BGH-2102 e BGH-2125 apresentaram menor número de adultos, ovos e ninfas por planta e tiveram menor densidade de tricomas. A resistência dos acessos de tomate à mosca-branca foi associada a uma menor densidade de tricomas.The objective of this work was to evaluate resistance to Bemisia tabaci biotype B in 34 tomato (Lycopersicon esculentum accessions from the Banco de Germoplasma de Hortaliças of UFV. The number of adults, eggs and nymphs per plant besides of trichome density were evaluated. Differences between accessions were found for the evaluated variables. Accessions BGH-166, BGH-616, BGH-850, BGH-990, BGH-2102 and BGH-2125 presented less infestation of adults, eggs and nymphs per plant and showed lower trichome density. The resistance of these tomato accessions to whitefly was associated to a lower trichome density.

  10. De novo genome assembly of the economically important weed horseweed using integrated data from multiple sequencing platforms.

    Science.gov (United States)

    Peng, Yanhui; Lai, Zhao; Lane, Thomas; Nageswara-Rao, Madhugiri; Okada, Miki; Jasieniuk, Marie; O'Geen, Henriette; Kim, Ryan W; Sammons, R Douglas; Rieseberg, Loren H; Stewart, C Neal

    2014-11-01

    Horseweed (Conyza canadensis), a member of the Compositae (Asteraceae) family, was the first broadleaf weed to evolve resistance to glyphosate. Horseweed, one of the most problematic weeds in the world, is a true diploid (2n = 2x = 18), with the smallest genome of any known agricultural weed (335 Mb). Thus, it is an appropriate candidate to help us understand the genetic and genomic bases of weediness. We undertook a draft de novo genome assembly of horseweed by combining data from multiple sequencing platforms (454 GS-FLX, Illumina HiSeq 2000, and PacBio RS) using various libraries with different insertion sizes (approximately 350 bp, 600 bp, 3 kb, and 10 kb) of a Tennessee-accessed, glyphosate-resistant horseweed biotype. From 116.3 Gb (approximately 350× coverage) of data, the genome was assembled into 13,966 scaffolds with 50% of the assembly = 33,561 bp. The assembly covered 92.3% of the genome, including the complete chloroplast genome (approximately 153 kb) and a nearly complete mitochondrial genome (approximately 450 kb in 120 scaffolds). The nuclear genome is composed of 44,592 protein-coding genes. Genome resequencing of seven additional horseweed biotypes was performed. These sequence data were assembled and used to analyze genome variation. Simple sequence repeat and single-nucleotide polymorphisms were surveyed. Genomic patterns were detected that associated with glyphosate-resistant or -susceptible biotypes. The draft genome will be useful to better understand weediness and the evolution of herbicide resistance and to devise new management strategies. The genome will also be useful as another reference genome in the Compositae. To our knowledge, this article represents the first published draft genome of an agricultural weed.

  11. Biotypes of Gardnerella vaginalis.

    OpenAIRE

    Piot, P; Van Dyck, E; Peeters, M; Hale, J.; Totten, P A; Holmes, K K

    1984-01-01

    A simple and reproducible scheme for identifying biotypes of Gardnerella vaginalis has been developed, based on reactions for lipase, hippurate hydrolysis, and beta-galactosidase. Among a total of 359 strains tested, eight biotypes were observed, the most common ones being types 1 (beta-galactosidase positive, lipase positive, hippurate positive), 2 (beta-galactosidase negative, lipase positive, hippurate positive), and 5 (beta-galactosidase negative, lipase negative, hippurate positive). The...

  12. Plasmid mediated antibiotic resistance ofVibrio cholerae O1 biotype El Tor serotype Ogawa associated with an outbreak in Kolkata, India

    Institute of Scientific and Technical Information of China (English)

    Shyamapada Mandal; Manisha DebMandal; Nishith Kumar Pal

    2010-01-01

    Objective:To determine the antibiotic resistance ofVibrio cholerae (V. cholerae)O1 biotype El Tor serotype Ogawa isolates involved in an outbreak of watery diarrhea in Kolkata, and to explore the role of plasmid in mediating antibiotic resistance.Methods: Antibiotic susceptibility and minimum inhibitory concentration(MIC) values of antibiotics for the isolated V. choleraeO1 Ogawa (n=12) were determined by disk diffusion and agar dilution methods, respectively, using ampicillin (Am), chloramphenicol (C), trimethoprim (Tm), tetracycline (T), erythromycine (Er), nalidixic acid (Nx), ciprofloxacin (Cp), amikacin (Ak) and cefotaxime (Cf). Plasmid curing of multidrug resistant(MDR)V. choleraeO1 Ogawa strains was done following ethidium bromide treatment. Following electrophoresis, the plasmidDNAs, extracted from the isolatedMDRV. choleraeO1 Ogawa strains and their cured derivatives, were visualized and documented in‘gel doc’ system.Results: The outbreak causingV. choleraeO1 Ogawa isolates wereMDR as determined by disk diffusion susceptibility test, andMIC determination. The isolates showed three different drug resistance patterns: AmTmTErNx (for6 isolates), TmTErCp (for 5 isolates), and AmTmNx (for one isolate), and showed uniform sensitivity to C, Ak and Cf. The loss of plasmids with the concomitant loss of resistance to Am, Tm, T and Er of the isolates occurred following ethidium bromide treatment.Conclusions: The current findings suggest that theV. choleraeO1Ogawa associated with the cholera outbreak wereMDR, and resistance to Am, Tm, T and Er among the isolates were plasmid mediated.

  13. Crescimento diferencial de biótipos de Conyza SPP. resistente e suscetível ao herbicida glifosato Differential growth of glyphosate-resistant and susceptible biotypes of Conyza SPP

    Directory of Open Access Journals (Sweden)

    Murilo Sala Moreira

    2010-01-01

    Full Text Available Este trabalho foi realizado com o objetivo de comparar, em condição controlada e não-competitiva, o crescimento de biótipos de Conyza canadensis e C. bonariensis resistente e suscetível ao herbicida glifosato, a fim de quantificar os efeitos da pressão de seleção para resistência nos biótipos. Dois experimentos foram desenvolvidos com tratamentos organizados em esquema fatorial 9 x 2, com nove avaliações periódicas de crescimento e dois biótipos de cada espécie. As variáveis avaliadas por planta foram: área foliar; massa seca da parte aérea, das raízes e total, obtendo-se, a partir desta última, a taxa de crescimento absoluto. O biótipo de C. canadensis resistente ao glifosato possui crescimento mais lento, menor acúmulo de área foliar e de massa seca que o biótipo suscetível. Menores áreas foliar e massa seca também foram registradas para o biótipo de C. bonariensis resistente ao glifosato quando comparado ao suscetível, porém com diferenças mais sutis que aquelas constatadas para C. canadensis. O crescimento absoluto do biótipo suscetível foi superior ao do resistente em ambas as espécies. A pressão de seleção para resistência ao glifosato teve impactos negativos na habilidade de crescimento dos biótipos.This work was carried out with the objective of comparing, under controlled and non-competitive condition, the growth of glyphosate-resistant and susceptible biotypes of Conyza canadensis and C. bonariensis; to quantify the effects of resistance selection pressure on the biotypes. Two trials were developed with treatments organized according to a factorial scheme 9 x 2, where nine were periodical growth evaluations and two were biotypes of each species. The variables evaluated per plant were: leaf area and dry mass (shoot, root and total; to determine absolute growth rate from the total dry mass. The glyphosate-resistant biotype of C. canadensis exhibits slower growth and smaller accumulation of leaf area

  14. Controlling herbicide-susceptible, -tolerant and -resistant weeds with microbial bioherbicides

    Science.gov (United States)

    The management of weeds is a necessary but expensive challenge. Public concerns of health, safety, and sustainability have increased interest in reducing the use of synthetic chemicals for weed control. Alternatives to chemical herbicides, such as bioherbicides, may offer an alternative to herbicide...

  15. Auxinic herbicides, mechanisms of action, and weed resistance: A look into recent plant science advances

    Directory of Open Access Journals (Sweden)

    Pedro Jacob Christoffoleti

    2015-08-01

    Full Text Available Auxin governs dynamic cellular processes involved at several stages of plant growth and development. In this review, we discuss the mechanisms employed by auxin in light of recent scientific advances, with a focus on synthetic auxins as herbicides and synthetic auxin resistance mechanisms. Two auxin receptors were reported. The plasma membrane receptor ABP1 (Auxin Binding Protein 1 alters the structure and arrangement of actin filaments and microtubules, leading to plant epinasty and reducing peroxisomes and mitochondria mobility in the cell environment. The second auxin receptor is the gene transcription pathway regulated by the SCFTir/AFB ubiquitination complex, which destroys transcription repressor proteins that interrupt Auxin Response Factor (ARF activation. As a result mRNA related with Abscisic Acid (ABA and ethylene are transcribed, producing high quantities of theses hormones. Their associated action leads to high production of Reactive Oxygen Species (ROS, leading to tissue and plant death. Recently, another ubiquitination pathway which is described as a new auxin signaling route is the F-box protein S-Phase Kinase-Associated Protein 2A (SKP2A. It is active in cell division regulation and there is evidence that auxin herbicides can deregulate the SKP2A pathway, which leads to severe defects in plant development. In this discussion, we propose that SFCSKP2A auxin binding site alteration could be a new auxinic herbicide resistance mechanism, a concept which may contribute to the current progress in plant biology in its quest to clarify the many questions that still surround auxin herbicide mechanisms of action and the mechanisms of weed resistance.

  16. Study of Metal Resistance Potential of the Cd, Cr Tolerant Alligator Weed

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    Suparna Pal

    2014-03-01

    Full Text Available Background – Environmental deterioration due to heavy metal pollution is a major global concern for its immense importance in the ecosystem. Indiscriminate use of heavy metals for rapid urbanization and industrial exploration is a pressing threat to human health. Among this Cd and Cr contamination is most dangerous as these metals directly enter into the food chain due to their higher solubility and mobility. Identification of a metal tolerant native plant species would be helpful to decontaminate Cd and Cr polluted land. In our previous study, field investigations were conducted to evaluate the tolerance potential of Alligator weed to Cd and Cr.Alligator weed [Alternanthera philoxeroides (Mart. Griseb ],is the most widely distributed perennial stoloniferous herb in these contaminated areas in and around Kolkata. Purpose of the study – To establish metal tolerant capacity of the species , different biochemical parameters assessing its metal accumulation capacity and reflecting its detoxification mechanism were studied. For these purpose, the same plant collected from the highest metal contaminated area was grown under laboratory condition with external application of various concentration of Cd and Cr individually and synergistically (0.5, 0.8, 1.0, 1.2, 1.5, 1.8 mM. To estimate the hazardous effects of Cd and Cr on this weed, membrane damage was quantified in form of lipid peroxidation i.e MDA production. The metal uptake and accumulation potential was estimated by measuring the Cd and Cr concentration in root and shoot. Some soil parameters such as Orgnaic Carbon, Cation exchange capacity were also studied to explain the bio availability of metals. Various biochemical parameters such as free proline content, non protein- thiol content and zymogram analysis of antioxidative isozymes (such as, Guiacol peroxidase, superoxide dismutase, glutathione reductase and ascorbate peroxidase were studied to assess its metal resistant capacity. Result

  17. Yield of glyphosate-resistant sugar beets and efficiency of weed management systems with glyphosate and conventional herbicides under German and Polish crop production.

    Science.gov (United States)

    Nichterlein, Henrike; Matzk, Anja; Kordas, Leszek; Kraus, Josef; Stibbe, Carsten

    2013-08-01

    In sugar beet production, weed control is one of the most important and most expensive practices to ensure yield. Since glyphosate-resistant sugar beets are not yet approved for cultivation in the EU, little commercial experience exists with these sugar beets in Europe. Experimental field trials were conducted at five environments (Germany, Poland, 2010, 2011) to compare the effects of glyphosate with the effects of conventional weed control programs on the development of weeds, weed control efficiency and yield. The results show that the glyphosate weed control programs compared to the conventional methods decreased not only the number of herbicide applications but equally in magnitude decreased the dosage of active ingredients. The results also showed effective weed control with glyphosate when the weed covering was greater and sugar beets had a later growth stage of four true leaves. Glyphosate-resistant sugar beets applied with the glyphosate herbicide two or three times had an increase in white sugar yield from 4 to 18 % in comparison to the high dosage conventional herbicide systems. In summary, under glyphosate management sugar beets can positively contribute to the increasingly demanding requirements regarding efficient sugar beet cultivation and to the demands by society and politics to reduce the use of chemical plant protection products in the environment.

  18. Análise de crescimento de biótipos de amendoim-bravo (Euphorbia heterophylla resistente e suscetível aos herbicidas inibidores da ALS Growth analysis of wild poinsettia (Euphorbia heterophylla biotypes resistant and susceptible to ALS inhibitor herbicides

    Directory of Open Access Journals (Sweden)

    A.M. Brighenti

    2001-04-01

    Full Text Available A aplicação contínua de herbicidas do grupo químico das imidazolinonas, nas mesmas áreas de produção de soja, durante anos seguidos, no município de Cafelândia, PR, favoreceu a seleção de um biótipo resistente de amendoim-bravo (Euphorbia heterophylla aos herbicidas inibidores da acetolactato sintase (ALS. Um estudo comparativo das características do crescimento do biótipo resistente e do suscetível foi realizado em casa de vegetação da Embrapa Soja, Londrina-PR, a fim de identificar diferenças no crescimento e no desenvolvimento das plantas e de seus órgãos. A produção de matéria seca total, a área foliar, a matéria seca dos caule, das raízes e das folhas, bem como a altura por planta, foram avaliadas em 13 vezes a intervalos regulares, iniciando aos 14 dias após a semeadura. A partir desses parâmetros, foram calculadas a taxa de crescimento relativo, a taxa assimilatória líquida, a razão de área foliar, a razão de peso foliar e a área foliar específica, que decrescem com a ontogenia das plantas de amendoim-bravo, sendo similares para ambos os biótipos. A matéria seca total acumulada pelas plantas e seus órgãos, a área foliar e a altura apresentaram comportamentos semelhantes para os biótipos resistente e suscetível. O ciclo vegetativo dos dois biótipos estudados não mostrou diferença significativa quanto ao crescimento e ao desenvolvimento.Repetitive spraying of imidazolinone herbicides year after year to control weeds in the soybean grown areas of Cafelândia, Paraná, Brazil, has favored the selection of an ALS (acetolactate synthase inhibitor herbicide resistant biotype of wild poinsettia (Euphorbia heterophylla. A comparative study of growth and development of wild poinsettia resistant and susceptible to ALS inhibitor herbicides was carried out in the greenhouse of the experimental station of Soybean Embrapa in Londrina, Paraná, Brazil. Total dry biomass yield, leaf area, shoot dry weight, leaf

  19. A new perspective with weed management

    Science.gov (United States)

    No-till cropping systems are increasing land productivity. Herbicides are a crucial tool for weed management in no-till, but weed resistance is decreasing control efficacy and increasing input costs. Producers are seeking a broader perspective with weed management. One approach is to disrupt weed...

  20. Is hormesis an underestimated factor in the development of herbicide resistance?

    Directory of Open Access Journals (Sweden)

    Belz, Regina G.

    2014-02-01

    Full Text Available The growing impact of herbicide resistant weeds increasingly affects weed management and the delay of resistance evolution has become a major task of chemical weed control. Hormesis and, thus, the phenomenon that low doses of herbicides can boost weed growth could be of importance in this regard since the recommended field rate may represent a low dose for weeds that have evolved resistance to the applied herbicide and, thus, a potential hormetic dose. Applying the field rate may thus not only directly select resistant biotypes, it may also indirectly promote the success and spread of resistant biotypes via hormesis. Nevertheless, hormetic effects in resistant weeds are hitherto merely randomly observed and, thus, a clear quantitative basis to judge the significance of hormesis for resistance evolution is lacking. Therefore, this study aimed at quantifying the degree and frequency of herbicide hormesis in sensitive and resistant weed species in order to provide a first indication of whether the phenomenon deserves consideration as a potential factor contributing to the development of herbicide resistance. In germination assays complete dose-response experiments were conducted with sensitive and resistant biotypes of Matricaria inodora (ALS-target-site resistant; treated with iodosulfuron-methyl-sodium/mesosulfuron-methyl, Eleusine indica (glyphosateresistant; treated with glyphosate, and Chenopodium album (triazine/triazinone-target-site resistant; treated with terbuthylazine. After 10 days of cultivation under controlled conditions plant growth was analyzed by measuring shoot/root length and mass. Results indicated that herbicide hormesis occurred on average with a total frequency of 29% in sensitive/resistant biotypes with an average growth increase of 53% occurring typically within a dose zone exceeding 350fold. Hormetic effects occurred, however, very variable and only for specific endpoints and not plant growth in general. If such a

  1. Biotyping of Bacillus cereus from the street vended Foods in Srinagar area of Kashmir

    Directory of Open Access Journals (Sweden)

    Yasir Hafeez

    Full Text Available Aim: The present study was undertaken to describe the biotyping of Bacillus cereus isolated from different street vended mutton tikka and chutney samples. Materials and Methods: A total of 100 street vended food samples comprising of 60 mutton tikka and 40 chutney samples were tested. Results: The biotype 3 and biotype 4 showed the highest occurrence with, 29.63% and 25.93% isolates falling in these biotypes, respectively. The percentage occurrence of the biotypes 1, 6, 2, 5, and 7 was 14.81%, 11.11%, 7.40%, 7.40% and 3.84%, respectively. The most common found biotypes in Mutton tikka were biotypes 3(29.63%, 4(25.93%, 1(14.81% and 6(11.11%. The Bacillus cereus strains isolated from chutney samples could be divided into 7 of the 9 possible biotypes. The biotypes 6 and 7 showed the highest occurrence with 38.46% and 30.76% falling in these biotypes, respectively. The biotype 5 and 2 were prevalent to the extent of 23.07%, 7.69%, respectively. The biotypes 3, 4 and 1 were absent. The mean bacterial count of 60 mutton tikka and 40 chutney samples was 4.6817 and 5.6575 log cfu/g. 10 Conclusion: The field isolates and the standard strains of Bacillus cereus had similar cultural, morphological and biochemical characteristics. The biotypes recovered from the Mutton tikka samples were biotypes 3, 4, 1 and 6 and in chutneys the biotypes recovered were 6, 7, 5 and 2. The strains of Bacillus cereus were highly resistant to penicillin G (92.59%. [Vet World 2012; 5(10.000: 590-593

  2. Cyperus difformis evolves resistance to propanil

    DEFF Research Database (Denmark)

    Valverde Mena, Bernal Eduardo; Boddy, Louis G.; Pedroso, Rafael M.

    2014-01-01

    Cyperus difformis L. is one of the worst weeds of rice world-wide and has evolved resistance to acetolactate synthase (ALS)-inhibiting herbicides in rice fields of California. Propanil use was intensified to control the widespread resistant biotypes. Rice growers have recently experienced poor...... control, suggesting resistance to this photosystem II-inhibiting herbicide may have evolved in C.difformis populations. The objectives of this study were to detect the presence of propanil resistance, to establish resistance levels, and to investigate involvement of enhanced herbicide detoxification...... resistance to an herbicide mechanism of action other than ALS inhibition. Carbaryl and malathion applied individually in mixture with propanil had minor effects on herbicide toxicity suggesting metabolic detoxification was not a resistance mechanism. A resistant biotype produced more than 80% biomass after...

  3. 抗草甘膦杂草的抗性机理研究进展%Advances on Resistance Mechanism of Glyphosate-Resistant Weeds

    Institute of Scientific and Technical Information of China (English)

    巩元勇; 郭书巧; 束红梅; 王庆南; 倪万潮

    2012-01-01

    草甘膦因其独特而优异的理化特性,自上市起便受到广泛的关注,现在已经成为全世界应用最广的除草剂之一.但是随着草甘膦抗性杂草的不断出现,草甘膦的应用前景受到严峻的挑战.文章综述了草甘膦生产及应用现状、草甘膦作用机理和草甘膦抗性杂草的发展,重点阐述了草甘膦抗性杂草的抗性机理.最后对如何通过延缓草甘膦抗性杂草的出现,保护草甘膦提出建议.%Glyphosate, because of its unique and excellent physical and chemical properties, has attracted much attention since it was commercialized. At present, glyphosate has become one of the most widely used herbicide around the world. But with the emergence of glyphosate - resistant weeds population, the application prospect of glyphosate has been seriously challenged. In this paper it was reviewed in the production and application status, the mechanism of action of glyphosate and the development of glyphosate — resistant weeds especially focused on introduction of the resistance mechanism of glyphosate - resistant weeds. Finally, how to delay the emergence of glyphosate - resistant weeds to protect the application of glyphosate has been also proposed in this paper.

  4. Aspectos morfofisiológicos de biótipos de azevém (Lolium multiflorum sensíveis e resistentes ao glyphosate Morphophysiological aspects of ryegrass biotypes (Lolium multiflorum sensitive and resistant to glyphosate

    Directory of Open Access Journals (Sweden)

    J Galvan

    2011-01-01

    Full Text Available O azevém é uma gramínea com elevado potencial de infestação em lavouras e pomares, e seu controle com glyphosate tem sido limitado devido à existência de biótipos resistentes a esse herbicida. Objetivou-se comparar quatro biótipos de azevém coletados em diferentes regiões do Rio Grande do Sul, com o intuito de testar a hipótese de que aspectos morfofisiológicos e fenológicos estejam vinculados à resistência. O experimento foi conduzido em casa de vegetação, onde um biótipo suscetível (B1S, Passo Fundo e três resistentes ao glyphosate (B2R, Santa Maria; B3R, Júlio de Castilhos; e B4R, Vacaria foram colhidos aos 126, 147, 168 e 189 dias de idade. O biótipo B1S mostrou 21 dias de antecipação no florescimento em relação aos demais biótipos. O biótipo B4R produziu significativamente mais folhas (43 por planta, afilhos (14 por planta, espigas (14 por planta, sementes (3.484 por planta e matéria seca total (raízes + parte aérea = 13,8 g por planta. Conclui-se que biótipos sensíveis não podem ser diferidos de biótipos resistentes apenas por aspectos morfológicos relacionados ao vigor.Ryegrass has a high potential for infestation in crops and orchads and its control with glyphosate has been limited due to the existence of herbicide-resistant biotypes. The objective of this work was to compare four ryegrass biotypes collected from different regions in the state of Rio Grande do Sul, Brazil, to test the hypothesis that morphophysiological aspects and phenology are linked to resistance. The experiment was conducted in a greenhouse, where four biotypes, one susceptible (B1S, Passo Fundo and three resistant to glyphosate (B2R, Santa Maria; B3R, Julio de Castillos; B4R, Vacaria were collected at 126, 147, 168 and 189 days of age. Biotype B1S showed 21 days in advance of flowering in relation to the other biotypes. Biotype B4R produced significantly more leaves (43 per plant, tillers (14 per plant, ears (14 per plant, seeds

  5. Mechanisms of resistance to paraquat in plants.

    Science.gov (United States)

    Hawkes, Timothy R

    2014-09-01

    The aim of this brief review is to draw information from studies of the mechanism of evolved resistance in weeds, together with information from laboratory studies of paraquat tolerance in model plants. Plants having mutations that limit paraquat uptake into cytoplasm, that confer various stress tolerances or that have transgenes that co-express two or more of the chloroplast Halliwell-Asada cycle enzymes can all exhibit enhanced tolerance to paraquat. However, none of these mechanisms correspond to the high-level resistances that have evolved naturally in weeds. Most, but not all, of the evidence from studies of paraquat-resistant biotypes of weeds can reasonably be reconciled with the proposal of a single major gene mechanism that sequesters paraquat away from chloroplasts and into the vacuole. However, the molecular details of this putative mechanism remain ill-defined.

  6. Resistance to lettuce aphid (Nasonovia ribisnigri) biotype 0 in wild lettuce accessions PI 491093 and PI 274378

    Science.gov (United States)

    Lettuce aphid, Nasonovia ribisnigri Mosley (Homoptera : Aphididae), is a major insect pest of lettuce, Lactuca sativa L, in many commercial lettuce productions areas around the world. Resistance to lettuce aphid was first reported in Lactuca virosa L. accession IVT 280 and characterized as complete,...

  7. Predicting spring barley yield from variety-specific yield potential, disease resistance and straw length, and from environment-specific disease loads and weed pressure

    DEFF Research Database (Denmark)

    Østergård, Hanne; Kristensen, Kristian; Pinnschmidt, Hans O.;

    2008-01-01

    For low-input crop production, well-characterised varieties increase the possibilities of managing diseases and weeds. This analysis aims at developing a framework for analyzing grain yield using external varietal information about disease resistance, weed competitiveness and yield potential...... and quantifying the impact of susceptibility grouping and straw length scores (as a measure for weed competitiveness) for predicting spring barley grain yield under variable biotic stress levels. The study comprised 52 spring barley varieties and 17 environments, i.e., combinations of location, growing system...... and year. Individual varieties and their interactions with environments were analysed by factorial regression of grain yield on external variety information combined with observed environmental disease loads and weed pressure. The external information was based on the official Danish VCU testing. The most...

  8. Advances in the Detection Methods of Glyphosate-Resistant Weeds%抗草甘膦杂草检测方法的研究进展

    Institute of Scientific and Technical Information of China (English)

    杨浩娜; 柏连阳

    2014-01-01

    Evolution of glyphosate-resistant weeds is becoming an increasingly serious problem.Relevant detection meth-ods of glyphosate-resistant weeds developed at home and abroad are summarized,with a simple overview and brief analy-sis.The paper aims to provide basis for the development of glyphosate-resistant weeds detection methods and the estab-lishment of the rapid detection methods.%目前,抗草甘膦杂草问题日趋严重。通过检索国内外抗草甘膦杂草的检测方法,总结出常用检测方法和其他检测方法,进行了简单概述,为抗草甘膦杂草检测体系的发展提供依据。

  9. Resistance to herbicides caused by single amino acid mutations in acetyl-CoA carboxylase in resistant populations of grassy weeds.

    Science.gov (United States)

    Jang, SoRi; Marjanovic, Jasmina; Gornicki, Piotr

    2013-03-01

    Eleven spontaneous mutations of acetyl-CoA carboxylase have been identified in many herbicide-resistant populations of 42 species of grassy weeds, hampering application of aryloxyphenoxypropionate, cyclohexadione and phenylpyrazoline herbicides in agriculture. IC(50) shifts (resistance indices) caused by herbicide-resistant mutations were determined using a recombinant yeast system that allows comparison of the effects of single amino acid mutations in the same biochemical background, avoiding the complexity inherent in the in planta experiments. The effect of six mutations on the sensitivity of acetyl-CoA carboxylase to nine herbicides representing the three chemical classes was studied. A combination of partially overlapping binding sites of the three classes of herbicides and the structure of their variable parts explains cross-resistance among and between the three classes of inhibitors, as well as differences in their specificity. Some degree of resistance was detected for 51 of 54 herbicide/mutation combinations. Introduction of new herbicides targeting acetyl-CoA carboxylase will depend on their ability to overcome the high degree of cross-resistance already existing in weed populations. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

  10. Biotechnology in weed control

    Science.gov (United States)

    Biotechnology can be used to enhance the management of weeds in several ways. Crops have been made resistant to herbicides by inserting transgenes that impart herbicide resistance into the plant genome. Glyphosate and glufosinate-resistant crops are commercialized in North America and crops made res...

  11. Agronomic Weeds.

    Science.gov (United States)

    Hartwig, Nathan L.

    This agriculture extension service publication from Pennsylvania State University examines agronomic weed problems and control. Contents include a listing of the characteristics of weeds, a section on herbicides, and a section on the important weeds of agronomic crops in Pennsylvania. The herbicide section discusses systemic herbicides, contact…

  12. Agronomic Weeds.

    Science.gov (United States)

    Hartwig, Nathan L.

    This agriculture extension service publication from Pennsylvania State University examines agronomic weed problems and control. Contents include a listing of the characteristics of weeds, a section on herbicides, and a section on the important weeds of agronomic crops in Pennsylvania. The herbicide section discusses systemic herbicides, contact…

  13. 杂草对百草枯的抗药性机制研究进展%Research advances in paraquat-resistance mechanisms of weeds

    Institute of Scientific and Technical Information of China (English)

    李颖慧; 陈勇

    2012-01-01

    The infestation of paraquat-resistant weeds can cause serious damage to food production , and indirectly increase environmental pollution. This paper reviewed the recent years' research advances in the occurrence, development, and damage of paraquat-resistant weeds, and discussed the mechanisms of paraquat-resistant weeds, with the focus on the relationship between transporter and resistance, restriction and isolation, protective effect of antioxidant enzymes, in fluence of light on resistant mechanisms, and genetics of paraquat resistance. It was considered that there would be an outbreak risk of paraquat-resistant weeds in China in the future, and the strategies of delaying the occurrence of paraquat-resistant weeds were suggested.%百草枯抗性杂草的产生严重危害粮食生产并间接加重环境污染.本文综述了近年来多种抗百草枯杂草的发生、发展与危害等方面的研究进展,重点对转运体与杂草抗药性关系、百草枯的限制隔离机制、抗氧化酶保护作用进行了分析,并从光照对抗性机的制影响和杂草抗药性遗传规律等方面对百草枯的抗性机制展开了讨论,认为未来中国存在出现大规模抗百草枯杂草的风险,提出了延缓杂草对百草枯产生抗性的策略.

  14. Herbicides as weed control agents: state of the art: II. Recent achievements.

    Science.gov (United States)

    Kraehmer, Hansjoerg; van Almsick, Andreas; Beffa, Roland; Dietrich, Hansjoerg; Eckes, Peter; Hacker, Erwin; Hain, Ruediger; Strek, Harry John; Stuebler, Hermann; Willms, Lothar

    2014-11-01

    In response to changing market dynamics, the discovery of new herbicides has declined significantly over the past few decades and has only seen a modest upsurge in recent years. Nevertheless, the few introductions have proven to be interesting and have brought useful innovation to the market. In addition, herbicide-tolerant or herbicide-resistant crop technologies have allowed the use of existing nonselective herbicides to be extended into crops. An increasing and now major challenge is being posed by the inexorable increase in biotypes of weeds that are resistant to herbicides. This problem is now at a level that threatens future agricultural productivity and needs to be better understood. If herbicides are to remain sustainable, then it is a must that we adopt diversity in crop rotation and herbicide use as well as increase the use of nonchemical measures to control weeds. Nevertheless, despite the difficulties posed by resistant weeds and increased regulatory hurdles, new screening tools promise to provide an upsurge of potential herbicide leads. Our industry urgently needs to supply agriculture with new, effective resistance-breaking herbicides along with strategies to sustain their utility.

  15. Metabolism-based herbicide resistance and cross-resistance in crop weeds: a threat to herbicide sustainability and global crop production.

    Science.gov (United States)

    Yu, Qin; Powles, Stephen

    2014-11-01

    Weedy plant species that have evolved resistance to herbicides due to enhanced metabolic capacity to detoxify herbicides (metabolic resistance) are a major issue. Metabolic herbicide resistance in weedy plant species first became evident in the 1980s in Australia (in Lolium rigidum) and the United Kingdom (in Alopecurus myosuroides) and is now increasingly recognized in several crop-weed species as a looming threat to herbicide sustainability and thus world crop production. Metabolic resistance often confers resistance to herbicides of different chemical groups and sites of action and can extend to new herbicide(s). Cytochrome P450 monooxygenase, glycosyl transferase, and glutathione S-transferase are often implicated in herbicide metabolic resistance. However, precise biochemical and molecular genetic elucidation of metabolic resistance had been stalled until recently. Complex cytochrome P450 superfamilies, high genetic diversity in metabolic resistant weedy plant species (especially cross-pollinated species), and the complexity of genetic control of metabolic resistance have all been barriers to advances in understanding metabolic herbicide resistance. However, next-generation sequencing technologies and transcriptome-wide gene expression profiling are now revealing the genes endowing metabolic herbicide resistance in plants. This Update presents an historical review to current understanding of metabolic herbicide resistance evolution in weedy plant species. © 2014 American Society of Plant Biologists. All Rights Reserved.

  16. Metabolism-Based Herbicide Resistance and Cross-Resistance in Crop Weeds: A Threat to Herbicide Sustainability and Global Crop Production1

    Science.gov (United States)

    Yu, Qin; Powles, Stephen

    2014-01-01

    Weedy plant species that have evolved resistance to herbicides due to enhanced metabolic capacity to detoxify herbicides (metabolic resistance) are a major issue. Metabolic herbicide resistance in weedy plant species first became evident in the 1980s in Australia (in Lolium rigidum) and the United Kingdom (in Alopecurus myosuroides) and is now increasingly recognized in several crop-weed species as a looming threat to herbicide sustainability and thus world crop production. Metabolic resistance often confers resistance to herbicides of different chemical groups and sites of action and can extend to new herbicide(s). Cytochrome P450 monooxygenase, glycosyl transferase, and glutathione S-transferase are often implicated in herbicide metabolic resistance. However, precise biochemical and molecular genetic elucidation of metabolic resistance had been stalled until recently. Complex cytochrome P450 superfamilies, high genetic diversity in metabolic resistant weedy plant species (especially cross-pollinated species), and the complexity of genetic control of metabolic resistance have all been barriers to advances in understanding metabolic herbicide resistance. However, next-generation sequencing technologies and transcriptome-wide gene expression profiling are now revealing the genes endowing metabolic herbicide resistance in plants. This Update presents an historical review to current understanding of metabolic herbicide resistance evolution in weedy plant species. PMID:25106819

  17. A Modified phosphate-carrier protein theory is proposed as a non-target site mechanism For glyphosate resistance in weeds Teoria das proteínas carregadoras fosfato modificadas proposta como mecanismo de resistência ao herbicida glyphosate em plantas daninhas

    Directory of Open Access Journals (Sweden)

    A.C. Roso

    2010-01-01

    Full Text Available Glyphosate is an herbicide that inhibits the enzyme 5-enolpyruvyl-shikimate-3-phosphate synthase (EPSPs (EC 2.5.1.19. EPSPs is the sixth enzyme of the shikimate pathway, by which plants synthesize the aromatic amino acids phenylalanine, tyrosine, and tryptophan and many compounds used in secondary metabolism pathways. About fifteen years ago it was hypothesized that it was unlikely weeds would evolve resistance to this herbicide because of the limited degree of glyphosate metabolism observed in plants, the low resistance level attained to EPSPs gene overexpression, and because of the lower fitness in plants with an altered EPSPs enzyme. However, today 20 weed species have been described with glyphosate resistant biotypes that are found in all five continents of the world and exploit several different resistant mechanisms. The survival and adaptation of these glyphosate resistant weeds are related toresistance mechanisms that occur in plants selected through the intense selection pressure from repeated and exclusive use of glyphosate as the only control measure. In this paper the physiological, biochemical, and genetic basis of glyphosate resistance mechanisms in weed species are reviewed and a novel and innovative theory that integrates all the mechanisms of non-target site glyphosate resistance in plants is presented.Glyphosate é uma glicina fosfonada e inibe a enzima 5-enolpiruvil-shikimato-3-fosfato sintase (EPSPS (EC 2.5.1.19. EPSPS é a sexta enzima da rota do shikimato, na qual são sintetizados os compostos do metabolismo secundário e os aminoácidos aromáticos fenilalanina, tirosina e triptofano. Alguns autores hipotetizaram que seria improvável a evolução de plantas daninhas resistentes a este herbicida. As justificativas estariam relacionadas à limitada metabolização de glyphosate nas plantas, ao baixo nível de resistência obtido com a superexpressão do gene EPSPS e à alta penalidade de adaptação oriunda de mutações no

  18. Impact of imazamox containing herbicides on the development of resistance in black-grass (Alopecurus myosuroides Huds. within an oilseed rape / wheat crop rotation

    Directory of Open Access Journals (Sweden)

    Rosenhauer, Marie

    2016-02-01

    Full Text Available The application of imazamox as an herbicide in oilseed-rape got possible due to the introduction of Clearfield oilseed-rape varieties which are tolerant to ALS inhibitors. The question of this investigation was, if the broader use of ALS-inhibitors increases the selection pressure on herbicide resistant weeds and increases their occurrence in the crop rotation. An outdoor container trial with 30 containers (350 l, 0,7 m² was performed, starting in autumn 2011. A winter wheat – oilseed-rape rotation was simulated for four years. Three different black-grass biotypes with different resistance pattern and 5 different herbicide programmes were analysed in this study in order to investigate the population dynamics of target-site resistance (TSR and the development of metabolic resistance. The trials showed interactions between the black-grass biotype and the herbicide strategy on the increase of the black-grass density. There was no interaction due to the use of propyzamide. The frequency of target-site resistance to ACCase inhibitors increased for the corresponding biotypes independently of the herbicide strategy during the trial period. The low frequency of ALS-TSR at trial start did not change during the trial period, independently of the use of imazamox in the oil-seed rape cultivation. The comparison of the resistance factors between the original biotypes and the seeds harvested after the four year container trial showed increasing resistances against pinoxaden for all biotypes. Within the different black-grass biotypes there was a slightly decrease as well as an increase in imazamox efficacy observed. There was no significant increase of meso- + iodosulfuron resistance compared to the original biotypes from 2011 caused by different herbicide treatments. The results indicated that the integration of imazamox tolerant oilseed rape in winter wheat crop rotations did not necessarily increase the development of herbicide resistant black-grass.

  19. Distribution of Bemisia tabaci (Hemiptera: Aleyrodidae) biotypes in North America after the Q invasion.

    Science.gov (United States)

    McKenzie, Cindy L; Bethke, James A; Byrne, Frank J; Chamberlin, Joseph R; Dennehy, Timothy J; Dickey, Aaron M; Gilrein, Dan; Hall, Paula M; Ludwig, Scott; Oetting, Ronald D; Osborne, Lance S; Schmale, Lin; Shatters, Robert G

    2012-06-01

    After the 2004 discovery of the Bemisia tabaci (Gennadius) (Hemiptera Aleyrodidae) Q biotype in the United States, there was a vital need to determine the geographical and host distribution as well as its interaction with the resident B biotype because of its innate ability to rapidly develop high-level insecticide resistance that persists in the absence of exposure. As part of a coordinated country-wide effort, an extensive survey of B. tabaci biotypes was conducted in North America, with the cooperation of growers, industry, local, state, and federal agencies, to monitor the introduction and distribution of the Q biotype. The biotype status of submitted B. tabaci samples was determined either by polymerase chain reaction amplification and sequencing of a mitochondrial cytochrome oxidase I small subunit gene fragment and characterization of two biotype discriminating nuclear microsatellite markers or esterase zymogram analysis. Two hundred and eighty collections were sampled from the United States, Bermuda, Canada, and Mexico during January 2005 through December 2011. Host plants were split between ornamental plant and culinary herb (67%) and vegetable and field crop (33%) commodities. The New World biotype was detected on field-grown tomatoes (Solanum lycopersicum L.) in Mexico (two) and in commercial greenhouses in Texas (three) and represented 100% of these five collections. To our knowledge, the latter identification represents the first report of the New World biotype in the United States since its rapid displacement in the late 1980s after the introduction of biotype B. Seventy-one percent of all collections contained at least one biotype B individual, and 53% of all collections contained only biotype B whiteflies. Biotype Q was detected in 23 states in the United States, Canada (British Columbia and Ontario territories), Bermuda, and Mexico. Forty-five percent of all collections were found to contain biotype Q in samples from ornamentals, herbs and a single

  20. Composição química da cera epicuticular de biótipos de azevém resistente e suscetível ao glyphosate Chemical composition of the epicuticular wax of Italian ryegrass biotypes resistant and susceptible to glyphosate

    Directory of Open Access Journals (Sweden)

    A.A. Guimarães

    2009-03-01

    Full Text Available Objetivou-se com este trabalho determinar a composição química da cera epicuticular dos biótipos de azevém (Lolium multiflorum resistente e suscetível ao glyphosate, buscando relações entre suas características e a resistência dos biótipos ao herbicida. A cera epicuticular foi extraída e quantificada e os seus constituintes analisados por cromatografia em fase gasosa, acoplada a espectrômetro de massa (CG-EM. Para determinação da composição química, amostras de lâmina foliar foram retiradas 30 dias após a emergência das plantas, coletando-se a primeira folha com lígula totalmente visível. A quantidade de cera epicuticular extraída não diferiu entre os biótipos. Entre os compostos que constituem a cera epicuticular, os álcoois são os mais abundantes, sendo representados por apenas um composto: o hexacosan-1-ol (46,80% no biótipo resistente e 52,20% no biótipo suscetível. Ao comparar a polaridade da cera epicuticular dos biótipos de azevém, constatou-se que tanto no biótipo resistente quanto no suscetível a cera epicuticular apresentou mais de 50% de componentes polares (álcoois e aldeídos em sua constituição, sendo esse valor igual a 69,80% no biótipo resistente e 64,94% no biótipo suscetível. Por meio da caracterização apresentada, pode-se afirmar que existem pequenas diferenças na cera epicuticular dos biótipos de azevém resistente e suscetível ao glyphosate; o biótipo resistente apresentou grau de polaridade pouco superior ao do biótipo suscetível, porém essa diferença não pode ser considerada marcante a ponto de determinar maior ou menor tolerância de um biótipo ou outro ao herbicida glyphosate.The objective of this work was to determine the chemical composition of epicuticular wax of Italian ryegrass (Lolium multiflorum biotypes resistant and susceptible to glyphosate, searching for relationships between their characteristics and the resistance of the biotypes to the product. The

  1. Development of a Geo-Referenced Database for Weed Mapping and Analysis of Agronomic Factors Affecting Herbicide Resistance in Apera spica-venti L. Beauv. (Silky Windgrass

    Directory of Open Access Journals (Sweden)

    Dario Massa

    2013-01-01

    Full Text Available In this work, we evaluate the role of agronomic factors in the selection for herbicide resistance in Apera spica-venti L. Beauv. (silky windgrass. During a period of three years, populations were collected in more than 250 conventional fields across Europe and tested for resistance in the greenhouse. After recording the field history of locations, a geo-referenced database has been developed to map the distribution of herbicide-resistant A. spica-venti populations in Europe. A Logistic Regression Model was used to assess whether and to what extent agricultural and biological factors (crop rotation, soil tillage, sowing date, soil texture and weed density affect the probability of resistance selection apart from the selection pressure due to herbicide application. Our results revealed that rotation management and soil tillage are the factors that have the greatest influence on the model. In addition, first order interactions between these two variables were highly significant. Under conventional tillage, a percentage of winter crops in the rotation exceeding 75% resulted in a 1280-times higher risk of resistance selection compared to rotations with less than 50% of winter crops. Under conservation tillage, the adoption of >75% of winter crops increased the risk of resistance 13-times compared to rotations with less than 50% of winter crops. Finally, early sowing and high weed density significantly increased the risk of resistance compared to the reference categories (later sowing and low weed density, respectively. Soil texture had no significant influence. The developed model can find application in management programs aimed at preventing the evolution and spread of herbicide resistance in weed populations.

  2. Interference of Selected Palmer Amaranth (Amaranthus palmeri Biotypes in Soybean (Glycine max

    Directory of Open Access Journals (Sweden)

    Aman Chandi

    2012-01-01

    Full Text Available Palmer amaranth (Amaranthus palmeri S. Wats. has become difficult to control in row crops due to selection for biotypes that are no longer controlled by acetolactate synthase inhibiting herbicides and/or glyphosate. Early season interference in soybean [Glycine max (L. Merr.] for 40 days after emergence by three glyphosate-resistant (GR and three glyphosate-susceptible (GS Palmer amaranth biotypes from Georgia and North Carolina was compared in the greenhouse. A field experiment over 2 years compared season-long interference of these biotypes in soybean. The six Palmer amaranth biotypes reduced soybean height similarly in the greenhouse but did not affect soybean height in the field. Reduction in soybean fresh weight and dry weight in the greenhouse; and soybean yield in the field varied by Palmer amaranth biotypes. Soybean yield was reduced 21% by Palmer amaranth at the established field density of 0.37 plant m−2. When Palmer amaranth biotypes were grouped by response to glyphosate, the GS group reduced fresh weight, dry weight, and yield of soybean more than the GR group. The results indicate a possible small competitive disadvantage associated with glyphosate resistance, but observed differences among biotypes might also be associated with characteristics within and among biotypes other than glyphosate resistance.

  3. Use of chlorophyll lfuorescence and P700 absorbance to rapidly detect glyphosate resistance in goosegrass (Eleusine indica)

    Institute of Scientific and Technical Information of China (English)

    ZHANG Tai-jie; FENG Li; TIAN Xing-shan; YANG Cai-hong; GAO Jia-dong

    2015-01-01

    The rapid detection of glyphosate resistance in goosegrass (Eleusine indica) wil enhance our ability to respond to new resistant populations of this major weed. Chlorophyl lfuorescence (Fluo) and P700 (reaction center chlorophyl of pho-tosystem I) absorbance were analyzed in one biotype of goosegrass that is resistant to glyphosate and in another that remains sensitive to the herbicide. Both biotypes were treated with a foliar spray of glyphosate. Differences in photosys-tem II maximum quantum yield (Fv/Fm), effective photochemical quantum yield (Y(II)), and non-photochemical quenching (NPQ) between the biotypes increased over time. Values for Fv/Fm and Y(II) differed between the two biotypes 24 h after treatment (HAT). Differentiated activities and energy dissipation processes of photosystem II (PSII) and energy dissipation processes of photosystem I (PSI) were manifested in the two biotypes 24 HAT with 20 mmol L–1 glyphosate. Differentiated energy dissipation processes of PSI were stil apparent 24 HAT with 200 mmol L–1 glyphosate. These results indicate that the Fluo parameters related to PSII activity and energy dissipation and the P700 parameters related to energy dissipation are suitable indicators that enable rapid detection of glyphosate resistance in goosegrass.

  4. 杂草抗药性及其治理策略研究进展%Research Progress on Weed Resistance to Herbicides and Control Methods

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    The mechanisms and factors that influence the evolution of herbicide resistance in weeds are reviewed along with the weed control practices available for the control of herbicide -resistant weeds.Weed resistance to herbicides can be of two types,namely target -site resistance that includes the alteration of the site of action,gene amplification and over-expression,and non -target -site resistance that includes enhancement of metabolic detoxification,limited uptake and translocation,and compartmentalization.The evolution of weed resistance is influenced by many factors,such as resistance mutation frequency,herbicide selective pressure,weed fitness and weed seed bank life.Additionally,gene mutation and genetic characteristics are directly related to its evolution.It is advisable to investigate and identify resistant weeds in fields regularly,apply herbicides properly (with rotation or mixture of active ingredients),and to integrate agronomic man-agement practices to prevent evolution of weed resistance to herbicides in the future.Additionally,fundamental research on allelopathy in plants should be emphasized for providing theoretical bases for developing safer herbicides.%综述了杂草抗药性产生机理、杂草抗药性演化影响因素,并对其治理途径进行阐述,为杂草抗药性治理提供参考。除草剂抗药机制分为靶标抗性、非靶标抗性,其中靶标抗性包括除草剂作用位点改变、基因倍增及过量表达;非靶标抗性主要包括代谢解毒能力增强、屏蔽作用或与作用位点的隔离作用等。杂草抗药性演化受多种因素共同影响,不仅包括抗药性突变频率、除草剂选择压、杂草适合度及杂草种子库寿命四大因素,还与基因突变和遗传特征直接相关。在未来的杂草治理中,要经常进行田间杂草调查与鉴定,正确使用除草剂(交替使用、混用),并辅以合理的农艺管理措施来减缓杂草抗药性的演化速

  5. Herbicide-tolerant Transgenic Soybean over 15 Years of Cultivation: Pesticide Use, Weed Resistance, and Some Economic Issues. The Case of the USA

    Directory of Open Access Journals (Sweden)

    Sylvie Bonny

    2011-08-01

    Full Text Available Genetically modified (GM herbicide-tolerant (HT crops have been largely adopted where they have been authorized. Nevertheless, they are fiercely criticized by some, notably because of the herbicide use associated with them. However, how much herbicide is applied to GMHT crops compared to conventional crops, and what impacts does the use of herbicide have? The paper first presents some factors explaining the predominance of GMHT crops. Then, trends in the use of herbicide for GM crops are studied in the case of the most widespread HT crop: HT soybean in the USA. The trends in the toxicity of herbicides applied to HT soybean are also addressed, as well as the appearance of glyphosate-resistant (GR weeds. Lastly, the paper examines the spread of GR weeds and its impact. How are farmers, weed scientists, and the industry coping with this development, and what are the prospects of glyphosate-tolerant crops given weed resistance? In conclusion, some issues of sustainability and innovation governance raised by genetically modified herbicide-tolerant crops are discussed.

  6. Examining the competitive advantage of Diuraphis noxia (Hemiptera: Aphididae) biotype 2 over biotype 1.

    Science.gov (United States)

    Merrill, Scott C; Randolph, Terri L; Peairs, Frank B; Michels, G J; Walker, C B

    2014-08-01

    The Russian wheat aphid, Diuraphis noxia (Kurdjumov) is a serious pest of small grains, such as wheat and barley. High population growth rates and a broad gramineae host range have allowed this aphid to successfully establish and become pestiferous across much of North America since its invasion in the mid-1980s. Resistant wheat cultivars were developed and provided control ofD. noxia until 2003, when a new biotype (designated RWA2, as contrasted with the original biotype's designation, RWA1) emerged and rapidly spread through dryland winter wheat-growing regions. RWA2 displaced RWA1 more quickly than expected, based on RWA2's advantage in RWA1-resistant wheat cultivars. Previous research suggested that RWA2 may out-compete RWA1 in cooler temperatures. Thus, we sought to determine if RWA2 had a competitive advantage over RWA1 during the overwintering period. We placed a known distribution of RWA1 and RWA2 aphids in the field for the winter at three sites across a latitudinal gradient (from northern Colorado to Texas) to test for a competitive advantage between these biotypes. We found overwhelming support for an overwintering competitive advantage by RWA2 over RWA1, with evidence suggesting a > 10-fold advantage even at our Texas site (i.e., the site with the mildest winter). This substantial overwintering advantage helps explain the quick dispersion and displacement of RWA1 by RWA2.

  7. Quantitative proteomics reveals ecological fitness cost of multi-herbicide resistant barnyardgrass (Echinochloa crus-galli L.).

    Science.gov (United States)

    Yang, Xia; Zhang, Zichang; Gu, Tao; Dong, Mingchao; Peng, Qiong; Bai, Lianyang; Li, Yongfeng

    2017-01-06

    Barnyardgrass (Echinochloa crus-galli) is one of the top 15 herbicide-resistant weeds around the world that interferes with rice growth, resulting in major losses of rice yield. Thus, multi-herbicide resistance in barnyardgrass presents a major threat, with the underlying mechanisms that contribute to resistance requiring elucidation. In an attempt to characterize this multi-herbicide resistance at the proteomic level, comparative analysis of resistant and susceptible barnyardgrasses was performed using iTRAQ, both with and without quinclorac, bispyribac-sodium and penoxsulam herbicidal treatment. A total of 1342 protein species were identified from 2248 unique peptides by searching the UniProt database and conducting data analysis. Approximately 904 protein species with 4774 Gene Ontology (GO) terms were grouped into the categories of biological process, cellular component and molecular function. Among these, 688 protein species were annotated into 1583 KEGG pathways, with 980 protein species relating to metabolism and 93 relating to environmental information processing. A total of 292 protein species showed more than a 1.2-fold change in abundance in the resistant biotype relative to the susceptible biotype. Furthermore, herbicide treatment resulted in 157 protein species that showed more than a 1.2-fold change in the resistant biotype. Moreover, physiological analyses demonstrated an ecological fitness cost in the resistant biotype.

  8. Strigolactone deficiency confers resistance in tomato line SL-ORT1 to the parasitic weeds Phelipanche and Orobanche spp.

    Science.gov (United States)

    Dor, Evgenia; Yoneyama, Koichi; Wininger, Smadar; Kapulnik, Yoram; Yoneyama, Kaori; Koltai, Hinanit; Xie, Xiaonan; Hershenhorn, Joseph

    2011-02-01

    The parasitic flowering plants of the genera Orobanche and Phelipanche (broomrape species) are obligatory chlorophyll-lacking root-parasitic weeds that infect dicotyledonous plants and cause heavy economic losses in a wide variety of plant species in warm-temperate and subtropical regions. One of the most effective strategies for broomrape control is crop breeding for broomrape resistance. Previous efforts to find natural broomrape-resistant tomato (Solanum lycopersicon) genotypes were unsuccessful, and no broomrape resistance was found in any wild tomato species. Recently, however, the fast-neutron-mutagenized tomato mutant SL-ORT1 was found to be highly resistant to various Phelipanche and Orobanche spp. Nevertheless, SL-ORT1 plants were parasitized by Phelipanche aegyptiaca if grown in pots together with the susceptible tomato cv. M-82. In the present study, no toxic activity or inhibition of Phelipanche seed germination could be detected in the SL-ORT1 root extracts. SL-ORT1 roots did not induce Phelipanche seed germination in pots but they were parasitized, at the same level as M-82, after application of the synthetic germination stimulant GR24 to the rhizosphere. Whereas liquid chromatography coupled to tandem mass spectrometry analysis of root exudates of M-82 revealed the presence of the strigolactones orobanchol, solanacol, and didehydro-orobanchol isomer, these compounds were not found in the exudates of SL-ORT1. It can be concluded that SL-ORT1 resistance results from its inability to produce and secrete natural germination stimulants to the rhizosphere.

  9. Becoming weeds.

    Science.gov (United States)

    Stewart, C Neal

    2017-04-26

    A new resequencing analysis of weedy rice (Oryza sativa L.) biotypes illuminates distinct evolutionary paths and outcomes of de-domestication and ferality. This largest effort to date in weedy plant genomics gives a better understanding of weediness while also providing a promising source of alleles for rice breeding.

  10. Occurrence, genetic control and evolution of non-target-site based resistance to herbicides inhibiting acetolactate synthase (ALS) in the dicot weed Papaver rhoeas.

    Science.gov (United States)

    Scarabel, Laura; Pernin, Fanny; Délye, Christophe

    2015-09-01

    Non-target-site resistance (NTSR) to herbicides is a major issue for the chemical control of weeds. Whilst predominant in grass weeds, NTSR remains largely uninvestigated in dicot weeds. We investigated the occurrence, inheritance and genetic control of NTSR to acetolactate synthase (ALS) inhibitors in Papaver rhoeas (corn poppy) using progenies from plants with potential NTSR to the imidazolinone herbicide imazamox. NTSR to imazamox was inherited from parents over two successive generations. NTSR to tritosulfuron (a sulfonylurea) was observed in F1 generations and inherited in F2 generations. NTSR to florasulam (a triazolopyrimidine) emerged in F2 generations. Our findings suggest NTSR was polygenic and gradually built-up by accumulation over generations of loci with moderate individual effects in single plants. We also demonstrated that ALS alleles conferring herbicide resistance can co-exist with NTSR loci in P. rhoeas plants. Previous research focussed on TSR in P. rhoeas, which most likely caused underestimation of NTSR significance in this species. This may also apply to other dicot species. From our data, resistance to ALS inhibitors in P. rhoeas appears complex, and involves well-known mutant ALS alleles and a set of unknown NTSR loci that confer resistance to ALS inhibitors from different chemical families.

  11. Resistência de Eleusine indica aos inibidores de ACCase Eleusine indica resistance to ACCase inhibitors

    Directory of Open Access Journals (Sweden)

    R.A. Vidal

    2006-01-01

    Full Text Available Dentre as causas da ineficácia no controle de plantas daninhas destaca-se a resistência delas aos herbicidas. Os objetivos deste trabalho foram avaliar a suspeita de resistência de Eleusine indica a inibidores de acetil-CoA carboxilase (ACCase e investigar a ocorrência de resistência cruzada entre os inibidores de ACCase. Biótipo de Eleusine indica originado do Mato Grosso com suspeita de resistência aos herbicidas inibidores de ACCase foi avaliado em casa de vegetação na sua suscetibilidade para diversos produtos do grupo dos ariloxifenoxipropionatos e cicloexanodionas. Estudos de resposta à dose confirmaram que o biótipo era 18 vezes mais insensível ao sethoxydim do que biótipo suscetível nunca aspergido com herbicidas. Também se constatou resistência cruzada ao fenoxaprop, cyhalofop, propaquizafop e butroxydim. Não se observou resistência cruzada aos produtos fluazifop, haloxyfop, quizalofop e clethodim.Among the causes for weed control inefficacy, the worst one is resistance to herbicides. The objectives of this work were to evaluate an Eleusine indica biotype suspected of resistance to ACCase inhibitors and to investigate the occurrence of cross- resistance to several ACCase inhibitors. One biotype of Eleusine indica originated from Mato Grosso with suspected resistance to ACCase inhibitors was evaluated in a greenhouse in relation to its susceptibility to several products of the ariloxyphenoxypropionate and cyclohexanedione groups. Studies on dose response confirmed that the suspected biotype was 18 times more insensitive to sethoxydim than the susceptible biotype that had never been treated with herbicides. Cross-resistance was confirmed for fenoxaprop, cyhalofop, propaquizafop and butroxydim. No cross-resistance was observed with fluazifop, haloxyfop, quizalofop, and clethodim.

  12. Choosing the best cropping systems to target pleiotropic effects when managing single-gene herbicide resistance in grass weeds. A blackgrass simulation study.

    Science.gov (United States)

    Colbach, Nathalie; Chauvel, Bruno; Darmency, Henri; Délye, Christophe; Le Corre, Valérie

    2016-10-01

    Managing herbicide-resistant weeds is becoming increasingly difficult. Here we adapted the weed dynamics model AlomySys to account for experimentally measured fitness costs linked to mutants of target-site resistance to acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicides in Alopecurus myosuroides. We ran simulations to test how effectively cultural practices manage resistance. Simulations of an oilseed rape/winter wheat/winter barley rotation showed that, when replacing one of the seven applied herbicides with an ACCase-inhibiting one, resistant mutants exceeded 1 plant m(-2) , with a probability of 40%, after an average of 18 years. This threshold was always exceeded when three or four ACCase-inhibiting herbicides were used, after an average of 8 and 6 years respectively. With reduced herbicide rates or suboptimal spraying conditions, resistance occurred 1-3 years earlier in 50% of simulations. Adding spring pea to the rotation or yearly mouldboard ploughing delayed resistance indefinitely in 90 and 60% of simulations respectively. Ploughing also modified the genetic composition of the resistant population by selecting a previously rare mutant that presented improved pre-emergent growth. The prevalence of the mutations was influenced more by their associated fitness cost or benefit than by the number of ACCase-inhibiting herbicides to which they conferred resistance. Simulations allowed us to rank weed management practices and suggest that pleiotropic effects are extremely important for understanding the frequency of herbicide resistance in the population. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  13. Flowers & Weeds.

    Science.gov (United States)

    Flannery, Maura C.

    1996-01-01

    Describes the topics and teaching strategies employed in an Issues in Biology course. Discusses flowers, plant breeding, potatoes and tomatoes, the chocolate tree, weeds, Arabidopis, gene transfers, and plant genes/human genes. Contains 22 references. (JRH)

  14. Flowers & Weeds.

    Science.gov (United States)

    Flannery, Maura C.

    1996-01-01

    Describes the topics and teaching strategies employed in an Issues in Biology course. Discusses flowers, plant breeding, potatoes and tomatoes, the chocolate tree, weeds, Arabidopis, gene transfers, and plant genes/human genes. Contains 22 references. (JRH)

  15. Effect of tillage on the efficacy of CGA362622 on weed control in maize

    African Journals Online (AJOL)

    STORAGESEVER

    2008-12-03

    Dec 3, 2008 ... help in managing herbicide resistance weeds and may also increase weed density as well as reduce crop yield. (Anderson, 2004). Higher dose of .... This change in weed compo- sition agrees with Richley et al. (1977) ...

  16. Investigating the mechanisms of glyphosate resistance in goosegrass (Eleusine indica) population from South China

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chun; FENG Li; HE Ting-ting; YANG Cai-hong; CHEN Guo-qi; TIAN Xing-shan

    2015-01-01

    Glyphosate has been used worldwide for nearly 40 years, and 30 types of resistant weeds have been reported. Glyphosate is mass-produced and widely used in China, but few studies and reports on glyphosate-resistant weeds and resistance mechanisms exist. Previous studies found a goosegrass species with high glyphosate resistance from orchards in South China and its glyphosate resistant mechanism was described in this study. The cDNA of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS, EC 2.5.1.19), the target enzyme of glyphosate, was cloned from the glyphosate-resistant and-suscep-tible goosegrass, respectively, and referred as EPSPS-R and EPSPS-S. The Pro106 residue was known to be involved in the glyphosate resistance in most goosegrass populations. However, sequence analysis did not ifnd the mutation at the Pro106 residue in the R biotype EPSPS amino acid sequence. The residue 133 and 382 was mutated in the R biotype EPSPS amino acid sequence instead, but it did not affect the EPSPS-S and EPSPS-R genes sensitivities to glyphosate. RT-PCR and Western blot analyses suggested that EPSPS mRNA and protein are mainly present in the shoot tissues both in the R and S goosegrass biotypes. The EPSPS-R rapidly responds to the glyphosate in R-biotype goosegrass and the induced expression was detected at 12 h post glyphosate treatment. The mRNA and protein expression of EPSPS-R increased constantly as the increasing concentration of glyphosate. However, the expression of the EPSPS-S was not induced signiifcantly by glyphosate in the S goosegrass biotype. Quantiifcation of real-time PCR results showed that the copy number of the EPSPS in R-biotype goosegrass was 4.7 times higher than that in the S goosegrass biotype. Al the results implied that EPSPS gene ampliifcation might mainly caused the glyphosate resistance of a goosegrass population col ected from orchards in South China.

  17. Non-target-site herbicide resistance: a family business.

    Science.gov (United States)

    Yuan, Joshua S; Tranel, Patrick J; Stewart, C Neal

    2007-01-01

    We have witnessed a dramatic increase in the frequency and diversity of herbicide-resistant weed biotypes over the past two decades, which poses a threat to the sustainability of agriculture at both local and global levels. In addition, non-target-site mechanisms of herbicide resistance seem to be increasingly implicated. Non-target-site herbicide resistance normally involves the biochemical modification of the herbicide and/or the compartmentation of the herbicide (and its metabolites). In contrast to herbicide target site mutations, fewer non-target mechanisms have been elucidated at the molecular level because of the inherently complicated biochemical processes and the limited genomic information available for weedy species. To further understand the mechanisms of non-target-site resistance, we propose an integrated genomics approach to dissect systematically the functional genomics of four gene families in economically important weed species.

  18. Weeding Your Collection.

    Science.gov (United States)

    Kerby, Ramona

    2002-01-01

    Offers guidelines for weeding as part of school library collection development. Highlights include developing a weeding policy; and the CREW (Continuous Review Evaluation and Weeding) method, including reasons for weeding, scheduling, and guidelines for fiction and for nonfiction. (LRW)

  19. Bermudagrass: Spring weed control programs and biotype research

    Science.gov (United States)

    Research conducted from 2008 through 2012 evaluated bermudagrass control with Sencor (metribuzin) and Command (clomazone) plus Direx (diuron). Averaged across experiments, bermudagrass was controlled 54, 41, and 43% four weeks after Sencor application at 3 lb/A in mid-February, early-March, and mid-...

  20. Cutting weed with an improved test bench and measurement of cutting resistance%3种杂草切割阻力试验

    Institute of Scientific and Technical Information of China (English)

    张林; 李明; 裴毅; 刘仲华

    2013-01-01

    对PC-B型带传动试验台进行改进:将主电机的传动轮改成切割装置,安装试验台架及夹持装置,更换更精确的压力传感器,研制出杂草切割试验台,以蒿草、狗尾草和牛筋草为材料,通过切割试验,确定杂草直径、含水率、电机转速、削切角对切割阻力的影响.结果表明,杂草切割阻力与电机转速平方成反比,与杂草直径平方成正比,与削切角平方成反比;不同杂草含水率对切割阻力影响不同,蒿草与狗尾草切割阻力与含水率平方成反比,狗尾草反之.单因素试验中,蒿草直径3.5~4.5mm,风干10h,含水率33.54%时,最大切割阻力为11.06N.以蒿草为材料的正交试验结果表明,直径、含水率、削切角和电机转速依次影响切割阻力.Spss软件分析表明,在风干含水率48.53%、削切角60°、直径最大组(3.5 ~ 4.5 mm)、电机转速为最低切断转速1.2倍时为最优组合.%PC-B type belt driving test bench was improved and modified into a test bench for cutting weed by modifying the driving wheel of the main motor into the cutting and the holding device and installing a pressure sensor which is more accurate than the original one.Humilis, Setaria and goose grass were cut to determine the influence of diameter and moisture content of weed, rotational speeds of motor and cutting angle on cutting resistance.The result suggests that cutting resistance was inversely proportional to the square of the rotational speed and the square of the cutting angle, and proportional to the square of the diameter of weed.Moisture content with different weeds showed different influence on cutting resistance.In contrast to goose grass, cutting resistances for Humilis and Setaria were inversely proportional to the moisture content.Single-factor test showed that a maximum strength of 11.06 N was achieved when the diameter of Humilis was 3.5-4.5 mm, and the moisture content of Humilis was 33.54% (achieved after 10 h drying

  1. Alternativas de manejo químico da planta daninha Digitaria ciliaris resistente aos herbicidas inibidores da ACCase na cultura de soja Chemical management alternatives of the weed Digitaria ciliaris resistant to ACCASE inhibiting herbicides in soybean crop

    Directory of Open Access Journals (Sweden)

    R.F. López-Ovejero

    2006-06-01

    Digitaria ciliaris, permitindo assim a recomendação destes tratamentos como alternativas de manejo de populações resistentes da planta daninha.The objective of this work was to evaluate the efficacy of aplying ACCase inhibiting herbicides on a population of the weed large crabgrass (Digitaria ciliaris with a history of control failure, as well as to propose alternative herbicides to be sprayed in pre- and post-emergence on the soybean crop. Thus, two field experiments were carried out in Palmeira (PR, Brazil, during the growing season 2003/2004. The first experiment evaluated the efficacy of the ACCase inhibiting herbicides (g ha-1: sethoxydim (230; clethodim (108; butroxydim (75; tepraloxydim (100; fluazifop-p-butyl (187.5; haloxyfop-r (60; propaquizafop (125; cyhalofop-butyl (225; fenoxaprop-p-ethyl + clethodim (50 + 50 and weeded check. The second experiment consisted of treatments using herbicides with alternative mechanism of action (g ha-1: trifluralina (2,700; clomazone (1,000; S-metolachlor (1,920; sulfentrazone (600; trifluralina + sulfentrazone (2,100 + 400; clomazone + sulfentrazone (600 + 400; S-metolachlor + sulfentrazone (768 + 400 in pre-emergence and a weeded check; all herbicides were applied with or without imazethapyr (100 application in post-emergence, sprayed when the weeds were at the stage of 2 to 4 leaves. The results suggested that the population studied is resistant to ACCase inhibiting herbicides; the best results of control efficacy with the ACCase inhibiting herbicides were obtained with tepraloxydim, clethodim and butroxydim; the treatments with sulfentrazone, alone or in mixture; the treatments with trifluralin, clomazone and S-metoalachlor, with imazethapyr complementation and imazethapyr alone were effective in controlling the resistant biotype of Digitaria ciliaris, showing that these treatments are management alternatives for the control of weed resistant populations.

  2. Agricultural impacts of glyphosate-resistant soybean cultivation in South America.

    Science.gov (United States)

    Cerdeira, Antonio L; Gazziero, Dionsio L P; Duke, Stephen O; Matallo, Marcus B

    2011-06-08

    In the 2009/2010 growing season, Brazil was the second largest world soybean producer, followed by Argentina. Glyphosate-resistant soybeans (GRS) are being cultivated in most of the soybean area in South America. Overall, the GRS system is beneficial to the environment when compared to conventional soybean. GRS resulted in a significant shift toward no-tillage practices in Brazil and Argentina, but weed resistance may reduce this trend. Probably the highest agricultural risk in adopting GRS in Brazil and South America is related to weed resistance due to use of glyphosate. Weed species in GRS fields have shifted in Brazil to those that can more successfully withstand glyphosate or to those that avoid the time of its application. Five weed species, in order of importance, Conyza bonariensis (L.) Cronquist, Conyza canadensis (L.) Cronquist, Lolium multiflorum Lam., Digitaria insularis (L.) Mez ex Ekman, and Euphorbia heterophylla L., have evolved resistance to glyphosate in GRS in Brazil. Conyza spp. are the most difficult to control. A glyphosate-resistant biotype of Sorghum halepense L. has evolved in GRS in Argentina and one of D. insularis in Paraguay. The following actions are proposed to minimize weed resistance problem: (a) rotation of GRS with conventional soybeans in order to rotate herbicide modes of action; (b) avoidance of lower than recommended glyphosate rates; (c) keeping soil covered with a crop or legume at intercrop intervals; (d) keeping machinery free of weed seeds; and (d) use of a preplant nonselective herbicide plus residuals to eliminate early weed interference with the crop and to minimize escapes from later applications of glyphosate due to natural resistance of older weeds and/or incomplete glyphosate coverage.

  3. A strategy to provide long-term control of weedy rice while mitigating herbicide resistance transgene flow, and its potential use for other crops with related weeds.

    Science.gov (United States)

    Gressel, Jonathan; Valverde, Bernal E

    2009-07-01

    Transgenic herbicide-resistant rice is needed to control weeds that have evolved herbicide resistance, as well as for the weedy (feral, red) rice problem, which has been exacerbated by shifting to direct seeding throughout the world-firstly in Europe and the Americas, and now in Asia, as well as in parts of Africa. Transplanting had been the major method of weedy rice control. Experience with imidazolinone-resistant rice shows that gene flow to weedy rice is rapid, negating the utility of the technology. Transgenic technologies are available that can contain herbicide resistance within the crop (cleistogamy, male sterility, targeting to chloroplast genome, etc.), but such technologies are leaky. Mitigation technologies tandemly couple (genetically link) the gene of choice (herbicide resistance) with mitigation genes that are neutral or good for the crop, but render hybrids with weedy rice and their offspring unfit to compete. Mitigation genes confer traits such as non-shattering, dwarfism, no secondary dormancy and herbicide sensitivity. It is proposed to use glyphosate and glufosinate resistances separately as genes of choice, and glufosinate, glyphosate and bentazone susceptibilities as mitigating genes, with a six-season rotation where each stage kills transgenic crop volunteers and transgenic crop x weed hybrids from the previous season.

  4. 抗草甘膦杂草及其检测方法发展现状%Advances in research on glyphosate-resistant weeds and the detection methods

    Institute of Scientific and Technical Information of China (English)

    陈景超; 张朝贤; 黄红娟; 魏守辉

    2011-01-01

    Glyphosate-resistant weeds have evolved as a result of the intensive use of glyphosate for weed control in the world. The development of glyphosate and the occurrence and development of 21 glyphosate-resistant weeds reported all over the world were discussed. The development of the detection methods for the glyphosate-resistant weeds was described through the whole plant bioassay and biochemical assay. The knowledge contained in this review will provide basis for developing methods to detect the sensitivity of weeds to glyphosate and the systematic methods to monitor glyphosate-resistant weeds.%草甘膦在世界范围的多年大量使用已经引起了抗草甘膦杂草的产生.本文针对全球迄今为止发现的21种抗草甘膦杂草的发生、发展状况进行了论述.探讨了抗草甘膦杂草抗药性检测方法,分别从整株生物测定及生物化学等方面介绍了抗草甘膦杂草检测方法的研究现状,为抗草甘膦杂草检测方法的发展及其抗性监测方法的建立提供参考.

  5. Resistence of Euphorbia Heterophylla L. to ALS-inhibiting herbicides in soybean

    Directory of Open Access Journals (Sweden)

    Gelmini Gerson Augusto

    2005-01-01

    Full Text Available Herbicides are widely used in soybean for weed control, and the selection pressure attributed to the repeated use of herbicides with similar modes of action on the same site has caused selection for resistant biotypes within and among previously susceptible species, such as Euphorbia heterophylla L., in relation to ALS enzyme inhibitors, in the states of Paraná, Rio Grande do Sul, and São Paulo, Brazil. Seeds of E. heterophylla were collected to examine possible new cases of resistant populations and to test alternative herbicide treatments to manage these populations, in the Caarapó region, State of Mato Grosso do Sul, Brazil, in areas where plants of this species have survived continuous herbicide applications. The experiment was carried out under greenhouse conditions, where biotypes with a history of suspected resistance were compared with a known susceptible biotype. Several post-emergence herbicides were sprayed at zero, one, two, four, and eight times the recommended field application rates. Twenty days after application, plants were harvested, and control percentage and fresh weight were determined to establish dose-response curves, in the aim to obtain the resistance factor using CD50 and RD50 data. The chlorimuron-ethyl resistance factor values for the control percentage and fresh weight parameters were higher than 16.5 and 16.9, respectively, while imazethapyr showed resistance factors higher than 25.0 and 23.5, respectively. The resistant biotype showed different resistance levels to chlorimuron-ethyl and imazethapyr, showing cross-resistance to the sulfonylurea and imidazolinone groups. Nevertheless, this biotype was effectively controlled by fomesafen (250 g ha-1, lactofen (120 g ha-1, flumiclorac-pentyl (40 g ha-1, glufosinate-ammonium (150 g ha-1, and glyphosate (360 g ha-1.

  6. Gene Amplification Is A Mechanism For Rapid Weed Evolution To Herbicide Resistance

    Science.gov (United States)

    The herbicide glyphosate became widely used in the U.S. and other parts of the world following the introduction of glyphosate-resistant crops. These crops were created by introduction of a modified 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene, the herbicide target site. Increased use of ...

  7. De novo assembly and annotation of the transcriptome of the agricultural weed Ipomoea purpurea uncovers gene expression changes associated with herbicide resistance.

    Science.gov (United States)

    Leslie, Trent; Baucom, Regina S

    2014-08-25

    Human-mediated selection can lead to rapid evolution in very short time scales, and the evolution of herbicide resistance in agricultural weeds is an excellent example of this phenomenon. The common morning glory, Ipomoea purpurea, is resistant to the herbicide glyphosate, but genetic investigations of this trait have been hampered by the lack of genomic resources for this species. Here, we present the annotated transcriptome of the common morning glory, Ipomoea purpurea, along with an examination of whole genome expression profiling to assess potential gene expression differences between three artificially selected herbicide resistant lines and three susceptible lines. The assembled Ipomoea transcriptome reported in this work contains 65,459 assembled transcripts, ~28,000 of which were functionally annotated by assignment to Gene Ontology categories. Our RNA-seq survey using this reference transcriptome identified 19 differentially expressed genes associated with resistance-one of which, a cytochrome P450, belongs to a large plant family of genes involved in xenobiotic detoxification. The differentially expressed genes also broadly implicated receptor-like kinases, which were down-regulated in the resistant lines, and other growth and defense genes, which were up-regulated in resistant lines. Interestingly, the target of glyphosate-EPSP synthase-was not overexpressed in the resistant Ipomoea lines as in other glyphosate resistant weeds. Overall, this work identifies potential candidate resistance loci for future investigations and dramatically increases genomic resources for this species. The assembled transcriptome presented herein will also provide a valuable resource to the Ipomoea community, as well as to those interested in utilizing the close relationship between the Convolvulaceae and the Solanaceae for phylogenetic and comparative genomics examinations.

  8. Metamitron-resistant Chenopodium album from sugar beet: cross-resistance profile.

    Science.gov (United States)

    Mechant, E; Bulcke, R

    2006-01-01

    In recent years, in several of the Belgian sugar beet growing regions, farmers have been confronted with unsatisfactory control of fat hen (Chenopodium album L.). Greenhouse bioassays conducted on reference C. album populations and on "suspected" populations from sugar beet fields where poor fat hen control had been observed, revealed that all "suspected" populations were resistant to metamitron, a key herbicide in the modern low rate weed control programs in sugar beet. These metamitron-resistant biotypes were all cross-resistant to atrazine. Since cross-resistance, particularly negative cross-resistance or reversed resistance, is known to play a major role in resistance management, other herbicides used in sugar beet and/or in rotational crops were tested to determine the cross-resistance profile of metamitron-resistant biotypes. Greenhouse bioassays were conducted using herbicides from different chemical families representing different modes of action. Cross-resistance was found for metribuzin, lenacil and chloridazon, all HRAC Group C1 herbicides that inhibit photosynthesis at PS II. The metamitron-resistant C. album populations examined showed negative cross-resistance to S-metolachlor (HRAC Group K3: inhibition of cell division), prosuifocarb (Group N: lipid synthesis, not AC-Case, inhibition), aclonifen and clomazone (both Group F3: inhibition of carotenoid biosynthesis).

  9. Indutores de resistência à mosca-branca Bemisia tabaci Biótipo B (GENN., 1889 (Hemiptera: Aleyrodidae em soja Resistance inducers to the whitefly Bemisia tabaci Biotype B (GENN., 1889 (Hemiptera: Aleyrodidae in soybeans

    Directory of Open Access Journals (Sweden)

    Jair Campos Moraes

    2009-10-01

    Full Text Available Objetivou-se, neste trabalho, avaliar o efeito da aplicação de indutores na resistência de duas cultivares de soja à mosca-branca Bemisia tabaci biótipo B. O experimento foi conduzido no Departamento de Entomologia - UFLA. As sementes de soja, cultivar IAC-19 e MONSOY-8001, foram previamente tratadas com o fungicida captan. Foram testados os seguintes tratamentos: T1- irrigação no solo, ao redor das plantas de cada vaso, de 250 mL de solução de ácido silícico a 1%; T2- pulverização das plantas, até o ponto de escorrimento, com solução a 0,3% de acibenzolar-s-methyl; T3- pulverização das plantas, até o ponto de escorrimento, com calda a 0,24% de pyraclostrobin+epoxiconazole e T4- testemunha. As plantas foram infestadas com 100 adultos da mosca-branca por vaso que liberados oito dias após a aplicação dos tratamentos. Avaliaram-se o número de ovos na face abaxial de cada folha, que foi marcada para posterior avaliação de ninfas; teores de taninos e de lignina; peso seco das raízes e da parte aérea. Não houve diferença para número de ovos e ninfas entre as cultivares de soja, porém, a viabilidade média de B. tabaci foi menor a cultivar IAC-19. O cultivar de soja IAC-19 demonstrou moderada resistência ao biótipo B de B. tabaci. A aplicação de silício ou acibenzolar-s-methyl induz um aumento no teor de lignina na cultivar de soja IAC-19.The objective of this paper was to evaluate the effect of the application of inducers on the resistance of two soybean cultivars to the whitefly B. tabaci Biotype B. The experiment was carried out at the Entomology Department - UFLA. The soybean seeds of cultivars IAC-19 and MONSOY-8001 were previously treated with Captan fungicide. The following treatments were tested: T1- irrigating the soil around the plants of each pot with 250 mL of solution of 1% silicic acid; T2- spraying of the plants, to the 'point of dripping', with a solution of 0.3% acibenzolar-s-methyl; T3- spraying of

  10. Resposta de biótipos de Euphorbia heterophylla a doses de glyphosate Response of Euphorbia heterophylla biotypes to glyphosate rates

    Directory of Open Access Journals (Sweden)

    L Vargas

    2011-01-01

    Full Text Available A leiteira (Euphorbia heterophylla é uma planta daninha de ciclo anual encontrada com frequência em lavouras de soja na região Sul do Brasil, controlada em lavouras de soja geneticamente modificada (Roundup Ready® - RR com uso do herbicida glyphosate. Entretanto, nos últimos anos, o controle dessa espécie não tem sido satisfatório em alguns locais, provocando a suspeita de que foram selecionados biótipos resistentes ao herbicida. Diante disso, o objetivo deste trabalho foi avaliar, por meio de curvas de dose-resposta, biótipos de leiteira com suspeita de resistência ao glyphosate. O experimento foi realizado em casa de vegetação, em delineamento experimental completamente casualizado, com quatro repetições. Os tratamentos constituíram-se de doses crescentes de glyphosate (0, 90, 180, 360, 720, 1.080, 1.440 e 2.160 g e.a. ha-1, aplicadas sobre cinco biótipos de leiteira, oriundos de lavouras de soja RR do Estado do Rio Grande do Sul. As variáveis avaliadas foram controle e matéria seca da parte aérea. Os resultados evidenciam que os biótipos de leiteira avaliados são suscetíveis ao glyphosate.Wild poinsettia is an annual cycle weed, commonly found in soybean crop in southern Brazil. It is controlled by glyphosate in genetically- modified soybean (Roundup Ready® - RR. The control of this species has not proven to be satisfactory in some places in the last years, leading to the suspicion that biotypes resistant to glyphosate have been selected. The objective this work was to evaluate, by response-dose curve, wild poinsettia biotypes with suspected resistance to glyphosate. The experiment was conducted under greenhouse conditions and the experiment was arranged in a randomized complete block design, with four replications. The treatments consisted of increased application rates of glyphosate (0, 90, 180, 360, 720, 1,080, 1,440 and 2,160 g a.e. ha-1 on five wild poinsettia biotypes, from crop soybean RR in the state of Rio

  11. Green Weeding

    Science.gov (United States)

    Penniman, Sarah; McColl, Lisa

    2008-01-01

    Gone are the days of tiptoeing to the dumpsters with boxes of weeded books in tow. Lots of libraries are now taking advantage of the many low-cost services and solutions that promise to help extend the lives of collection discards. Some of these options can be very profitable. Some create goodwill within the local community. Some may seem more…

  12. Changes in the Russian Wheat Aphid (Hemiptera: Aphididae) Biotype Complex in South Africa.

    Science.gov (United States)

    Jankielsohn, Astrid

    2016-04-01

    Russian wheat aphid Diuraphis noxia (Kurdjumov) has spread from its native area in central Asia to all the major wheat-producing countries in the world to become an international wheat pest. Because the Russian wheat aphid is a serious threat to the wheat industry in South Africa, it is important to investigate the key factors involved in the distribution of Russian wheat aphid biotypes and in the changes of the Russian wheat aphid biotype complex in South Africa. There are currently four known Russian wheat aphid biotypes occurring in South Africa. Russian wheat aphid samples were collected from 2011 to 2014 during the wheat-growing season in spring and summer and these samples were screened to determine the biotype status. RWASA1 occurred predominantly in the Western Cape, while RWASA2 and RWASA3 occurred predominantly in the Eastern Free State. Following the first record of RWASA4 in 2011, this biotype was restricted to the Eastern Free State. The surveys suggest that the Russian wheat aphid bioype complex was more diverse in the Eastern Free State than in the other wheat production areas. There was also a shift in Russian wheat aphid biotype composition over time. The Russian wheat aphid biotype complex is dynamic, influenced by environmental factors such as host plants, altitude, and climate, and it can change and diversify over time causing fluctuation in populations over sites and years. This dynamic nature of the Russian wheat aphid will continue to challenge the development of Russian wheat aphid-resistant wheat cultivars in South Africa, and the continued monitoring of the biotypic and genetic structure, to determine genetic relatedness and variation in different biotypes, of Russian wheat aphid populations is important for protecting wheat.

  13. Limited fitness advantages of crop-weed hybrid progeny containing insect-resistant transgenes (Bt/CpTI in transgenic rice field.

    Directory of Open Access Journals (Sweden)

    Xiao Yang

    Full Text Available BACKGROUND: The spread of insect-resistance transgenes from genetically engineered (GE rice to its coexisting weedy rice (O. sativa f. spontanea populations via gene flow creates a major concern for commercial GE rice cultivation. Transgene flow to weedy rice seems unavoidable. Therefore, characterization of potential fitness effect brought by the transgenes is essential to assess environmental consequences caused by crop-weed transgene flow. METHODOLOGY/PRINCIPAL FINDINGS: Field performance of fitness-related traits was assessed in advanced hybrid progeny of F(4 generation derived from a cross between an insect-resistant transgenic (Bt/CpTI rice line and a weedy strain. The performance of transgene-positive hybrid progeny was compared with the transgene-negative progeny and weedy parent in pure and mixed planting of transgenic and nontransgenic plants under environmental conditions with natural vs. low insect pressure. Results showed that under natural insect pressure the insect-resistant transgenes could effectively suppress target insects and bring significantly increased fitness to transgenic plants in pure planting, compared with nontransgenic plants (including weedy parent. In contrast, no significant differences in fitness were detected under low insect pressure. However, such increase in fitness was not detected in the mixed planting of transgenic and nontransgenic plants due to significantly reduced insect pressure. CONCLUSIONS/SIGNIFICANCE: Insect-resistance transgenes may have limited fitness advantages to hybrid progeny resulted from crop-weed transgene flow owning to the significantly reduced ambient target insect pressure when an insect-resistant GE crop is grown. Given that the extensive cultivation of an insect-resistant GE crop will ultimately reduce the target insect pressure, the rapid spread of insect-resistance transgenes in weedy populations in commercial GE crop fields may be not likely to happen.

  14. Unravelling the genetic bases of non-target-site-based resistance (NTSR) to herbicides: a major challenge for weed science in the forthcoming decade.

    Science.gov (United States)

    Délye, Christophe

    2013-02-01

    Non-target-site-based resistance (NTSR) can confer unpredictable cross-resistance to herbicides. However, the genetic determinants of NTSR remain poorly known. The current, urgent challenge for weed scientists is thus to elucidate the bases of NTSR so that detection tools are developed, the evolution of NTSR is understood, the efficacy of the shrinking herbicide portfolio is maintained and integrated weed management strategies, including fully effective herbicide applications, are designed and implemented. In this paper, the importance of NTSR in resistance to herbicides is underlined. The most likely way in which NTSR evolves-by accumulation of different mechanisms within individual plants-is described. The NTSR mechanisms, which can interfere with herbicide penetration, translocation and accumulation at the target site, and/or protect the plant against the consequences of herbicide action, are then reviewed. NTSR is a part of the plant stress response. As such, NTSR is a dynamic process unrolling over time that involves 'protectors' directly interfering with herbicide action, and also regulators controlling 'protector' expression. NTSR is thus a quantitative trait. On this basis, a three-step procedure is proposed, based on the use of the 'omics' (genomics, transcriptomics, proteomics or metabolomics), to unravel the genetic bases of NTSR.

  15. Interspecific variation in persistence of buried weed seeds follows trade-offs among physiological, chemical and physical seed defences

    Science.gov (United States)

    Soil seedbanks drive infestations of annual weeds, yet weed management focuses largely on seedling mortality. As weed seedbanks increasingly become reservoirs of herbicide resistance, species-specific seedbank management approaches will be essential. Limited understanding of interspecific variation ...

  16. Invasive mechanism and management strategy of Bemisia tabaci(Gennadius) biotype B:Progress report of 973 Program on invasive alien species in China

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Bemisia tabaci(Gennadius) biotype B,called a "superbug",is one of the most harmful biotypes of this species complex worldwide.In this report,the invasive mechanism and management of B.tabaci biotype B,based on our 5-year studies,are presented.Six B.tabaci biotypes,B,Q,ZHJ1,ZHJ2,ZHJ3 and FJ1,have been identified in China.Biotype B dominates the other biotypes in many regions of the country.Genetic diversity in biotype B might be induced by host plant,geographical conditions,and/or insecticidal application.The activities of CarE(carboxylesterase) and GSTs(glutathione-S-transferase) in biotype B reared on cucumber and squash were greater than on other host plants,which might have increased its resistance to insecticides.The higher activities of detoxification enzymes in biotype B might be induced by the secondary metabolites in host plants.Higher adaptive ability of biotype B adults to adverse conditions might be linked to the expression of heat shock protein genes.The indigenous B.tabaci biotypes were displaced by the biotype B within 225 d.The asymmetric mating interactions and mutualism between biotype B and begomoviruses via its host plants speed up widespread invasion and displacement of other biotypes.B.tabaci biotype B displaced Trialeurodes vaporariorum(Westwood) after 4-7 generations under glasshouse conditions.Greater adaptive ability of the biotype B to adverse conditions and its rapid population increase might be the reasons of its successful displacement of T.vaporariorum.Greater ability of the biotype B to switch to different host plants may enrich its host plants,which might enable it to better compete with T.vaporariorum.Native predatory natural enemies possess greater ability to suppress B.tabaci under field conditions.The kairomones in the 3rd and 4th instars of biotype B may provide an important stimulus in host searching and location by its parasitoids.The present results provide useful information in explaining the mechanisms of genetic diversity

  17. Invasive mechanism and management strategy of Bemisia tabaci (Gennadius) biotype B: progress report of 973 Program on invasive alien species in China.

    Science.gov (United States)

    Wan, FangHao; Zhang, GuiFen; Liu, ShuSheng; Luo, Chen; Chu, Dong; Zhang, YouJun; Zang, LianSheng; Jiu, Min; Lü, ZhiChuang; Cui, XuHong; Zhang, LiPing; Zhang, Fan; Zhang, QingWen; Liu, WanXue; Liang, Pei; Lei, ZhongRen; Zhang, YongJun

    2009-01-01

    Bemisia tabaci (Gennadius) biotype B, called a "superbug", is one of the most harmful biotypes of this species complex worldwide. In this report, the invasive mechanism and management of B. tabaci biotype B, based on our 5-year studies, are presented. Six B. tabaci biotypes, B, Q, ZHJ1, ZHJ2, ZHJ3 and FJ1, have been identified in China. Biotype B dominates the other biotypes in many regions of the country. Genetic diversity in biotype B might be induced by host plant, geographical conditions, and/or insecticidal application. The activities of CarE (carboxylesterase) and GSTs (glutathione-S-transferase) in biotype B reared on cucumber and squash were greater than on other host plants, which might have increased its resistance to insecticides. The higher activities of detoxification enzymes in biotype B might be induced by the secondary metabolites in host plants. Higher adaptive ability of biotype B adults to adverse conditions might be linked to the expression of heat shock protein genes. The indigenous B. tabaci biotypes were displaced by the biotype B within 225 d. The asymmetric mating interactions and mutualism between biotype B and begomoviruses via its host plants speed up widespread invasion and displacement of other biotypes. B. tabaci biotype B displaced Trialeurodes vaporariorum (Westwood) after 4-7 generations under glasshouse conditions. Greater adaptive ability of the biotype B to adverse conditions and its rapid population increase might be the reasons of its successful displacement of T. vaporariorum. Greater ability of the biotype B to switch to different host plants may enrich its host plants, which might enable it to better compete with T. vaporariorum. Native predatory natural enemies possess greater ability to suppress B. tabaci under field conditions. The kairomones in the 3rd and 4th instars of biotype B may provide an important stimulus in host searching and location by its parasitoids. The present results provide useful information in

  18. Invasive mechanism and manasement stratesy of Bemisia tabaci (Gennadius) biotype B: Progress report of 973 Program on invasive alien species in China

    Institute of Scientific and Technical Information of China (English)

    WAN FangHao; CUI XuHong; ZHANG LiPing; ZHANG Fan; ZHANG QingWen; LIU WanXue; LIANG Pei; LEI ZhongRen; ZHANG YongJun; ZHANG GuiFen; LIU ShuSheng; LUO Chen; CHU Dong; ZHANG YouJun; ZANG LianSheng; JIU Min; Lǖ ZhiChuang

    2009-01-01

    Bemisia tabaci (Gennadius) biotype B, called a "superbug", is one of the most harmful biotypes of this species complex worldwide. In this report, the invasive mechanism and management of B. tabaci bio-type B, based on our 5-year studies, are presented. Six B. tabaci biotypes, B, Q, ZHJ1, ZHJ2, ZHJ3 and FJ1, have been identified in China. Biotype B dominates the other biotypes in many regions of the country. Genetic diversity in biotype B might be induced by host plant, geographical conditions, and/or insecticidal application. The activities of CarE (carboxylesterase) and GSTs (glutathione-S-transferase) in biotype B reared on cucumber and squash were greater than on other host plants, which might have increased its resistance to insecticides. The higher activities of detoxification enzymes in biotype B might be induced by the secondary metabolites in host plants. Higher adaptive ability of biotype B adults to adverse conditions might be linked to the expression of heat shock protein genes. The in-digenous B. tabaci biotypes were displaced by the biotype B within 225 d. The asymmetric mating in-teractions and mutualism between biotype B and begomoviruses via its host plants speed up wide-spread invasion and displacement of other biotypes. B. tabaci biotype B displaced Trialeurodes vapo-rariorum (Westwood) after 4-7 generations under glasshouse conditions. Greater adaptive ability of the biotype B to adverse conditions and its rapid population increase might be the reasons of its suc-cessful displacement of T. vaporariorum. Greater ability of the biotype B to switch to different host plants may enrich its host plants, which might enable it to better compete with T. vaporariorum. Native predatory natural enemies possess greater ability to suppress B. tabaci under field conditions. The kairomones in the 3rd and 4th instars of biotype B may provide an important stimulus in host searching and location by its parasitoids. The present results provide useful information in

  19. New Rice for Africa (NERICA) cultivars exhibit different levels of post-attachment resistance against the parasitic weeds Striga hermonthica and Striga asiatica.

    Science.gov (United States)

    Cissoko, Mamadou; Boisnard, Arnaud; Rodenburg, Jonne; Press, Malcolm C; Scholes, Julie D

    2011-12-01

    Striga hermonthica and S. asiatica are root parasitic weeds that infect the major cereal crops of sub-Saharan Africa causing severe losses in yield. The interspecific upland NEw RICe for Africa (NERICA) cultivars are popular amongst subsistence farmers, but little is known about their post-attachment resistance against Striga. Here, we evaluate the post-attachment resistance levels of the NERICA cultivars and their parents against ecotypes of S. hermonthica and S.asiatica, characterize the phenotype of the resistance mechanisms and determine the effect of Striga on host biomass. Some NERICA cultivars showed good broad-spectrum resistance against several Striga ecotypes, whereas others showed intermediate resistance or were very susceptible. The phenotype of a resistant interaction was often characterized by an inability of the parasite to penetrate the endodermis. Moreover, some parasites formed only a few connections to the host xylem, grew slowly and remained small. The most resistant NERICA cultivars were least damaged by Striga, although even a small number of parasites caused a reduction in above-ground host biomass. The elucidation of the molecular genetic basis of the resistance mechanisms and tolerance would allow the development of cultivars with multiple, durable resistance for use in farmers' fields. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

  20. The future for weed control and technology.

    Science.gov (United States)

    Shaner, Dale L; Beckie, Hugh J

    2014-09-01

    This review is both a retrospective (what have we missed?) and prospective (where are we going?) examination of weed control and technology, particularly as it applies to herbicide-resistant weed management (RWM). Major obstacles to RWM are discussed, including lack of diversity in weed management, unwillingness of many weed researchers to conduct real integrated weed management research or growers to accept recommendations, influence or role of agrichemical marketing and governmental policy and lack of multidisciplinary research. We then look ahead to new technologies that are needed for future weed control in general and RWM in particular, in areas such as non-chemical and chemical weed management, novel herbicides, site-specific weed management, drones for monitoring large areas, wider application of 'omics' and simulation model development. Finally, we discuss implementation strategies for integrated weed management to achieve RWM, development of RWM for developing countries, a new classification of herbicides based on mode of metabolism to facilitate greater stewardship and greater global exchange of information to focus efforts on areas that maximize progress in weed control and RWM. There is little doubt that new or emerging technologies will provide novel tools for RMW in the future, but will they arrive in time? © 2013 Her Majesty the Queen in Right of Canada Pest Management Science © 2013 Society of Chemical Industry.

  1. Control of ALS resistant volunteer oil seed rape and other dicotyledonous weeds with GF-145, a new cereal herbicide product containing isoxaben and florasulam

    Directory of Open Access Journals (Sweden)

    Becker, Jörg

    2014-02-01

    Full Text Available GF-145 contains the active ingredients isoxaben (610 g ai/kg and florasulam (40 g ai/kg and is formulated as a Wettable Granule (WG. The active ingredients are found in commercial products such as Primus™2 (florasulam, Starane XL™ (fluroxypyr + florasulam, Ariane C™ (fluroxypyr + florasulam + clopyralid or Flexidor™ (isoxaben. While florasulam has been widely used in cereal crops in recent years, isoxaben offers a new mode of action (MOA for use in German cereal herbicides even when considering that Flexidor™ has had regulatory approval in 1988 to 1991. The MOA of isoxaben is inhibition of cellulose synthesis (HRAC class L, while florasulam inhibits Acetolactate Synthase (ALS and is a representative of the HRAC class B. It is known that florasulam works through uptake by green leaves. Isoxaben is a herbicide with soil activity and with a very low activity when foliar applied, except on some species in the cruciferae family. GF-145 is intended to be applied in the autumn in cereals (wheat, barley, rye, triticale for the control of ALS resistant volunteer oil seed rape and annual dicotyledonous weeds including Matricaria spp., Stellaria media, Papaver rhoeas, Capsella bursa-pastoris, Myosotis arvensis, Lamium spp., Galium aparine, Veronica spp. and others when applied at early post-emergence from BBCH 10 to 13 of the crop. The use rate in winter cereals is 95 g product/ha (58 g ai/ha isoxaben plus 3.75 g ai/ha florasulam. Field trials conducted in previous years confirmed excellent selectivity in all cereal crops and efficacy trials initiated in autumn 2012 show that GF-145 provides excellent and superior control to ALS resistant oil seed rape that was better than straight florasulam and other ALS active ingredients. GF-145 adds a new MOA to the cereal herbicide portfolio and controls volunteer oil seed rape, cruciferous weeds and broad-leaved weeds and is more robust than florasulam based products that do not contain isoxaben.

  2. Performance and feeding behaviour of two biotypes of the black currant-lettuce aphid, Nasonovia ribisnigri, on resistant and susceptible Lactuca sativa near-isogenic lines

    NARCIS (Netherlands)

    Broeke, ten C.J.M.; Dicke, M.; Loon, van J.J.A.

    2013-01-01

    The black currant-lettuce aphid, Nasonovia ribisnigri, is an important pest of cultivated lettuce, Lactuca sativa. Since 1982, the control of this aphid on lettuce is largely based on host plant resistance, conferred by the Nr gene, introgressed from Lactuca virosa. The resistance mechanism remains

  3. Molecular biology approaches to weed management

    Science.gov (United States)

    Global climate change appears to be favorable for invasive weed development and spread because invasive species in general are proficient at succeeding in new environments. To worsen matters, herbicide-resistant weeds have become a severe threat in modern agricultural systems due to the extensive us...

  4. Cross-resistance profile of mesosulfuron-methyl-resistant Italian ryegrass in the southern United States.

    Science.gov (United States)

    Kuk, Yong In; Bugos, Nilda R

    2007-04-01

    Diclofop-resistant Lolium species (ryegrass) is a major weed problem in wheat production worldwide. This study was conducted to determine the resistance pattern of diclofop-resistant ryegrass accessions from the southern United States to mesosulfuron-methyl, a recently commercialized herbicide for ryegrass control in wheat; to determine the cross-resistance pattern of a Lolium multiflorum Lam. (Italian ryegrass) accession, 03-1, to acetolactate synthase (ALS) and acetyl-CoA carboxylase (ACCase) inhibitors; and to determine the resistance mechanism of Italian ryegrass to mesosulfuron-methyl. Seventeen ryegrass accessions from Arkansas and Louisiana, including standard resistant and susceptible accessions, were used in this experiment. Fourteen of the 17 accessions were more resistant (four- to > 308-fold) to diclofop than the standard susceptible biotype. One accession, 03-1, was resistant to mesosulfuron-methyl as well as to other ALS inhibitor herbicides such as chlorsulfuron, imazamox and sulfometuron. Accession 03-1, however, did not show multiple resistance to the ACCase inhibitor herbicides diclofop, fluazifop, clethodim, sethoxydim and pinoxaden, nor to glyphosate. The in vivo ALS activity of the 03-1 biotype was less affected by mesosulfuron-methyl than the susceptible biotype. This indicates that the resistance mechanism of Italian ryegrass to mesosulfuron-methyl is partly due to an alteration in the target enzyme, ALS. It is concluded that diclofop-resistant ryegrass in the southern United States can be generally controlled by mesosulfuron-methyl. However, mesosulfuron-methyl must be used with caution because not all ryegrass populations are susceptible to it. There is a need for more thorough profiling of ryegrass resistance to herbicides.

  5. Proteomic analysis of secreted saliva from Russian wheat aphid (Diuraphis noxia Kurd.) biotypes that differ in virulence to wheat

    Science.gov (United States)

    Diuraphis noxia, Russian Wheat Aphid (RWA), biotypes are classified by their differential virulence to wheat varieties containing resistance genes. RWA salivary proteins, unlike those of most aphid species, cause foliar damage and physiological alterations in plants. A comparative proteomic analys...

  6. Herbicide resistance in German and Swiss Lolium spp. populations – resistance factors and cross-resistance spectrum

    Directory of Open Access Journals (Sweden)

    Petersen, Jan

    2016-02-01

    Full Text Available In monitoring trials investigating the occurrence and spread of herbicide resistance in German and Swiss Lolium populations 26 samples could be included since 2008. Biotypes which showed resistance to postemergence herbicides were included into a detailed greenhouse trial in 2014. Based on dose-response experiments, resistance factors and cross resistance patterns for cycloxydim, flufenacet, glyphosate, iodosulfuron, meso- and iodosulfuron, pinoxaden and pyroxsulam could be determined. Resistance to ALS as well as ACCase inhibitors was found. In a few cases also resistance to flufenacet could be detected. In contrast, no resistance to glyphosate was discovered. Resistant populations were found in four German federal states (Hessen, Mecklenburg-Vorpommern, Sachsen and Schleswig-Holstein. Two populations were resistant to all cereal selective post-emergence herbicides and to flufenacet. Some populations from Switzerland indicated presence of ACCase inhibitor resistance. In the future, more problems with herbicide resistant Lolium species as weeds in cereals may arise due to limited amount of available selective herbicides and climatic change with more favourable conditions for Lolium spp. as weeds.

  7. 农田杂草抗药性检测方法研究进展%Research Advance on Detection Methods for Weed Herbicide-resistance

    Institute of Scientific and Technical Information of China (English)

    董立尧; 吕波; 徐江艳; 李俊

    2011-01-01

    The weed herbicide - resistance problem has become a global concern recently. In order to provide a rapid, accurate and economic detection methods for agricultural research and extension workers, documents concerning detection methods of weed herbicide - resistance reported at home and abroad were outlined and analyzed according to its research level on whole plant, organ or tissue, cells or organelles and molecular base respectively.%杂草抗药性问题备受全球关注.文章通过检索国内外已报道的有关杂草抗药性的文献,对实验室常用的杂草抗药性检测方法进行了概述,并将杂草抗药性检测方法归纳为整株水平、器官或组织水平、细胞或细胞器水平以及分子水平,并对这些方法进行了简要分析,可为研究人员或农技推广人员根据快速、准确、经济等不同需要提供相应的杂草抗药性检测方法.

  8. Suscetibilidade comparativa a herbicidas pós-emergentes de biótipos de Digitaria ciliaris resistente e suscetível aos inibidores da ACCase Relative susceptibility to post-emergence herbicides of ACCase-resistant and susceptible biotypes of Digitaria ciliaris

    Directory of Open Access Journals (Sweden)

    R.F. López-Ovejero

    2006-12-01

    Full Text Available Esta pesquisa foi conduzida com o objetivo de avaliar a possibilidade de resistência múltipla aos herbicidas inibidores da ACCase, ALS e síntese de carotenos em um biótipo de capim-colchão (Digitaria ciliaris resistente aos inibidores da ACCase. O experimento foi conduzido em casa de vegetação, utilizando dois biótipos de capim-colchão: um resistente (R e outro suscetível (S aos herbicidas inibidores da ACCase. O delineamento experimental utilizado foi o de blocos ao acaso, com quatro repetições. Foram utilizados 11 herbicidas: fluazifop-p-butil, haloxyfop-r-methyl, propaquizafop, sethoxydim, tepraloxydim, clethodim, fenoxaprop + clethodim, imazethapyr, nicosulfuron, iodosulfuron + foramsulfuron e mesotrione. Para cada herbicida, os tratamentos resultaram da combinação fatorial entre os dois biótipos de capim-colchão e 10 doses (0,0D; 0,016D; 0,03D; 0,06D; 0,25D; 0,5D; 1,0D; 2,0D; 4,0D; e 16,0D, em que D é a dose recomendada para cada produto. Os herbicidas foram aplicados sobre as plantas de capim-colchão em estádio de desenvolvimento de 3-4 folhas. Avaliou-se a porcentagem de controle aos 28 dias após a aplicação (DAA. O biótipo R foi confirmado como resistente aos herbicidas inibidores da ACCase (grupos químicos dos ariloxifenoxipropionatos e cicloexanodionas com níveis variáveis de resistência cruzada. O biótipo R foi controlado satisfatoriamente pela dose de campo de todos os herbicidas alternativos aplicados (sulfoniluréias, imidazolinonas e inibidores da síntese de caroteno, excluindo a hipótese de resistência múltipla nesse biótipo de capim-colchão.This research was conducted to evaluate the possibility of multiple resistances to ACCase, ALS and carotene synthesis inhibiting herbicides in one ACCase-resistant biotype of crab-grass (Digitaria ciliaris. The experiment was conducted in a greenhouse, using two crab-grass biotypes: one resistant (R and another susceptible (S to ACCase inhibiting herbicides

  9. Local spread of metamitron resistant Chenopodium album L. patches.

    Science.gov (United States)

    Aper, J; De Riek, J; Mechant, E; Bulcke, R; Reheul, D

    2011-01-01

    Molecular markers can provide valuable information on the spread of resistant weed biotypes. In particular, tracing local spread of resistant weed patches will give details on the importance of seed migration with machinery, manure, wind or birds. This study investigated the local spread of metamitron resistant Chenopodium album L. patches in the southwest region of the province West-Flanders (Belgium). During the summer of 2009, leaf and seed samples were harvested in 27 patches, distributed over 10 sugar beet fields and 1 maize field. The fields were grouped in four local clusters. Each cluster corresponded with the farmer who cultivated these fields. A cleaved amplified polymorphic sequence (CAPS) procedure identified the Ser264 to Gly mutation in the D1 protein, endowing resistance to metamitron, a key herbicide applied in sugar beet. The majority of the sampled plants within a patch (97% on average) carried this mutation. Amplified fragment length polymorphism (AFLP) analysis was performed with 4 primer pairs and yielded 270 molecular markers, polymorphic for the whole dataset (303 samples). Analysis of molecular variance revealed that a significant part of the genetic variability was attributed to variation among the four farmer locations (12 %) and variation among Chenopodium album patches within the farmer locations (14%). In addition, Mantel tests revealed a positive correlation between genetic distances (linearised phipt between pairs of patches) and geographic distances (Mantel-coefficient significant at p = 0.002), suggesting isolation-by-distance. In one field, a decreased genetic diversity and strong genetic relationships between all the patches in this field supported the hypothesis of a recent introduction of resistant biotypes. Furthermore, genetic similarity between patches from different fields from the same farmer and from different farmers indicated that seed transport between neighbouring fields is likely to have an important impact on the

  10. Robotic weeding and automated weed measurements

    DEFF Research Database (Denmark)

    Christensen, S.; Søgaard, H.T.; Jørgensen, R.N.

    2003-01-01

    The goal of decreasing herbicide usage has so far focused on reducing the herbicide dosage or replacing chemical weed control by hoeing and harrowing. The conventional weed control strategy is to apply the same dose of herbicide or the same intensity of hoeing and harrowing in the whole field....... The strategy may be changed in the coming years because experiments in Germany, USA, Australia, and Denmark have shown that site-specific weed management can reduce herbicide usage significantly. One of the promising technologies for site specific weed management is robotic weeding. This paper reviews...... the state-of-the-art of automated weed measurement methods and the research projects concerning autonomous platform and information system for crop and weed monitoring and robotic weeding....

  11. Soft tissue biotype affects implant success.

    Science.gov (United States)

    Lee, Angie; Fu, Jia-Hui; Wang, Hom-Lay

    2011-06-01

    The influence of tissue biotype in natural dentition is already well demonstrated in the literature, with numerous articles showing that thicker tissue is a preferred biotype for optimal surgical and prosthetic outcomes. In this same line of thought, current studies are directed to explore whether mucosal thickness would have similar implications around dental implants. The purpose of this review was to investigate the effects of soft tissue biotype in relation to success of implant therapy. The influence of tissue biotype was divided into 3 main categories: its relationship with periimplant mucosa and the underlying bone, immediate implant placement, and restorative outcomes. Soft tissue biotype is an important parameter to consider in achieving esthetic implant restoration, improving immediate implant success, and preventing future mucosal recession.

  12. Interaction between resistant tomato genotypes and plant extracts on Bemisia tabaci (Genn. biotype B Interação de genótipos resistentes de tomateiro e extratos vegetais sobre Bemisia tabaci (Genn. biótipo B

    Directory of Open Access Journals (Sweden)

    Edson Luiz Lopes Baldin

    2007-10-01

    Full Text Available The tomato (Lycopersicon spp. productivity is severely reduced by attack of several insects and microorganisms. It is economically one of the most important crops that has been extensively cultivated in the Americas. Therefore, assays were performed in the greenhouse and the laboratory to evaluate the possible interaction between resistant tomato genotypes and plant extracts on the control of the pest Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae biotype B. This evaluation was performed for genotypes IAC-Santa Clara, PI-134417, LA-716, PI-134418, and PI-127826, and aqueous extracts from seeds of Azadirachta indica A. de Jussieu (Rutales: Meliaceae, branches and leaves of Trichilia pallida Swartz (Rutales: Meliaceae. In the greenhouse, spraying with extracts from seeds of A. indica, and leaves and branches of T. pallida reduced whitefly attraction with IAC-Santa Clara; on PI-134417, LA-716, PI-134418, and PI-127826 the extracts did not affect the attractiveness to the B. tabaci biotype B. Extracts from A. indica seeds and T. pallida leaves and branches reduced oviposition on IAC-Santa Clara; extracts from T. pallida branches reduced oviposition on PI-134417, PI-134418, and PI-127826, while the extract from A. indica seeds reduced oviposition in PI-127826. The extracts did not affect oviposition on LA-716. In the laboratory, the extracts increased the mortality of nymphs on the genotypes. The "genotype × extract" interaction was significant, indicating an addictive effect between resistant genotypes and plant extracts on whitefly control.O tomate (Lycopersicon spp. é uma das hortaliças mais importantes do mundo em termos econômicos e tem sido extensivamente cultivado nas Américas há séculos. Entretanto, a produtividade poderia ser mais alta se ela não fosse suscetível a ataques de insetos e microorganismos. Foram realizados ensaios em casa-de-vegetação e laboratório visando avaliar a possível interação de genótipos de tomateiro

  13. Análise de crescimento de biótipos de leiteira (Euphorbia heterophylla resistentes e suscetível aos herbicidas inibidores da ALS Growth analysis of resistant and susceptible wild poinsettia (Euphorbia heterophylla biotypes to ALS-inhibiting herbicides

    Directory of Open Access Journals (Sweden)

    R.A. Vidal

    2000-01-01

    Full Text Available Foram conduzidos dois experimentos em condições de casa de vegetação, com o objetivo de analisar comparativamente o crescimento de três biótipos de leiteira (Euphorbia heterophylla - EPHHL resistentes (R (Passo Fundo, Não-Me-Toque e Rio Pardo e um suscetível (S (Porto Alegre aos herbicidas inibidores da ALS, por meio do cálculo da taxa de crescimento relativo (TCR e dos índices que a compõem. Utilizou-se o delineamento experimental completamente casualizado, com três repetições e tratamentos organizados em fatorial 2 x 4 x 4, em que o fator A correspondeu às duas estações de crescimento (outono e primavera, o fator B aos quatro biótipos de EPHHL e o fator C às quatro épocas de determinação dos índices de crescimento das plantas de leiteira - no primeiro experimento, aos 15, 25, 35 e 45, e, no segundo, aos 23, 33, 43 e 53 dias após a emergência (DAE. No experimento realizado no outono não houve interação entre época de avaliação e biótipo nem efeito simples de biótipo. No experimento realizado na primavera, a razão de peso foliar (RPF do biótipo de Não-Me-Toque foi superior em média à dos demais biótipos; a razão de área foliar (RAF foi superior no biótipo de Não-Me-Toque aos 23 e 53 DAE; e não houve diferenças da TAL e TCR entre os biótipos. Esses resultados sugerem produtividade semelhante entre os biótipos R e S e, portanto, sua equivalência competitiva.Two trials were carried out under greenhouse conditions to compare the development of three ALS inhibitor herbicides resistant (R wild poinsettia (Euphorbia heterophylla biotypes (Passo Fundo, Não-Me-Toque and Rio Pardo - RS - Brazil and one susceptible (S (Porto Alegre - RS - Brazil using relative growth rate (RGR and related indices. The experiment was arranged as a completely randomized design, with three replications, in a 2 x 4 x 4 factorial, where factor A was two growth seasons (fall and spring; factor B, four biotypes of wild poinsettia

  14. Differential reactions of soybean isolines with combinations of aphid resistance genes Rag1, Rag2, and Rag3 to four soybean aphid biotypes

    Science.gov (United States)

    With the discovery of the soybean aphid (Aphis glycines Matsumura) as a devastating insect pest of soybean (Glycine max (L.) Merr.) in the United States, host resistance was recognized as an important management option. However, the identification of soybean aphid isolates exhibiting strong virulenc...

  15. Evolution of new disease specificity at a simple resistance locus in a crop-weed complex: reconstitution of the Lr21 gene in wheat.

    Science.gov (United States)

    Huang, Li; Brooks, Steven; Li, Wanlong; Fellers, John; Nelson, James C; Gill, Bikram

    2009-06-01

    The wheat leaf-rust resistance gene Lr21 was first identified in an Iranian accession of goatgrass, Aegilops tauschii Coss., the D-genome donor of hexaploid bread wheat, and was introgressed into modern wheat cultivars by breeding. To elucidate the origin of the gene, we analyzed sequences of Lr21 and lr21 alleles from 24 wheat cultivars and 25 accessions of Ae. tauschii collected along the Caspian Sea in Iran and Azerbaijan. Three basic nonfunctional lr21 haplotypes, H1, H2, and H3, were identified. Lr21 was found to be a chimera of H1 and H2, which were found only in wheat. We attempted to reconstitute a functional Lr21 allele by crossing the cultivars Fielder (H1) and Wichita (H2). Rust inoculation of 5876 F(2) progeny revealed a single resistant plant that proved to carry the H1H2 haplotype, a result attributed to intragenic recombination. These findings reflect how plants balance the penalty and the necessity of a resistance gene and suggest that plants can reuse "dead" alleles to generate new disease-resistance specificity, leading to a "death-recycle" model of plant-resistance gene evolution at simple loci. We suggest that selection pressure in crop-weed complexes contributes to this process.

  16. Manejo de populações de plantas daninhas resistentes aos herbicidas inibidores da acetolactato sintase Management of weed populations resistant to ALS-Inhibitor herbicides

    Directory of Open Access Journals (Sweden)

    P.A. Monquero

    2001-04-01

    ência, bem como populações de áreas que não tinham histórico da aplicação de herbicidas inibidores da ALS, foram obtidos resultados que confirmaram a resistência destas populações e a eficácia dos herbicidas alternativos obtidos em condições de campo. Como conclusão geral da pesquisa, ressalta-se que as populações resistentes de picão-preto e caruru estudadas possuem resistência cruzada às sulfoniluréias e imidazolinonas, mas não possuem resistência múltipla aos herbicidas inibidores do fotossistema II e aos inibidores da PROTOX, sugerindo que estes herbicidas alternativos podem ser utilizados para prevenção e manejo da resistência aos herbicidas inibidores da ALS.Soybean production areas of the central region of Brazil are commonly infested by the weed beggarticks (a mixture of the species Bidens pilosa and Bidens subalternans, similarly to soybean in Argentina, commonly infested by the redroot pigweed (Amaranthus quitensis. These weeds are usually controlled by several herbicides among which the most used are the ALS inhibitors. The intensive and repetitive use of these herbicides in São Gabriel do Oeste, MS - Brazil and in the provinces of Córdoba and Tucumã (Argentina has selected resistant populations of these weeds. Therefore, the objective of this research was carry out field and greenhouse experiments to study the management of these resistant populations, spraying as treatments the ALS-inhibitor herbicides chlorimuron-ethyl and imazethapyr and herbicides with alternative mechanism of action, protoporphyrinogen oxidase - PROTOX inhibitors (lactofen and fomesafen and photosystem II inhibitor (bentazon. The field experiment was conducted at São Gabriel do Oeste, MS - Brazil, where the suspected resistant population of beggarticks has not been controlled by ALS-inhibitor herbicides, in the last years, which had been sprayed annually for, at least, eight years. It was concluded that the herbicides chlorimuron-ethyl and imazethapyr were not

  17. Herbicide Application and Resistance in Wheat Field of China%我国小麦田除草剂应用及杂草抗药性现状

    Institute of Scientific and Technical Information of China (English)

    吴明荣; 唐伟; 陈杰

    2013-01-01

    我国常年遭受严重草害的麦田面积有0.4亿亩,造成产量损失约30%,运用化学除草剂防除麦田杂草已经成为小麦生产中的重要手段,形成了包括多种作用类别的除草剂品种和全方位化学防除体系.但随着化学除草剂的不断推广和应用,杂草抗药性问题也日益凸显和加重,目前播娘蒿、日本看麦娘、菵草等杂草抗药性已经较为严重.通过查阅相关文献,综述了近几年我国小麦田的优势杂草种类,主要应用的除草剂以及麦田杂草的抗药性现状及防治对策.%About 40 million hectares of wheat fields are heavily infested by weeds and the annual reduction of crop yields is 30% (weighted average) in China.Chemical weed control has changed cultural practices to save weeding labor in wheat.At the same time,continuous use of the same herbicides has caused weed shift problems and weed resistance to herbicides.Resistant biotypes of Descuminia sophia,Alopecurus japonicus and Beckmannia syzigachne were reported in recent years.The main worst weed species,application status of herbicides and herbicide-resistant weeds in wheat fields of China were introduced in this paper,and integrated management strategies for resistant weeds were also described.

  18. Capture and utilization of solar radiation by the soybean and common bean crops and by weeds; Captacao e aproveitamento da radiacao solar pelas culturas da soja e do feijao e por plantas daninhas

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Jose Barbosa dos; Procopio, Sergio de Oliveira; Silva, Antonio Alberto da [Universidade Federal de Vicosa (UFV), MG (Brazil). FItotecnia; Costa, Luiz Claudio [Universidade Federal de Vicosa (UFV), 36571-000, MG (Brazil). Dept. de Engenharia Agricola

    2003-07-01

    Aiming to develop techniques for the establishment of a Weed Integrated Management Program, the performance of common bean (Phaseolus vulgaris L.) and soybean (Glycine max (L.) Merrill) and of weeds Bidens pilosa L., Euphorbia heterophylla L. (two biotypes), sensitive and resistant to ALS inhibitor - herbicides and [ Desmodium tortuosum (SW.) DC.], was evaluated in relation to their efficiency in capturing and utilizing solar radiation.The following indices were calculated: total dry biomass production rate (Ct), leaf dry biomass production rate (Cf), radiation efficient use (x), net assimilation rate (EA), specific leaf area (SA), leaf area index (L), leaf matter ratio (FW) and leaf area ratio (FA). No difference was observed for all characteristics evaluated among E. heterophylla biotypes. Soybean showed the highest rate of total dry biomass production along its cycle and also the highest leaf area index, indicating its greater capacity in capturing light and providing shade to competitive plants. Especially after flowering, common bean was the most efficient in draining its photoassimilates for leaf formation. Soybean showed greater efficiency in converting radiation intercepted in the biomass. (author)

  19. Assesing Bemisia tabaci (Genn. biotype B resistance in soybean genotypes: Antixenosis and antibiosis Evaluación de la resistencia de genotipos de soya a Bemisia tabaci (Genn. biotipo B: Antixenosis y antibiosis

    Directory of Open Access Journals (Sweden)

    José Paulo Gonçalves Franco da Silva

    2012-12-01

    Full Text Available Since it was first reported in Brazil in the 1990s, the B biotype of silverleaf whitefly (Bemisia tabaci Genn., Hemiptera: Aleyrodidae has been recognized as an important pest in soybeans (Glycine max L., reducing the productivity of this legume species in some areas of the country. As an alternative to chemical control, the use of resistant genotypes represents an important tool for integrated pest management (IPM. This study evaluated the performance of 10 soybean genotypes prior to whitefly infestation, by testing attractiveness and preference for oviposition in the greenhouse and antibiosis in the laboratory. In a multiple-choice test, 'IAC-17' was the least attractive to insects. In a no-choice test, 'IAC-17' was the least attractive for egg deposition, indicating the occurrence of non-preference for oviposition on this genotype. Trichome density was positively correlated with the oviposition site and may be associated with the resistance of 'IAC-17' to infestation. The genotypes 'IAC-PL1', 'IAC-19', 'Conquista', 'IAC-24' and 'IAC-17' extended the insect's life cycle, indicating the occurrence of a small degree of antibiosis and/or non-preference for feeding.Desde que se registró por primera vez en Brasil en la década de 1990, el biotipo B de la mosca-blanca (Bemisia tabaci Genn., Hemiptera: Aleyrodidae, se reconoce como una importante plaga de la soya (Glycine max L. y es lo que reduce la productividad de estas especies de leguminosas en algunas zonas del pais. Como una alternativa al control químico, el uso de genotipos resistentes representa una herramienta importante para la gestión integrada de plagas (MIP. Este trabajo evaluó el comportamiento de 10 genotipos de soya frente al ataque de la mosca-blanca, por medio de ensayos de atractividad y preferencia para ovipostura en invernaderos y antibiosis en laboratorio. En una prueba de elección multiple, 'IAC-17' fue el menos atractivo para los insectos. En una prueba sin elecci

  20. Genomic profile of antibiotic resistant, classical ctxB positive Vibrio cholerae O1 biotype El Tor isolated in 2003 and 2005 from Puri, India: A retrospective study

    Directory of Open Access Journals (Sweden)

    T Bhotra

    2016-01-01

    Full Text Available Objectives: To examine eight strains of Vibrio cholerae O1 isolated in 2003 and 2005 from Puri, India, for antibiotic susceptibility, presence of virulence and regulatory genes, cholera toxin (CT production, CTX arrangement and genomic profiles. Materials and Methods: Bacterial strains were tested for antibiotic susceptibility using disc diffusion assay. Polymerase chain reaction determined the presence of antibiotic resistance, virulence and regulatory genes. To determine the type of cholera toxin subunit B (ctxB, nucleotide sequencing was performed. Southern hybridisation determined the number and arrangement of CTXΦ. Ribotyping and pulsed-field gel electrophoresis (PFGE were used to determine the genomic profile of isolates. Results: All the eight strains, except one strain, showed resistant to nalidixic acid, sulphamethoxazole, streptomycin and trimethoprim and possessed the sullI, strB, dfrA1 and int SXT genes. All the strains carried the toxin-co-regulated pilus pathogenicity island, the CTX genetic element, the repeat in toxin and produced CT. Restriction fragment length polymorphism (RFLP analysis showed that V. cholerae O1 possess a single copy of the CTX element flanked by tandemly arranged RS element. Nucleotide sequencing of the ctxB gene showed the presence of classical ctxB. RFLP analysis of conserved rRNA gene showed two ribotype patterns. PFGE analysis also showed at least three PFGE patterns, irrespective of year of isolations, indicating the genomic relatedness among them. Conclusion: Overall, these data suggest that classical ctxB-positive V. cholerae O1 El Tor strains that appeared in 2003 continue to cause infection in 2005 in Puri, India, and belong to identical ribotype(s and/or pulsotype(s. There is need to continuous monitor the emergence of variant of El Tor because it will improve our understanding of the evolution of new clones of variant of V. cholerae.

  1. BIOLOGICAL CONTROL OF WEEDS BY MEANS OF PLANT PATHOGENS

    Directory of Open Access Journals (Sweden)

    Marija Ravlić

    2014-06-01

    Full Text Available Biological control is the use of live beneficial organisms and products of their metabolism in the pests control. Plant pathogens can be used for weed control in three different ways: as classical, conservation and augmentative (inoculative and inundated biological control. Inundated biological control involves the use of bioherbicides (mycoherbicides or artificial breeding of pathogens and application in specific stages of crops and weeds. Biological control of weeds can be used where chemical herbicides are not allowed, if resistant weed species are present or in the integrated pest management against weeds with reduced herbicides doses and other non-chemical measures, but it has certain limitations and disadvantages.

  2. Chlorophyll fluorescence protocol for quick detection of triazinone resistant Chenopodium album L.

    Science.gov (United States)

    Mechant, E; De Marez, T; Aper, J; Bulcke, R

    2010-01-01

    Sugar beet growers in Europe are more often confronted with an unsatisfactory control of Chenopodium album L. (fat-hen), possibly due to the presence of a triazinone resistant biotype. So far, two mutations on the psbA-gene, i.e. Ser264-Gly and Ala251-Val, are known to cause resistance in C. album to the photosystem II-inhibiting triazinones metamitron, a key herbicide in sugar beet, and metribuzin. The Ser264-Gly biotype, cross-resistant to many other photosystem II-inhibitors like the triazines atrazine and terbuthylazine, is most common. The second resistant C. album biotype, recorded in Sweden, is highly resistant to triazinones but only slightly cross-resistant to terbuthylazine. Since farmers should adapt their weed control strategy when a resistant biotype is present, a quick and cheap detection method is needed. Therefore, through trial and error, a protocol for detection with chlorophyll fluorescence measurements was developed and put to the test. First, C. album leaves were incubated in herbicide solution (i.e. 0 microM, 25 microM metribuzin, 200 microM metamitron or 25 microM terbuthylazine) during three hours under natural light. After 30 minutes of dark adaptation, photosynthesis yield was measured with Pocket PEA (Hansatech Instruments). In Leaves from sensitive C. album, herbicide treatment reduces photosynthesis yield due to inhibition of photosynthesis at photosystem II. This results in a difference of photosynthesis yield between the untreated control and herbicide treatment. Based on the relative photosynthesis yield (as a percentage of untreated), a classification rule was formulated: C. album is classified as sensitive when its relative photosynthesis yield is less than 90%, otherwise it is resistant. While metribuzin, and to a lesser extent, metamitron treatment allowed a quick detection of triazinone resistant C. album, terbuthylazine treatment was able to distinguish the Ser264-Gly from the Ala251-Val biotype. As a final test, 265 plants

  3. 玉米田主要杂草对烟嘧磺隆的抗性%Resistance of weeds to nicosulfuron in corn fields in China

    Institute of Scientific and Technical Information of China (English)

    吴翠霞; 张宏军; 张佳; 宋敏; 孔繁华; 路兴涛

    2016-01-01

    为明确我国玉米田杂草对烟嘧磺隆的抗性水平及分布现状,于2010—2011年自山东、吉林、四川、河北4省采集连续多年施用烟嘧磺隆的玉米田杂草种子样本121个,在温室内采用盆栽法测定了其对烟嘧磺隆的抗性。结果显示:4个杂草样本对烟嘧磺隆产生了抗性,其中山东淄博张店区傅家镇高家村的牛筋草抗性种群的 GR50为25.76 g/hm2,是敏感种群(1.33 g/hm2)的19.37倍,已产生明显的抗药性;四川彭山县谢家镇岳油村的稗草、河北大城县广安镇夏屯村的虎尾草和河北邯郸的狗尾草分别产生了6.14、5.43和5.65倍的低水平抗性;其余杂草样本均无明显抗性。同一杂草不同采集地点的敏感样本对烟嘧磺隆的敏感性存在差异。%To investigate the resistance level and distribution of weed species to nicosulfuron in corn fields in Chi-na,a total of 121 populations of weed in nicosulfuron continuously used fields were collected from Shandong,Ji-lin,Sichuan and Hebei provinces from 2010 to 2011.The resistance was detected in the greenhouse by whole plant pot method.The results showed that four populations of weeds were resistant to nicosulfuron.Among them,the GR50 value of a resistant Eleusine indica population collected from Gaojia village,Fujia Town,Zhangdian Dis-trict,Zibo,Shandong Province was 25.76 g/hm2 ,which was 19.37-fold higher than the corresponding susceptible population (GR50 =1.33 g/hm2 ).The Echinochloa crusgalli from Pengshan,Sichuan Province,Chloris virgata from Dacheng,and Setaria viridis from Handan,Hebei Province showed low level resistance to nicosulfuron with resist-ance ratios of 6.14,5.43 and 5.65,respectively.The rest samples were all susceptible to the nicosulfuron.

  4. Best management practices for herbicide resistance

    Science.gov (United States)

    In spite of the recent focus on herbicide resistant weeds, herbicide resistant weeds are not new to agriculture; the first herbicide resistant weed was documented in 1957, with the first widespread resistance occurring in common groundsel with atrazine in the early 1970’s. Glyphosate resistant weed...

  5. Cholera outbreaks in the classical biotype era.

    Science.gov (United States)

    Siddique, A K; Cash, Richard

    2014-01-01

    In the Indian subcontinent description of a disease resembling cholera has been mentioned in Sushruta Samita, estimated to have been written between ~400 and 500 BC. It is however not clear whether the disease known today as cholera caused by Vibrio cholerae Vibrio cholerae O1 is the evolutionary progression of the ancient disease. The modern history of cholera began in 1817 when an explosive epidemic broke out in the Ganges River Delta region of Bengal. This was the first of the seven recorded cholera pandemics cholera pandemics that affected nearly the entire world and caused hundreds of thousands of deaths. The bacterium responsible for this human disease was first recognised during the fifth pandemic and was named V. cholerae which was grouped as O1, and was further differentiated into Classical and El Tor biotypes. It is now known that the fifth and the sixth pandemics were caused by the V. cholerae O1 of the Classical biotype Classical biotype and the seventh by the El Tor biotype El Tor biotype . The El Tor biotype of V. cholerae, which originated in Indonesia Indonesia and shortly thereafter began to spread in the early 1960s. Within the span of 50 years the El Tor biotype had invaded nearly the entire world, completely displacing the Classical biotype from all the countries except Bangladesh. What prompted the earlier pandemics to begin is not clearly understood, nor do we know how and why they ended. The success of the seventh pandemic clone over the pre-existing sixth pandemic strain remains largely an unsolved mystery. Why classical biotype eventually disappeared from the world remains to be explained. For nearly three decades (1963-1991) during the Seventh cholera pandemic seventh pandemic, cholera in Bangladesh has recorded a unique history of co-existence of Classical and El Tor biotypes of V. cholerae O1 as epidemic and endemic strain. This long co-existence has provided us with great opportunity to improve our understanding of the disease itself

  6. Wild Birds as biological indicators of environmental pollution: biotyping and antimicrobial resistance patterns of Escherichia coli isolated from Audouin's gulls (Larus Audouinii living in the Bay of Gallipoli (Italy

    Directory of Open Access Journals (Sweden)

    Antonio Camarda

    2006-01-01

    Full Text Available E. Coli biotyping and antimicrobial succeptibility tests were performed on fortyeight cloacal swabs collected from a popoulation of Audouin's gulls ((Larus Audouinii living in the Bay of Gallipoli (Lecce, Italy. The aim was to assess the pathogenic potential of the strains the gulls carry and shed into the environment and to gain a better understanding of the microbial pollution of the aera they live in.

  7. Wild Birds as biological indicators of environmental pollution: biotyping and antimicrobial resistance patterns of Escherichia coli isolated from Audouin's gulls (Larus Audouinii living in the Bay of Gallipoli (Italy

    Directory of Open Access Journals (Sweden)

    Egidio Mallia

    2010-01-01

    Full Text Available E. Coli biotyping and antimicrobial succeptibility tests were performed on fortyeight cloacal swabs collected from a popoulation of Audouin's gulls ((Larus Audouinii living in the Bay of Gallipoli (Lecce, Italy. The aim was to assess the pathogenic potential of the strains the gulls carry and shed into the environment and to gain a better understanding of the microbial pollution of the aera they live in.

  8. Marijuana (Weed, Pot) Facts

    Science.gov (United States)

    ... That People Abuse » Marijuana (Weed, Pot) Facts Marijuana (Weed, Pot) Facts Listen Marijuana is a green, brown, or gray mix of dried, shredded leaves and flowers from the marijuana plant. Marijuana can be rolled up and smoked ...

  9. Eradication of Major Weeds

    Science.gov (United States)

    Indian Journal of Adult Education, 1975

    1975-01-01

    Strategies for weed control in cropped and non-cropped areas are presented together with an operational plan for implementing a program for weed control at the national level. The program includes training personnel and community education procedures. (EC)

  10. Eradication of Major Weeds

    Science.gov (United States)

    Indian Journal of Adult Education, 1975

    1975-01-01

    Strategies for weed control in cropped and non-cropped areas are presented together with an operational plan for implementing a program for weed control at the national level. The program includes training personnel and community education procedures. (EC)

  11. Utility of MtCOI polymerase chain reaction-restriction fragment length polymorphism in differentiating between Q and B whitefly Bemisia tabaci biotypes

    Institute of Scientific and Technical Information of China (English)

    Wei-Hua Ma; Xian-Chun Li; Timothy J. Dennehy; Chao-Liang Lei; Mo Wang; Benjamin A. Degain; Robert L. Nichols

    2009-01-01

    The invasive, insecticide-resistant, Q whitefly biotype, has gradually spread to other countries including the US via human-mediated movement of plant materials. We assessed the utility of the VspI-based mtCOl (mitochondrion cytochrome oxidase I) polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) tech-nique as a rapid, cost-effective, and reliable alternative for differentiating the Q from the dominant B biotype in Arizona. Using the standard mtCOI gene sequencing and mtCOI PCR-RFLP techniques, we biotyped eight whitefly strains of five individuals each collected from poinsettia and cotton at different locations in Arizona. Complete concordance was observed between the two methods, with three strains being identified as the Q biotype and five samples as the B biotype. We also scanned the mtCOI gene sequences for VspI polymorphisms in the B and Q biotype whiteflies currently available in the GenBank database. This global screening revealed the existence of three and four VspI polymorphic types for the Q and B biotypes, respectively. Nevertheless, all three VspI polymorphic Q biotype whiteflies shared a common and unique VspI site that can be used to differentiate Q biotype from the four VspI polymorphic B biotype whiteflies identified. These results demonstrate that the VspI-based mtCOI gene PCR-RFLP provides a reliable diagnostic tool for differentiating the Q and B biotype whiteflies in the US and elsewhere.

  12. Crop–weed competition

    DEFF Research Database (Denmark)

    Gallandt, Eric R.; Weiner, Jacob

    2015-01-01

    on crops. Longer term management of crop–weed competition can be achieved through crop rotations, specifically crop sequences that reduce the weed seed bank, and therefore seedling density, and prevent proliferation of perennial weeds. Key ConceptsKey Concepts * Plant growth requires sunlight, water...

  13. Horny Goat Weed

    Science.gov (United States)

    Horny goat weed is an herb. The leaves are used to make medicine. As many as 15 horny goat weed species are known as “yin yang huo” in Chinese medicine. Horny goat weed is used for weak back and knees, joint ...

  14. Resistance to acetyl-CoA carboxylase-inhibiting herbicides.

    Science.gov (United States)

    Kaundun, Shiv S

    2014-09-01

    Resistance to acetyl-CoA carboxylase herbicides is documented in at least 43 grass weeds and is particularly problematic in Lolium, Alopecurus and Avena species. Genetic studies have shown that resistance generally evolves independently and can be conferred by target-site mutations at ACCase codon positions 1781, 1999, 2027, 2041, 2078, 2088 and 2096. The level of resistance depends on the herbicides, recommended field rates, weed species, plant growth stages, specific amino acid changes and the number of gene copies and mutant ACCase alleles. Non-target-site resistance, or in essence metabolic resistance, is prevalent, multigenic and favoured under low-dose selection. Metabolic resistance can be specific but also broad, affecting other modes of action. Some target-site and metabolic-resistant biotypes are characterised by a fitness penalty. However, the significance for resistance regression in the absence of ACCase herbicides is yet to be determined over a practical timeframe. More recently, a fitness benefit has been reported in some populations containing the I1781L mutation in terms of vegetative and reproductive outputs and delayed germination. Several DNA-based methods have been developed to detect known ACCase resistance mutations, unlike metabolic resistance, as the genes remain elusive to date. Therefore, confirmation of resistance is still carried out via whole-plant herbicide bioassays. A growing number of monocotyledonous crops have been engineered to resist ACCase herbicides, thus increasing the options for grass weed control. While the science of ACCase herbicide resistance has progressed significantly over the past 10 years, several avenues provided in the present review remain to be explored for a better understanding of resistance to this important mode of action.

  15. History of the race structure of Orobanche cumana and the breeding of sunflower for resistance to this parasitic weed: A review

    Energy Technology Data Exchange (ETDEWEB)

    Molinero-Ruiz, L.; Delavault, P.; Pérez-Vich, B.; Pacureanu-Joita, M.; Bulos, M.; Altieri, E.; Domínguez, J.

    2015-07-01

    Broomrape, caused by Orobanche cumana, has affected sunflowers since the early 20th century in Eastern Europe. Currently, it limits sunflower oil production in Southern and Eastern Europe and in some areas of Asia, causing around 50% seed losses when susceptible hybrids are grown. Covered in this review are aspects such as: biological processes that are common to Orobanche spp. and/or particular to O. cumana in sunflower, genetic resistance and its mechanisms, races of the parasite identified in different countries throughout the time and their increasing virulence, and breeding for resistance to some herbicides as a novel control option. The main purpose is to present an updated and, as far as possible, complete picture of the way both the parasitic weed and its host crop have evolved in time, and how they co-exist in the current agriculture. Additionally, we propose a system for determining the races of the parasite that can be internationally adopted from now. In the context of minimal harmful effects on the environment, changing patterns of land use in farming systems, and global environment changes, the final goal of this work is to provide all those interested in parasites from field crops and their integrated management compiled information on the sunflower – O. cumana system as a case study. (Author)

  16. History of the race structure of Orobanche cumana and the breeding of sunflower for resistance to this parasitic weed: A review

    Directory of Open Access Journals (Sweden)

    Leire Molinero-Ruiz

    2015-12-01

    Full Text Available Broomrape, caused by Orobanche cumana, has affected sunflowers since the early 20th century in Eastern Europe. Currently, it limits sunflower oil production in Southern and Eastern Europe and in some areas of Asia, causing around 50% seed losses when susceptible hybrids are grown. Covered in this review are aspects such as: biological processes that are common to Orobanche spp. and/or particular to O. cumana in sunflower, genetic resistance and its mechanisms, races of the parasite identified in different countries throughout the time and their increasing virulence, and breeding for resistance to some herbicides as a novel control option. The main purpose is to present an updated and, as far as possible, complete picture of the way both the parasitic weed and its host crop have evolved in time, and how they co-exist in the current agriculture. Additionally, we propose a system for determining the races of the parasite that can be internationally adopted from now. In the context of minimal harmful effects on the environment, changing patterns of land use in farming systems, and global environment changes, the final goal of this work is to provide all those interested in parasites from field crops and their integrated management compiled information on the sunflower – O. cumana system as a case study.

  17. Análisis de la sensibilidad de biotipos de Lolium multiflorum a herbicidas inhibidores de la enzima ALS, ACCasa y Glifosato Sensitivity analysis of Lolium multiflorum biotypes to Glyphosate, ACCase and ALS-inhibiting herbicides

    Directory of Open Access Journals (Sweden)

    P. Diez De Ulzurrun

    2012-09-01

    Full Text Available A pesar de los avances logrados en el control de las malezas con el uso de herbicidas, el manejo de las mismas no se simplificó, sino que, al contrario, surgieron nuevos desafíos, como la aparición de resistencia a herbicidas. En 2007, se reportó en Lolium multiflorum el segundo caso de resistencia a glifosato detectado en Argentina. En el sudeste de la provincia de Buenos Aires se registraron fallas de control a campo en poblaciones de Lolium multiflorum debido a su resistencia a distintos herbicidas de las familias de los inhibidores de ALS y de ACCasa y al herbicida glifosato. El objetivo de este estudio fue caracterizar el nivel de resistencia a ciertos herbicidas inhibidores de la ALS y de la ACCasa y al glifosato en una población de L. multiflorum de Lobería (Bs As, Argentina supuestamente resistente (LmR. Se realizaron bioensayos en cajas de Petri y se determinó la GR50 mediante la variación en la longitud de coleoptile. Las curvas de dosis-respuesta se obtuvieron por medio de la ecuación log-logística. El biotipo LmR presentó resistencia múltiple a herbicidas con tres modos de acción diferentes: glifosato, inhibidores de ALS y de ACCasa. Dicho ensayo demostró la aparición de un biotipo de L. multiflorum con resistencia a múltiples principios activos.Despite progress in weed control using herbicides, management has not been simplified, but new challenges such as herbicides resistance have arisen. In 2007, a Lolium multiflorum population resistant to glyphosate was reported, as the second case of glyphosate resistant weeds in Argentina. In the southeast of Buenos Aires province, control failures in populations of L. multiflorum to different families of herbicide such as ALS and ACCase inhibitors and to glyphosate at field level have been registered. The aim of this study was to characterize the level of resistance to certain herbicides inhibitors of ALS, ACCase and glyphosate in a putatively resistant (LmR population of L

  18. Controlling weeds with fungi, bacteria and viruses: a review

    OpenAIRE

    Harding, Dylan P.; Raizada, Manish N

    2015-01-01

    Weeds are a nuisance in a variety of land uses. The increasing prevalence of both herbicide resistant weeds and bans on cosmetic pesticide use has created a strong impetus to develop novel strategies for controlling weeds. The application of bacteria, fungi and viruses to achieving this goal has received increasingly great attention over the last three decades. Proposed benefits to this strategy include reduced environmental impact, increased target specificity, reduced development costs comp...

  19. Immersion vaccination against Yersinia ruckeri O1, biotype 2 confers cross protection against Y. ruckeri O1 biotype 1

    DEFF Research Database (Denmark)

    Raida, Martin Kristian; Neumann, Lukas; Kragelund Strøm, Helene

    A new biotype 2 of Y. ruckeri O1, which lacks motility has proven highly virulent for rainbow trout, and is causing disease in cultured trout even in fish vaccinated with commercial ERM biotype 1 vaccines. Not much is known about immunity against biotype 2, and therefore have we produced a Y. ruc...

  20. Introduction to Weeds and Herbicides.

    Science.gov (United States)

    Hartwig, Nathan L.

    This agriculture extension service publication from Pennsylvania State University is an introduction to weed control and herbicide use. An initial discussion of the characteristics of weeds includes scientific naming, weed competition with crops, weed dispersal and dormancy, and conditions affecting weed seed germination. The main body of the…

  1. Introduction to Weeds and Herbicides.

    Science.gov (United States)

    Hartwig, Nathan L.

    This agriculture extension service publication from Pennsylvania State University is an introduction to weed control and herbicide use. An initial discussion of the characteristics of weeds includes scientific naming, weed competition with crops, weed dispersal and dormancy, and conditions affecting weed seed germination. The main body of the…

  2. CHARACTERIZATION OF A NEW BIOTYPE Moringa OF SAUDI ARABIA USING RAPD AND ISSR MARKERS

    Directory of Open Access Journals (Sweden)

    Iyan Robiansyah

    2015-11-01

    Full Text Available Moringa peregrina and M. oleifera are the only Moringa species found in Saudi Arabia. Both species are drought resistant and have very high nutritional and medicinal properties. Detection of genetic diversity is of great value for the improvement of nutritional and medicinal value of these plants. The aim of the present study was to characterize a new biotype Moringa observed in Al Bahah Region, Saudi Arabia. We used 11 RAPD and 15 ISSR primers to characterize and compare the new biotype with M. peregrina and M. oleifera. Level of polymorphism generated by each marker was calculated. We also calculate Nei and Li’s coefficient to measure the genetic distance between the studied species. Level of polymorphism generated by RAPD and ISSR was 46% and 57%, respectively. RAPD and ISSR primers revealed that the new biotype shared 55 amplicons (45.08% with both M. peregrina and M. oleifera, 28 amplicons with M. peregrina (22.95%, 21 amplicons (17.21% with M. oleifera, and displayed 18 unshared amplicons (14.75%. Based on RAPD data, genetic distance between M. oleifera and M. peregrina was 0.32, whereas genetic distance between the new biotype and M. oleifera and M. peregrina was 0.21 and 0.29, respectively. For ISSR data, genetic distance between M. oleifera and M. peregrina was 0.5, whereas genetic distance between the new biotype and M. oleifera and M. peregrina was 0.36 and 0.34, respectively. Based on these results we suggested that the new biotype is a hybrid crossbred between M. peregrina and M. oleifera.

  3. Resistência de plantas aos herbicidas inibidores da acetolactato sintase Plant resistance to acetolactate synthase-inhibiting herbicides

    Directory of Open Access Journals (Sweden)

    M.A. Rizzardi

    2002-04-01

    inhibitors, its effects on weed ecophysiology and mutations which confer resistance to weeds, as well as the possibilities to develop resistant crops to ALS inhibitors. In weeds, resistance to ALS-inhibiting herbicides results from one or more mutations in the gene that codifies the ALS, which possesses dominant or semi-dominant characteristics when resistance is codified by one gene. Substitutions on a single nucleotide sequence cause alterations in the ALS, conferring resistance to herbicides inhibitors of this enzyme. Although the resistant biotype presents genetic and enzymatic alteration, when compared to the susceptible biotype, the ecophysiological behaviour of resistant and susceptible biotypes is similar. Resistant cultivars have already been developed in various crops, including rice and corn, which vary in their level of resistance to different chemical groups of ALS-inhibiting herbicides.

  4. Resistência à compactação de um Latossolo cultivado com cafeeiro, sob diferentes sistemas de manejo de plantas invasoras Resistance to soil compaction of an Oxisol cultivated with coffee plants under different weed Management systems

    Directory of Open Access Journals (Sweden)

    Cezar Francisco Araujo-Junior

    2008-02-01

    ção.The knowledge of the pressure levels that can be applied to the soil under different weed management system (WMS is importante for coffee plantations management. The objective of this study was to evaluate the influence of different weed management systems on the susceptibility to compaction of a Red-Yellow Latossol (Oxisol (LVA using soil support capacity (CSC models. This study was carried out at the Epamig Research Farm in Patrocínio, state of Minas Gerais, Brazil, in a coffee plantation using Ruby 1192 coffee variety in a 3.8 x 0.7 m spacing, planted in February 1999. Four WMS were used and the soil samples were collected in-between the rows under the following management systems: (1 no weed control (SC; (2 hoe-weeded (CM; (3 weed control with post-emergence herbicide Glyphosate (HPÓS; (4 weed control with pre-emergence Oxyfluorfen (HPRÉ. Fifteen undisturbed soil samples from each system were collected (in the layers 0-3, 10-13 and 25-28 cm in July 2004, totaling 180 samples. The undisturbed soil samples were equilibrated at different moisture contents and subjected to the uniaxial compression test to obtain the soil CSC models. Results suggested that the support capacity of the LVA decreases in the center of the inter rows in the following order: HPRÉ in the 0-3 cm layer > CM in the 10-13 cm layer > SC in the 0-3, 10-13, 25-28 cm layers = HPÓS in the 0-3, 10-13, 25-28 cm layers = CM at 0-3 and 25-28 cm layers = HPRÉ in the 10-13 cm layer > HPRÉ in the 25-28 cm layer. Weed control with HPRÉ in the 25-28 cm layer was most susceptible, while HPRÉ in the 0-3 cm layer was most resistant to soil compaction. The management systems SC and HPÓS in the 0-3, 10-13, 25-28 cm layers and the managements CM in the 0-3 and 25-28 cm layers and HPRÉ in the 10-13 cm layer were equally susceptible to soil compaction.

  5. Transfer of auxinic herbicide resistance from Brassica kaber to Brassica juncea and Brassica rapa through embryo rescue.

    Science.gov (United States)

    Mithila, J; Hall, J Christopher

    2013-01-01

    Auxinic herbicides are widely used in agriculture to selectively control broadleaf weeds. Prolonged use of auxinic herbicides has resulted in the evolution of resistance to these herbicides in some biotypes of Brassica kaber (wild mustard), a common weed in agricultural crops. In this study, auxinic herbicide resistance from B. kaber was transferred to Brassica juncea and Brassica rapa, two commercially important Brassica crops, by traditional breeding coupled with in vitro embryo rescue. A high frequency of embryo regeneration and hybrid plant establishment was achieved. Transfer of auxinic herbicide resistance from B. kaber to the hybrids was assessed by whole-plant screening of hybrids with dicamba, a widely used auxinic herbicide. Furthermore, the hybrids were tested for fertility (both pollen and pistil) and their ability to produce backcross progeny. The auxinic herbicide-resistant trait was introgressed into B. juncea by backcross breeding. DNA ploidy of the hybrids as well as of the backcross progeny was estimated by flow cytometry. Creation of auxinic herbicide-resistant Brassica crops by non-transgenic approaches should facilitate effective weed control, encourage less tillage, provide herbicide rotation options, minimize occurrence of herbicide resistance, and increase acceptance of these crops.

  6. Ozone and Water Stress: Effects on the Behaviour of Two White Clover Biotypes

    Directory of Open Access Journals (Sweden)

    Massimo Fagnano

    Full Text Available ozone pollution, water stress, stomata conductance, ozone uptake, clover, OTC.Ozone is a strong oxidizing pollutant which derives by alteration of the photolytic NOx cycle and it accumulates in the troposphere spreading in rural areas and therefore determining injuries on natural vegetation and crops. Since its penetration occurs mainly through stomata, all factors which alter plant-atmosphere relations could be able to modify plant response to ozone. Interaction between ozone and water stress in Mediterranean environment was studied on ozone resistant and sensitive biotypes of white clover, which were grown in charcoal filtered and notfiltered Open Top Chambers in factorial combination with different levels of water supply. Measurements of biomass, leaf area and stomatal conductance were made during the growth period. Ozone injuries were estimated as not-filtered/filtered OTC yield ratio; the stomatal flux of ozone was estimated multiplying stomata conductance x diffusivity ratio between ozone and water vapour (0.613 x ozone hourly concentrations. The hourly values of ozone uptake were cumulated throughout the cropping periods of the two years. In the sensitive biotype, water stress reduced yield losses due to ozone from 38% to 22%, as well as yield losses due to water stress were reduced by the presence of ozone from 43% to 29%, while no interaction between ozone and water stress was observed in the resistant biotype. Biomass yield losses of the sensitive biotype were strictly correlated to cumulated ozone uptake (R2 = 0.99, while biomass yield losses of the resistant biotype were not affected by the ozone fluxes variations created by the treatments. Flux based models could better estimate yield losses due to ozone in Mediterranean environments in which other stresses could be contemporary present; therefore, the new European directives might replace the actual thresholds based

  7. Economics of weed suppressive rice cultivars in flood- and furrow-irrigated systems

    Science.gov (United States)

    Weeds are a major constraint to rice production. In the U.S, weeds in rice are controlled primarily with synthetic herbicides. Intensive herbicide application in rice also has many potential drawbacks, resulting in environmental pollution, human health concerns, and development of weed resistance. B...

  8. Evaluation of resistance in Cyperus difformis populations to ALS inhibiting herbicides.

    Science.gov (United States)

    Ruiz-Santaella, J P; Bakkaliu, Y; Osuna, M D; de Prado, R

    2004-01-01

    Due to the intensification of rice cultivation in Spain and the repeated use of herbicides as an effective tool to control weeds, one important fact is the appearance of resistant populations of weeds, which are no longer controlled effectively at field doses. Therefore, it is necessary to increase doses to such an extent as to produce phytotoxicity in the rice crop. In paddy fields in Badajoz (Spain), a few years ago, populations of Cyperus difformis resistant to bensulfuron-methyl appeared. In order to characterize this resistance, whole plant assays were carried out in fourteen populations, eight of them originating from treated Spanish paddy fields. The results were expressed as resistance factor (RF) = ED50(R)/ED50(S). Two populations of Cyperus difformis, resistant (R) and tolerant (T) to bensulfuron-methyl, displayed resistance factors greater than 30 and 12.5, respectively. Furthermore, in order to evaluate the existence of a possible cross-resistance, the recommended field doses of 3 other herbicides (imazamox, ethoxysulfuron and bentazone + MCPA) were applied to the plants. All populations were susceptible to both imazamox and bentazone + MCPA and two populations showed cross-resistance to ethoxysulfuron. ALS activity was assayed in vitro in four biotypes, the R/S ratios of the I50 values calculated indicate that resistance involves a reduction in the sensitivity of the ALS mainly in the R population (biotype 4) to bensulfuron-methyl and ethoxysulfuron, displaying R/S ratios of 37500 and 142857, respectively, which may be attributed to inherent differences in the ALS protein itself and/or in the stability of the enzyme.

  9. Mind your elders: wild soybean’s contribution to soybean aphid resistance

    Science.gov (United States)

    Currently, biotype 4 soybean aphid (Aphis glycines Matsamura, SBA) is the most virulent SBA biotype. Overcoming the most aphid resistant genes, SBA biotype 4 has become the greatest challenge in utilizing plant resistance in soybean [Glycine max (L.) Merr.]. Soybean’s wild ancestor Glycine soja (Sie...

  10. Germination test as a fast method to detect glyphosate-resistant sourgrass

    Directory of Open Access Journals (Sweden)

    Marcos Altomani Neves Dias

    2015-09-01

    Full Text Available The occurrence of weed species with different levels of resistance to glyphosate has increasingly spread in agricultural areas. In Brazil, sourgrass is among the main species presenting issues in this regard. Thus, fast and reliable methods to detect glyphosate resistance are of special interest for this specie, either for research or rational management purposes. This study was carried out to verify the feasibility of using the germination test to detect glyphosate resistance in sourgrass. The experiment was conducted with two sourgrass biotypes, with different levels of susceptibility to glyphosate. The seeds were previously imbibed in solutions composed of 0, 0.1875%, 0.25%, 0.75%, 1.5%, 3% and 6% of glyphosate during two periods, five and ten minutes, and submitted to germination tests. The results indicate the germination test as a feasible and time-saving approach to evaluate glyphosate-resistant sourgrass, with results available in seven days.

  11. Germination test as a fast method to detect glyphosate-resistant sourgrass

    Directory of Open Access Journals (Sweden)

    Marcos Altomani Neves Dias

    2015-01-01

    Full Text Available The occurrence of weed species with different levels of resistance to glyphosate has increasingly spread in agricultural areas. In Brazil, sourgrass is among the main species presenting issues in this regard. Thus, fast and reliable methods to detect glyphosate resistance are of special interest for this specie, either for research or rational management purposes. This study was carried out to verify the feasibility of using the germination test to detect glyphosate resistance in sourgrass. The experiment was conducted with two sourgrass biotypes, with different levels of susceptibility to glyphosate. The seeds were previously imbibed in solutions composed of 0, 0.1875%, 0.25%, 0.75%, 1.5%, 3% and 6% of glyphosate during two periods, five and ten minutes, and submitted to germination tests. The results indicate the germination test as a feasible and time-saving approach to evaluate glyphosate-resistant sourgrass, with results available in seven days.

  12. Human immunodeficiency virus type 1 stimulatory activity by Gardnerella vaginalis: relationship to biotypes and other pathogenic characteristics.

    Science.gov (United States)

    Simoes, J A; Hashemi, F B; Aroutcheva, A A; Heimler, I; Spear, G T; Shott, S; Faro, S

    2001-07-01

    Stimulation of human immunodeficiency virus (HIV) type 1 expression by Gardnerella vaginalis is one possible cause for an increase in the amount of virus in the genital tract. The ability of G. vaginalis to induce HIV expression in chronically infected U1 cells was investigated, along with its possible relationship to biotype, genotype, and resistance to metronidazole and bacteriocin. Significant HIV stimulatory activity was found in 5 (50%) lysates of G. vaginalis. The ability to induce HIV expression in U1 cells was statistically associated with G. vaginalis biotype (P=.048) but not with genotype or resistance to metronidazole and bacteriocin. Further studies to explore the in vivo relevance of HIV activation by G. vaginalis in the female genital tract are warranted, since prevention strategies of bacterial vaginosis and colonization by certain biotypes of G. vaginalis may be valuable in reducing the risk of sexual transmission of HIV.

  13. The Fish Pathogen Vibrio vulnificus Biotype 2: Epidemiology, Phylogeny, and Virulence Factors Involved in Warm-Water Vibriosis.

    Science.gov (United States)

    Amaro, Carmen; Sanjuán, Eva; Fouz, Belén; Pajuelo, David; Lee, Chung-Te; Hor, Lien-I; Barrera, Rodolfo

    2015-06-01

    Vibrio vulnificus biotype 2 is the etiological agent of warm-water vibriosis, a disease that affects eels and other teleosts, especially in fish farms. Biotype 2 is polyphyletic and probably emerged from aquatic bacteria by acquisition of a transferable virulence plasmid that encodes resistance to innate immunity of eels and other teleosts. Interestingly, biotype 2 comprises a zoonotic clonal complex designated as serovar E that has extended worldwide. One of the most interesting virulence factors produced by serovar E is RtxA13, a multifunctional protein that acts as a lethal factor for fish, an invasion factor for mice, and a survival factor outside the host. Two practically identical copies of rtxA13 are present in all biotype 2 strains regardless of the serovar, one in the virulence plasmid and the other in chromosome II. The plasmid also contains other genes involved in survival and growth in eel blood: vep07, a gene for an outer membrane (OM) lipoprotein involved in resistance to eel serum and vep20, a gene for an OM receptor specific for eel-transferrin and, probably, other related fish transferrins. All the three genes are highly conserved within biotype 2, which suggests that they are under a strong selective pressure. Interestingly, the three genes are related with transferable plasmids, which emphasizes the role of horizontal gene transfer in the evolution of V. vulnificus in nutrient-enriched aquatic environments, such as fish farms.

  14. Reproduction and Population Dynamics as Biotypic Markers of Russian Wheat Aphid Diuraphis noxia (Kurdjumov

    Directory of Open Access Journals (Sweden)

    Watson Ngenya

    2016-04-01

    Full Text Available Russian wheat aphid Diuraphis noxia (Kurdjumov is widely established in wheat-growing countries where it causes significant economic losses. The development and use of Russian wheat aphid (RWA-resistant wheat varieties has been constrained by the variation in resident RWA populations and the evolution of virulent biotypes. An experiment was set up at the Kenya Agricultural and Livestock Research Organization (KALRO, Njoro, to characterize RWA populations based on phenotypic characteristics of reproduction, development and population dynamics. RWA populations from the regions of Eldoret, Mau Narok and Njoro were used in the study. A factorial experiment was set up in randomized complete block design replicated eleven times. A single day-old nymph was placed on a new, fully-open leaf in a 0.5 cm-diameter clear plastic straw leaf cage and observed daily for its entire lifetime. The results showed that there were variations in aphid lifespan, reproductive longevity and aphid fecundity between populations, indicating that the phenotypic markers used to determine biotypes were good enough to show distinct biotypes among populations of the RWA in Kenya. Further, the study concluded that the use of phenotypic life and reproductive markers was a valid way of characterizing biotypes of RWA worldwide.

  15. Reproduction and Population Dynamics as Biotypic Markers of Russian Wheat Aphid Diuraphis noxia (Kurdjumov).

    Science.gov (United States)

    Ngenya, Watson; Malinga, Joyce; Tabu, Isaiah; Masinde, Emily

    2016-04-02

    Russian wheat aphid Diuraphis noxia (Kurdjumov) is widely established in wheat-growing countries where it causes significant economic losses. The development and use of Russian wheat aphid (RWA)-resistant wheat varieties has been constrained by the variation in resident RWA populations and the evolution of virulent biotypes. An experiment was set up at the Kenya Agricultural and Livestock Research Organization (KALRO), Njoro, to characterize RWA populations based on phenotypic characteristics of reproduction, development and population dynamics. RWA populations from the regions of Eldoret, Mau Narok and Njoro were used in the study. A factorial experiment was set up in randomized complete block design replicated eleven times. A single day-old nymph was placed on a new, fully-open leaf in a 0.5 cm-diameter clear plastic straw leaf cage and observed daily for its entire lifetime. The results showed that there were variations in aphid lifespan, reproductive longevity and aphid fecundity between populations, indicating that the phenotypic markers used to determine biotypes were good enough to show distinct biotypes among populations of the RWA in Kenya. Further, the study concluded that the use of phenotypic life and reproductive markers was a valid way of characterizing biotypes of RWA worldwide.

  16. Site Specific Weed Control Technologies

    DEFF Research Database (Denmark)

    Christensen, Svend; Søgaard, Henning Tangen; Kudsk, Per;

    2009-01-01

    describe the basic parts of site specific weed control technologies, comprising of weed sensing systems, weed management models and precision weed control implements. A review of state-of-the-art technologies shows that several weed sensing systems and precision implements have been developed over the last...... of knowledge about the economic and environmental potential for increasing the resolution of weed control. The integration of site-specific information on weed distribution, weed species composition and density, and the effect on crop yield, is decisive for successful site-specific weed management.   Keywords......Site-specific weed control technologies are defined as machinery or equipment embedded with technologies that detect weeds growing in a crop and, taking into account predefined factors such as economics, takes action to maximise the chances of successfully controlling them. In the article, we...

  17. Sensitivity of imidazolinone-resistant red rice (Oryza sativa L. to glyphosate and glufosinate

    Directory of Open Access Journals (Sweden)

    Guilherme Vestena Cassol

    2015-09-01

    Full Text Available Dose-response experiments were carried out to evaluate the sensitivity of imidazolinone-resistant red rice to nonselective herbicides currently used in rice-soybean rotation in Rio Grande do Sul. Two red rice biotypes previously identified as resistant and susceptible to the imidazolinone herbicides were treated with imazapic plus imazapic, glyphosate and glufosinate under nine herbicide rates. A non-linear log-logistic analysis was used to estimate the herbicide rate that provided 50% red rice control and dry weight reduction (GR50. Imidazolinone-resistant red rice exhibited greater GR50 values than imidazolinone-susceptible biotype for imazapyr plus imazapic. In contrast, both imidazolinone-resistant and susceptible red rice showed similar GR50values for glyphosate and glufosinate. These results indicate that glyphosate and glufosinate effectively control imidazolinone-resistant red rice at similar herbicide rates used to control imidazolinone-susceptible; however, integrated weed management practices must be adopted in rice-soybean rotation to delay resistance evolution of red rice populations to glyphosate and glufosinate

  18. Weeding Library Collections.

    Science.gov (United States)

    Slote, Stanley J.

    This work, based on two recent research projects in the weeding of library collections and the identification of core collections, provides a comprehensive summary of the literature and research on these topics. It also presents practical guidance in weeding for the professional librarian or for the library school student. The book is divided into…

  19. RoboWeedSupport

    DEFF Research Database (Denmark)

    Dyrmann, Mads; Nyholm Jørgensen, Rasmus

    2015-01-01

    Information about the weed population in fields is important for determining the optimal herbicides for the fields. A system based on images is presented that can provide support in determining the species and density of the weeds. Firstly, plants are segmented from the soil. Plants that after th...

  20. Manejo da Planta Daninha Brachiaria plantaginea Resistente aos herbicidas Inibidores da ACCase Management of the Weed Brachiaria plantaginea Resistant to ACCase Inhibitor Herbicides

    Directory of Open Access Journals (Sweden)

    P.J. Christoffoleti

    2001-04-01

    study a population of alexandergrass (Brachiaria plantaginea resistant to ACCase inhibitor herbicides (ariloxyphenoxypropionic and cyclohexanodiones, usually sprayed on soybean under the conservation tillage system. Two experiments were conducted, one under field conditions, comparing the efficacy of non-selective herbicides to ACCase inhibitors, and another under greenhouse conditions, using ACCase inhibitors with nitrogenous additives in the spray solution. Resistant seeds were collected from a site of suspected resistant population, and compared to a population of alexandergrass that had never been sprayed with ACCase inhibitors, the susceptible population. The experiment with non-selective herbicides was conducted under field conditions, but plants were confined to pots of 50 L capacity, avoiding the dissemination of the seeds to adjacent areas. It was then concluded that resistant plants did not show multiple resistance to non selective herbicides with alternative mechanisms of action, with glyphosate, paraquat, paraquat + diuron, MSMA and glufosinate alternative herbicides being possible to be used to control the weed during the winter to manage populations of alexandergrass resistant to ACCase inhibitor herbicides. The additive experiment was conducted under greenhouse conditions in pots, using seeds from the same populations used in the non selective experiment. The herbicides tested were ACCase inhibitors, and the additive treatments were ammonium sulfate and urea. It was then concluded that the additives did not enhance ACCase inhibitor herbicide efficacy in neither of the alexandergrass populations.

  1. Exploring the effects of glyphosate products on weed composition

    Directory of Open Access Journals (Sweden)

    Koning, Laurie Anne

    2016-02-01

    Full Text Available Glyphosate is a non-selective, broad-spectrum, systematic herbicide that is the world’s most widely used herbicide since its introduction in the 1970s as a pre-plant, post-directed and post-harvest herbicide application with further technological developments leading to its use within glyphosate resistant crops (GRCs as of the 1990s. In countries around the world, weed shifts have accompanied weed management systems employing glyphosate products. The farmer actions and weed reactions that have contributed to these weed shifts will be discussed. Evidence of glyphosate-induced weed shifts has not yet been documented in Germany, but through consideration of the conditions that have lead to glyphosate-induced weed shifts elsewhere the outlook for Germany will be assessed. An ongoing research project will be introduced in which weed monitoring is being employed to find out if glyphosate-induced weed shifts can be identified in northeastern German arable farm fields and in which field experiments are also being conducted to further explore the reactions of weed communities and populations under the intensive application of glyphosate products.

  2. Biotyping of thermophilic Campylobacter spp. isolated from poultry in and around Anand city, Gujarat, India

    Directory of Open Access Journals (Sweden)

    R. S. Tayde

    2014-05-01

    Full Text Available Aim: To study the prevalence of different biotypes of thermophilic Campylobacter spp. in the study area. Materials and Methods: A total of 150 samples comprising 90 chicken and 60 caecal content were collected from retail meat market and processed for isolation of Campylobacter spp. 52 Campylobacter isolates obtained from raw poultry meat (6 and caecal content (46 were subjected to biotyping using Lior's biotyping scheme. Results: Among the 52 Campylobacter isolates studied, 60.46 % isolates were identified as Campylobacter jejuni Biotype I and 39.53% were C. jejuni Biotype II, whereas 83.33 % were C. coli Biotype I and 16.66 % C. coli Biotype II. No other biotypes were identified. Conclusions: The present study revealed that C. jejuni Biotype I was more prevalent than Biotype II whereas in case of C. coli, Biotype I was more prevalent than Biotype II providing basis for further epidemiological study.

  3. Microwave Technologies as Part of an Integrated Weed Management Strategy: A Review

    Directory of Open Access Journals (Sweden)

    Graham Brodie

    2012-01-01

    Full Text Available Interest in controlling weed plants using radio frequency or microwave energy has been growing in recent years because of the growing concerns about herbicide resistance and chemical residues in the environment. This paper reviews the prospects of using microwave energy to manage weeds. Microwave energy effectively kills weed plants and their seeds; however, most studies have focused on applying the microwave energy over a sizable area, which requires about ten times the energy that is embodied in conventional chemical treatments to achieve effective weed control. A closer analysis of the microwave heating phenomenon suggests that thermal runaway can reduce microwave weed treatment time by at least one order of magnitude. If thermal runaway can be induced in weed plants, the energy costs associated with microwave weed management would be comparable with chemical weed control.

  4. Cultural control of weeds in herbicide-free annual forages

    Science.gov (United States)

    The adoption of zero tillage systems improves soil water conservation, allowing for increased crop intensification and diversification in the semiarid northern Great Plains. Zero tillage systems rely primarily on herbicides for weed management, increasing selection pressure for herbicide resistance...

  5. Bionomics of brown planthopper biotype 2 from field and greenhouse

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Two biotype 2 populations of brown planthopper (BPH), Nilaparvata lugens stal, were used in this experiment. One was purified by determining the weight of honeydew excreted on susceptible rice variety TN1 and resistant rice varieties Mudgo (bearing resistant gene Bph1) and ASD7 (bearing resistant gene bph2) by female adult in paddy field in Guangxi Province, south China, and the other was obtained from greenhouse and continuously reared on rice resistant variety Mudgo in IRRI, Philippines. One newly hatched nymph was introduced into the test tube containing two 60 day old rice plants and cultured at 26± 1℃ , L∶ D =12 h∶ 12 h. Sixty replications were set up for each tested rice variety. The number and instar of nymphes were recorded every day. The body weight and honeydew excreted by female adult emerged within 24 h and 72 h, the number of eggs laid, and newly hatched nymph on different resistant rice varieties were measured. The hatchability, net reproductive rate, female adult nutritional indices such as relative growth rate (RGR)and efficiency of conversion of ingested food (ECI) were calculated.

  6. Resistência de amendoim-bravo aos herbicidas inibidores da enzima acetolactato sintase Wild poinsettia resistance to acetolactate synthase inhibitor herbicides

    Directory of Open Access Journals (Sweden)

    Ribas A. Vidal

    1999-12-01

    Full Text Available O controle contínuo de plantas daninhas através da aplicação de herbicidas que apresentam atividade em um único local de ação nas plantas favorece a seleção de biótipos resistentes a estes herbicidas, em certas espécies vegetais. Quatro experimentos foram conduzidos em condições casa-de-vegetação, na Faculdade de Agronomia da Universidade Federal do Rio Grande do Sul, com os objetivos de avaliar a ocorrência de resistência aos herbicidas inibidores da enzima acetolactato sintase (ALS em vários biótipos de leiteiro ou amendoim-bravo (Euphorbia heterophylla EPHHL e avaliar a ocorrência de resistência múltipla a herbicidas com atividade em outros locais de ação. Biótipo oriundo de Passo Fundo foi resistente ao imazethapyr, enquanto biótipo oriundo de Porto Alegre foi suscetível. O biótipo de Passo Fundo apresentou resistência cruzada aos herbicidas imidazolinonas: imazapyr, imazaquin e imazethapyr; sulfoniluréias: chlorimuron, nicosulfuron e metsulfuron; e sulfonanilida: flumetsulan. Este biótipo não foi resistente aos herbicidas com os seguintes mecanismos de ação: inibidores de EPSPs, mimetizadores de auxina, inibidores dos fotossistemas I e II e inibidores de PROTOX. A confirmação de resistência aos inibidores de ALS em biótipos oriundos de Nãome-Toque, Passo Fundo e Rio Pardo sugere ampla dispersão no Rio Grande do Sul de resistência de E. heterophylla aos herbicidas deste mecanismo de ação.The continuous weed control with herbicides of only one site of action selects biotypes resistant to these herbicides. Four experiments were conducted in greenhouse of UFRGS, Brazil, to confirm the occurence of wild poinsettia (Euphorbia heterophylla biotypes resistance to herbicides inhibitors of acetholactate synthase (ALS, and to determine whether there was cross resistance to herbicides with other site of action. A biotype from Passo Fundo -RS was resistant to imazethapyr, whereas a biotype from Porto Alegre -RS

  7. Integrated pest management and weed management in the United States and Canada.

    Science.gov (United States)

    Owen, Micheal D K; Beckie, Hugh J; Leeson, Julia Y; Norsworthy, Jason K; Steckel, Larry E

    2015-03-01

    There is interest in more diverse weed management tactics because of evolved herbicide resistance in important weeds in many US and Canadian crop systems. While herbicide resistance in weeds is not new, the issue has become critical because of the adoption of simple, convenient and inexpensive crop systems based on genetically engineered glyphosate-tolerant crop cultivars. Importantly, genetic engineering has not been a factor in rice and wheat, two globally important food crops. There are many tactics that help to mitigate herbicide resistance in weeds and should be widely adopted. Evolved herbicide resistance in key weeds has influenced a limited number of growers to include a more diverse suite of tactics to supplement existing herbicidal tactics. Most growers still emphasize herbicides, often to the exclusion of alternative tactics. Application of integrated pest management for weeds is better characterized as integrated weed management, and more typically integrated herbicide management. However, adoption of diverse weed management tactics is limited. Modifying herbicide use will not solve herbicide resistance in weeds, and the relief provided by different herbicide use practices is generally short-lived at best. More diversity of tactics for weed management must be incorporated in crop systems.

  8. The Politics of Weeding.

    Science.gov (United States)

    Tillman, Hope N.

    1988-01-01

    Reviews the literature that deals with the political ramifications of weeding material from academic library collections and the need to involve users and other libraries within the institution in the decision process. (14 references) (CLB)

  9. Robotic weed monitoring

    DEFF Research Database (Denmark)

    Bochtis, Dionysis; Sørensen, Claus Aage Grøn; Jørgensen, R N

    2011-01-01

    -farm operating console, the mobile robotic unit, and a field server for generating and storingmaps. The hypothesis is that it is possible to automate the planning and execution of theoperation of monitoring of the in-field weed density and species distribution. The developedplanning system includes the automatic...... of the weed monitoring operation.Key words: autonomous vehicles, farm management, mission planning, route planning,sampling....

  10. Non-target-site glyphosate resistance in Conyza bonariensis is based on modified subcellular distribution of the herbicide.

    Science.gov (United States)

    Kleinman, Ziv; Rubin, Baruch

    2017-01-01

    Conyza spp. were the first broadleaf weeds reported to have evolved glyphosate resistance. Several mechanisms have been proposed for glyphosate resistance. In an effort to elucidate the mechanism of this resistance in Conyza bonariensis, possible target-site and non-target-site mechanisms were investigated in glyphosate-resistant (GR) C. bonariensis biotypes. Using differential glyphosate applications and analyses of shikimate accumulation, we followed the herbicide effect in different plant organs and monitored the herbicide's apparent mobility. We found high shikimate levels in the roots and young leaves of glyphosate-sensitive (GS) plants, regardless of the site of application, whereas in GR plants, shikimate accumulated mainly in treated young leaves. (14) C-glyphosate studies, however, revealed the expected source-to-sink translocation pattern in both GS and GR plants. Sequencing of the appropriate EPSPS DNA fragments of GR and GS plants revealed no alteration at the Pro106 position. These data support the hypothesis that the glyphosate resistance of our C. bonariensis GR biotypes is associated with altered subcellular distribution of glyphosate, which keeps the herbicide sequestered away from the EPSPS target site in the chloroplast. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  11. Evaluating Weeds as Hosts of Tomato yellow leaf curl virus.

    Science.gov (United States)

    Smith, Hugh A; Seijo, Teresa E; Vallad, Gary E; Peres, Natalia A; Druffel, Keri L

    2015-08-01

    Bemisia tabaci (Gennadius) biotype B transmits Tomato yellow leaf curl virus (TYLCV), which affects tomato production globally. Prompt destruction of virus reservoirs is a key component of virus management. Identification of weed hosts of TYLCV will be useful for reducing such reservoirs. The status of weeds as alternate hosts of TYLCV in Florida remains unclear. In greenhouse studies, B. tabaci adults from a colony reared on TYLCV-infected tomato were established in cages containing one of four weeds common to horticultural fields in central and south Florida. Cages containing tomato and cotton were also infested with viruliferous whiteflies as a positive control and negative control, respectively. Whitefly adults and plant tissue were tested periodically over 10 wk for the presence of TYLCV using PCR. After 10 wk, virus-susceptible tomato plants were placed in each cage to determine if whiteflies descended from the original adults were still infective. Results indicate that Bidens alba, Emilia fosbergii, and Raphanus raphanistrum are not hosts of TYLCV, and that Amaranthus retroflexus is a host. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  12. Stable Isotope Resolved Metabolomics Reveals the Role of Anabolic and Catabolic Processes in Glyphosate-Induced Amino Acid Accumulation in Amaranthus palmeri Biotypes.

    Science.gov (United States)

    Maroli, Amith; Nandula, Vijay; Duke, Stephen; Tharayil, Nishanth

    2016-09-21

    Biotic and abiotic stressors often result in the buildup of amino acid pools in plants, which serve as potential stress mitigators. However, the role of anabolic (de novo amino acid synthesis) versus catabolic (proteolytic) processes in contributing to free amino acid pools is less understood. Using stable isotope-resolved metabolomics (SIRM), we measured the de novo amino acid synthesis in glyphosate susceptible (S-) and resistant (R-) Amaranthus palmeri biotypes. In the S-biotype, glyphosate treatment at 0.4 kg ae/ha resulted in an increase in total amino acids, a proportional increase in both (14)N and (15)N amino acids, and a decrease in soluble proteins. This indicates a potential increase in de novo amino acid synthesis, coupled with a lower protein synthesis and a higher protein catabolism following glyphosate treatment in the S-biotype. Furthermore, the ratio of glutamine/glutamic acid (Gln/Glu) in the glyphosate-treated S- and R-biotypes indicated that the initial assimilation of inorganic nitrogen to organic forms is less affected by glyphosate. However, amino acid biosynthesis downstream of glutamine is disproportionately disrupted in the glyphosate treated S-biotype. It is thus concluded that the herbicide-induced amino acid abundance in the S-biotype is contributed by both protein catabolism and de novo synthesis of amino acids such as glutamine and asparagine.

  13. Tolerance and selectivity of cereal species and cultivars to postemergence weed harrowing

    DEFF Research Database (Denmark)

    Rasmussen, Jesper; Nielsen, Helle Højland; Gundersen, Hanne

    2009-01-01

    for analyzing crop tolerance on the basis of digital image analysis. Crop tolerance is defined as the ability of the crop to avoid yield loss from cultivation in the absence of weeds, and it has two components: resistance and recovery. Resistance is the ability of the crop to resist soil covering and recovery......POST weed harrowing and other cultivation methods to control weeds in early crop growth stages may result in crop damage due to low selectivity between crop and weeds. Crop tolerance to cultivation plays an important role but it has not been clearly defined and analyzed. We introduce a procedure...... abilities to suppress weeds. The order of species' tolerance to weed harrowing was triticale > wheat > barley > oat and the differences were mainly caused by different abilities to recover from soil covering. At 25% soil covering, grain yield loss in triticale was 0.5%, in wheat 2.5%, in barley 3...

  14. Weeds and Wildlife: Perceptions and Practices of Weed Managers

    Directory of Open Access Journals (Sweden)

    Emma H Carlos

    2014-01-01

    Full Text Available Negative impacts of invasive plants or weeds on biodiversity have been well established yet their role in providing key habitats and resources for wildlife has been little understood. Weed removal thus has the potential to adversely affect wildlife but whether this is considered during weed management is poorly known. To determine the extent of this knowledge, we examined the perceptions of weed managers regarding wildlife and weed management in Victoria, Australia. We surveyed 81 weed managers of varying levels of experience from different types of organisations, including state and local government, community groups and private companies. We found 90% of managers had observed wildlife-weed interactions and that most (70% adjusted management programmes to accommodate wildlife. Despite this, few (19% had adopted the recommended practice of combining gradual weed removal with re-vegetation. While management programmes included monitoring of native vegetation, consideration of wildlife monitoring in weed management was rare. This highlights the need for management to better understand and respond to wildlife-weed relationships. If the improvement of wildlife habitat is included in the objectives of weed programmes, as it should be, then wildlife should also be incorporated in project monitoring. This would lead to a greater understanding of the role weeds and their management have in each situation and, ultimately, more informed decision making.

  15. Transdisciplinary weed research: new leverage on challenging weed problems?

    NARCIS (Netherlands)

    Jordan, N.; Schut, M.; Graham, S.; Barney, J.N.; Childs, D.Z.; Christensen, S.B.; Cousens, R.D.; Davis, A.S.; Eizenberg, H.; Ervin, D.E.; Fernandez-Quintanilla, C.; Harrison, L.J.; Harsch, M.A.; Heijting, S.; Liebman, M.; Loddo, D.; Mirsky, S.B.; Riemens, M.; Neve, P.; Peltzer, D.A.; Renton, M.; Williams, M.; Recasens, J.; Sønderskov, M.

    2016-01-01

    Transdisciplinary weed research (TWR) is a promising path to more effective management of challenging weed problems. We define TWR as an integrated process of inquiry and action that addresses complex weed problems in the context of broader efforts to improve economic, environmental and social

  16. Transdisciplinary weed research: new leverage on challenging weed problems?

    Science.gov (United States)

    Transdisciplinary Weed Research (TWR) is a promising path to more effective management of challenging weed problems. We define TWR as an integrated process of inquiry and action that addresses complex weed problems in the context of broader efforts to improve economic, environmental and social aspec...

  17. Longitudinal study of the biotypes of Gardnerella vaginalis.

    Science.gov (United States)

    Briselden, A M; Hillier, S L

    1990-12-01

    Gardnerella vaginalis is the predominant vaginal microorganism in women with bacterial vaginosis. However, this organism is also frequently isolated from women without signs or symptoms of vaginitis. Earlier studies have not revealed whether certain biotypes of G. vaginalis are more often associated with bacterial vaginosis or are more common in women who acquire bacterial vaginosis. We used a typing scheme based on tests for beta-galactosidase, hippurate hydrolysis, and lipase, using oleate as a substrate. Of 261 strains tested, the distribution of biotypes observed was as follows: 1, 13%; 2, 9%; 3, 5%; 4, 7%; 5, 41%; 6, 15%; and 8, 10%. Biotype 7 was not observed. The distributions of biotypes from women with and without bacterial vaginosis were found to be significantly different, with the lipase-positive biotypes (biotypes 1, 2, 3, and 4) being more predominant in women with vaginosis (41 versus 23%, P = 0.003). Of 40 women with normal vaginal flora at the index visit who remained normal at follow-up, 23 (57%) acquired a new biotype of G. vaginalis. By comparison, 90% of the 30 women who developed bacterial vaginosis acquired a new biotype of G. vaginalis (P = 0.003). Women with bacterial vaginosis at the index visit who were not treated were no more likely than normal women to have a shift in G. vaginalis biotype. However, 86% of the 30 women with bacterial vaginosis who were treated with an antibiotic at the index visit acquired a different biotype (P = 0.04 compared with the value for untreated women) regardless of treatment success. A trend toward the acquisition of a new biotype was observed among women who had contact with a new sexual partner (81 versus 65%, P = 0.15). These data demonstrate that the lipase-positive isolates of G. vaginalis are associated with bacterial vaginosis. Women who acquire bacterial vaginosis are more likely to have a shift in biotype than women who had normal flora at he follow-up, suggesting that the G. vaginalis isolates

  18. Grass and weed killer poisoning

    Science.gov (United States)

    ... medlineplus.gov/ency/article/002838.htm Grass and weed killer poisoning To use the sharing features on this page, please enable JavaScript. Many weed killers contain dangerous chemicals that are harmful if ...

  19. Characterization of red rice in the province of Sancti Spiritus, Cuba. I. Biotypes of straw-colored glumes.

    Directory of Open Access Journals (Sweden)

    Jorge García de la Osa

    2013-12-01

    Full Text Available Trials were made in The Research Local Station of Grains areas, Sur del Jíbaro from 2005 through 2011. 27 morpho-agronomic characters were evaluated regarding the main red rice biotypes of straw-colored glumes in the province of Sancti Spíritus, Cuba, and in three commercial varieties of witness rice (IACuba-31, Perla de Cuba y Jucarito-104. It also was determined a broad diversity and variations in these features that permitted to differenciate the biotypes between them and with other rice cultivars. The purple pigmentation in some parts of the plants in the great majority of such biotype is an observable feature, seen easily, that make contrasts with the already researched, by which it helps a lot in identifying them. The great majority of the biotypes of straw-colored glumes featured an over-growned size in their sprouts, lengths and longer flag leaves, with also a prone feature to loose its grain, its nighty, broad seed and a particular resistance to Pyricularia grisea; but shorter and lighter but it also yields less per hectares. it has shown resistant to Tagosodes orizicolus, respecting the witness cultivars.

  20. Biotypes and virulence factors of Gardnerella vaginalis isolated from cases of bacterial vaginosis.

    Science.gov (United States)

    Udayalaxmi, J; Bhat, G K; Kotigadde, S

    2011-01-01

    The present study was conducted to correlate the biotypes of Gardnerella vaginalis strains isolated from cases of bacterial vaginosis and their virulence factors. Thirty-two strains of G. vaginalis isolated from cases of bacterial vaginosis were biotyped. Adherence to vaginal epithelial cells, biofilm production, surface hydrophobicity, phospholipase C and protease activity were tested on these isolates. Biotype 1 was the most prevalent (8; 25%), followed by biotype 2 (7; 21.9%) and biotypes 5 and 8 (5; 15.6%). We did not find any statistical correlation between G. vaginalis biotypes and its virulence factors. Virulence factors expressed by G. vaginalis were not associated with a single biotype.

  1. Biotypes and virulence factors of Gardnerella vaginalis isolated from cases of bacterial vaginosis

    Directory of Open Access Journals (Sweden)

    J Udayalaxmi

    2011-01-01

    Full Text Available The present study was conducted to correlate the biotypes of Gardnerella vaginalis strains isolated from cases of bacterial vaginosis and their virulence factors. Thirty-two strains of G. vaginalis isolated from cases of bacterial vaginosis were biotyped. Adherence to vaginal epithelial cells, biofilm production, surface hydrophobicity, phospholipase C and protease activity were tested on these isolates. Biotype 1 was the most prevalent (8; 25%, followed by biotype 2 (7; 21.9% and biotypes 5 and 8 (5; 15.6%. We did not find any statistical correlation between G. vaginalis biotypes and its virulence factors. Virulence factors expressed by G. vaginalis were not associated with a single biotype.

  2. Intercropping leeks to suppress weeds

    NARCIS (Netherlands)

    Baumann, D.T.; Kropff, M.J.; Bastiaans, L.

    2000-01-01

    Many field vegetables such as leek are weak competitors against weeds, causing high costs for weed management practice. Using celery as a companion cash crop was suggested to improve the weed suppression of leek. Three field experiments were carried out to study the intra- and interspecific competit

  3. Biotypes and virulence factors of Gardnerella vaginalis isolated from cases of bacterial vaginosis

    OpenAIRE

    Udayalaxmi, J.; Bhat, G. K.; S Kotigadde

    2011-01-01

    The present study was conducted to correlate the biotypes of Gardnerella vaginalis strains isolated from cases of bacterial vaginosis and their virulence factors. Thirty-two strains of G. vaginalis isolated from cases of bacterial vaginosis were biotyped. Adherence to vaginal epithelial cells, biofilm production, surface hydrophobicity, phospholipase C and protease activity were tested on these isolates. Biotype 1 was the most prevalent (8; 25%), followed by biotype 2 (7; 21.9%) and biotypes ...

  4. Characterization of rhizobacteria associated with weed seedlings.

    Science.gov (United States)

    Kremer, R J; Begonia, M F; Stanley, L; Lanham, E T

    1990-06-01

    Rhizobacteria were isolated from seedlings of seven economically important weeds and characterized for potential phytopathogenicity, effects on seedling growth, and antibiosis to assess the possibility of developing deleterious rhizobacteria as biological control agents. The abundance and composition of rhizobacteria varied among the different weed species. For example, fluorescent pseudomonads represented from 11 to 42% of the total rhizobacterial populations from jimsonweed and lambsquarters, respectively. Other bacteria frequently isolated were nonfluorescent pseudomonads, Erwinia herbicola, Alcaligenes spp., and Flavobacterium spp. Only 18% of all isolates were potentially phytopathogenic, based on an Escherichia coli indicator bioassay. However, the proportion of isolates that inhibited growth in seedling assays ranged from 35 to 65% depending on the weed host. Antibiosis was most prevalent among isolates of fluorescent Pseudomonas spp., the activity of which was due to siderophore production in over 75% of these isolates. Overall, rhizobacterial isolates exhibited a complex array of properties that were inconsistent with accepted definitions for plant growth-promoting and deleterious rhizobacteria. It is suggested that for development of effective biological control agents for weed control, deleterious rhizobacteria must be screened directly on host seedlings and must possess several properties including high colonizing ability, specific phytotoxin production, and resistance or tolerance to antibiotics produced by other rhizosphere microorganisms, and they must either synthesize or utilize other bacterial siderophores.

  5. Analysis of Glyphosate Resistant Weeds Development from Selective Herbicides Market Recovery%从选择性除草剂市场恢复情况分析草甘膦抗性杂草的发展

    Institute of Scientific and Technical Information of China (English)

    孙克

    2012-01-01

    介绍了磺酰脲类、咪唑啉酮类、环己烯酮类、二苯醚类等选择性除草剂近年来市场变化情况和草甘膦市场现状,描述了草甘膦抗性杂草的发展,对选择性除草剂和草甘膦未来市场变化进行了分析.%The market changes in recent years of some selective herbicides such as sulfonylurea, imidazolinone, cyclohexenone, diphenyl ethers and current situation of market of glyphosate were introduced. The development of resistant weeds to glyphosate was described and the future changes in the market of selective herbicides and glyphosate were analysed.

  6. What Price Weeding?

    Science.gov (United States)

    Ettelt, Harold J.

    1985-01-01

    Describes a study conducted at Columbia-Greene Community College's library to determine whether a book's previous non-use is indicative of future non-use; whether books are progressively less likely to be used with time; the circulation costs of weeding previously unused books; and the circulation rates of old and new books. (DMM)

  7. Controlling Landscape Weeds.

    Science.gov (United States)

    Nuss, James Robert, Jr.

    This agriculture extension service publication from Pennsylvania State University discusses the control of common grass and broadleaf weeds through the use of mulches and herbicides. The section on mulches discusses the different types of mulching materials, their advantages and disadvantages, herbicide-mulch combinations, and lists source of…

  8. Weed Research in Mint

    Science.gov (United States)

    Weeds present in peppermint and spearmint reduce mint oil yield and quality. Flumioxazin combinations with clomazone and pendimethalin applied to dormant peppermint controlled prickly lettuce and flixweed without significant injury to the crop. Low rates of flumioxazin and sulfentrazone applied imm...

  9. Controlling Landscape Weeds.

    Science.gov (United States)

    Nuss, James Robert, Jr.

    This agriculture extension service publication from Pennsylvania State University discusses the control of common grass and broadleaf weeds through the use of mulches and herbicides. The section on mulches discusses the different types of mulching materials, their advantages and disadvantages, herbicide-mulch combinations, and lists source of…

  10. Reducing the risks of herbicide resistance: best management practices and recommendations

    Science.gov (United States)

    Herbicides are the foundation of weed control in commercial crop production. However, herbicide-resistant weed populations are developing rapidly in response to selection pressure. Critical practices include reducing selection through diversification of weed control techniques, minimizing spread of ...

  11. Microwave Technologies as Part of an Integrated Weed Management Strategy: A Review

    OpenAIRE

    Graham Brodie; Carmel Ryan; Carmel Lancaster

    2012-01-01

    Interest in controlling weed plants using radio frequency or microwave energy has been growing in recent years because of the growing concerns about herbicide resistance and chemical residues in the environment. This paper reviews the prospects of using microwave energy to manage weeds. Microwave energy effectively kills weed plants and their seeds; however, most studies have focused on applying the microwave energy over a sizable area, which requires about ten times the energy that is embodi...

  12. Pneumonia due to Haemophilus influenzae (H. aegyptius) biotype 3.

    Science.gov (United States)

    Marraro, R V; McCleskey, F K; Mitchell, J L

    1977-08-01

    Haemophilus influenzae (H. aegyptius) biotype 3 was isolated from eye, nasopharyngeal, and sputum cultures of a 23-month-old male and from sputum and transtracheal aspirate cultures of his 39-year-old mother, both with diffuse bronchopneumonia.

  13. Impact of imazamox containing herbicides on the development of resistance in black-grass (Alopecurus myosuroides Huds.

    Directory of Open Access Journals (Sweden)

    Rosenhauer, Maria

    2014-02-01

    Full Text Available Winter oilseed-rape was the most common crop in Western Europe where no ALS-inhibitor was used. Due to the introduction of Clearfield winter oilseed-rape varieties the use of ALS-inhibitors also in oilseed-rape is possible. If the broader use of ALS-inhibitors increases the selection pressure on herbicide resistant weeds and increases their occurrence in the crop rotation is the question of this investigation. Therefore, an outdoor container trial (á 350 l, 0.7 m² was performed starting in autumn 2011. A typical crop rotation of winter wheat/oilseed-rape/winter wheat was simulated in the following three years. Three different black-grass biotypes with characterised resistance pattern and 5 different herbicide programs were analysed. The blackgrass biotypes showed different target-site resistance against ACCase- and/or ALS-inhibitor, as well as metabolic resistance. Before and after each treatment the numbers of black-grass plants per container were counted. Also the numbers of heads were counted before harvest. Additionally genetic analysis due to PCRs and pyrosequencing of ten survivors per container and year were performed. Till now results of the winter wheat and oilseed-rape cultivation were obtained. Herbicide efficacy was between 77 and 98% for the treatments during the winter wheat cultivation. The genetic analysis showed nearly similar portion of TSR in the black-grass populations when compared with the initial frequencies. Only one container showed no TSR. The comparison of the herbicide programs sprayed during the oilseed-rape cultivation showed the best results for all black-grass biotypes for the application of: Metazachlor + dimethenamid (BBCH 09/10, imazamox + quinmerac + Dash (BBCH 14 and propyzamide (BBCH 21/22.

  14. MSMA resistance studies.

    Science.gov (United States)

    Camper, N D; Keese, R J; Coker, P S

    2004-05-01

    Monosodium methanearsonate (MSMA)-resistant and -susceptible common cocklebur (Xanthium strumarium L.) and cotton (Gossypium hirsutum L.) were treated with MSMA. Plant parameters analyzed were: glutathione synthetase activity, selected amino acid (arginine, glutamic acid, alanine, citrulline, glutamine, and glutathione) content and arsenic content (MSMA, total arsenic, and arsonate). No reduction of arsenic from the parent pentavalent form present in MSMA to the trivalent form was detected. Arginine, glutamic acid, and glutamine content increased in tissue three days after MSMA treatment. Glutathione content decreased during the first three days after treatment; however, five days after treatment the resistant biotype of cocklebur and cotton had elevated glutathione levels (8-20 times greater, respectively). Glutathione Synthetase activity was higher in cotton than in either of the cocklebur biotypes; MSMA did not affect its activity in cotton or either cocklebur biotype. Resistant biotypes have a slightly higher activity than the susceptible biotype. Tolerance of cotton to MSMA may be related to glutathione synthetase activity and possibly to the presence of phytochelatins. Also, increased glutathione levels in the resistant biotype may implicate phytochelatin involvement in the resistance mechanism.

  15. Uso da água por plantas de arroz em competição com biótipos de Echinochloa crusgalli resistente e suscetível ao herbicida quinclorac Water use by rice plants under competition with Echinochloa crusgalli biotypes resistant and susceptible to quinclorac

    Directory of Open Access Journals (Sweden)

    G. Concenço

    2009-06-01

    de arroz quando em interação com outros fatores.The objective of this work was to evaluate the characteristics related to water use efficiency of rice plants, under competition with different densities of Echinochloa crusgalli plants. The trial was installed under greenhouse conditions, in a completely randomized block design, and factorial scheme 2 x 6 (two biotypes and six infestation densities, with four replications. The treatments consisted of one rice plant at the center of the plot, under competition with 0, 1, 2, 3, 4 or 5 plants of Echinochloa crusgalli, resistant or susceptible to quinclorac, at the periphery of the plot. Fifty days after emergence, water vapor stomatal conductance, sub-stomatal water pressure, leaf temperature and transpiration rate were evaluated, as well as water use efficiency. The plants were cut at the soil level and put into paper bags and dried at 70 ± 1 ºC until dry mass stabilization. Data were analyzed by the F-test and, in case of significance, submitted to the DMRT test to evaluate the effect of increasing competition with Echinochloa over the rice plants, and to DMS test to compare the rice plants submitted to the biotypes at each competition level. Rice plants were more affected as the barnyardgrass density increased, but differences related to the biotype were not observed. Important variables, such as water use efficiency, were more affected when rice plants were under competition with plants of the susceptible biotype. Under field conditions, this characteristic may not be relevant to rice plant development, when interacted with other factors.

  16. Distribution of Streptococcus mutans biotypes in five human populations.

    Science.gov (United States)

    Keene, H J; Shklair, I L; Mickel, G J; Wirthlin, M R

    1977-01-01

    The distribution of S mutans biotypes in five geographically separated human populations was investigated. Samples of dental plaque were obtained from recruits at the US Naval Training Center in Orlando, Fl (N=49) in San Diego, Calif (N=25), and in Great Lakes, Ill (N=194), and from a sample of Hawaiian school children (N=55) and Saudi Arabian Navy personnel (N-217). Cultural and biochemical methods were used for the isolation and identification of the five different biotypes of S mutans which correlate with Bratthall's serotypes a through e. Geographic differences in S mutans biotype distribution were most apparent when the Saudi Arabian sample was compared to the other four groups. Single and multiple biotypes were observed in each group. Multiple biotypes occurred most frequently in the Saudi Arabians. Biotypes a and b were rarely observed; c was the most common in each of the populations; and d and e were more prevalent in the Saudi Arabians than in the other groups. Because of the multifactorial nature of dental caries, caution should be exercised in the interpretation of population differences in caries experience that seem to be associated with differences in S mutans-type distribution.

  17. Weed Identification and Control in Vegetable Crops.

    Science.gov (United States)

    Ferretti, Peter A., Comp.

    This agriculture extension service publication from Pennsylvania State University examines weed control and identification in vegetable crops. Contents include: (1) Types of weeds; (2) Reducing losses caused by weeds, general control methods and home garden weed control; (3) How herbicides are used; (4) Specific weeds in vegetable plantings; and…

  18. Weed Identification and Control in Vegetable Crops.

    Science.gov (United States)

    Ferretti, Peter A., Comp.

    This agriculture extension service publication from Pennsylvania State University examines weed control and identification in vegetable crops. Contents include: (1) Types of weeds; (2) Reducing losses caused by weeds, general control methods and home garden weed control; (3) How herbicides are used; (4) Specific weeds in vegetable plantings; and…

  19. INTEGRATED WEED CONTROL IN MAIZE.

    Science.gov (United States)

    Latré, J; Dewitte, K; Derycke, V; De Roo, B; Haesaert, G

    2015-01-01

    Integrated pest management has been implemented as a general practice by EU legislation. As weed control actually is the most important crop protection measure in maize for Western Europe, the new legislation will have its impact. The question is of course which systems can be successfully implemented in practice with respect to labour efficiency and economical parameters. During 3 successive growing seasons (2007, 2008, 2009) weed control in maize was evaluated, the main focus was put on different techniques of integrated weed control and was compared with chemical weed control. Additionally, during 4 successive growing seasons (2011, 2012, 2013 and 2014) two objects based on integrated weed control and two objects based on mechanical weed control were compared to about twenty different objects of conventional chemical weed control. One of the objects based on mechanical weed control consisted of treatment with the flex-tine harrow before and after emergence in combination with chemical weed control at a reduced rate in 3-4 leave stage. The second one consisted of broadcast mechanical treatments before and after emergence followed by a final in-row application of herbicides and an inter-row cultivation at 6-7(8) leave stage. All trials were conducted on the Experimental farm of Bottelare HoGent-UGent on a sandy loam soil. Maize was growing in 1/3 crop rotation. The effect on weed growth as well as the economic impact of the different applications was evaluated. Combining chemical and mechanical weed control is a possible option in conventional farming but the disadvantages must be taken into account. A better planned weed control based on the real present weed-population in combination with a carefully thought-out choice of herbicides should also be considered as an IPM--approach.

  20. Resistance to ACCase inhibitors in Eleusine indica from Brazil involves a target site mutation Resistência aos inibidores de ACCase em Eleusine indica do Brasil envolve uma mutação na enzima alvo

    Directory of Open Access Journals (Sweden)

    M.D. Osuna

    2012-09-01

    Full Text Available Eleusine indica (goosegrass is a diploid grass weed which has developed resistance to ACCase inhibitors during the last ten years due to the intensive and frequent use of sethoxydim to control grass weeds in soybean crops in Brazil. Plant dose-response assays confirmed the resistant behaviour of one biotype obtaining high resistance factor values: 143 (fenoxaprop, 126 (haloxyfop, 84 (sethoxydim to 58 (fluazifop. ACCase in vitro assays indicated a target site resistance as the main cause of reduced susceptibility to ACCase inhibitors. PCR-generated fragments of the ACCase CT domain of the resistant and sensitive reference biotype were sequenced and compared. A point mutation was detected within the triplet of aspartate at the amino acid position 2078 (referred to EMBL accession no. AJ310767 and resulted in the triplet of glycine. These results constitute the first report on a target site mutation for a Brazilian herbicide resistant grass weed.Eleusine indica (ELEIN é uma espécie monocotiledônea, diploide. No Brasil, ela desenvolveu resistência aos inibidores da ACCase durante os últimos dez anos, devido ao uso intensivo e frequente desses graminicidas para controlar plantas daninhas em lavouras de soja. Experimentos de dose-resposta realizados com a planta confirmaram a resistência de um biótipo. Houve elevada tolerância aos herbicidas, com fatores de resistência da ordem de 143 (fenoxaprop, 126 (haloxyfop, 84 (sethoxydim e 58 (fluazifop. Ensaios com a enzima ACCase in vitro indicaram a insensibilidade desta como a principal causa de suscetibilidade reduzida a esses herbicidas. Fragmentos de PCR gerados do domínio CT da enzima ACCase dos biótipos resistente e sensível de referência foram sequenciados e comparados. Foi detectada uma mutação dentro do tripleto de asparagina na posição do aminoácido 2078 (referente ao acesso número AJ310767 no EMBL, que resultou no tripleto de glicina. Esses resultados constituem o primeiro caso

  1. Identification of Aphis gossypii Glover (Hemiptera: Aphididae Biotypes from Different Host Plants in North China.

    Directory of Open Access Journals (Sweden)

    Li Wang

    Full Text Available The cotton-melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae, is a polyphagous species with a worldwide distribution and a variety of biotypes. North China is a traditional agricultural area with abundant winter and summer hosts of A. gossypii. While the life cycles of A. gossypii on different plants have been well studied, those of the biotypes of North China are still unclear.Host transfer experiments showed that A. gossypii from North China has two host-specialized biotypes: cotton and cucumber. Based on complete mitochondrial sequences, we identified a molecular marker with five single-nucleotide polymorphisms to distinguish the biotypes. Using this marker, a large-scale study of biotypes on primary winter and summer hosts was conducted. All A. gossypii collected from three primary hosts-hibiscus, pomegranate, and Chinese prickly ash-were cotton biotypes, with more cotton-melon aphids found on hibiscus than the other two species. In May, alate cotton and cucumber biotypes coexisted on cotton and cucumber seedlings, but each preferred its natal host. Both biotypes existed on zucchini, although the cucumber biotype was more numerous. Aphids on muskmelon were all cucumber biotypes, whereas most aphids on kidney bean were cotton biotypes. Aphids on seedlings of potato and cowpea belong to other species. In August, aphids on cotton and cucumber were the respective biotypes, with zucchini still hosting both biotypes as before. Thus, the biotypes had different fitnesses on different host plants.Two host-specialized biotypes (cotton and cucumber are present in North China. Hibiscus, pomegranate, and Chinese prickly ash can serve as winter hosts for the cotton biotype but not the cucumber biotype in North China. The fitnesses of the two host-specialized biotypes differ on various summer hosts. When alate aphids migrate to summer hosts, they cannot accurately land on the corresponding plant.

  2. WeedML: a Tool for Collaborative Weed Demographic Modeling

    OpenAIRE

    Holst, Niels

    2010-01-01

    WeedML is a proposed standard to formulate models of weed demography, or maybe even complex models in general, that are both transparent and straightforward to re-use as building blocks for new models. The paper describes the design and thoughts behind WeedML which relies on XML and object-oriented systems development. Proof-of-concept software is provided as open-source C++ code and executables that can be downloaded freely.

  3. A specific PCR-assay for resistance to Biotypes 1 and 2 of the rosy leaf curling aphid in apple based on an RFLP marker closely linked to the Sd1 gene

    NARCIS (Netherlands)

    Roche, P.; Arkel, van G.; Heusden, van A.W.

    1997-01-01

    This report describes the conversion of a restriction fragment length polymorphism (RFLP) marker (the 2B12a locus), linked to the Sd1 aphid resistance gene, to a polymerase chain reaction (PCR) based marker. A section of the 2B12 probe was sequenced and two primers were designed to amplify this

  4. A specific PCR-assay for resistance to Biotypes 1 and 2 of the rosy leaf curling aphid in apple based on an RFLP marker closely linked to the Sd1 gene

    NARCIS (Netherlands)

    Roche, P.; Arkel, van G.; Heusden, van A.W.

    1997-01-01

    This report describes the conversion of a restriction fragment length polymorphism (RFLP) marker (the 2B12a locus), linked to the Sd1 aphid resistance gene, to a polymerase chain reaction (PCR) based marker. A section of the 2B12 probe was sequenced and two primers were designed to amplify this sequ

  5. AHAS herbicide resistance endowing mutations: effect on AHAS functionality and plant growth.

    Science.gov (United States)

    Yu, Qin; Han, Heping; Vila-Aiub, Martin M; Powles, Stephen B

    2010-09-01

    Twenty-two amino acid substitutions at seven conserved amino acid residues in the acetohydroxyacid synthase (AHAS) gene have been identified to date that confer target-site resistance to AHAS-inhibiting herbicides in biotypes of field-evolved resistant weed species. However, the effect of resistance mutations on AHAS functionality and plant growth has been investigated for only a very few mutations. This research investigates the effect of various AHAS resistance mutations in Lolium rigidum on AHAS functionality and plant growth. The enzyme kinetics of AHAS from five purified L. rigidum populations, each homozygous for the resistance mutations Pro-197-Ala, Pro-197-Arg, Pro-197-Gln, Pro-197-Ser or Trp-574-Leu, were characterized and the pleiotropic effect of three mutations on plant growth was assessed via relative growth rate analysis. All these resistance mutations endowed a herbicide-resistant AHAS and most resulted in higher extractable AHAS activity, with no-to-minor changes in AHAS kinetics. The Pro-197-Arg mutation slightly (but significantly) increased the K(m) for pyruvate and remarkably increased sensitivity to feedback inhibition by branched chain amino acids. Whereas the Pro-197-Ser and Trp-574-Leu mutations exhibited no significant effects on plant growth, the Pro-197-Arg mutation resulted in lower growth rates. It is clear that, at least in L. rigidum, these five AHAS resistance mutations have no major impact on AHAS functionality and hence probably no plant resistance costs. These results, in part, explain why so many Pro-197 AHAS resistance mutations in AHAS have evolved and why the Pro-197-Ser and the Trp-574-Leu AHAS resistance mutations are frequently found in many weed species.

  6. Weeding with transgenes.

    Science.gov (United States)

    Duke, Stephen O

    2003-05-01

    Transgenes promise to reduce insecticide and fungicide use but relatively little has been done to significantly reduce herbicide use through genetic engineering. Recently, three strategies for transgene utilization have been developed that have the potential to change this. These are the improvement of weed-specific biocontrol agents, enhancement of crop competition or allelopathic traits, and production of cover crops that will self-destruct near the time of planting. Failsafe risk mitigation technologies are needed for most of these strategies.

  7. Laboratory tests to assess optimal agricultural residue traits for an abrasive weed control system

    Science.gov (United States)

    One of the biggest challenges to organic agricultural production and herbicide resistant crops in industrialized countries today is the non-chemical control of weed plants. Studies of new tools and methods for weed control have been motivated by an increased consumer demand for organic produce and c...

  8. PAGMan - propelled abrasive grit to manage weeds in soybean and corn

    Science.gov (United States)

    New tools for controlling weeds would be useful for soybean and corn production in organic systems or in systems in which weeds developed resistance to multiple herbicides. Here we report on two developments: (i) the safety to soybean seedlings of using air-propelled abrasive grit (PAG) for managing...

  9. Real World of Industrial Chemistry: The Challenge of Herbicides for Aquatic Weeds.

    Science.gov (United States)

    Martin, Dean F.; Martin, Barbara B.

    1985-01-01

    Discusses problems in selecting the correct herbicide for use in controlling aquatic weeds, considering specificity, size of the market, fear of trace contaminants, and herbicide resistance in weeds. Also summarizes some successful herbicides, providing a table listing mode of action of some herbicides used for control of aquatic plants. (JN)

  10. How weeds emerge: a taxonomic and trait-based examination using United States data.

    Science.gov (United States)

    Kuester, Adam; Conner, Jeffrey K; Culley, Theresa; Baucom, Regina S

    2014-05-01

    Weeds can cause great economic and ecological harm to ecosystems. Despite their importance, comparisons of the taxonomy and traits of successful weeds often focus on a few specific comparisons - for example, introduced versus native weeds. We used publicly available inventories of US plant species to make comprehensive comparisons of the factors that underlie weediness. We quantitatively examined taxonomy to determine if certain genera are overrepresented by introduced, weedy or herbicide-resistant species, and we compared phenotypic traits of weeds to those of nonweeds, whether introduced or native. We uncovered genera that have more weeds and introduced species than expected by chance and plant families that have more herbicide-resistant species than expected by chance. Certain traits, generally related to fast reproduction, were more likely to be associated with weedy plants regardless of species' origins. We also found stress tolerance traits associated with either native or introduced weeds compared with native or introduced nonweeds. Weeds and introduced species have significantly smaller genomes than nonweeds and native species. These results support trends for weedy plants reported from other floras, suggest that native and introduced weeds have different stress adaptations, and provide a comprehensive survey of trends across weeds within the USA. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

  11. Inheritance and mechanism of resistance to herbicides inhibiting acetolactate synthase in Sonchus oleraceus L.

    Science.gov (United States)

    Boutsalis, P; Powles, S B

    1995-07-01

    A biotype of Sonchus oleraceus L. (Compositae) has developed resistance to herbicides inhibiting acetolactate synthase (ALS) following field selection with chlorsulfuron for 8 consecutive years. The aim of this study was to determine the inheritance and mechanism of resistance in this biotype. Determination of ALS activity and inhibition kinetics revealed that Km and Vmax did not vary greatly between the resistant and susceptible biotypes. ALS extracted from the resistant biotype was resistant to five ALS-inhibiting herbicides in an in vitro assay. ALS activity from the resistant biotype was 14 19, 2, 3 and 3 times more resistant to inhibition by chlorsulfuron, sulfometuron, imazethapyr, imazapyr and flumetsulam, respectively, than the susceptible biotype. Hybrids between the resistant and a susceptible biotype were produced, and inheritance was followed through the F1, F2 and F3 generations. F1 hybrids displayed a uniform intermediate level of resistance between resistant and susceptible parents. Three distinct phenotypes, resistant, intermediate and susceptible, were identified in the F2 generation following chlorsulfuron application. A segregation ratio of 1∶2∶1 was observed, indicative of the action of a single, nuclear, incompletely dominant gene. F3 families, derived from intermediate F2 individuals, segregated in a similar manner. Resistance to herbicides inhibiting ALS in this biotype of S. oleraceus is due to the effect of a single gene coding for a resistant form of the target enzyme, ALS.

  12. Pool of resistance mechanisms to glyphosate in Digitaria insularis.

    Science.gov (United States)

    de Carvalho, Leonardo Bianco; Alves, Pedro Luis da Costa Aguiar; González-Torralva, Fidel; Cruz-Hipolito, Hugo Enrique; Rojano-Delgado, Antonia María; De Prado, Rafael; Gil-Humanes, Javier; Barro, Francisco; de Castro, María Dolores Luque

    2012-01-18

    Digitaria insularis biotypes resistant to glyphosate have been detected in Brazil. Studies were carried out in controlled conditions to determine the role of absorption, translocation, metabolism, and gene mutation as mechanisms of glyphosate resistance in D. insularis. The susceptible biotype absorbed at least 12% more (14)C-glyphosate up to 48 h after treatment (HAT) than resistant biotypes. High differential (14)C-glyphosate translocation was observed at 12 HAT, so that >70% of the absorbed herbicide remained in the treated leaf in resistant biotypes, whereas 42% remained in the susceptible biotype at 96 HAT. Glyphosate was degraded to aminomethylphosphonic acid (AMPA), glyoxylate, and sarcosine by >90% in resistant biotypes, whereas a small amount of herbicide (up to 11%) was degraded by the susceptible biotype up to 168 HAT. Two amino acid changes were found at positions 182 and 310 in EPSPS, consisting of a proline to threonine and a tyrosine to cysteine substitution, respectively, in resistant biotypes. Therefore, absorption, translocation, metabolism, and gene mutation play an important role in the D. insularis glyphosate resistance.

  13. Weeding Library Collections: Library Weeding Methods. Fourth Edition.

    Science.gov (United States)

    Slote, Stanly J.

    Weeding is one of the best ways to make long-term improvements to library collections, but it is also a difficult and sometimes painful task. In the tradition of previous editions, this book guides librarians in the process of methodical and efficient weeding. The book shows how to identify core collections versus the weedable items. The approach…

  14. Weed management practices in natural ecosystems: a critical overview

    Directory of Open Access Journals (Sweden)

    C.F. Reinhardt

    2000-07-01

    Full Text Available Increasing public pressure against the use of pesticides and other agricultural inputs has placed increased emphasis on the development of ecologically based pest management. One distinct reaction of the Weed Science discipline has been the swing away from herbicide research to increased research on the basic biology and ecology of weeds in hopes of reduced reliance on "technological crutches" such as herbicides and other practices that are potentially harmful to the environment. Biological control is the long-standing alternative to the use of herbicides and interest in the former practice has been boosted by the realization that the use of herbicides may lead to the development of herbicide resistance in weed populations, and that herbicide residues occur in surface and groundwater. Supporters of herbicide use would point out that biological control is generally not effective in crop production systems, and is basically slow-acting. Debates between protagonists for the exclusive use of one or the other weed management practice tend to obscure the benefits that integration of different techniques are likely to have. For natural ecosystems it is proposed that integration of the more subtle practice of biological control with the use of herbicides, which relatively quickly overwhelm a biological system with mortality, is likely to be the most effective weed management tool. Different weed management practices that could be considered in natural ecosystems are discussed in terms of three key performance rating criteria, viz. activity, selec- tivity and persistence In this concise review, general discussion is focussed on the fundamentals of weed management practices, with the view to promote concept-based approaches that are critical for the development of effective weed management strate- gies.

  15. The biology of habitat dominance; can microbes behave as weeds?

    Science.gov (United States)

    Cray, Jonathan A; Bell, Andrew N W; Bhaganna, Prashanth; Mswaka, Allen Y; Timson, David J; Hallsworth, John E

    2013-09-01

    Competition between microbial species is a product of, yet can lead to a reduction in, the microbial diversity of specific habitats. Microbial habitats can resemble ecological battlefields where microbial cells struggle to dominate and/or annihilate each other and we explore the hypothesis that (like plant weeds) some microbes are genetically hard-wired to behave in a vigorous and ecologically aggressive manner. These 'microbial weeds' are able to dominate the communities that develop in fertile but uncolonized--or at least partially vacant--habitats via traits enabling them to out-grow competitors; robust tolerances to habitat-relevant stress parameters and highly efficient energy-generation systems; avoidance of or resistance to viral infection, predation and grazers; potent antimicrobial systems; and exceptional abilities to sequester and store resources. In addition, those associated with nutritionally complex habitats are extraordinarily versatile in their utilization of diverse substrates. Weed species typically deploy multiple types of antimicrobial including toxins; volatile organic compounds that act as either hydrophobic or highly chaotropic stressors; biosurfactants; organic acids; and moderately chaotropic solutes that are produced in bulk quantities (e.g. acetone, ethanol). Whereas ability to dominate communities is habitat-specific we suggest that some microbial species are archetypal weeds including generalists such as: Pichia anomala, Acinetobacter spp. and Pseudomonas putida; specialists such as Dunaliella salina, Saccharomyces cerevisiae, Lactobacillus spp. and other lactic acid bacteria; freshwater autotrophs Gonyostomum semen and Microcystis aeruginosa; obligate anaerobes such as Clostridium acetobutylicum; facultative pathogens such as Rhodotorula mucilaginosa, Pantoea ananatis and Pseudomonas aeruginosa; and other extremotolerant and extremophilic microbes such as Aspergillus spp., Salinibacter ruber and Haloquadratum walsbyi. Some microbes

  16. Interference of allelopathic wheat with different weeds.

    Science.gov (United States)

    Zhang, Song-Zhu; Li, Yong-Hua; Kong, Chui-Hua; Xu, Xiao-Hua

    2016-01-01

    Interference of allelopathic wheat with weeds involves a broad spectrum of species either independently or synergistically with competitive factors. This study examined the interference of allelopathic wheat with 38 weeds in relation to the production of allelochemical 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) in wheat with and without root-root interactions. There were substantial differences in weed biomass and DIMBOA concentration in wheat-weed coexisting systems. Among 38 weeds, nine weeds were inhibited significantly by allelopathic wheat but the other 29 weeds were not. DIMBOA levels in wheat varied greatly with weed species. There was no significant relationship between DIMBOA levels and weed suppression effects. Root segregation led to great changes in weed inhibition and DIMBOA level. Compared with root contact, the inhibition of eight weeds was lowered significantly, while significantly increased inhibition occurred in 11 weeds with an increased DIMBOA concentration under root segregation. Furthermore, the production of DIMBOA in wheat was induced by the root exudates from weeds. Interference of allelopathic wheat with weeds not only is determined by the specificity of the weeds but also depends on root-root interactions. In particular, allelopathic wheat may detect certain weeds through the root exudates and respond by increasing the allelochemical, resulting in weed identity recognition. © 2015 Society of Chemical Industry.

  17. Uso da eletroforese de isoenzimas para avaliação da competitividade de biotipos de tiririca Isoenzyme evaluation of intra-specific competitivity of purple nutsedge biotypes

    Directory of Open Access Journals (Sweden)

    Carlos A. R. Silva

    2000-08-01

    Full Text Available O presente trabalho teve o objetivo de avaliar, por meio de eletroforese de isoenzimas, em casa de vegetação, a competitividade dos biotipos de tiririca (Cyperus rotundus L. mais freqüentes que ocorrem no estado de São Paulo. Dos quatorze sistemas enzimáticos testados, seis apresentaram polimorfismo (a e b-EST, ACP, IDH, MDH e SKDH e foram utilizados para a identificação das 66 amostras coletadas, classificando-as em 10 biotipos de Cyperus rotundus. Durante a amostragem, foram identificadas as espécies C. flavus, C. iria e C. esculentus. Foram identificados diferentes biotipos de C. rotundus, com diferentes freqüências de ocorrência no estado de São Paulo. Houve predominância de dois biotipos, que estiveram presentes em 48,5% e 21,2% dos pontos de amostragem. Os diferentes biotipos de C. rotundus mostraram-se distintos em termos de competitividade intra-específica. Os biotipos mais competitivos foram os mais freqüentes nas avaliações de campo.The objective of this research was to evaluate intra-specific competition ability of purple nutsedge Cyperus rotundus biotypes, using isoenzymes. We sampled weed populations in 66 sites all around São Paulo State - Brazil. Polymorphism was observed in six out of fourteen enzymatic systems studied (aand b-EST, ACP, IDH, MDH, and SKDH. Polymorphism was not observed for ADH, CAT, GDH, AAT, LAP, MADH, PER, and SDH. Using the information of the six polymorphic isoenzymes, it was possible to identify 10 biotypes of Cyperus rotundus and C. flavus, C. iria e C. esculentus species. The two major biotypes were predominant in 48.5% and 21.2% of the sampling sites. The competition ability assay was carried out showing that the most widely spread biotypes were the most competitive ones.

  18. Weed Identification Field Training Demonstrations.

    Science.gov (United States)

    Murdock, Edward C.; And Others

    1986-01-01

    Reviews efforts undertaken in weed identification field training sessions for agriprofessionals in South Carolina. Data over a four year period (1980-1983) revealed that participants showed significant improvement in their ability to identify weeds. Reaffirms the value of the field demonstration technique. (ML)

  19. Weed Identification Field Training Demonstrations.

    Science.gov (United States)

    Murdock, Edward C.; And Others

    1986-01-01

    Reviews efforts undertaken in weed identification field training sessions for agriprofessionals in South Carolina. Data over a four year period (1980-1983) revealed that participants showed significant improvement in their ability to identify weeds. Reaffirms the value of the field demonstration technique. (ML)

  20. Identification of beer spoilage microorganisms using the MALDI Biotyper platform.

    Science.gov (United States)

    Turvey, Michelle Elizabeth; Weiland, Florian; Meneses, Jon; Sterenberg, Nick; Hoffmann, Peter

    2016-03-01

    Beer spoilage microorganisms present a major risk for the brewing industry and can lead to cost-intensive recall of contaminated products and damage to brand reputation. The applicability of molecular profiling using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) in combination with Biotyper software was investigated for the identification of beer spoilage microorganisms from routine brewery quality control samples. Reference mass spectrum profiles for three of the most common bacterial beer spoilage microorganisms (Lactobacillus lindneri, Lactobacillus brevis and Pediococcus damnosus), four commercially available brewing yeast strains (top- and bottom-fermenting) and Dekkera/Brettanomyces bruxellensis wild yeast were established, incorporated into the Biotyper reference library and validated by successful identification after inoculation into beer. Each bacterial species could be accurately identified and distinguished from one another and from over 5600 other microorganisms present in the Biotyper database. In addition, wild yeast contaminations were rapidly detected and distinguished from top- and bottom-fermenting brewing strains. The applicability and integration of mass spectrometry profiling using the Biotyper platform into existing brewery quality assurance practices within industry were assessed by analysing routine microbiology control samples from a local brewery, where contaminating microorganisms could be reliably identified. Brewery-isolated microorganisms not present in the Biotyper database were further analysed for identification using LC-MS/MS methods. This renders the Biotyper platform a promising candidate for biological quality control testing within the brewing industry as a more rapid, high-throughput and cost-effective technology that can be tailored for the detection of brewery-specific spoilage organisms from the local environment.

  1. Association of plasmid typing to biotyping and antibiotyping in the characterization of outbreaks by Acinetobacter baumannii

    Directory of Open Access Journals (Sweden)

    Maria Cristina Bronharo Tognim

    1999-01-01

    Full Text Available During an outbreak at an University Hospital, from April to September, in 1994, sixteen strains of Acinetobacter baumannii were isolated from patients and one strain from an enteral solution. We afterwards analyzed the outbreak by means of plasmid typing, antibiotic resistance typing and biotyping. Two main plasmid profiles were identified. Twelve strains belonged to biotype 2, and five to biotype 19. Susceptibility to amikacin and to carbenicillin allowed classification of the strains into two groups. The results show that association of those three typing methods allowed the differentiation of what was at first considered as a single outbreak into two apparently unrelated outbreaks.Durante um surto ocorrido de abril a setembro de 1994 em um Hospital Universitário, dezesseis cepas de Acinetobacter baumannii foram isoladas de pacientes e uma de solução enteral. Nós posteriormente analizamos as cepas isoladas durante o surto pelos seguintes métodos de tipagem : perfil de DNA plasmidial, perfil de antibiograma e biotipagem. Dois padrões de tipagem foram identificados pela análise do perfil plasmidial. Doze cepas foram caracterizadas como sendo do biotipo 2, e cinco do biotipo 19. O padrão de sensibilidade a amicacina e a carbenicilina possibilitou a classificação das cepas em dois grupos. Os resultados demonstraram que estes três métodos de tipagem associados possibilitaram a diferenciação do que primeiramente foi considerado como um único surto, em dois surtos aparentemente não relacionados.

  2. Competição entre soja resistente ao glyphosate e plantas daninhas em solo compactado Competition between glyphosate resistant soybean and weeds in compacted soil

    Directory of Open Access Journals (Sweden)

    J.B. Santos

    2008-03-01

    Full Text Available Objetivou-se com este trabalho avaliar a competição entre a soja (var. BRS 243 RR e as plantas daninhas Bidens pilosa e Brachiaria brizantha, em diferentes níveis de compactação do solo. Para isso, foram confeccionadas colunas de PVC (10 cm de diâmetro com três anéis: superior (com 5 cm de altura e densidade de 1,2 kg dm-3, intermediário (com 10 cm de altura e densidade variando entre 1,0 e 1,6 kg dm-3, conforme tratamento e inferior (com 10 cm de altura e densidade de 1,2 kg dm-3. Sobre as colunas foram realizados cinco cultivos: soja, B. pilosa, B. brizantha, soja e B. pilosa e soja e B. brizantha, em esquema fatorial com as densidades, perfazendo um total de 20 tratamentos. Aos 30 dias após emergência da soja, foram avaliadas a altura, a massa seca de folhas, de caule e de raízes (em cada anel, separadamente, a área foliar e a área foliar específica. Observou-se que B. brizantha foi mais competitiva que B. pilosa; contudo, esta última possui maior capacidade de exploração radicular em solos com maior nível de compactação, indicando maior adaptabilidade a condições como déficit hídrico e escassez de nutrientes. Considerando a capacidade competitiva da soja sobre as plantas daninhas, maiores níveis de compactação favorecem a cultura, em relação a B. pilosa.This work aimed to evaluate competition between soybean (BRS 243 RR and the weeds Bidens pilosa and Brachiaria brizantha, in soil with simulated compactation. Thus columns of PVC tubes (10 cm of diameter were made with three rings (superior (5 cm high and 1.2 kg dm-3 density; intermediate (10 cm high and around 1.0 and 1.6 kg dm-3 density and inferior (10 cm high and 1.2 kg dm-3 density. Five crops, soybean, B. pilosa, B. brizantha, soybean and B. pilosa, and soybean and B. brizantha, were cultivated on the columns in a factorial scheme with the densities, totaling 20 treatments. At 30 days after soybean emergence, height leaf, stem and root dry matter, leaf area

  3. Weeding the School Library Media Collection.

    Science.gov (United States)

    School Library Media Quarterly, 1984

    1984-01-01

    This document prepared by Calgary Board of Education, Calgary, Alberta, Canada, discusses a systematic approach to strengthening the library media collection. A statement of principle, what to weed, specific guides to weeding (by Dewey Decimal classification and type of material), what not to weed, procedures, and weeding follow-up are…

  4. 7 CFR 201.50 - Weed seed.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Weed seed. 201.50 Section 201.50 Agriculture... REGULATIONS Purity Analysis in the Administration of the Act § 201.50 Weed seed. Seeds (including bulblets or tubers) of plants shall be considered weed seeds when recognized as weed seeds by the law or rules and...

  5. 7 CFR 201.15 - Weed seeds.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Weed seeds. 201.15 Section 201.15 Agriculture... REGULATIONS Labeling Agricultural Seeds § 201.15 Weed seeds. The percentage of weed seeds shall include seeds of plants considered weeds in the State into which the seed is offered for transportation or...

  6. Applicator Training Manual for: Aquatic Weed Control.

    Science.gov (United States)

    Herron, James W.

    The aquatic weeds discussed in this manual include algae, floating weeds, emersed weeds, and submerged weeds. Specific requirements for pesticide application are given for static water, limited flow, and moving water situations. Secondary effects of improper application rates and faulty application are described. Finally, techniques of limited…

  7. Applicator Training Manual for: Aquatic Weed Control.

    Science.gov (United States)

    Herron, James W.

    The aquatic weeds discussed in this manual include algae, floating weeds, emersed weeds, and submerged weeds. Specific requirements for pesticide application are given for static water, limited flow, and moving water situations. Secondary effects of improper application rates and faulty application are described. Finally, techniques of limited…

  8. Weeding the School Library Media Collection.

    Science.gov (United States)

    School Library Media Quarterly, 1984

    1984-01-01

    This document prepared by Calgary Board of Education, Calgary, Alberta, Canada, discusses a systematic approach to strengthening the library media collection. A statement of principle, what to weed, specific guides to weeding (by Dewey Decimal classification and type of material), what not to weed, procedures, and weeding follow-up are…

  9. Integrated weed management systems with herbicide-tolerant crops in the European Union: lessons learnt from home and abroad

    DEFF Research Database (Denmark)

    Lamichhane, Jay Ram; Devos, Yann; Beckie, Hugh J.

    2017-01-01

    Conventionally bred (CHT) and genetically modified herbicide-tolerant (GMHT) crops have changed weed management practices and made an important contribution to the global production of some commodity crops. However, a concern is that farm management practices associated with the cultivation...... of herbicide-tolerant (HT) crops further deplete farmland biodiversity and accelerate the evolution of herbicide-resistant (HR) weeds. Diversification in crop systems and weed management practices can enhance farmland biodiversity, and reduce the risk of weeds evolving herbicide resistance. Therefore, HT crops...... are most effective and sustainable as a component of an integrated weed management (IWM) system. IWM advocates the use of multiple effective strategies or tactics to manage weed populations in a manner that is economically and environmentally sound. In practice, however, the potential benefits of IWM...

  10. Identification of three major Bemisia tabaci biotypes in China based on morphological and DNA polymorphisms

    Institute of Scientific and Technical Information of China (English)

    Baoli Qiu; Yanping Chen; Li Liu; Weilu Peng; Xiaoxi Li; Yuzhou Du; Shunxiang Ren

    2009-01-01

    The sweet potato whitefly, Bemisia tabaci, is a complex species, and many of its biotypes are important agricultural pests. The B and Q biotypes are invasive and coexist with the native Cv biotype on vegetable and ornamental crops in China. In this study, these three bio-types were identified based on their morphological characteristics, RAPD-PCR analysis, and DNA sequences of the COl gene. The ante-rior and posterior wax fringes of the B, Q, and Cv biotypes significantly differed from each other. Based on this morphological characteristic, the three biotypes can easily be distinguished in greenhouses and fields. Genomic DNA RAPD-PCR band patterns also revealed differences between these biotypes using the H16 primer. The B biotype has three bright DNA bands between 250 and 600 bp, the Q biotype only has one bright band at ~300 bp, while the Cv biotype has no band between 250 and 500 bp. Both the Cv and Q biotypes have two bright bands at ~750 and 1000 bp while the B biotype has only one band at ~1000 bp. Based on the COI gene, the genetic identity between B and Cv, B and Q, and Q and CV was 85.8%, 94.7%, and 86.0%, respectively. The MP tree indicated that the phylogenetic relationship between the B and Q biotypes is much closer than that between the B and Cv or the Q and Cv biotypes. The uses of the morphological, RAPD-PCR, and DNA sequencing methods in biotype identification of B. tabaci are discussed.

  11. Loss of glyphosate efficacy: a changing weed spectrum in Georgia cotton

    Science.gov (United States)

    Introduction of glyphosate resistance into crops through genetic modification has revolutionized crop protection. Glyphosate, the proverbial silver bullet, is a broad spectrum herbicide with favorable environmental characteristics and effective broad-spectrum weed control that has greatly improved ...

  12. Mechanism of resistance to ACCase-inhibiting herbicides in wild oat (Avena fatua ) from Latin America.

    Science.gov (United States)

    Cruz-Hipolito, Hugo; Osuna, Maria D; Dominguez-Valenzuela, Jose A; Espinoza, Nelson; De Prado, Rafael

    2011-07-13

    Whole-plant response of two suspected resistant Avena fatua biotypes from Chile and Mexico to ACCase-inhibiting herbicides [aryloxyphenoxypropionate (APP), cyclohexanedione (CHD), and pinoxaden (PPZ)] and the mechanism behind their resistance were studied. Both dose-response and ACCase enzyme activity assays revealed cross-resistance to the three herbicide families in the biotype from Chile. On the other hand, the wild oat biotype from Mexico exhibited resistance to the APP herbicides and cross-resistance to the CHD herbicides, but no resistance to PPZ. Differences in susceptibility between the two biotypes were unrelated to absorption, translocation, and metabolism of the herbicides. PCR generated fragments of the ACCase CT domain spanning the potential mutations sited in the resistant and susceptible biotypes were sequenced and compared. A point mutation was detected in the aspartic acid triplet at the amino acid position 2078 in the Chilean biotype and in isoleucine at the amino acid position 2041 in the Mexican wild oat biotype, which resulted in a glycine triplet and an asparagine triplet, respectively. On the basis of in vitro assays, the target enzyme (ACCase) in these resistant biotypes contains a herbicide-insensitive form. This is the first reported evidence of resistance to pinoxaden in A. fatua.

  13. The role of absorption and translocation as a mechanism of resistance to glyphosate

    Science.gov (United States)

    The continuous use of glyphosate has resulted in the selection of resistant biotypes in 13 different species. Three different mechanisms of resistance have been proposed for these biotypes: 1) Decreased translocation to meristems; 2) Mutation of target site (EPSPS) and 3) Increased expression of EP...

  14. Chemical control of California arrowhead (Sagittaria montevidensis resistant to acetolactate synthase and photosystem II inhibiting herbicides in irrigated rice

    Directory of Open Access Journals (Sweden)

    Diogo da Silva Moura

    Full Text Available ABSTRACT: California arrowhead is one of the primary weeds infesting paddy rice fields in the Brazilian states of Santa Catarina and Rio Grande do Sul, where the system of pre-germinated seeding is used. The objective of this study was to evaluate the selectivity and effectiveness of saflufenacil application in irrigated rice, either singly or in combination with other herbicides in the same application or sequentially, for the control of Sagittaria montevidensis biotype that is resistant to ALSand PSII-inhibiting herbicides. In the first experiment carried out in a greenhouse, saflufenacil was applied, either singly or in combination with penoxsulam, bispyribac-sodium, pyrazosulfuron-ethyl, bentazon, or propanil to the S. montevidensis (SAGMO 32 biotype and the irrigated rice variety Epagri 108. In the second experiment, single or combined (including sequential applications of saflufenacil, bentazon, and cyhalofop-butyl were applied to Epagri 108 in open field conditions. Saflufenacil combined with propanil showed a high degree of phytotoxicity and a reduction in the accumulation of dry mass in Epagri 108. Application of saflufenacil, bentazon, and cyhalofop-butyl in combination or sequentially resulted in an increase in phytotoxicity in Epagri 108 compared to when applied singly. A pplication of saflufenacil singly or in combination with penoxsulam, bispyribac-sodium, bentazon, or pyrazosulfuron-ethyl did not adequately control SAGMO 32.

  15. What do we really know about alien plant invasion? A review of the invasion mechanism of one of the world's worst weeds.

    Science.gov (United States)

    Bajwa, Ali Ahsan; Chauhan, Bhagirath Singh; Farooq, Muhammad; Shabbir, Asad; Adkins, Steve William

    2016-07-01

    This review provides an insight into alien plant invasion taking into account the invasion mechanism of parthenium weed ( Parthenium hysterophorus L.). A multi-lateral understanding of the invasion biology of this weed has pragmatic implications for weed ecology and management. Biological invasions are one of the major drivers of restructuring and malfunctioning of ecosystems. Invasive plant species not only change the dynamics of species composition and biodiversity but also hinder the system productivity and efficiency in invaded regions. Parthenium weed, a well-known noxious invasive species, has invaded diverse climatic and biogeographic regions in more than 40 countries across five continents. Efforts are under way to minimize the parthenium weed-induced environmental, agricultural, social, and economic impacts. However, insufficient information regarding its invasion mechanism and interference with ecosystem stability is available. It is hard to devise effective management strategies without understanding the invasion process. Here, we reviewed the mechanism of parthenium weed invasion. Our main conclusions are: (1) morphological advantages, unique reproductive biology, competitive ability, escape from natural enemies in non-native regions, and a C3/C4 photosynthesis are all likely to be involved in parthenium weed invasiveness. (2) Tolerance to abiotic stresses and ability to grow in wide range of edaphic conditions are thought to be additional invasion tools on a physiological front. (3) An allelopathic potential of parthenium weed against crop, weed and pasture species, with multiple modes of allelochemical expression, may also be responsible for its invasion success. Moreover, the release of novel allelochemicals in non-native environments might have a pivotal role in parthenium weed invasion. (4) Genetic diversity found among different populations and biotypes of parthenium weed, based on geographic, edaphic, climatic, and ecological ranges, might also

  16. Controlling weeds with fungi, bacteria and viruses: a review.

    Science.gov (United States)

    Harding, Dylan P; Raizada, Manish N

    2015-01-01

    Weeds are a nuisance in a variety of land uses. The increasing prevalence of both herbicide resistant weeds and bans on cosmetic pesticide use has created a strong impetus to develop novel strategies for controlling weeds. The application of bacteria, fungi and viruses to achieving this goal has received increasingly great attention over the last three decades. Proposed benefits to this strategy include reduced environmental impact, increased target specificity, reduced development costs compared to conventional herbicides and the identification of novel herbicidal mechanisms. This review focuses on examples from North America. Among fungi, the prominent genera to receive attention as bioherbicide candidates include Colletotrichum, Phoma, and Sclerotinia. Among bacteria, Xanthomonas and Pseudomonas share this distinction. The available reports on the application of viruses to controlling weeds are also reviewed. Focus is given to the phytotoxic mechanisms associated with bioherbicide candidates. Achieving consistent suppression of weeds in field conditions is a common challenge to this control strategy, as the efficacy of a bioherbicide candidate is generally more sensitive to environmental variation than a conventional herbicide. Common themes and lessons emerging from the available literature in regard to this challenge are presented. Additionally, future directions for this crop protection strategy are suggested.

  17. Controlling weeds with fungi, bacteria and viruses: A review

    Directory of Open Access Journals (Sweden)

    Dylan Patrick Harding

    2015-08-01

    Full Text Available Weeds are a nuisance in a variety of land uses. The increasing prevalence of both herbicide resistant weeds and bans on cosmetic pesticide use has created a strong impetus to develop novel strategies for controlling weeds. The application of bacteria, fungi and viruses to achieving this goal has received increasingly great attention over the last three decades. Proposed benefits to this strategy include reduced environmental impact, increased target specificity, reduced development costs compared to conventional herbicides, and the identification of novel herbicidal mechanisms. This review focuses on examples from North America. Among fungi, the prominent genera to receive attention as bioherbicide candidates include Colletotrichum, Phoma, and Sclerotinia. Among bacteria, Xanthomonas and Pseudomonas share this distinction. The available reports on the application of viruses to controlling weeds are also reviewed. Focus is given to the phytotoxic mechanisms associated with bioherbicide candidates. Achieving consistent suppression of weeds in field conditions is a common challenge to this control strategy, as the efficacy of a bioherbicide candidate is generally more sensitive to environmental variation than a conventional herbicide. Common themes and lessons emerging from the available literature in regard to this challenge are presented. Additionally, future directions for this crop protection strategy are suggested.

  18. Effects of host plants on insecticide susceptibility and carboxylesterase activity in Bemisia tabaci biotype B and greenhouse whitefly, Trialeurodes vaporariorum.

    Science.gov (United States)

    Liang, Pei; Cui, Jian-Zhou; Yang, Xiu-Qing; Gao, Xi-Wu

    2007-04-01

    Bemisia tabaci (Gennadius) biotype B and the greenhouse whitefly, Trialeurodes vaporariorum (Westwood), have become serious pests of cotton and vegetable crops in China since the early 1990s. In recent years, however, B. tabaci have broken out more frequently and widely than have T. vaporariorum. The B. tabaci biotype B has also developed higher resistance to several insecticides. Here, the effects of four different host plants on the insecticide susceptibility of B. tabaci biotype B and T. vaporariorum have been compared. The LC(50) values of imidacloprid, abamectin, deltamethrin and omethoate in T. vaporariorum reared on cucumber were significantly higher than those in B. tabaci (the LC(50) values in T. vaporariorum were respectively 3.13, 2.63, 2.78 and 6.67 times higher than those in B. tabaci). On the other hand, the B. tabaci population reared on cotton was more tolerant to all four insecticides tested than the T. vaporariorum population from the same host, especially to abamectin (up to 8.4-fold). The effects of the four host plants on the activity of carboxylesterase (CarE) in B. tabaci biotype B and T. vaporariorum were also compared. The results showed that, although the CarE activity of B. tabaci and T. vaporariorum varied depending on the host plants, the B. tabaci population possessed significantly higher CarE activity than the T. vaporariorum population reared on the same host plant. This was especially so on cucumber and cotton, where the CarE activities of the B. tabaci population were over 1.6 times higher than those of T. varporariorum. The frequency profiles for this activity in B. tabaci and T. vaporariorum populations reared on same host plant were apparently different.

  19. INTEGRATED WEED MANAGEMENT ON THE PROCESSING TOMATO CROP AND TOMATO FOR CONSUMPTION IN NATURA

    Directory of Open Access Journals (Sweden)

    Y. O. Castro

    2016-11-01

    Full Text Available Weeds cause direct and indirect damage to processing tomato and tomato for consumption in natura. The coexistence period is decisive for the intensity of damage, although the economic cost is also considered for decision making when to control the weeds. There are similarities between processing tomato and tomato for consumption in natura cropping system and peculiarities. This causes the management has adopted its common applications and its variables within each system. As control alternative, the farmer has basically the preventive control, mechanical, cultural, biological and chemical. The application of a single method is not recommended. Ideally, the methods needs to be integrated in order to combat weeds, highly evolved populations and resistant to unfavorable conditions. Consider weed management taking only one control measure is to underestimate the evolutionary ability of such species. Therefore, it is necessary to integrate the various methods available to the weed interference not impede the tomato production.

  20. The Use of Weed Control Robot (WCR for Achieve to the Sustainable Agriculture

    Directory of Open Access Journals (Sweden)

    Behzad Sani

    2013-10-01

    Full Text Available Today, weeds control is very difficult because they are resistant to the herbicide due to excessive use of chemical herbicides in agriculture. Many studies have shown that mechanical and biological control of weeds can be much less damage to the environment of chemical herbicides. Develop of biological herbicides in agriculture was slow due to high prices and this subject the researchers to move toward the elimination of agricultural weed mechanically. This work was originally done by a many number of workers because and workers' rights didn’t work was ultimately economic value. Now solve this subject by the use of robotic technology in agriculture has been studied and a many number of agricultural researchers with the help of computer scientists move towards making robots to remove the weeds. Of course this is difficult due to excessive weeds similar to the plants, but the final results will help to increase crop and save the environment by eliminating chemical herbicides.

  1. [Alfalfa Planting as weed control

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This document is a letter to farming cooperators regarding the stipulations surrounding alfalfa plantings in lieu of small grain plantings to provide weed control,...

  2. Ecologically sustainable weed management: How do we get from proof-of-concept to adoption?

    Science.gov (United States)

    Liebman, Matt; Baraibar, Bàrbara; Buckley, Yvonne; Childs, Dylan; Christensen, Svend; Cousens, Roger; Eizenberg, Hanan; Heijting, Sanne; Loddo, Donato; Merotto, Aldo; Renton, Michael; Riemens, Marleen

    2016-07-01

    Weed management is a critically important activity on both agricultural and non-agricultural lands, but it is faced with a daunting set of challenges: environmental damage caused by control practices, weed resistance to herbicides, accelerated rates of weed dispersal through global trade, and greater weed impacts due to changes in climate and land use. Broad-scale use of new approaches is needed if weed management is to be successful in the coming era. We examine three approaches likely to prove useful for addressing current and future challenges from weeds: diversifying weed management strategies with multiple complementary tactics, developing crop genotypes for enhanced weed suppression, and tailoring management strategies to better accommodate variability in weed spatial distributions. In all three cases, proof-of-concept has long been demonstrated and considerable scientific innovations have been made, but uptake by farmers and land managers has been extremely limited. Impediments to employing these and other ecologically based approaches include inadequate or inappropriate government policy instruments, a lack of market mechanisms, and a paucity of social infrastructure with which to influence learning, decision-making, and actions by farmers and land managers. We offer examples of how these impediments are being addressed in different parts of the world, but note that there is no clear formula for determining which sets of policies, market mechanisms, and educational activities will be effective in various locations. Implementing new approaches for weed management will require multidisciplinary teams comprised of scientists, engineers, economists, sociologists, educators, farmers, land managers, industry personnel, policy makers, and others willing to focus on weeds within whole farming systems and land management units. © 2016 by the Ecological Society of America.

  3. Site-specific weed control technologies

    DEFF Research Database (Denmark)

    Christensen, S; Søgaard, H T; Kudsk, P

    2009-01-01

    Site-specific weed control technologies are defined as machinery or equipment embedded with technologies that detect weeds growing in a crop and, taking into account predefined factors such as economics, takes action to maximise the chances of successfully controlling them. In the article, we...... describe the basic parts of site specific weed control technologies, comprising of weed sensing systems, weed management models and precision weed control implements. A review of state-of-the-art technologies shows that several weed sensing systems and precision implements have been developed over the last...... two decades, though barriers prevent their breakthrough. Most important among these is the lack of a truly robust weed recognition method, owing to mutual shading among plants and limitations in the capacity of highly accurate spraying and weeding apparatuses.   Another barrier is the lack...

  4. WEED INFESTATION IN DIFFERENT FARMING SYSTEMS

    Directory of Open Access Journals (Sweden)

    MAGDALENA LACKO-BARTOŠOVÁ

    2002-05-01

    Full Text Available The aim of this work was to investigate the influence of ecological and conventional farming systems on weed seedbank and actual weed infestation of winter wheat at agricultural farms Sebechleby, Plavé Vozokany and Dačov Lom. Significant differences between systems were determined only at the co-operative Sebechleby where the higher weed seedbank was in ecological system. Higher number of determined weed species in weed seedstock was in ecological system at Plavé Vozokany and Sebechleby. Dominant weed species in both systems were Chenopodium album L. and Amaranthus retroflexus L.. Higher degree of actual weed infestation was determined in ecological system. Characteristics of systems was the occurrence of perennial species Cirsium arvense and non detection of Amaranthus retroflexus L., weed that had very high weed seedbank in soil.

  5. Late-season grass weed management with in-crop and post-harvest herbicides in twin-row glyphosate-resistant soybean

    Science.gov (United States)

    A 3-yr field study was conducted from 2011 to 2013 at Stoneville, MS to determine efficacy of post-harvest and pyroxasulfone-based in-crop herbicides on late-season grasses and yield in twin-row glyphosate-resistant (GR) soybean. Experiments were conducted in a split-plot arrangement of treatments i...

  6. Influence of Seeding Rate on Weed Density in Soybean Planting System for Southeastern Coastal Plains

    Directory of Open Access Journals (Sweden)

    Pawel Wiatrak

    2011-01-01

    Full Text Available Problem statement: Increasing seeding rates may help decrease weed pressure in soybean [Glycine max (L. Merr.] wide row spacing. Approach: The objective of this study was to evaluate the influence of five glyphosate-resistant soybean Maturity Groups (MG (IV, V, VI, VII and VIII and six seeding rates (68,000,136,000, 204,000, 272,000, 340,000 and 408,000 seeds ha-1 on weed density under dryland conditions on the Southeastern coastal plain in 2007-2009. Results: Weed decrease with increasing seeding rate varied over years. Weed density was generally lower at higher seeding rates for most MG soybeans at 30 and 60 DAP, except MG IV and VIII at 30 DAP in 2007 and MG VI at 30 DAP in 2008. At 60 DAP, soybean leaf area index (LAI and normalized difference vegetation index (NDVI were greater with lower weed density. Conclusion: Additionally, negative correlations were observed between weed density and plant LAI/NDVI for all MG in 2008 and MG IV through VI in 2009. These results suggest that increased seeding rates may help decrease weed pressure and improve soybean growth at early growth stages. However the response of weed pressure to seeding rate may vary over years and depend on MG soybean.

  7. Can global weed assemblages be used to predict future weeds?

    Directory of Open Access Journals (Sweden)

    Louise Morin

    Full Text Available Predicting which plant taxa are more likely to become weeds in a region presents significant challenges to both researchers and government agencies. Often it is done in a qualitative or semi-quantitative way. In this study, we explored the potential of using the quantitative self-organising map (SOM approach to analyse global weed assemblages and estimate likelihoods of plant taxa becoming weeds before and after they have been moved to a new region. The SOM approach examines plant taxa associations by analysing where a taxon is recorded as a weed and what other taxa are recorded as weeds in those regions. The dataset analysed was extracted from a pre-existing, extensive worldwide database of plant taxa recorded as weeds or other related status and, following reformatting, included 187 regions and 6690 plant taxa. To assess the value of the SOM approach we selected Australia as a case study. We found that the key and most important limitation in using such analytical approach lies with the dataset used. The classification of a taxon as a weed in the literature is not often based on actual data that document the economic, environmental and/or social impact of the taxon, but mostly based on human perceptions that the taxon is troublesome or simply not wanted in a particular situation. The adoption of consistent and objective criteria that incorporate a standardized approach for impact assessment of plant taxa will be necessary to develop a new global database suitable to make predictions regarding weediness using methods like SOM. It may however, be more realistic to opt for a classification system that focuses on the invasive characteristics of plant taxa without any inference to impacts, which to be defined would require some level of research to avoid bias from human perceptions and value systems.

  8. Can Global Weed Assemblages Be Used to Predict Future Weeds?

    Science.gov (United States)

    Morin, Louise; Paini, Dean R.; Randall, Roderick P.

    2013-01-01

    Predicting which plant taxa are more likely to become weeds in a region presents significant challenges to both researchers and government agencies. Often it is done in a qualitative or semi-quantitative way. In this study, we explored the potential of using the quantitative self-organising map (SOM) approach to analyse global weed assemblages and estimate likelihoods of plant taxa becoming weeds before and after they have been moved to a new region. The SOM approach examines plant taxa associations by analysing where a taxon is recorded as a weed and what other taxa are recorded as weeds in those regions. The dataset analysed was extracted from a pre-existing, extensive worldwide database of plant taxa recorded as weeds or other related status and, following reformatting, included 187 regions and 6690 plant taxa. To assess the value of the SOM approach we selected Australia as a case study. We found that the key and most important limitation in using such analytical approach lies with the dataset used. The classification of a taxon as a weed in the literature is not often based on actual data that document the economic, environmental and/or social impact of the taxon, but mostly based on human perceptions that the taxon is troublesome or simply not wanted in a particular situation. The adoption of consistent and objective criteria that incorporate a standardized approach for impact assessment of plant taxa will be necessary to develop a new global database suitable to make predictions regarding weediness using methods like SOM. It may however, be more realistic to opt for a classification system that focuses on the invasive characteristics of plant taxa without any inference to impacts, which to be defined would require some level of research to avoid bias from human perceptions and value systems. PMID:23393591

  9. Biotypic diversity in greenbug (Hemiptera: Aphididae): microsatellite-based regional divergence and host-adapted differentiation.

    Science.gov (United States)

    Weng, Yiqun; Perumal, Azhaguvel; Burd, John D; Rudd, Jackie C

    2010-08-01

    Nineteen isolates of the cereal aphid pest greenbug, Schizaphis graminum (Rondani) (Hemiptera: Aphididae), were collected from wheat, Triticum aestivum L.; barley, Hordeum vulgare L.; or noncultivated grass hosts in five locations from Colorado and Wyoming. Parthenogenetic colonies were established. Biotypic profiles of the 19 isolates were determined based on their abilities to damage a set of host plant differentials, and 13 new biotypes were identified. Genetic diversity among the 19 isolates and five previously designated greenbug biotypes (E, G, H, I, and K) was examined with 31 cross-species transferable microsatellite (simple sequence repeat) markers. Neighbor-joining clustering analysis of marker data revealed host-adapted genetic divergence as well as regional differentiation of greenbug populations. Host associated biotypic variation seems to be more obvious in "agricultural biotypes," whereas isolates collected from noncultivated grasses tend to show more geographic divergence. It seems that the biotype sharing the most similar biotypic profiles and the same geographic region with current prevailing one may have the greatest potential to become the new prevailing biotype. Close monitoring of greenbug population dynamics especially biotypic variation on both crop plants and noncultivated grasses in small grain production areas may be a useful strategy for detecting potentially new prevailing virulent biotypes of the greenbug.

  10. 牙龈生物型%Gingival biotype

    Institute of Scientific and Technical Information of China (English)

    林璐

    2015-01-01

    Gingival biotype is used to describe the features of the marginal periodontium and tooth form, and it is one predicting indicator for dental implant and periodontal treatment. It was presumed that the gingival biotype in individuals may be different. Different types of gingival biotype respond to chronic stimulations differently. Current-ly, gingival biotype is clinically classified as thin or thick according to the thickness at a point 2 mm apicaly to gingival margin examined by means of transgingival probing, probe transparency, CBCT and so on. So far, the classification and characteristics of ginvival biotype are still controversial. This paper reviews the definition, classification, character-istics, measurement methods and clinical application of various gingival biotypes.%牙龈生物型泛指牙周围组织及牙体组织的形态特征,是种植、牙周等美学治疗术后成功率的预测参考因素之一. 个体间的牙龈生物型是存在差异的,并且不同的牙龈生物型对外界刺激的反应不同.目前临床上多根据龈缘下2 mm处的牙龈厚度将牙龈生物型分为厚型和薄型,其检测手段主要有直接测量法、牙周探诊法、CBCT扫描法等. 由于牙龈生物型受地域、种族、遗传、牙根位置的影响较大,目前为止,关于牙龈生物型的分型、特征等仍存在争议,尚未达成共识. 本文就牙龈生物型的定义、临床分型和特征、测量方法、临床应用等作一综述.

  11. Pollen-mediated gene flow from glyphosate-resistant common waterhemp (Amaranthus rudis Sauer): consequences for the dispersal of resistance genes

    Science.gov (United States)

    Sarangi, Debalin; Tyre, Andrew J.; Patterson, Eric L.; Gaines, Todd A.; Irmak, Suat; Knezevic, Stevan Z.; Lindquist, John L.; Jhala, Amit J.

    2017-01-01

    Gene flow is an important component in evolutionary biology; however, the role of gene flow in dispersal of herbicide-resistant alleles among weed populations is poorly understood. Field experiments were conducted at the University of Nebraska-Lincoln to quantify pollen-mediated gene flow (PMGF) from glyphosate-resistant (GR) to -susceptible (GS) common waterhemp using a concentric donor-receptor design. More than 130,000 common waterhemp plants were screened and 26,199 plants were confirmed resistant to glyphosate. Frequency of gene flow from all distances, directions, and years was estimated with a double exponential decay model using Generalized Nonlinear Model (package gnm) in R. PMGF declined by 50% at pollen source, whereas 90% reduction was found at 88 m (maximum) depending on the direction of the pollen-receptor blocks. Amplification of the target site gene, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), was identified as the mechanism of glyphosate resistance in parent biotype. The EPSPS gene amplification was heritable in common waterhemp and can be transferred via PMGF, and also correlated with glyphosate resistance in pseudo-F2 progeny. This is the first report of PMGF in GR common waterhemp and the results are critical in explaining the rapid dispersal of GR common waterhemp in Midwestern United States. PMID:28327669

  12. Effect of cowpea intercropping on weed control and corn yieid Efeito da consorciação do feijão-caupi no controle de plantas daninhas e no rendimento do milho

    Directory of Open Access Journals (Sweden)

    P.S.L. Silva

    2009-01-01

    Full Text Available Herbicides have simplified weed control, but the use of herbicides, besides being costly, resulted in the selection of herbicide-resistant weed biotypes and has become an environmental contamination factor. Herbicide use reduction is one of the goals of modern agriculture, with several alternatives being investigated, including intercropping. The objective of this study was to evaluate the effects of cowpea and corn cultivar intercropping on weed control and corn green-ear (immature ears with 80% humidity grains and grain yield. A completely randomized block design with split-plots and four replications was used. AG 1051, AG 2060 and PL 6880 corn cultivars (assigned to plots were submitted to the four treatments: no weeding, two hoe-weeding (22 and 41 days after planting, and intercropping with cowpea (BR 14 and IPA 206 cultivars, with indeterminate growth. The cowpea was planted (with corn planting between the corn rows, in pits 1.0 m apart, with two plants per pit. The corn cultivars did not differ from each other as to weed density (WD, fresh above-ground weed biomass (WB, green-ear yield and grain yields. Higher WD and WB mean values were found in no weeding subplots; lower mean values in two hoe-weeding subplots; and intermediate mean values in intercropped subplots, indicating that cowpea plants had, to a certain extent, control over weeds. The no-weeded plots and the intercropped plots had lower green-ear and grain yields. Although the cowpea cultivars had a certain control over weeds (mean reductions of 22.5 and 18.3%, in terms of green matter density and weight of the above-ground part of weeds, respectively, they also competed against the corn plants, leading to yield reduction (mean reductions of 17.0 and 32% in green ear and grain yield, respectively. The cowpea cultivars did not produce grain, certainly due to the strong competition exerted by the corn and weeds on cowpea plants.Os herbicidas têm simplificado o controle de plantas

  13. Características fisiológicas das culturas de soja e feijão e de três espécies de plantas daninhas Physiological caracteristics of soybean and common bean crops and three weed species

    Directory of Open Access Journals (Sweden)

    S.O. Procópio

    2004-06-01

    Full Text Available O objetivo do trabalho foi avaliar os características fisiológicas taxa de fotossíntese líquida (A, taxa de transpiração (E, condutância estomática (gs e eficiência do uso da água (WUE e os índices de crescimento biomassa seca total (Wt e índice de área foliar (L para as culturas de soja (Glycine max e feijão (Phaseolus vulgaris e para as das plantas daninhas Bidens pilosa, Desmodium tortuosum e dois biótipos de Euphorbia heterophylla (um suscetível e outro resistente aos herbicidas inibidores da ALS, em duas épocas de avaliação: 39 e 67 dias após a semeadura (DAS. O experimento foi conduzido a campo em um Argissolo Vermelho-Amarelo, fase terraço, utilizando-se o delineamento experimental de blocos ao acaso, com parcelas subdivididas, sendo o fator da parcela principal as espécies vegetais e o da subparcela as épocas de avaliação, com quatro repetições por tratamento. Foi observado maior Wt da soja em relação às plantas daninhas. As culturas de soja e feijão apresentaram maior L do que as plantas daninhas. Os biótipos de E. heterophylla apresentaram a maior A, bem como a maior gs. Com exceção de D. tortuosum, as plantas daninhas apresentaram maior WUE em relação às culturas nos estádios iniciais de desenvolvimento. Não foram observadas diferenças em relação a qualquer parâmetro fisiológico avaliado entre os biótipos de E. heterophylla.This work aimed to evaluate the physiological caracteristics net photosynthesis (A, transpiration rate (E, stomatal conductance (gs and water use efficiency (WUE and growth indexes of total dry matter (Wt and leaf area index (L for soybean (Glycine max, common bean (Phaseolus vulgaris and weeds Bidens pilosa, Desmodium tortuosum and two biotypes of Euphorbia heterophylla (one susceptible and other resistant to ALS inhibitor herbicides during two periods of evaluation, 39 and 67 days after sowing (DAS. The experiment was conducted under field conditions in a Red

  14. Evolution of New Disease Specificity at a Simple Resistance Locus in a Crop–Weed Complex: Reconstitution of the Lr21 Gene in Wheat

    OpenAIRE

    Huang, Li; Brooks, Steven; Li, Wanlong; Fellers, John; Nelson, James C.; Gill, Bikram

    2009-01-01

    The wheat leaf-rust resistance gene Lr21 was first identified in an Iranian accession of goatgrass, Aegilops tauschii Coss., the D-genome donor of hexaploid bread wheat, and was introgressed into modern wheat cultivars by breeding. To elucidate the origin of the gene, we analyzed sequences of Lr21 and lr21 alleles from 24 wheat cultivars and 25 accessions of Ae. tauschii collected along the Caspian Sea in Iran and Azerbaijan. Three basic nonfunctional lr21 haplotypes, H1, H2, and H3, were ide...

  15. Genetically Modified Herbicide-Tolerant Crops, Weeds, and Herbicides: Overview and Impact

    Science.gov (United States)

    Bonny, Sylvie

    2016-01-01

    Genetically modified (GM) crops have been and continue to be a subject of controversy despite their rapid adoption by farmers where approved. For the last two decades, an important matter of debate has been their impact on pesticide use, particularly for herbicide-tolerant (HT) crops. Some claim that these crops bring about a decrease in herbicide use, while others claim the opposite. In fact, since 1996, most cultivated GMOs have been GMHT crops, which involve the use of an associated herbicide, generally glyphosate. In their very first years of adoption, HT crops often led to some decrease in herbicide use. However, the repetition of glyphosate-tolerant crops and of glyphosate only applications in the same fields without sufficient alternation and herbicide diversity has contributed to the appearance of glyphosate-resistant weeds. These weeds have resulted in a rise in the use of glyphosate and other herbicides. This article explores this situation and the impacts of herbicide-resistant weeds, using an interdisciplinary approach and drawing on recent data. The paper analyzes the spread of GMHT crops worldwide and their consequences on herbicide use in the USA in particular. It then addresses the global development of glyphosate-resistant weeds and their impact, particularly focusing on the USA. Finally, the last section explores how industry, farmers, and weed scientists are coping with the spread of resistant weeds. The concluding comments deal more widely with trends in GM crops.

  16. Differential content of glyphosate and its metabolites in Digitaria insularis biotypes

    Directory of Open Access Journals (Sweden)

    Leonardo Bianco de Carvalho

    2013-07-01

    Full Text Available Experiments were carried out in controlled conditions to analyze the role of metabolism of glyphosate in Digitaria insularis (sourgrass biotypes with differential response to the herbicide. Contents of glyphosate, aminomethylphosphonic acid (AMPA, glyoxylate, and sarcosine was detected in leaf tissues by using reversed-polarity capillarity electrophoresis. Glyphosate content in the A biotype increased from 19.7 up to 65.5 µg g fresh weight-1, whereas decreasing from 19.9 down to 5.0 µg g fresh weight-1 in the B biotype, from 48 up to 168 hours after treatment. At 168 hours after treatment, percentage of the sum of AMPA, glyoxylate, and sarcosine was > 56% in the B biotype, whereas a small percentage of metabolites (< 10% was found in the A biotype. Thus, the faster herbicide degradation in the B biotype is evidence that a differential metabolism of glyphosate can be conferring its lesser susceptibility to the herbicide.

  17. Little Pend Oreille - Weeding for Wildlife

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The project builds on previous funding to work with volunteers to manage weeds. Our hope is train volunteers in the use of GPS units, map the extent of specific weed...

  18. Sheldon-Hart - High Desert Weed Management

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — (1)Treat 500 acres of previously mapped invasive weeds on Hart Mountain; followup monitoring and spot treatment where needed, (2)treat 110 acres of invasive weeds...

  19. Inter-seasonal population dynamics and pest status of Bemisia tabaci (Gennadius) biotype B in an Australian cropping system.

    Science.gov (United States)

    Sequeira, R V; Shields, A; Moore, A; De Barro, P

    2009-08-01

    Bemisia tabaci, biotype B, commonly known as the silverleaf whitefly (SLW) is an alien species that invaded Australia in the mid-90s. This paper reports on the invasion ecology of SLW and the factors that are likely to have contributed to the first outbreak of this major pest in an Australian cotton cropping system. Population dynamics of SLW within whitefly-susceptible crop (cotton and cucurbit) and non-crop vegetation (sowthistle, Sonchus spp.) components of the cropping system were investigated over four consecutive growing seasons (September-June) 2001/02-2004/05 in the Emerald Irrigation Area (EIA) of Queensland, Australia. Based on fixed geo-referenced sampling sites, variation in spatial and temporal abundance of SLW within each system component was quantified to provide baseline data for the development of ecologically sustainable pest management strategies. Parasitism of large (3rd and 4th instars) SLW nymphs by native aphelinid wasps was quantified to determine the potential for natural control of SLW populations. Following the initial outbreak in 2001/02, SLW abundance declined and stabilised over the next three seasons. The population dynamics of SLW is characterised by inter-seasonal population cycling between the non-crop (weed) and cotton components of the EIA cropping system. Cotton was the largest sink for and source of SLW during the study period. Over-wintering populations dispersed from weed host plant sources to cotton in spring followed by a reverse dispersal in late summer and autumn to broad-leaved crops and weeds. A basic spatial source-sink analysis showed that SLW adult and nymph densities were higher in cotton fields that were closer to over-wintering weed sources throughout spring than in fields that were further away. Cucurbit fields were not significant sources of SLW and did not appear to contribute significantly to the regional population dynamics of the pest. Substantial parasitism of nymphal stages throughout the study period

  20. Longitudinal study of the biotypes of Gardnerella vaginalis.

    OpenAIRE

    Briselden, A M; Hillier, S L

    1990-01-01

    Gardnerella vaginalis is the predominant vaginal microorganism in women with bacterial vaginosis. However, this organism is also frequently isolated from women without signs or symptoms of vaginitis. Earlier studies have not revealed whether certain biotypes of G. vaginalis are more often associated with bacterial vaginosis or are more common in women who acquire bacterial vaginosis. We used a typing scheme based on tests for beta-galactosidase, hippurate hydrolysis, and lipase, using oleate ...

  1. Characterization of dental anatomy and gingival biotype in Asian populations.

    Science.gov (United States)

    Lee, Stacey A; Kim, Alexis C; Prusa, Louis A; Kao, Richard T

    2013-01-01

    Gingival and dental characteristics are risk factors for periodontal problems. With short or fused roots, a decreased periodontium results in some attachment loss, compromising periodontal stability. Similarly, with an increased incidence of thin gingival biotype, inflammatory and traumatic insults may result in gingival recession. Anecdotally, Asian dentitions have been described as having short roots with "thin gingiva". This cross-sectional study will utilize clinical data and radiographic interpretation to ascertain whether this clinical impression is valid.

  2. Are herbicides a once in a century method of weed control?

    Science.gov (United States)

    Davis, Adam S; Frisvold, George B

    2017-11-01

    The efficacy of any pesticide is an exhaustible resource that can be depleted over time. For decades, the dominant paradigm - that weed mobility is low relative to insect pests and pathogens, that there is an ample stream of new weed control technologies in the commercial pipeline, and that technology suppliers have sufficient economic incentives and market power to delay resistance - supported a laissez faire approach to herbicide resistance management. Earlier market data bolstered the belief that private incentives and voluntary actions were sufficient to manage resistance. Yet, there has been a steady growth in resistant weeds, while no new commercial herbicide modes of action (MOAs) have been discovered in 30 years. Industry has introduced new herbicide tolerant crops to increase the applicability of older MOAs. Yet, many weed species are already resistant to these compounds. Recent trends suggest a paradigm shift whereby herbicide resistance may impose greater costs to farmers, the environment, and taxpayers than earlier believed. In developed countries, herbicides have been the dominant method of weed control for half a century. Over the next half-century, will widespread resistance to multiple MOAs render herbicides obsolete for many major cropping systems? We suggest it would be prudent to consider the implications of such a low-probability, but high-cost development. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  3. Testing Tools for Glyphosate Resistance

    Science.gov (United States)

    There are multiple tools available for testing for glyphosate resistance. Whole plant screens, whether in the field or greenhouse, should be used as an initial method to determine if a biotype is glyphosate resistant. Screening for resistance using seedling assays such as in Petri plates, sand cul...

  4. Oleate lipase activity in Gardnerella vaginalis and reconsideration of existing biotype schemes

    Directory of Open Access Journals (Sweden)

    Moncla Bernard J

    2009-04-01

    Full Text Available Abstract Background Gardnerella vaginalis is a facultative gram positive organism that requires subculture every 1–2 days to maintain viability. It has been linked with bacterial vaginosis (BV, a syndrome that has been associated with increased risk for preterm delivery, pelvic inflammatory disease and HIV acquisition. About 10% of the G. vaginalis isolates have been reported to produce sialidase, but there have not been any studies relating sialidase production and biotype. Sialidase activity is dramatically increased in the vaginal fluid of women with BV and bacterial sialidases have been shown to increase the infectivity of HIV in vitro. There are 8 different biotypes of G. vaginalis. Biotypes 1–4 produce lipase and were reported to be associated with BV and the association of these biotypes with BV is under dispute. Other studies have demonstrated that G. vaginalis biotype 1 can stimulate HIV-1 production. Because of the discrepancies in the literature we compared the methods used to biotype G. vaginalis and investigated the relationship of biotype and sialidase production. Results A new medium for maintenance of Gardnerella vaginalis which allows survival for longer than one week is described. Some isolates only grew well under anaerobic conditions. Sialidase producing isolates were observed in 5 of the 6 biotypes tested. Using 4-methylumbelliferyl-oleate to determine lipase activity, instead of egg yolk agar, resulted in erroneous biotypes and does not provide reliable results. Conclusion Previous studies associating G. vaginalis biotype with bacterial vaginosis were methodologically flawed, suggesting there is not an association of G. vaginalis biotypes and bacterial vaginosis. Sialidase activity was observed in 5 of the 8 biotypes.

  5. A REVIEW OF WEED MANAGEMENT IN INDIA: THE NEED OF NEW DIRECTIONS FOR SUSTAINABLE AGRICULTURE

    Directory of Open Access Journals (Sweden)

    S K VERMA

    2016-03-01

    Full Text Available Weeds are the major deterrent to the development of sustainable crop production. Since weeds dictate most of the crop production practices and causes enormous losses (37 per cent due to their interference. Farmers follow several practices for managing weeds in different crops/cropping systems, of which at present the use of herbicides are on the top due to the scarcity of labors. The sustainability of these systems is being questioned because of environmental, social, and economic concerns caused by global competition, production cost, soil erosion, environmental pollution, and concern over the quality of rural life. Enhancing the crop competitiveness through preventive methods, cultural practices, mechanical methods, plant breeding, biotechnology, biological control and crop diversification will be the central thesis in new paradigms of weed management. Integration of above techniques will be key to sustainable weed management that maintain or enhance the crop productivity, profitability and environmental quality. This article explores the scope of sustainable weed management, growing concerns over herbicide resistance, environmental and health hazards of pesticides including herbicides and declining profitability are the major challenges of ‘high input’ agriculture. The goal of this review is to facilitate the development of ecologically based alternative methods for sustainable weed management that will support crop production systems, which require less tillage, herbicide and other inputs. To accomplish this goal, research efforts must be radically expanded in crop ecology and in the development of ecologically based technologies for weed management. Adoption of sustainable agricultural practices reduces the intensity of soil manipulation thereby creates an unfavorable condition for weed seed germination, reduces the organic matter depletion and soil erosion. Thus, the sustainable approaches could be an option for weed and soil

  6. Simulating changes in cropping practises in conventional and glyphosate-tolerant maize. I. Effects on weeds.

    Science.gov (United States)

    Colbach, Nathalie; Fernier, Alice; Le Corre, Valérie; Messéan, Antoine; Darmency, Henri

    2017-04-01

    Herbicide-tolerant (HT) crops such as those tolerant to glyphosate simplify weed management and make it more efficient, at least at short-term. Overreliance on the same herbicide though leads to the spread of resistant weeds. Here, the objective was to evaluate, with simulations, the impact on the advent of glyphosate resistance in weeds of modifications in agricultural practises resulting from introducing HT maize into cropping systems. First, we included a single-gene herbicide resistance submodel in the existing multispecific FLORSYS model. Then, we (1) simulated current conventional and probable HT cropping systems in two European regions, Aquitaine and Catalonia, (2) compared these systems in terms of glyphosate resistance, (3) identified pertinent cultural practises influencing glyphosate resistance, and (4) investigated correlations between cultural practises and species traits, using RLQ analyses. The simulation study showed that, during the analysed 28 years, (1) glyphosate spraying only results in glyphosate resistance in weeds when combined with other cultural factors favouring weed infestation, particularly no till; (2) pre-sowing glyphosate applications select more for herbicide resistance than post-sowing applications on HT crops; and (3) glyphosate spraying selects more for species traits avoiding exposure to the herbicide (e.g. delayed early growth, small leaf area) or compensating for fitness costs (e.g. high harvest index) than for actual resistance to glyphosate, (4) actual resistance is most frequent in species that do not avoid glyphosate, either via plant size or timing, and/or in less competitive species, (5) in case of efficient weed control measures, actual resistance proliferates best in outcrossing species. An advice table was built, with the quantitative, synthetic ranking of the crop management effects in terms of glyphosate-resistance management, identifying the optimal choices for each management technique.

  7. First report and differential colonization of Passiflora species by the B biotype of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) in Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Nunes, Endson S.; Vieira, Maria L.C. [Escola Superior de Agricultura Luiz de Queiroz (ESALQ-USP), Piracicaba, SP (Brazil). Dept. de Genetica]. E-mail: esnunes@carpa.ciagri.usp.br; mlcvieir@esalq.usp.br; Brown, Judith K. [University of Arizona, Tucson, AZ (United States). Dept. of Plant Sciences]. E-mail: jbrown@Ag.arizona.edu; Moreira, Adriana G.; Rezende, Jorge A.M. [Escola Superior de Agricultura Luiz de Queiroz (ESALQ-USP), Piracicaba, SP (Brazil). Dept. de Entomologia, Fitopatologia e Zoologia Agricola]. E-mails: agmoreir@esalq.usp.br; amrezen@esalq.usp.br; Watson, Gillian [California Dept. of Food and Agriculture, Sacramento, CA (United States)]. E-mail: gwatson@cdfa.ca.gov; Lourencao, Andre L. [Instituto Agronomico, Campinas, SP (Brazil). Centro de Pesquisa e Desenvolvimento de Fitossanidade]. E-mail: andre@iac.sp.gov.br; Piedade, Sonia M.S. [Escola Superior de Agricultura Luiz de Queiroz (ESALQ-USP), Piracicaba, SP (Brazil). Dept. de Ciencias Exatas]. E-mail: jsoniamsp@esalq.usp.br

    2008-11-15

    This note is the first report of Bemisia tabaci (Gennadius) biotype B colonizing passionvine in Brazil. We examined the colonization of nine Passiflora species by a wild B type population under greenhouse conditions. P. amethystina Mikan was the most preferred species for oviposition and colonization, whereas P. suberosa L., P. coriacea Juss. and two commercially cultivated species, P. alata Curtis and P. edulis Sims f. flavicarpa Degener, were mostly uncolonised. P. morifolia Mast., P. cincinnata Mast., P. foetida L. and P. caerulea L. showed intermediate levels of colonization. Such differential colonization might suggest some degree of resistance by certain Passiflora species or oviposition preference by B. tabaci. (author)

  8. Occurrence of Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae parasitizing Bemisia tabaci (Genn. biotype B (Hemiptera: Aleyrodidae in Brazil

    Directory of Open Access Journals (Sweden)

    André Luiz Lourenção

    2014-06-01

    Full Text Available The parasitism of Bemisia tabaci (Genn. biotype B nymphs on cotton plants was observed during a research on resistance of cotton genotypes to this whitefly. The experiment was set in a greenhouse at the Experimental Station of the Instituto Agronômico (IAC, in Campinas, São Paulo State, Brazil. Samples of the parasitized nymphs were collected and maintained in laboratory to monitor the parasitism and obtain the adult parasitoids. A total of 129 adult parasitoids were obtained, including one Encarsia inaron (Walker, 13 En. lutea (Masi, and 115 Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae. This is the first report of Er. mundus in Brazil.

  9. The Weeding of a Historical Society Library.

    Science.gov (United States)

    Drake, Cindy Steinhoff

    1992-01-01

    Describes a major deaccessioning (weeding) project begun in 1985 at the library of the Nebraska State Historical Society, including a brief history of the Society and the events leading to the decision to weed. Public controversy over the handling of the project, benefits of the weeding, and new acquisitions policies are also discussed. (MES)

  10. Prospects for site specific weed management

    DEFF Research Database (Denmark)

    Christensen, Svend; Rasmussen, Jesper; Pedersen, Søren Marcus;

    2014-01-01

    Research on Site Specific Weed Management (SSWM) started in the late 80's. Since that moment, considerable research has been conducted on different aspects of SSWM, from fundamental studies on the spatial ecology of weeds to the applied development and testing of new technologies for weed detection...

  11. Supracrestal gingival tissue: assessing relation with periodontal biotypes in a healthy periodontium.

    Science.gov (United States)

    Arora, Ritika; Narula, Satish C; Sharma, Rajinder K; Tewari, Shikha

    2013-01-01

    This cross-sectional study assessed the variability in supracrestal gingival tissue (SGT) dimensions in a healthy periodontium. SGT dimensions were evaluated for differences across various locations, tooth types, and periodontal biotypes. All measurements were made with a vernier caliper to the nearest 0.1 mm. A total of 1,932 sites in 366 teeth were statistically analyzed. Median overall SGT was recorded as 3.50 mm with a range from 1.80 to 6.20 mm. The thick-flat biotype exhibited greater median SGT than the thinscalloped biotype. When planning crown lengthening surgery, periodontal biotype may have a significant role in determining SGT dimensions.

  12. What's a Weed? Knowledge, Attitude and Behaviour of Park Visitors about Weeds.

    Directory of Open Access Journals (Sweden)

    Michael Ansong

    Full Text Available Weeds are a major threat to biodiversity globally degrading natural areas of high conservation value. But what are our attitudes about weeds and their management including weeds in national parks? Do we know what a weed is? Do we consider weeds a problem? Do we support their management? Are we unintentionally spreading weeds in parks? To answer these questions, we surveyed visitors entering a large popular national park near the city of Brisbane, Australia. Park visitors were knowledgeable about weeds; with >75% correctly defining weeds as 'plants that grow where they are not wanted'. About 10% of the visitors, however, provided their own sophisticated definitions. This capacity to define weeds did not vary with people's age, sex or level of education. We constructed a scale measuring visitors' overall concern about weeds in parks using the responses to ten Likert scale statements. Over 85% of visitors were concerned about weeds with older visitors, hikers, and those who could correctly define weeds more concerned than their counterparts. The majority think visitors unintentionally introduce seeds into parks, with many (63% having found seeds on their own clothing. However, over a third disposed of these seeds in ways that could facilitate weed spread. Therefore, although most visitors were knowledgeable and concerned about weeds, and support their control, there is a clear need for more effective communication regarding the risk of visitors unintentionally dispersing weed seeds in parks.

  13. What's a Weed? Knowledge, Attitude and Behaviour of Park Visitors about Weeds.

    Science.gov (United States)

    Ansong, Michael; Pickering, Catherine

    2015-01-01

    Weeds are a major threat to biodiversity globally degrading natural areas of high conservation value. But what are our attitudes about weeds and their management including weeds in national parks? Do we know what a weed is? Do we consider weeds a problem? Do we support their management? Are we unintentionally spreading weeds in parks? To answer these questions, we surveyed visitors entering a large popular national park near the city of Brisbane, Australia. Park visitors were knowledgeable about weeds; with >75% correctly defining weeds as 'plants that grow where they are not wanted'. About 10% of the visitors, however, provided their own sophisticated definitions. This capacity to define weeds did not vary with people's age, sex or level of education. We constructed a scale measuring visitors' overall concern about weeds in parks using the responses to ten Likert scale statements. Over 85% of visitors were concerned about weeds with older visitors, hikers, and those who could correctly define weeds more concerned than their counterparts. The majority think visitors unintentionally introduce seeds into parks, with many (63%) having found seeds on their own clothing. However, over a third disposed of these seeds in ways that could facilitate weed spread. Therefore, although most visitors were knowledgeable and concerned about weeds, and support their control, there is a clear need for more effective communication regarding the risk of visitors unintentionally dispersing weed seeds in parks.

  14. What’s a Weed? Knowledge, Attitude and Behaviour of Park Visitors about Weeds

    Science.gov (United States)

    Ansong, Michael; Pickering, Catherine

    2015-01-01

    Weeds are a major threat to biodiversity globally degrading natural areas of high conservation value. But what are our attitudes about weeds and their management including weeds in national parks? Do we know what a weed is? Do we consider weeds a problem? Do we support their management? Are we unintentionally spreading weeds in parks? To answer these questions, we surveyed visitors entering a large popular national park near the city of Brisbane, Australia. Park visitors were knowledgeable about weeds; with >75% correctly defining weeds as ‘plants that grow where they are not wanted’. About 10% of the visitors, however, provided their own sophisticated definitions. This capacity to define weeds did not vary with people’s age, sex or level of education. We constructed a scale measuring visitors’ overall concern about weeds in parks using the responses to ten Likert scale statements. Over 85% of visitors were concerned about weeds with older visitors, hikers, and those who could correctly define weeds more concerned than their counterparts. The majority think visitors unintentionally introduce seeds into parks, with many (63%) having found seeds on their own clothing. However, over a third disposed of these seeds in ways that could facilitate weed spread. Therefore, although most visitors were knowledgeable and concerned about weeds, and support their control, there is a clear need for more effective communication regarding the risk of visitors unintentionally dispersing weed seeds in parks. PMID:26252004

  15. 81 FR 35767 - Pesticides; Draft Guidance for Pesticide Registrants on Herbicide Resistance Management Labeling...

    Science.gov (United States)

    2016-06-03

    ... draft PR Notice (2016-XX) communicates the Agency's approach to addressing herbicide-resistant weeds by...-resistant weeds by providing guidance on labeling, education, training, and stewardship for herbicides... approach to slow the development and spread of herbicide- resistant weeds, and prolong the useful...

  16. Research progress on the role of polyamines and their transporters in paraquat resistance in weeds%多胺及其转运体在杂草对百草枯抗性机制中的作用研究进展

    Institute of Scientific and Technical Information of China (English)

    安静; 沈雪峰; 陈勇

    2013-01-01

    The forms,transportation and metabolism of polyamines,as well as the roles of polyamines in plant were reviewed,and the latest paraquat resistance mechanism in weed was summarized.Much discussion was focus on the alleviation of the paraquat toxicity by polyamines and the important role of polyamines transporter plays in the weed resistance to paraquat.Polyamines and their transporters may be one important area in the study of paraquat resistance mechanism.%通过对多胺在植物体内的形态分布、转运、代谢及其参与植物生长发育和胁迫反应的作用机制,以及杂草对百草枯的抗性机制最新研究进展进行综述,重点围绕多胺对百草枯毒性的缓解作用及多胺转运体在杂草对百草枯抗性机制中的作用进行评述,揭示了多胺及其转运体将是杂草对百草枯抗性机制研究的重要领域.

  17. Glyphosate effects on gas exchange and chlorophyll fluorescence responses of two Lolium perenne L. biotypes with differential herbicide sensitivity.

    Science.gov (United States)

    Yanniccari, Marcos; Tambussi, Eduardo; Istilart, Carolina; Castro, Ana María

    2012-08-01

    Despite the extensive use of glyphosate, how it alters the physiology and metabolism of plants is still unclear. Photosynthesis is not regarded to be a primary inhibitory target of glyphosate, but it has been reported to be affected by this herbicide. The aim of the current research was to determine the effects of glyphosate on the light and dark reactions of photosynthesis by comparing glyphosate-susceptible and glyphosate-resistant Lolium perenne biotypes. After glyphosate treatment, accumulation of reduced carbohydrates occurred before a decrease in gas exchange. Stomatal conductance and CO(2) assimilation were reduced earlier than chlorophyll fluorescence and the amount of chlorophyll in susceptible plants. In the glyphosate-resistant biotype, stomatal conductance was the only parameter slightly affected only 5 days post-application. In susceptible plants, the initial glyphosate effects on gas exchange could be a response to a feedback regulation of photosynthesis. Since the herbicide affects actively growing tissues regardless of the inhibition of photosynthesis, the demand of assimilates decreased and consequently induced an accumulation of carbohydrates in leaves. We concluded that stomatal conductance could be a very sensitive parameter to assess both the susceptibility/resistance to glyphosate before the phytotoxic symptoms become evident.

  18. DEVELOPMENT OF A PROXIMAL MACHINE VISION SYSTEM FOR OFF-SEASON WEED MAPPING IN BROADACRE NO-TILLAGE FALLOWS

    Directory of Open Access Journals (Sweden)

    H. Liu

    2013-01-01

    Full Text Available Weeds are among the most significant and costly environmental threats in Australian agriculture. Weeds compete with crop plants for moisture, nutrients and sunlight and can have a detrimental impact on crop yields and quality if uncontrolled. The distribution, size, density and species of the weeds are often heterogeneous in the cropping land. Instead of uniformly spray the same type of herbicide to the whole farm land, selective spray can reduce the herbicide usage therefore can reduce the serious problems of herbicide resistance, soil damage and food safety. This study describes a weed mapping method which could be used for broadacre no-tillage fallow weed management. The weed maps have the potential to be used as powerful herbicide prescription maps for spot spray. The weed mapping is realized by the machine vision technologies which including image acquisition, image stitching and photomosaic processing. The sampling points are continuous and the interpolation methods are used at the minimum levels. The experiment result shows that this weed mapping method can map weed under limited conditions.

  19. Comparative Analysis of Population Genetic Structure in Bemisia tabaci (Gennadius) Biotypes B and Q Based on ISSR Marker

    Institute of Scientific and Technical Information of China (English)

    CHU Dong; WAN Fang-hao; XU Bao-yun; WU Qing-jun; ZHANG You-jun

    2008-01-01

    Bemisia tabaci (Gennadius) biotypes B and Q are two invasive biotypes in the species complex. The comparison of the population genetic structure of the two biotypes is of significance to show their invasive mechanism and to their control. The intersimple sequence repeats (ISSR) marker was used to analyze the 16 B-biotype populations and 4 Q-biotype populations worldwide with a Trialeurodes vaporariorum population in Shanxi Province, China, and a B. tabaci non-B/Q-biotype population in Zhejiang Province, China, was used as control populations. The analysis of genetic diversity showed that the diversity indexes of biotype Q including Nei's gene diversity index, Shannon informative index, and the percentage of polymorphic loci were higher than those of biotype B. The high genetic diversity of biotype Q might provide the genetic basis for the excellent ecological adaptation. Cluster analysis suggested that the ISSR could not be used in the phylogenetic analysis though it could easily distinguish the biotypes of B. tabaci. The difference of the population genetic structure between the biotype B and the biotype Q exists based on the ISSR marker. Meanwhile, the results suggested that the molecular marker has its limitation in the phylogenetic analysis among the biotypes of B. tabaci.

  20. Breeding cereal crops for enhanced weed suppression: optimizing allelopathy and competitive ability.

    Science.gov (United States)

    Worthington, Margaret; Reberg-Horton, Chris

    2013-02-01

    Interest in breeding grain crops with improved weed suppressive ability is growing in response to the evolution and rapid expansion of herbicide resistant populations in major weeds of economic importance, environmental concerns, and the unmet needs of organic producers and smallholder farmers without access to herbicides. This review is focused on plant breeding for weed suppression; specifically, field and laboratory screening protocols, genetic studies, and breeding efforts that have been undertaken to improve allelopathy and competition in rice, wheat, and barley. The combined effects of allelopathy and competition determine the weed suppressive potential of a given cultivar, and research groups worldwide have been working to improve both traits simultaneously to achieve maximum gains in weed suppression. Both allelopathy and competitive ability are complex, quantitatively inherited traits that are heavily influenced by environmental factors. Thus, good experimental design and sound breeding procedures are essential to achieve genetic gains. Weed suppressive rice cultivars are now commercially available in the U.S. and China that have resulted from three decades of research. Furthermore, a strong foundation has been laid during the past 10 years for the breeding of weed suppressive wheat and barley cultivars.

  1. Arachnoid granules: Dandy was Dandy, Cushing and Weed were not.

    Science.gov (United States)

    Maurizi, Charles P

    2010-08-01

    Errors can be instructive. It seems that Harvey Cushing and Louis Weed provided the medical world with a faulty theory of cerebrospinal fluid absorption. Louis Weed, working in Harvey Cushing's laboratory, initially studied the movement of substances in the cerebrospinal fluid by using low-pressure studies. Results of the low-pressure studies were considered unsatisfactory and high pressure experiments were undertaken and these had results similar to earlier work done by others in human cadavers. High pressure results demonstrating movement of fluid through the arachnoid granules were deemed correct. Because of Cushing's position of authority, the theory became accepted as fact and in time proved to be entrenched dogma. Walter Dandy demonstrated in experiments on hydrocephalus and the surgical removal of the arachnoid granule system that the fluid was produced by the choroid plexuses and not absorbed by the arachnoid granules. His work was dismissed by Weed as unreliable. Examination of the pattern of deposition of corpora amylacea on the surface of the brain provides evidence that cerebrospinal fluid does not pass through arachnoid granules but passes through the choroid fissure and is recycled through choroid plexus portals. The choroid plexus portal theory can explain the findings in the low-pressure experiments of Weed. Bias and pride seem to be the source of the faulty theory. Entrenched dogma is resistant to challenge.

  2. Weed suppression ability of spring barley varieties

    DEFF Research Database (Denmark)

    Christensen, Svend

    1995-01-01

    Three years of experiments with spring barley showed significant differences in weed suppression ability among varieties. Weed dry matter in the most suppressive variety, Ida, was 48% lower than the mean weed dry matter of all varieties, whereas it was 31% higher in the least suppressive variety......, Grit. Ranking varietal responses to weed competition in terms of grain yield loss corresponded well to ranking weed dry matter produced in crop weed mixtures. There was no correspondence between the varietal grain yields in pure stands and their competitiveness, suggesting that breeding to optimize...... interception model was developed to describe the light interception profiles of the varieties. A study of the estimated parameters showed significant correlation between weed dry matter, rate of canopy height development and the light interception profile. However, when estimates were standardized to eliminate...

  3. Enhanced resistance to CYSDV in melon (Cucumis melo L.) and identification of significant reservoir hosts for virus transmission in the southwestern US

    Science.gov (United States)

    Cucurbit yellow stunting disorder virus (CYSDV), which is transmitted by the sweet potato whitefly (Bemisia tabaci Gennadius) biotype B, emerged in the Southwest US in 2006. CYSDV can infect diverse regional weed and crop species, some of which serve as sources for virus transmission to melon. To de...

  4. Weed biocontrol in landscape restoration

    Science.gov (United States)

    Weed biological control programs in natural areas are often undertaken with the goal of restoring native plant communities and/or ecosystem services to a pre-invasion level. These objectives may be achieved in some areas with biological control alone; however, in other sites integration of biologica...

  5. Rounding Up the Astrophysical Weeds

    Science.gov (United States)

    McMillan, James P.

    2016-09-01

    New instruments used for astronomy such as ALMA, Herschel, and SOFIA have greatly increased the quality of available astrophysical data. These improved data contain spectral lines and features which are not accounted for in the quantum mechanical (QM) catalogs. A class of molecules has been identified as being particularly problematic, the so-called "weeds". These molecules have numerous transitions, of non-trivial intensity, which are difficult to model due to highly perturbed low lying vibrational states. The inability to properly describe the complete contribution of these weeds to the astrophysical data has led directly to the misidentification of other target molecules. Ohio State's Microwave Laboratory has developed an alternative approach to this problem. Rather than relying on complex QM calculations, we have developed a temperature dependent approach to laboratory based terahertz spectroscopy. We have developed a set of simple packages, in addition to traditional line list catalogs, that enable astronomers to successfully remove the weed signals from their data. This dissertation will detail my laboratory work and analysis of three keys weeds: methanol, methyl formate and methyl cyanide. Also, discussed will be the analytical technique I used to apply these laboratory results to astrophysical data.

  6. Effects of over-expressing a native gene encoding 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) on glyphosate resistance in Arabidopsis thaliana

    Science.gov (United States)

    Beres, Zachery T.; Jin, Lin; Parrish, Jason T.; Zhao, Wanying; Mackey, David; Snow, Allison A.

    2017-01-01

    Widespread overuse of the herbicide glyphosate, the active ingredient in RoundUp®, has led to the evolution of glyphosate-resistant weed biotypes, some of which persist by overproducing the herbicide’s target enzyme, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). EPSPS is a key enzyme in the shikimic acid pathway for biosynthesis of aromatic amino acids, lignin, and defensive compounds, but little is known about how overproducing EPSPS affects downstream metabolites, growth, or lifetime fitness in the absence of glyphosate. We are using Arabidopsis as a model system for investigating phenotypic effects of overproducing EPSPS, thereby avoiding confounding effects of genetic background or other mechanisms of herbicide resistance in agricultural weeds. Here, we report results from the first stage of this project. We designed a binary vector expressing a native EPSPS gene from Arabidopsis under control of the CaMV35S promoter (labelled OX, for over-expression). For both OX and the empty vector (labelled EV), we obtained nine independent T3 lines. Subsets of these lines were used to characterize glyphosate resistance in greenhouse experiments. Seven of the nine OX lines exhibited enhanced glyphosate resistance when compared to EV and wild-type control lines, and one of these was discarded due to severe deformities. The remaining six OX lines exhibited enhanced EPSPS gene expression and glyphosate resistance compared to controls. Glyphosate resistance was correlated with the degree of EPSPS over-expression for both vegetative and flowering plants, indicating that glyphosate resistance can be used as a surrogate for EPSPS expression levels in this system. These findings set the stage for examination of the effects of EPSPS over-expression on fitness-related traits in the absence of glyphosate. We invite other investigators to contact us if they wish to study gene expression, downstream metabolic effects, and other questions with these particular lines. PMID

  7. Tribenuron-Methyl Resistant Flixweed(Descurainia sophia)

    Institute of Scientific and Technical Information of China (English)

    CUI Hai-lan; ZHANG Chao-xian; ZHANG Hong-jun; HUANG Hong-juan; WEI Shou-hui; LIU Xue; WANG Gui-qi; LIU Yan

    2009-01-01

    Flixweed seeds were collected from suspected winter wheat fields and remote hillside in Shaanxi Province,China,their sensitivities to tribenuron-methyl were evaluated in the greenhouse.Results revealed that biotype S was susceptible to tribenuron,and its GR50 was 0.23 g a.i.ha-1,whereas biotypes R1,R2,R3,and R4 were resistant to the tribenuron,and their GR50 were 161.99,79.70,439.80,and 312.30,respectively.Biotypes R1 and R2 showed moderate resistance with resistant indices(RI)of 615.23 and 302.7,respectively.Whereas biotypes R3 and R4 showed high resistance to the herbicide with RI values as high as 1670.34 and 1186.10,respectively.

  8. Resistencia de Amaranthus quitensis a imazetapir y clorimurón-etil Resistance of Amaranthus quitensis to imazethapyr and clhorimuron-ethyl

    Directory of Open Access Journals (Sweden)

    Daniel Tuesca

    2001-04-01

    Full Text Available El objetivo de este trabajo fue establecer la existencia de biotipos de A. quitensis H.B.K. resistentes a imazetapir y clorimurón-etil. Se utilizaron semillas recolectadas en las localidades de Zavalla, General Baldissera, Marcos Juárez y Las Rosas. Las dosis de herbicidas utilizadas fueron 1/8x, 1/4x, 1/2x, 1x, 5x, 10x y 20x de la dosis de uso recomendada. Se determinó la mortalidad y biomasa de las plantas tratadas. Se calcularon las dosis de herbicidas requeridas para reducir en un 50% la biomasa de las plantas de la maleza (GR50 y se estimó la relación entre GR50 del biotipo resistente y GR50 del susceptible (factor de resistencia. El biotipo Zavalla resultó muy susceptible; con la mitad de la dosis de uso de ambos herbicidas la mortalidad fue 95%. El biotipo General Baldissera presentó resistencia cruzada; con dosis 20 veces superiores a las recomendadas, la mortalidad fue 57,5% y 20% para imazetapir y clorimurón-etil, respectivamente. El factor de resistencia de este biotipo respecto a Zavalla fue 165 y 246 para imazetapir y clorimurón-etil, respectivamente. Los biotipos Las Rosas y Marcos Juárez fueron resistentes a imazetapir y sin embargo resultaron muy susceptibles a clorimurón-etil. Las diferencias en los patrones de resistencia estarían asociadas con distintos niveles de presión de selección en las poblaciones analizadas.The objective was to determine the magnitude of resistance of A. quitensis H.B.K. biotypes to imazethapyr and chlorimuron-ethyl. Weed biotypes were collected at Zavalla, General Baldissera, Marcos Juárez y Las Rosas. The herbicides were applied at 1/8x, 1/4x, 1/2x, 1x, 5x, 10x and 20x the suggested rate. Weed mortality and reduction of biomass related with untreated plants were evaluated. Herbicides concentrations required to reduce growth by 50% (GR50 were determined. Resistance ratio (GR50 resistant/GR50 susceptible was calculated to indicate the degree of resistance. Zavalla showed high

  9. Genome Sequence of the "Indian Bison Type" Biotype of Mycobacterium avium subsp. paratuberculosis Strain S5.

    Science.gov (United States)

    Singh, Shoor Vir; Kumar, Naveen; Singh, Shree Narayan; Bhattacharya, Tapas; Sohal, Jagdip Singh; Singh, Pravin Kumar; Singh, Ajay Vir; Singh, Brajesh; Chaubey, Kundan Kumar; Gupta, Saurabh; Sharma, Nitu; Kumar, Shailesh; Raghava, Gajendra Pal Singh

    2013-01-01

    We report the 4.79-Mb genome sequence of the "Indian Bison Type" biotype of Mycobacterium avium subsp. paratuberculosis strain S5, isolated from a terminally sick Jamunapari goat at the CIRG (Central Institute for Research on Goats) farm in India. This draft genome will help in studying novelties of this biotype, which is widely distributed in animals and human beings in India.

  10. Is colonoscopy necessary in cases of infection by Streptococcus bovis biotype II?

    NARCIS (Netherlands)

    Corredoira, J.C.; Alonso, M.P.; Garcia-Pais, M.J.; Rabunal, R.; Garcia-Garrote, F.; Lopez-Roses, L.; Lancho, A.; Coira, A.; Pita, J.; Velasco, D.; Lopez-Alvarez, M.J.; Tjalsma, H.; Varela, J.

    2014-01-01

    The association of colorectal neoplasia (CRN) with Streptococcus bovis biotype I (SBI) infection is well recognized. However, this is not the case for Streptococcus bovis biotype II (SBII). We conducted this study in order to analyze the relationship between SBII and CRN. We analyzed all cases of ba

  11. Independent emergence of biotype 2 Yersinia ruckeri in the United States and Europe

    Science.gov (United States)

    Biotype 2 (BT2) variants of the bacterium Yersinia ruckeri are an increasing disease problem in United States (US) and European aquaculture and have been characterized as serovar 1 isolates that lack peritrichous flagella and secreted phospholipase activity. The emergence of this biotype has been as...

  12. Multiple independent emergence of biotype 2 Yersinia ruckeri in the United States and Europe

    Science.gov (United States)

    Biotype 2 (BT2) variants of the bacterium Yersinia ruckeri are an emerging disease problem in US and European salmonid aquaculture. The emergence of this biotype has been associated with an increased frequency of enteric redmouth disease (ERM) outbreaks in previously vaccinated salmonid fish. We use...

  13. Independent Emergence of Yersinia ruckeri Biotype 2 in the United States and Europe

    DEFF Research Database (Denmark)

    Welch, Timothy J.; Verner-Jeffreys, David W.; Dalsgaard, Inger

    2011-01-01

    Biotype 2 (BT2) variants of the bacterium Yersinia ruckeri are an increasing disease problem in U.S. and European aquaculture and have been characterized as serovar 1 isolates that lack both peritrichous flagella and secreted phospholipase activity. The emergence of this biotype has been associat...

  14. Independent Emergence of Yersinia ruckeri Biotype 2 in the United States and Europe

    DEFF Research Database (Denmark)

    Welch, Timothy J.; Verner-Jeffreys, David W.; Dalsgaard, Inger

    2011-01-01

    Biotype 2 (BT2) variants of the bacterium Yersinia ruckeri are an increasing disease problem in U.S. and European aquaculture and have been characterized as serovar 1 isolates that lack both peritrichous flagella and secreted phospholipase activity. The emergence of this biotype has been associat...

  15. Differentiation of Yersinia enterocolitica biotype 1A from pathogenic Yersinia enterocolitica biotypes by detection of β-glucosidase activity: comparison of two chromogenic culture media and Vitek2.

    Science.gov (United States)

    Karhukorpi, Jari; Päivänurmi, Marjut

    2014-01-01

    Aesculin hydrolysis (ESC) is one of the key reactions in differentiating pathogenic Yersinia enterocolitica biotypes 1B, 2, 3, 4 and 5 from the less-pathogenic biotype 1A. Because the ESC reaction is caused by β-glucosidase (βGLU) activity of the bacteria, we studied whether two commonly used methods (BBL CHROMagar Orientation and Vitek2 Gram-negative identification card) could be used in assessing βGLU activity of 74 Yersinia strains. Both methods were sensitive (100 % and 97 %) and specific (100 % and 100 %) in differentiating βGLU-positive YE BT1A from βGLU-negative Y. enterocolitica biotypes. For a subset of strains (n = 69), a new selective CHROMagar Yersinia showed excellent agreement with the strains' βGLU activity. Thus all the methods evaluated in this study may be used to differentiate between YE BT1A and other Y. enterocolitica biotypes.

  16. Compatible results obtained from biotyping and serotyping in Serratia marcescens.

    Science.gov (United States)

    Grimont, P A; Grimont, F; Le Minor, S; Davis, B; Pigache, F

    1979-10-01

    The correspondence between complete serotype and biotype (P.A.D. Grimont and F. Grimont, J. Clin. Microbiol. 8:73-83, 1978) of 474 Serratia marcescens strains was studied. Of 127 serotypes, 70 were represented by two or more strains of the same serotype belonged to one biotype. However, for 91% of serotypes, strains of the same serotype belonged to one biogroup--i.e., a group of closely related biotypes. Biogroups are A1 (A1a, A1b); A2/6 (A2a, A2b, A6a, A6b); A3 (A3a, A3b, A3c, A3d); A4 (A4a, A4b); A5/8 (A5, A8a, A8b, A8c); and TCT (TCT, TT). Only two serotypes were composed of a mixture of pigmented and nonpigmented biogroups. Pigmented biogroups (A1 and A2/6) were otherwise differentiated from nonpigmented biogroups (A3, A4, A5/8, and TCT) by serotyping. Some biogroups preferentially occurred in some O serogroups: A4 in 01; A2/6 in O6, O8, and O14; and A3 in O9, O12, and O15. Three H serogroups were found to be biochemically homogeneous: H1, H7, and H20 were respectively and uniquely composed of biogroups A4, TCT, and A3. A square matrix of O versus H serogroups, with the corresponding biogroup for each O X H combination, was used for comparisons between O groups and between H groups. Identical patterns of biogroups were shown by serogroups O6, O8, and O14. Taxonomical, ecological, and practical consequences of these findings are discussed.

  17. Current state of herbicides in herbicide-resistant crops.

    Science.gov (United States)

    Green, Jerry M

    2014-09-01

    Current herbicide and herbicide trait practices are changing in response to the rapid spread of glyphosate-resistant weeds. Growers urgently needed glyphosate when glyphosate-resistant crops became available because weeds were becoming widely resistant to most commonly used selective herbicides, making weed management too complex and time consuming for large farm operations. Glyphosate made weed management easy and efficient by controlling all emerged weeds at a wide range of application timings. However, the intensive use of glyphosate over wide areas and concomitant decline in the use of other herbicides led eventually to the widespread evolution of weeds resistant to glyphosate. Today, weeds that are resistant to glyphosate and other herbicide types are threatening current crop production practices. Unfortunately, all commercial herbicide modes of action are over 20 years old and have resistant weed problems. The severity of the problem has prompted the renewal of efforts to discover new weed management technologies. One technology will be a new generation of crops with resistance to glyphosate, glufosinate and other existing herbicide modes of action. Other technologies will include new chemical, biological, cultural and mechanical methods for weed management. From the onset of commercialization, growers must now preserve the utility of new technologies by integrating their use with other weed management technologies in diverse and sustainable systems.

  18. Cyclical parthenogenetic reproduction in the Russian wheat aphid (Hemiptera: Aphididae) in the United States: sexual reproduction and its outcome on biotypic diversity.

    Science.gov (United States)

    Puterka, G J; Hammon, R W; Burd, J D; Peairs, F B; Randolph, T L; Cooper, W R

    2012-06-01

    In 1986, the Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Hemiptera: Aphididae), became an invasive species of United States. Nearly 20 yr later, new biotypes appeared that were capable of overcoming most sources of resistance and became a renewed threat to wheat, Triticum aestivum L., production. Cyclical (CP) and obligate (OP) parthenogenesis enables aphids to both adapt to changing environments and exploit host resources. We documented these forms of reproduction for Russian wheat aphid in wheat and wild grasses in the Central Great Plains and Rocky Mountain regions during falls 2004-2009. Colonies from sample sites also were held under unheated greenhouse conditions and observed for the presence of sexual morphs and eggs through the winter. Russian wheat aphid populations were mainly OP and attempted to overwinter as adults, regardless of region sampled. A few populations contained oviparae but no males (gynocyclic) and were not specific to any particular region. Observation of the Russian wheat aphid colonies under greenhouse conditions failed to produce males or eggs. In spring 2007, CP was confirmed in a small population of Russian wheat aphid that eclosed from eggs (fundatricies) on wild grasses and wheat near Dove Creek, CO, in the Colorado Plateau region where other aphid species undergo CP. Lineages from ninety-three fundatricies were screened against 16 resistant and susceptible cereal entries to determine their biotypic classification. A high degree of biotypic diversity (41.4%) was detected in this population. Although CP was a rare in Russian wheat aphid populations, genetic recombination during the sexual cycle creates new biotypes and can have significant effects on population genetics.

  19. A Review on Reasons of Increasing Perennial Weeds and Control Technology of Perennial Weeds in Heilongjiang Province

    Institute of Scientific and Technical Information of China (English)

    ZHAO Changshan; HE Fuli; SHI Na; YAN Chunxiu

    2009-01-01

    The main reasons that perennial weeds has becoming the dominant weeds in Heilongjiang Province were summarized.The biological mechanism that explained why it was difficult to control perennial weeds was analyzed. During dormancy course,variation regularity of some inner matters in perennial weeds was researched and new tentative for controlling the perennial weeds was pointed out.

  20. Glyphosate no controle de biótipos de azevém e impacto na microbiota do solo Glyphosate application for italian ryegrass biotype control and impact on soil microbiota

    Directory of Open Access Journals (Sweden)

    E.A. Ferreira

    2006-09-01

    Full Text Available Avaliou-se neste trabalho a resistência de azevém (L. multiflorum ao glyphosate e o impacto do controle desses biótipos sobre a respiração e biomassa microbiana do solo. Foram conduzidos dois ensaios: no primeiro foram avaliadas a intoxicação e a massa seca das plantas de biótipos de três populações de azevém: população 1 (reconhecidamente resistente, população 2 (resistência intermediária, e população 3 (sensível ao glyphosate, submetidas a diferentes doses de glyphosate (200, 400, 800, 1.600 e 3.200 g ha-1. No segundo ensaio foram avaliados a massa seca da parte aérea, a altura de plantas, o número de folhas de azevém e a respiração e massa microbiana do solo cultivado com os biótipos resistente e sensível, com e sem aplicação de glyphosate (480 g ha-1. Aos 14 DAT, observou-se morte do biótipo sensível quando tratado com doses a partir de 200 g ha-1 de glyphosate. Nos biótipos resistentes e com nível intermediário de resistência, a toxicidade do glyphosate às plantas de azevém foi de 85% na maior dose avaliada. O biótipo resistente apresentou maior produção de massa seca da parte aérea aos 42 DAT e na rebrota, aos 72 DAT, quando comparado ao biótipo intermediário. O biótipo sensível apresentou maior altura de plantas, número de folhas e massa seca da parte aérea, em comparação ao resistente, quando não tratados com o glyphosate. Não foi observada diferença na atividade microbiana do solo entre os tratamentos avaliados.This study aimed to evaluate the resistance Italian ryegrass (L. multiflorum against glyphosate and the impact of the control of these biotypes on soil respiration and microbial biomass. Two essays were conducted: the first evaluated intoxication and dry mass of the plants of biotypes of three Italian ryegrass population (population 1 - resistant; population 2 - intermediary resistance; and population 3 - sensitive to glyphosate submitted to different glyphosate rates. The

  1. Transmission of Squash vein yellowing virus to and From Cucurbit Weeds and Effects on Sweetpotato Whitefly (Hemiptera: Aleyrodidae) Behavior.

    Science.gov (United States)

    Shrestha, D; McAuslane, H J; Adkins, S T; Smith, H A; Dufault, N; Webb, S E

    2016-08-01

    Since 2003, growers of Florida watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] have periodically suffered large losses from a disease caused by Squash vein yellowing virus (SqVYV), which is transmitted by the whitefly Middle East-Asia Minor 1 (MEAM1), formerly Bemisia tabaci (Gennadius) biotype B. Common cucurbit weeds like balsam apple (Momordica charantia L.) and smellmelon [Cucumis melo var. dudaim (L.) Naud.] are natural hosts of SqVYV, and creeping cucumber (Melothria pendula L.) is an experimental host. Study objectives were to compare these weeds and 'Mickylee' watermelon as sources of inoculum for SqVYV via MEAM1 transmission, to determine weed susceptibility to SqVYV, and to evaluate whitefly settling and oviposition behaviors on infected vs. mock-inoculated (inoculated with buffer only) creeping cucumber leaves. We found that the lowest percentage of watermelon recipient plants was infected when balsam apple was used as a source of inoculum. Watermelon was more susceptible to infection than balsam apple or smellmelon. However, all weed species were equally susceptible to SqVYV when inoculated by whitefly. For the first 5 h after release, whiteflies had no preference to settle on infected vs. mock-inoculated creeping cucumber leaves. After 24 h, whiteflies preferred to settle on mock-inoculated leaves, and more eggs were laid on mock-inoculated creeping cucumber leaves than on SqVYV-infected leaves. The transmission experiments (source of inoculum and susceptibility) show these weed species as potential inoculum sources of the virus. The changing settling preference of whiteflies from infected to mock-inoculated plants could lead to rapid spread of virus in the agroecosystem.

  2. Resistência de azevém (Lolium multiflorum ao herbicida glyphosate Resistance of italian ryegrass (Lolium multiflorum to glyphosate

    Directory of Open Access Journals (Sweden)

    E.S. Roman

    2004-06-01

    for sowing wheat under no-till system. The experimental design was a completely randomized design for the greenhouse experiment and a completely randomized block design for the field experiment. Herbicides with different mechanisms of action were evaluated on the weed control: glyphosate, glufosinate, clethodim, haloxyfop-r and diclofop, paraquat and paraquat+diuron. The results obtained under greenhouse conditions indicated the glyphosate susceptible biotype was controlled by the rate of 360 g e.a. ha-1. The resistant ryegrass biotype had no reduction in dry matter production and less than 15 % phytotoxicity caused by glyphosate up to 1,440 g e.a. ha-1. However, glyphosate rates between 1440 and 5,760 g e.a. ha-1 reduced dry matter accumulation and resulted in toxicities under45%. Under field conditions, the best Lolium multiflorum control was given by clethodim 79.2 g ha-1 and diuron + paraquat at 300+600 g ha¹, respectively. The results obtained in these studies indicated that the population was composed predominantly by a biotype resistant to EPSPs inhibitor herbicides.

  3. Epianthropochory in Mexican weed communities.

    Science.gov (United States)

    Vibrans, H

    1999-04-01

    The diaspores of the 50 most important maize field weed species (agrestals) in a traditional maize-growing area of south-central Mexico (region of Puebla and Tlaxcala) were analyzed for morphological adaptations to long-distance dispersal. Adaptations to wind-dispersal were absent and to endozoochory were minimal. Most species had no visible adaptations and are presumably transported with mud. However, about one-quarter of the taxa, particularly the tall and dominant ones, relied at least partially on burrs with hooks or awns. The possible vectors for these exo- or epizoochorous species are discussed: the most likely regular dispersers are humans (epianthropochory). Interviews with farmers confirm this conclusion. Using humans as vectors allows the plant to transport relatively large seeds to favorable habitats (directed dispersal). The importance of this relatively rare dispersal adaptation in Mexican maize field weeds leads to questions on the origin and evolution of these agrestals.

  4. Virulent Diuraphis noxia Aphids Over-Express Calcium Signaling Proteins to Overcome Defenses of Aphid-Resistant Wheat Plants.

    Science.gov (United States)

    Sinha, Deepak K; Chandran, Predeesh; Timm, Alicia E; Aguirre-Rojas, Lina; Smith, C Michael

    2016-01-01

    The Russian wheat aphid, Diuraphis noxia, an invasive phytotoxic pest of wheat, Triticum aestivum, and barley, Hordeum vulgare, causes huge economic losses in Africa, South America, and North America. Most acceptable and ecologically beneficial aphid management strategies include selection and breeding of D. noxia-resistant varieties, and numerous D. noxia resistance genes have been identified in T. aestivum and H. vulgare. North American D. noxia biotype 1 is avirulent to T. aestivum varieties possessing Dn4 or Dn7 genes, while biotype 2 is virulent to Dn4 and avirulent to Dn7. The current investigation utilized next-generation RNAseq technology to reveal that biotype 2 over expresses proteins involved in calcium signaling, which activates phosphoinositide (PI) metabolism. Calcium signaling proteins comprised 36% of all transcripts identified in the two D. noxia biotypes. Depending on plant resistance gene-aphid biotype interaction, additional transcript groups included those involved in tissue growth; defense and stress response; zinc ion and related cofactor binding; and apoptosis. Activation of enzymes involved in PI metabolism by D. noxia biotype 2 aphids allows depletion of plant calcium that normally blocks aphid feeding sites in phloem sieve elements and enables successful, continuous feeding on plants resistant to avirulent biotype 1. Inhibition of the key enzyme phospholipase C significantly reduced biotype 2 salivation into phloem and phloem sap ingestion.

  5. Precise tillage systems for enhanced non-chemical weed management

    NARCIS (Netherlands)

    Kurstjens, D.A.G.

    2007-01-01

    Soil and residue manipulation can assist weed management by killing weeds mechanically, interfering in weed lifecycles, facilitating operations and enhancing crop establishment and growth. Current tillage systems often compromise these functions, resulting in heavy reliance on herbicides,

  6. Chapter Three - Weed Dynamics and Management in Wheat

    DEFF Research Database (Denmark)

    Jabran, Khawar; Mahmood, Khalid; Melander, Bo

    2017-01-01

    pest of wheat causing in total 24% losses in wheat grain yield. In this chapter, we discuss the (i) weed flora in different wheat-growing regions of world; (ii) the yield losses caused by weeds in wheat; (iii) the preventive and cultural options for weed management; (iv) physical weed control; (v......) chemical weed control; and (vi) integrated weed management strategy in wheat. A critical analysis of recent literature indicated that broadleaved weeds are the most common group of weeds in wheat fields followed by grass weeds, while sedges were rarely noted in wheat fields. Across the globe, the most...... important weeds in wheat fields were Avena fatua L., Chenopodium album L., Phalaris minor Retz., Galium aparine L., Stellaria media (L.) Vill., and Veronica persica Poir., respectively. Adoption of wise weed management strategies may help control weeds and avoid yield losses. Both preventive measures...

  7. 不同除草剂配方组合对直播稻田抗药性杂草控制作用评价%Control Effects of Different Herbicides Combinations on the Resistance Weeds in Direct Seeding Rice Fields

    Institute of Scientific and Technical Information of China (English)

    马国兰; 柏连阳; 刘都才; 刘雪源; 陆永良; 余柳青

    2012-01-01

    为了明确不同除草剂配方组合防除直播稻田抗药性杂草的情况,于2009-2010年在洞庭湖稻区进行了田间试验.结果表明:处理后45天,二次使用二氯喹啉酸对稗草的株防效和鲜重防效仅分别为53.1%和65.5%,表明该稻区稗草对二氯喹啉酸已产生抗药性.2年的试验结果显示,除草剂配方组合1、2、3对抗药性稗草及其群落具有优良的防效,均在90%以上.通过2年的田间试验研究发现洞庭湖稻区稻田稗草对二氯喹啉酸已产生抗药性,试验中采用的3个除草剂配方组合在不同年份轮换使用,可避免或延缓新的抗药性杂草发生,具有良好的推广应用前景.%The objective of this study was to confirmed control efficacy that the different herbicides combinations were used to control the resistance weed in direct seeding rice fields in the region of Dongting Lake in 2009-2010. The results showed that, Echinohloa crusgalli (L.). Beauv. (barnyardgrass) were resistant to quinclorac in the area. The control of double use quinclorac only gave the 53.1% of barnyardgrass plant density control and 65.5% of barnyardgrass plant fresh weight control in the experiment of 2010. The three combination herbicides of 1, 2, 3 in the test gave excellent control effect to resistance barnyardgrass and its population. The control effect was more than 90% to the weed in two years experiments. The three combination herbicides were used with ring application form in different years and to avoid or delay appearing of new resistance weeds. So that, the three combination herbicides should be extension promoting in direct seeding rice area of Dongting Lake.

  8. Reproduction of Pratylenchus zeae on Weeds

    OpenAIRE

    BELLÉ,C.; KASPARY, T. E.; KUHN,P.R.; Schmitt, J.; LIMA-MEDINA, I.

    2017-01-01

    ABSTRACT Weeds can be hosts of root-lesion nematode (Pratylenchus spp.), maintaining or increasing their population in the soil. The objective of this study was to evaluate the reaction of 25 weeds species to the nematode Pratylenchus zeae. The weed plants were individually inoculated with 1,000 individuals of P. zeae and maintained in a greenhouse for 90 days. After this period, eggs and nematodes were extracted, quantified, and the reproduction factor (RF = final population/initial populati...

  9. Weeding Is Not Just for Gardeners: A Case Study on Weeding a Reference Collection

    Science.gov (United States)

    Lee, Marta

    2009-01-01

    Weeding a reference collection can be time consuming, a thankless job, and an endless task. It is a dusty job and can add to the librarian's workload. Weeding the collection can add to its currency and usability; plus it removes outdated materials. Periodically weeding allows librarians to remember what is in the collection and what can be removed…

  10. Linking Farmer Weed Management Behavior with Weed Pressure: More than Just Technology

    NARCIS (Netherlands)

    Riemens, M.M.; Groeneveld, R.M.W.; Kropff, M.J.; Lotz, L.A.P.; Renes, R.J.; Sukkel, W.; Weide, van der R.Y.

    2010-01-01

    Most studies on weed population dynamics in farming systems have focused on the effects of different weed control strategies. Those studies usually assume that farmers, operating within a particular system, have a uniform management style. However, it is likely that weed management decision making

  11. Combining a weed traits database with a population dynamics model predicts shifts in weed communities

    NARCIS (Netherlands)

    Storkey, J.; Holst, N.; Bøjer, Q.; Bigongiali, F.; Bocci, G.; Colbach, N.; Dorner, Z.; Riemens, M.M.; Sartorato, I.; Sønderskov, M.; Verschwele, A.

    2015-01-01

    A functional approach to predicting shifts in weed floras in response to management or environmental change requires the combination of data on weed traits with analytical frameworks that capture the filtering effect of selection pressures on traits. A weed traits database (WTDB) was designed, popul

  12. Integration of herbicides with manual weeding for controlling the weeds in rice under saline environment.

    Science.gov (United States)

    Hakim, M A; Juraimi, Abdul Shukor; Hanafi, M M; Rafii, Mohd Y; Ismail, Mohd Razi; Karim, S M Rezaul; Kausar, H

    2015-11-01

    The pot experiment was conducted to select appropriate integrated weed management method in rice under different salinity levels (0, 4 and 8 dS m(-1)). All the parameters including rice and weed measured were significantly influenced by weed control treatments at all salinity levels. Treatments including weed-free condition, Pretilachlor @0.375 kg ai ha(-1) + hand weeding, Propanil + Thiobencarb @ 0.9 kg ai ha(-1) and 1.8 kg ai ha(-1)+ hand weeding performed better under all salinity levels. Pretilachlor @ 0.375 kg ai ha(-1) with one round of hand weeding and propanil + thiobencarb 0.9 kg ai ha(-1) + 1.8 kg ai ha(-1) with one round of hand weeding were comparable to weed-free yields, and were superior to other treatments under salinity condition. Considering all the parameters, pretilachlor @ 0.375 kg ai ha(-1) + one round of hand weeding (at 65 DAT), propanil + thiobencarb 0.9 kg ai ha(-1) +1.8 kg ai ha(-1) + one round of hand weeding (at 65 DAT) gave the most effective control of weeds in rice under saline environments.

  13. Effect of stale seedbed preparations and subsequent weed control in lettuce (cv. Iceboll) on weed densities

    NARCIS (Netherlands)

    Riemens, M.M.; Weide, van der R.Y.; Bleeker, P.O.; Lotz, L.A.P.

    2007-01-01

    The effects of stale seedbed preparations and several weed control methods on the emergence of weeds in lettuce were studied. The specific goal was to evaluate the use of a stale seedbed in combination with chemical or mechanical weed control methods in the field. Depending on location and year,

  14. Effect of stale seedbed preparations and subsequent weed control in lettuce (cv. Iceboll) on weed densities

    NARCIS (Netherlands)

    Riemens, M.M.; Weide, van der R.Y.; Bleeker, P.O.; Lotz, L.A.P.

    2007-01-01

    The effects of stale seedbed preparations and several weed control methods on the emergence of weeds in lettuce were studied. The specific goal was to evaluate the use of a stale seedbed in combination with chemical or mechanical weed control methods in the field. Depending on location and year, sta

  15. Critical Period of Weed Control in Aerobic Rice

    OpenAIRE

    Anwar, M. P.; A. S. Juraimi; Samedani, B.; Puteh, A.; Man, A.

    2012-01-01

    Critical period of weed control is the foundation of integrated weed management and, hence, can be considered the first step to design weed control strategy. To determine critical period of weed control of aerobic rice, field trials were conducted during 2010/2011 at Universiti Putra Malaysia. A quantitative series of treatments comprising two components, (a) increasing duration of weed interference and (b) increasing length of weed-free period, were imposed. Critical period was determined th...

  16. Nutrient absorbtion of weeds in maize.

    Science.gov (United States)

    Lehoczky, E; Kismányoky, A; Nagy, P; Németh, T

    2008-01-01

    Our study was carried out in Hungary at Keszthely, in 2007. The effect of different cultivation methods: no-till drill, disk tillage, conventional tillage (ploughing) and five increasing N doses were studied on the weediness. The bi-factorial trial was arranged in split plot design with four replications. Crop rotation: winter wheat-winter wheat-maize-maize. The seeding of maize was 23rd of April in 2007. The weed survey was made with Balázs-Ujvárosi coenological method on the 17th of May. In the experiment were found 21 weed species. We collected all plants of every weed species by plots. The sample area was 1 m2. Furthermore five maize plants per plot were sampled on the 22nd of May. Maize was at 3-4 leaves stage. For reason of competition studies no herbicides were applied on sampling sites. The aerial parts of weeds and maize plants were collected, and the fresh and dry matter weight was measured. We analyzed in detail, the occurrence of weed species, and the biomass production of weeds in comparison with maize. The effect of different cultivation methods markedly demonstrated the weed cover, the number of perennial and annual weeds and the number of occurring weed species.

  17. A STUDY ON WEED CONTROL IN SOYBEAN

    Directory of Open Access Journals (Sweden)

    S. TJITROSEMITO

    1991-01-01

    Full Text Available Two field experiments on weed control in soybeans were carried out at BIOTROP, Bogor, Indonesia from February to June, 1989. The critical period for weed control was found to be between 20 - 40 days after planting of soybean (c. v. Wilis grown at a planting distance of 40 x 10 cm. It did not coincide with the fastest growth in terms of trifoliate leaf number. Further studies were suggested to understand the physiological growth of soybean related to weed control. Pendimethalin at 660- 1320 g a.e./ha applied one day after sowing did not cause any phytotoxic effect to soybean and had good weed control performance.

  18. Parthenium Weed (Parthenium hysterophorusL.)

    African Journals Online (AJOL)

    plant compounds (parthenin, chlorogenic acid, isocholorogenic acid, vanilic ... Parthenium Weed (Parthenium hysterophorus L.) Research in Ethiopia ..... other infested areas in Austaralia and America was conducted using cluster analysis.

  19. Weed detection in 3D images

    OpenAIRE

    Piron, Alexis; Van der heijden, F.; Destain, Marie-France

    2011-01-01

    Machine vision has been successfully used for mechanical destruction of weeds between rows of crops. Knowledge of the position of the rows where crops should be growing and the assumption that plants growing outside such positions are weeds may be used in such systems. However for many horticultural crops, the automatic removal of weeds from inside a row or bands of crops in which the weeds are mixed with plants in a random manner is not solved. The aim of this study was to verify that plant ...

  20. Polymorphisms in salivary-gland transcripts of Russian wheat aphid biotypes 1 and 2

    Institute of Scientific and Technical Information of China (English)

    Feng Cui; C.Michael Smith; John Reese; Owain Edwards; Gerald Reeck

    2012-01-01

    The Russian wheat aphid (RWA),Diuraphis noxia (Mordvilko) (Homoptera:Aphididae),is a major pest of small grains.As with plant-feeding aphids in general,the interaction between RWA and host plants is governed,on the insect side,by proteins and enzymes in saliva.In this work,we examined sequence variations in transcripts encoding proteins and enzymes of RWA salivary glands.We conducted reverse transcription - polymerase chain reaction in RWA biotypes 1 and 2 using primers derived from pea aphid orthoiogs,and cloned regions of 17 putative salivary gland transcripts.For four of the transcripts,we observed no difference in sequences between the two biotypes.For the other 13 transcripts,for example,the transcripts encoding sucrase,trehalase and protein C002,large amount of variations,both within each biotype and between the two biotypes,were observed.Usually the two biotypes shared only one variant,which was typically the most common variant in both biotypes.Most of the transcripts had more non-synonymous than synonymous codon changes among their variants.Our results offer possible molecular markers for distinguishing the two biotypes and insights into their evolution.

  1. Stratification requirements for seed dormancy alleviation in a wetland weed.

    Science.gov (United States)

    Boddy, Louis G; Bradford, Kent J; Fischer, Albert J

    2013-01-01

    Echinochloaoryzicola(syn.E. phyllopogon) is an exotic weed of California rice paddies that has evolved resistance to multiple herbicides. Elimination of seedlingsthroughcertain weed control methods can limit the spread of this weed, but is contingent on accurate predictions of germination and emergence timing, which are influenced by seed dormancy levels.In summer annuals, dormancy can often be relieved through stratification, a period of prolonged exposure to cold and moist conditions.We used population-based threshold models to quantify the effects of stratification on seed germination of four E. Oryzicola populations at a range of water potential (Ψ) and oxygen levels. We also determined how stratification temperatures, moisture levels and durations contributed to dormancy release. Stratification released dormancy by decreasing base Ψ and hydrotimerequired for germination and by eliminating any germination sensitivity to oxygen. Stratification also increased average germination rates (GR), which were used as a proxy for relative dormancy levels. Alternating temperatures nearly doubled GR in all populations, indicating that seeds could be partially dormant despite achieving high final germination percentages. Stratification at Ψ = 0 MPa increased GR compared to stratification at lower water potentials, demonstrating that Ψ contributed to regulating dormancy release. Maximum GR occurred after 2-4 weeks of stratification at 0 MPa; GR were often more rapid for herbicide-resistant than for herbicide-susceptible seeds, implying greater dormancy in the latter. Manipulation of field conditions to promote dormancy alleviation of E. oryzicola seeds might improve the rate and uniformity of germination for seed bank depletion through seedling weed control. Our results suggest field soil saturation in winter would contribute towards E. oryzicola dormancy release and decrease the time to seedling emergence.

  2. Development of Bemisia tabaci (Gennadius,1889 biotype B on Lycopersicon spp. genotypes

    Directory of Open Access Journals (Sweden)

    Marilene Fancelli

    2002-01-01

    Full Text Available Whiteflies are phytophagous insects, whose nymphs and adults suck the phloem sap, causing direct damage due to host plant weakness. In tomato (Lycopersicon spp. crops, they are important vectors of limiting fitoviruses. The objective of this study was to determine the effects of Lycopersicon spp. genotypes on Bemisia tabaci (Gennadius, 1889 biotype B development under greenhouse conditions. The evaluated genotypes were LA462 (L. peruvianum, LA716 (L. pennellii, LA1584 (L. pimpinellifolium, LA1609 (L. peruvianum, LA1739 (L. hirsutum, P25 (L. esculentum, PI134417 (L. hirsutum f. glabratum and Santa Clara (L. esculentum. LA716 was non-preferred for oviposition by the whitefly, which suggests an antixenotic effect. LA1584 showed an antibiotic resistance because nymphal survival was reduced and nymphal developmental time was increased. Antixenotic resistance was observed in LA1739 and PI134417, based on a reduction of oviposition. PI134417 also reduced nymphal survival, which suggests an antibiotic effect, but LA1739 was suitable for insect development. LA1609 was highly preferred for oviposition, however it reduced insect survival. P25 and Santa Clara (L. esculentum were highly preferred for oviposition.

  3. Use of multicopy transposons bearing unfitness genes in weed control: four example scenarios.

    Science.gov (United States)

    Gressel, Jonathan; Levy, Avraham A

    2014-11-01

    We speculate that multicopy transposons, carrying both fitness and unfitness genes, can provide new positive and negative selection options to intractable weed problems. Multicopy transposons rapidly disseminate through populations, appearing in approximately 100% of progeny, unlike nuclear transgenes, which appear in a proportion of segregating populations. Different unfitness transgenes and modes of propagation will be appropriate for different cases: (1) outcrossing Amaranthus spp. (that evolved resistances to major herbicides); (2) Lolium spp., important pasture grasses, yet herbicide-resistant weeds in crops; (3) rice (Oryza sativa), often infested with feral weedy rice, which interbreeds with the crop; and (4) self-compatible sorghum (Sorghum bicolor), which readily crosses with conspecific shattercane and with allotetraploid johnsongrass (Sorghum halepense). The speculated outcome of these scenarios is to generate weed populations that contain the unfitness gene and thus are easily controllable. Unfitness genes can be under chemically or environmentally inducible promoters, activated after gene dissemination, or under constitutive promoters where the gene function is utilized only at special times (e.g. sensitivity to an herbicide). The transposons can be vectored to the weeds by introgression from the crop (in rice, sorghum, and Lolium spp.) or from planted engineered weed (Amaranthus spp.) using a gene conferring the degradation of a no longer widely used herbicide, especially in tandem with an herbicide-resistant gene that kills all nonhybrids, facilitating the rapid dissemination of the multicopy transposons in a weedy population.

  4. Biotype Characterization, Developmental Profiling, Insecticide Response and Binding Property of Bemisia tabaci Chemosensory Proteins: Role of CSP in Insect Defense

    Science.gov (United States)

    Liu, Guoxia; Ma, Hongmei; Xie, Hongyan; Xuan, Ning; Guo, Xia; Fan, Zhongxue; Rajashekar, Balaji; Arnaud, Philippe; Offmann, Bernard; Picimbon, Jean-François

    2016-01-01

    Chemosensory proteins (CSPs) are believed to play a key role in the chemosensory process in insects. Sequencing genomic DNA and RNA encoding CSP1, CSP2 and CSP3 in the sweet potato whitefly Bemisia tabaci showed strong variation between B and Q biotypes. Analyzing CSP-RNA levels showed not only biotype, but also age and developmental stage-specific expression. Interestingly, applying neonicotinoid thiamethoxam insecticide using twenty-five different dose/time treatments in B and Q young adults showed that Bemisia CSP1, CSP2 and CSP3 were also differentially regulated over insecticide exposure. In our study one of the adult-specific gene (CSP1) was shown to be significantly up-regulated by the insecticide in Q, the most highly resistant form of B. tabaci. Correlatively, competitive binding assays using tryptophan fluorescence spectroscopy and molecular docking demonstrated that CSP1 protein preferentially bound to linoleic acid, while CSP2 and CSP3 proteins rather associated to another completely different type of chemical, i.e. α-pentyl-cinnamaldehyde (jasminaldehyde). This might indicate that some CSPs in whiteflies are crucial to facilitate the transport of fatty acids thus regulating some metabolic pathways of the insect immune response, while some others are tuned to much more volatile chemicals known not only for their pleasant odor scent, but also for their potent toxic insecticide activity. PMID:27167733

  5. Biotype Characterization, Developmental Profiling, Insecticide Response and Binding Property of Bemisia tabaci Chemosensory Proteins: Role of CSP in Insect Defense.

    Directory of Open Access Journals (Sweden)

    Guoxia Liu

    Full Text Available Chemosensory proteins (CSPs are believed to play a key role in the chemosensory process in insects. Sequencing genomic DNA and RNA encoding CSP1, CSP2 and CSP3 in the sweet potato whitefly Bemisia tabaci showed strong variation between B and Q biotypes. Analyzing CSP-RNA levels showed not only biotype, but also age and developmental stage-specific expression. Interestingly, applying neonicotinoid thiamethoxam insecticide using twenty-five different dose/time treatments in B and Q young adults showed that Bemisia CSP1, CSP2 and CSP3 were also differentially regulated over insecticide exposure. In our study one of the adult-specific gene (CSP1 was shown to be significantly up-regulated by the insecticide in Q, the most highly resistant form of B. tabaci. Correlatively, competitive binding assays using tryptophan fluorescence spectroscopy and molecular docking demonstrated that CSP1 protein preferentially bound to linoleic acid, while CSP2 and CSP3 proteins rather associated to another completely different type of chemical, i.e. α-pentyl-cinnamaldehyde (jasminaldehyde. This might indicate that some CSPs in whiteflies are crucial to facilitate the transport of fatty acids thus regulating some metabolic pathways of the insect immune response, while some others are tuned to much more volatile chemicals known not only for their pleasant odor scent, but also for their potent toxic insecticide activity.

  6. 植物谷胱甘肽转硫酶及其与杂草抗药性的关系%Plant Glutathione S-Transferases and Its Relation to Herbicide-Resistance of Weed

    Institute of Scientific and Technical Information of China (English)

    李岗; 吴声敢; 俞瑞鲜; 陈丽萍; 苍涛; 蔡磊明; 王强; 吴长兴

    2012-01-01

    hydrophobic foreign glutathione synthefase, glutathione - dependent isomerizarion dia-mutase, glutathione peroxidase and organic peroxidase with restore toxicity ,etc. They also protect plant cells in non - enzymatic binding manner.for example,the ligand (chaperone or carrier) of plant hormones or flavonoid as substances of endogenous poison can be combined with GSTs. Those two kinds of enzymology and non -enzymatic function are associated with of xenobiotics or endogenous poison detoxification and prevention of cells oxidative injury. Herbicide 5 - glutathionylation is one of mechanisms for evolution of herbicide. Glutathione indirectly involved in the process of weeds herbicide - resistance via peroxi-3ase function to eliminate the oxidative stress caused by herbicides.

  7. A review of the potential for competitive cereal cultivars as a tool in integrated weed management.

    Science.gov (United States)

    Andrew, I K S; Storkey, J; Sparkes, D L

    2015-06-01

    Competitive crop cultivars offer a potentially cheap option to include in integrated weed management strategies (IWM). Although cultivars with high competitive potential have been identified amongst cereal crops, competitiveness has not traditionally been considered a priority for breeding or farmer cultivar choice. The challenge of managing herbicide-resistant weed populations has, however, renewed interest in cultural weed control options, including competitive cultivars. We evaluated the current understanding of the traits that explain variability in competitive ability between cultivars, the relationship between suppression of weed neighbours and tolerance of their presence and the existence of trade-offs between competitive ability and yield in weed-free scenarios. A large number of relationships between competitive ability and plant traits have been reported in the literature, including plant height, speed of development, canopy architecture and partitioning of resources. There is uncertainty over the relationship between suppressive ability and tolerance, although tolerance is a less stable trait over seasons and locations. To realise the potential of competitive crop cultivars as a tool in IWM, a quick and simple-to-use protocol for assessing the competitive potential of new cultivars is required; it is likely that this will not be based on a single trait, but will need to capture the combined effect of multiple traits. A way needs to be found to make this information accessible to farmers, so that competitive cultivars can be better integrated into their weed control programmes.

  8. The effect of sowing strategy, row distance and mechanical weed control on weeds and yield in organic winter wheat

    OpenAIRE

    Rasmussen, Ilse A.

    2002-01-01

    A series of field experiments were carried out in winter wheat grown under organic conditions in Denmark on fields with different weed pressure. The treatments were sowing strategy (normal sowing time, late sowing and false seedbed), row distance (12 cm and 24 cm row distance) and weed control method (untreated, mechanical weed control (weed harrowing at 12 cm supplemented with row hoeing at 24 cm), and herbicide weed control). Weed biomass was largest at the normal sowing time and was reduce...

  9. Weeds in a Changing Climate: Vulnerabilities, Consequences, and Implications for Future Weed Management.

    Science.gov (United States)

    Ramesh, Kulasekaran; Matloob, Amar; Aslam, Farhena; Florentine, Singarayer K; Chauhan, Bhagirath S

    2017-01-01

    Whilst it is agreed that climate change will impact on the long-term interactions between crops and weeds, the results of this impact are far from clear. We suggest that a thorough understanding of weed dominance and weed interactions, depending on crop and weed ecosystems and crop sequences in the ecosystem, will be the key determining factor for successful weed management. Indeed, we claim that recent changes observed throughout the world within the weed spectrum in different cropping systems which were ostensibly related to climate change, warrant a deeper examination of weed vulnerabilities before a full understanding is reached. For example, the uncontrolled establishment of weeds in crops leads to a mixed population, in terms of C3 and C4 pathways, and this poses a considerable level of complexity for weed management. There is a need to include all possible combinations of crops and weeds while studying the impact of climate change on crop-weed competitive interactions, since, from a weed management perspective, C4 weeds would flourish in the increased temperature scenario and pose serious yield penalties. This is particularly alarming as a majority of the most competitive weeds are C4 plants. Although CO2 is considered as a main contributing factor for climate change, a few Australian studies have also predicted differing responses of weed species due to shifts in rainfall patterns. Reduced water availability, due to recurrent and unforeseen droughts, would alter the competitive balance between crops and some weed species, intensifying the crop-weed competition pressure. Although it is recognized that the weed pressure associated with climate change is a significant threat to crop production, either through increased temperatures, rainfall shift, and elevated CO2 levels, the current knowledge of this effect is very sparse. A few models that have attempted to predict these interactions are discussed in this paper, since these models could play an integral

  10. Dominant species of dicot-weeds and weed biodiversity in spring barley in Latvia.

    Science.gov (United States)

    Vanaga, I; Mintale, Z; Smirnova, O

    2010-01-01

    The composition of weed species in spring barley and weed biodiversity was evaluated in experiments in different growing seasons and with different previous crops. The aim of the experiments was to evaluate the composition of weed species in spring barley during a four year period in weather conditions of different growing seasons and with different previous crop as well as to assess the biodiversity in the experiments where the different groups of herbicides were applied. Over years and previous crops, the dicotyledonous weed community was dominated by Chenopodium album, followed by Viola arvensis. The herbicides from different groups had significant influences on the biodiversity of weeds.

  11. Weeds in a Changing Climate: Vulnerabilities, Consequences, and Implications for Future Weed Management

    Science.gov (United States)

    Ramesh, Kulasekaran; Matloob, Amar; Aslam, Farhena; Florentine, Singarayer K.; Chauhan, Bhagirath S.

    2017-01-01

    Whilst it is agreed that climate change will impact on the long-term interactions between crops and weeds, the results of this impact are far from clear. We suggest that a thorough understanding of weed dominance and weed interactions, depending on crop and weed ecosystems and crop sequences in the ecosystem, will be the key determining factor for successful weed management. Indeed, we claim that recent changes observed throughout the world within the weed spectrum in different cropping systems which were ostensibly related to climate change, warrant a deeper examination of weed vulnerabilities before a full understanding is reached. For example, the uncontrolled establishment of weeds in crops leads to a mixed population, in terms of C3 and C4 pathways, and this poses a considerable level of complexity for weed management. There is a need to include all possible combinations of crops and weeds while studying the impact of climate change on crop-weed competitive interactions, since, from a weed management perspective, C4 weeds would flourish in the increased temperature scenario and pose serious yield penalties. This is particularly alarming as a majority of the most competitive weeds are C4 plants. Although CO2 is considered as a main contributing factor for climate change, a few Australian studies have also predicted differing responses of weed species due to shifts in rainfall patterns. Reduced water availability, due to recurrent and unforeseen droughts, would alter the competitive balance between crops and some weed species, intensifying the crop-weed competition pressure. Although it is recognized that the weed pressure associated with climate change is a significant threat to crop production, either through increased temperatures, rainfall shift, and elevated CO2 levels, the current knowledge of this effect is very sparse. A few models that have attempted to predict these interactions are discussed in this paper, since these models could play an integral

  12. Ecological weed management by cover cropping : effects on weed growth in autumn and weed establishment in spring

    NARCIS (Netherlands)

    Kruidhof, H.M.; Bastiaans, L.; Kropff, M.J.

    2008-01-01

    Cover crops grown in the period between two main crops have potential as an important component of a system-oriented ecological weed management strategy. In late summer and autumn, the cover crop can suppress growth and seed production of weeds, whereas the incorporation of cover crop residues in sp

  13. Effects of Planting Date, Time and Methods of Weed Control on Weed Density and Biomass in Cumin Fields

    Directory of Open Access Journals (Sweden)

    R. Ghorbani

    2011-01-01

    Full Text Available Abstract Two field experiments were carried out in order to evaluate the effect of planting date, method and date of weed control on weed density and biomass in the experimental research field, Faculty of Agriculture, Ferdowsi University of Mashhad, during 2006 and 2007. Treatments included planting date (30 December, 20 January and 30 February, weeding date (first true leaf, start of branching and beginning of flowering stages and weed control methods (hand weeding, fire treatment and control. The results showed that there were significant differences in the number of weeds between different sowing dates, weeding dates and control methods. The highest mean density and biomass of weeds were obtained on the planting date, 30 February, and when weed was controlled at the first leaf appearance stage with fire treatment. The most appropriate time for weed control was at the beginning of cumin flowering. Fire treatment reduced weed growth in the first half of growing season. However, hand weeding significantly reduced weed density and biomass in the second half of cumin growing season. The first planting date caused the lowest mean weed biomass and the highest cumin yield compared to later planting dates. Hand weeding treatment contained lower mean weed density and biomass compared to fire treatment, however, cumin yield was lower in hand weeding plots than fire treatment. Keywords: Cultural control, Cuminum cyminum, Fire, Hand weeding, Control time

  14. WEED SURVEYING OF PHACELIA (PHACELIA TANACETIFOLIA L.) AND EVALUATING THE EFFICIENCY OF THE WEED CONTROL.

    Science.gov (United States)

    Horváth, E; Szabó, R

    2014-01-01

    The experiment was set up in an area of 9 ha that was split into 4 plots: in plot 1 the row spacing was 12 cm and the seeding rate was 10 kg; in plot 2 the row spacing was 24 cm and the seeding rate was 10 kg; in plot 3 the row spacing was 24 cm and the seeding rate was 8 kg; in plot 4 the row spacing was 12 cm and the seeding rate was 8 kg. After the weed surveying, the total weed coverage was established as follows: in plot 1 the total weed coverage was 11.34%, in plot 2 it was 12.3%, in plot 3 it was 18%, and in plot 4 the total weed coverage was 15%. Based on the weed survey, on the test area the following dicotyledon weeds belonging to the T4 Raunkiaer plant life-form category occupied the highest percentage: heal-all, black-bindweed, goosefoot. The proportion of the perennial dicotyledons: field bindweed (G3), tuberous pea (G1), white campion (H3) was negligible. In all four cases the weed control was executed using the same herbicide in the same doses and with regard to the weed species it showed the same level of efficiency. The smaller row spacing and higher seeding rate has a beneficial effect on the weed suppressing capacity of the crop, the crop's weed suppressing capacity is better and the development of the weeds becomes worse.

  15. IMPORTANCE OF CRITICAL PERIOD OF WEED COMPETITION FOR CROP GROWING

    Directory of Open Access Journals (Sweden)

    Marijana Ivanek-Martinčić

    2010-06-01

    Full Text Available A concept of critical period of weed competition has been introduced for more than 40 years ago. The concept is based on the assumption that weeds are not equally harmful to a crop during the whole season and that there is a period in crop development in which weeds impact on the yield is the biggest. This period is called critical period of weed competition (CPWC, critical period of weed interference, or critical period of weed control. There is a difference in CPWC between crops, but CPWC for a certain crop can vary a lot because it depends on many factors which can affect the crop or weeds competition ability. The critical period of weed competition identification is essential for integrated weed control and precise planning of a weed control strategy as well as for rationale use of herbicides and other weed control measures.

  16. Preventing and Weeding Application Technology of Farmland Weeds%浅议农田杂草的防除应用技术

    Institute of Scientific and Technical Information of China (English)

    张惠良

    2011-01-01

    Now weeding of farmland more and more depend on chemicals, which inevitably results in environment (soil, water, etc.) pollution and ecological destruction, and weeds resistant. Weeding using agricultural practices is environmental protected, cheap, efficient and is worth promoting strongly.%现在农田杂草的防除越来越依赖化学除草,这就不可避免地出现了环境(土壤、水源等)被污染、生态被破坏、杂草产生抗药性等问题.采用农业措施防除杂草具有环保、廉价、高效的优点,值得大力推广.

  17. Weeding the Library Media Center Collections.

    Science.gov (United States)

    Buckingham, Betty Jo

    These guidelines for weeding library media collections are addressed to elementary and secondary school library media centers and to community college and vocational school library resource centers in Iowa. The publication includes some philosophy about weeding, and specific guidelines are summarized in bold-faced type for ease of use. The…

  18. Obsolescence, Weeding, and the Utilization of Space.

    Science.gov (United States)

    Lancaster, F. W.

    1988-01-01

    Suggests an objective approach to weeding library materials and discusses ways of measuring obsolescence and of controlling variables to provide a true picture of aging. Weeding is shown to improve space utilization and the quality of a collection. (5 references) (MES)

  19. Weeded Books Inspire Student Art Projects

    Science.gov (United States)

    Lincoln, Margaret

    2004-01-01

    The rationale behind weeding books is to remove dated, obsolete, erroneous material and worn books in disrepair from the collection to make room for current titles. Students of Lakeview have discovered an innovative idea of creating an altered book from the weeded book by taking a hardcover book and changing the original cover by means of a…

  20. Weed Recognition Framework for Robotic Precision Farming

    DEFF Research Database (Denmark)

    Kounalakis, Tsampikos; Triantafyllidis, Georgios; Nalpantidis, Lazaros

    2016-01-01

    In this paper, we introduce a novel framework which applies known image features combined with advanced linear image representations for weed recognition. Our proposed weed recognition framework, is based on state-of-the-the art object/image categorization methods exploiting enhanced performance ...

  1. Weeds as important vegetables for farmers

    NARCIS (Netherlands)

    Cruz Garcia, G.S.; Price, L.L.

    2012-01-01

    The objective of this study was to investigate the multiple uses and cognitive importance of edible weeds in Northeast Thailand. Research methods included focus group discussions and freelistings. A total of 43 weeds consumed as vegetable were reported, including economic, naturalized, agricultural

  2. An autonomous weeding robot for organic farming

    NARCIS (Netherlands)

    Bakker, T.; Asselt, van C.J.; Bontsema, J.; Müller, J.; Straten, van G.

    2006-01-01

    The objective of this research is the replacement of hand weeding in organic farming by a device working autonomously at ¯eld level. The autonomous weeding robot was designed using a structured design approach, giving a good overview of the total design. A vehicle was developed with a diesel engine,

  3. Weed detection in 3D images

    NARCIS (Netherlands)

    Piron, A.; Heijden, van der F.; Destain, M.F.

    2011-01-01

    Machine vision has been successfully used for mechanical destruction of weeds between rows of crops. Knowledge of the position of the rows where crops should be growing and the assumption that plants growing outside such positions are weeds may be used in such systems. However for many horticultural

  4. Weed management strategies for castor bean crops

    Directory of Open Access Journals (Sweden)

    Augusto Guerreiro Fontoura Costa

    2014-04-01

    Full Text Available Castor bean crops are agriculturally relevant due to the quality and versatility of their oil, both for the chemical industry and for biodiesel production. Proper weed management is important for both the cultivation and the yield of castor bean crops; therefore, the intention of the present work is to review pertinent information regarding weed management, including the studies regarding weed interference periods, chemical controls for use in different crop production systems and herbicide selectivity, for castor bean crops. Weed science research for castor bean crops is scarce. One of the main weed management challenges for castor bean crops is the absence of herbicides registered with the Ministry of Agriculture, Livestock and Food Supply (MALFS. Research for viable herbicides for weed control in castor bean crops should be directed by research and/or rural extension institutions, associations and farmers cooperatives, as well as by manufactures, for the registration of these selective herbicides, which would be primarily used to control eudicotyledons in castor bean crops. New studies involving the integration of weed control methods in castor bean also may increase the efficiency of weed management, for both small farmers using traditional crop methods in the Brazilian Northeast region, as well as for areas with the potential for large scale production, using conservation tillage systems, such as the no-tillage crop production system.

  5. Weeds as important vegetables for farmers

    NARCIS (Netherlands)

    Cruz Garcia, G.S.; Price, L.L.

    2012-01-01

    The objective of this study was to investigate the multiple uses and cognitive importance of edible weeds in Northeast Thailand. Research methods included focus group discussions and freelistings. A total of 43 weeds consumed as vegetable were reported, including economic, naturalized, agricultural

  6. An autonomous weeding robot for organic farming

    NARCIS (Netherlands)

    Bakker, T.; Asselt, van C.J.; Bontsema, J.; Müller, J.; Straten, van G.

    2006-01-01

    The objective of this research is the replacement of hand weeding in organic farming by a device working autonomously at ¯eld level. The autonomous weeding robot was designed using a structured design approach, giving a good overview of the total design. A vehicle was developed with a diesel engine,

  7. Diversifying cereal-based rotations to improve weed control. Evaluation with the AlomySys model quantifying the effect of cropping systems on a grass weed

    Directory of Open Access Journals (Sweden)

    Colbach Nathalie

    2010-09-01

    Full Text Available Simplified rotations often select weed flora consisting of one or several dominant species. In rotations consisting mainly of winter cereals, one of the most frequent weeds in Atlantic European countries is blackgrass (Alopecurus myosuroides Huds.. In order to reduce environmental impacts and avoid the selection of herbicide-resistant populations, alternative weed management strategies are necessary. The objective of the present study was to develop a methodology for using a weed dynamics model called ALOMYSYS for evaluating prospective diversified crop rotations based on expert opinion. These prospective rotations were developed for a particular region aiming at reducing herbicide use while keeping weed infestation similar to that in current cropping systems. The prospective systems were also evaluated economically by calculating costs and margins for the farmer. The simulations showed that the more diverse the rotation, the better blackgrass was controlled and the less herbicides (rates and frequencies were necessary. Optimal herbicide spraying conditions and mouldboard ploughing were also less essential in diverse rotations. It was though essential to reason herbicide programs over the whole rotation and not simply as function of the preceding crop. The economic evaluation identified the interest of spring or winter pea either replacing or preceding oilseed rape (OSR in OSR/wheat/barley rotations.

  8. Biological and Agricultural Studies on Application of Discharge Plasma and Electromagnetic Fields 4. Destruction of Weeds by High Voltage Discharge

    Science.gov (United States)

    Mizuno, Akira

    In an attempt to replace chemicals for weed control, high voltage spark discharge has been applied. With the application of high voltage, discharge takes place, and current flows through the stem and root. Microscopic observation indicates that cells are damaged. The electrical resistance of the damage plant’s stems and roots decreased significantly. Several different types of apparatus were constructed, and field test results show the effectiveness of electrical discharge for weed control.

  9. Impact of atrazine prohibition on the sustainability of weed management in Wisconsin maize production.

    Science.gov (United States)

    Dong, Fengxia; Mitchell, Paul D; Davis, Vince M; Recker, Ross

    2017-02-01

    Controversy has surrounded atrazine owing to its susceptibility to leaching and run-off, with regular calls for a ban or restrictions on its use. In the context of a decreasing trend in the percentage of US maize using no-till since 2008, coinciding with the trend of glyphosate-resistant weeds becoming problematic in the Midwestern United States, we empirically examine how atrazine use restrictions have impacted the diversity of weed management practices used by Wisconsin maize farmers. Using survey data from farms inside and outside atrazine prohibition areas, we found that prohibiting atrazine did not directly impact tillage practices, but rather it increased the adoption of herbicide-resistant seed, which then increased adoption of conservation tillage systems. We also found that prohibiting atrazine and using herbicide-resistant seed reduced the number of herbicide sites of action used. The results indicate that prohibiting atrazine reduced the diversity of weed management practices, which increased the risk of herbicide resistance. Our concern is that a regulatory policy to address one issue (atrazine in groundwater) has induced farmer responses that increase problems with another issue (herbicide-resistant weeds) that longer term will contribute to water quality problems from increased soil erosion and offset the initial benefits. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  10. Experience with GOLTIX® TITAN® controlling annual dicotyledonous weeds in beets

    Directory of Open Access Journals (Sweden)

    Fell, Martina

    2014-02-01

    Full Text Available The herbicide GOLTIX® TITAN® is the unique combination of two active ingredients, Metamitrone (525 g/L and Quinmerac (40 g/L. GOLTIX® TITAN® is used for the control of annual dicotyledonous weeds in sugar and fodder beets. Registration was granted for the post emergence splitting application with 3 x 2,0 L/ha (3 applications. This corresponds to the amount of 3150 g Metamitrone and 240 g Quinmerac per hectare at maximum application rate. The registration application for pre-emergence application has been submitted. Several field trials were carried out between 2009 and 2013. These trials revealed the optimized efficacy on important weeds in sugar beet production including Fool´s parsley (Aethusa cynapium, Cleavers (Gallium aparine and Fat-hen (Chenopodium album. Selectivity was examined in all of these trials and showed good results with all relevant mixtures at all application times. The two active ingredients have different modes of action; hence, the product plays an important role in resistance management. They can be applied flexibly and do not have any known negative influence on the environment. The successful formulation of this highly sophisticated sugar beet herbicide was confirmed by the available trial results. GOLTIX® TITAN® with its specified characteristics is the base for every weed control measure.

  11. Serological characterization of Actinobacillus pleuropneumoniae biotype 1 strains antigenically related to both serotypes 2 and 7

    DEFF Research Database (Denmark)

    Nielsen, R.; Andresen, Lars Ole; Plambeck, Tamara

    1996-01-01

    Nine Danish Actinobacillus pleuropneumoniae biotype 1 isolates were shown by latex agglutination and indirect haemagglutination to possess capsular polysaccharide epitopes identical to those of serotype 2 strain 1536 (reference strain of serotype 2) and strain 4226 (Danish serotype 2 strain...

  12. Applicability of the Moyers' Probability Tables in Adolescents with Different Facial Biotypes.

    Science.gov (United States)

    Carrillo, Jorge J Pavani; Rubial, Maria C; Albornoz, Cristina; Villalba, Silvina; Damiani, Patricia; de Cravero, Marta Rugani

    2017-01-01

    The Moyers' probability tables are used in mixed dentition analysis to estimate the extent of space required for the alignment of canines and premolars, by correlating the mesiodistal size of lower incisors with the size of permanent canines and premolars. This study intended to evaluate the applicability of the Moyer's probability tables for predicting the mesiodistal space needed for the correct location of premolars and permanent canines non-erupted, in adolescents of the city of Cordoba, Argentina, who show different facial biotypes. Models and tele-radiographies of 478 adolescents of both genders from 10 to 15 years of age were analyzed. The tele-radiographies were measured manually in order to determine the facial biotype. The models were scanned with a gauged scanner (HP 3670) and measured by using Image Pro Plus 4.5 software. According to this study, the comparison between the Moyer´s probability table, and the table created at the National University of Córdoba (UNC) (at 95%, 75%, and 50%) shows that, in both tables, a higher value of mesiodistal width of lower incisors corresponds to a bigger difference in the space needed for permanent canines and premolars; being the need for space for permanents canines and premolars bigger in the UNC´s table. On the other hand, when contrasting the values of mesiodistal space for permanent canines and premolars associated with each facial biotype, the discrepancies between groups were not statistically significant (P >0.05). However, we found differences in the size of the space required according to the mesiodistal width range of the lower incisors for each biotype: a) The comparison of lower-range values, with a mesialdistal width of lower incisors less than 22 mm, the space required for permanent canines and premolars resulted smaller in patients with dolichofacial biotype than in patients with mesofacial and braquifacial biotypes. The latter biotypes have meager differences between them. b) The comparison of

  13. Comparison of outer membrane protein and biochemical profiles of Haemophilus aegyptius and Haemophilus influenzae biotype III.

    OpenAIRE

    Carlone, G M; Sottnek, F O; Plikaytis, B. D.

    1985-01-01

    Haemophilus aegyptius and Haemophilus influenzae biotype III are morphologically and biochemically similar; however, their outer membrane protein (Sarkosyl insoluble) profiles are distinct. Of 18 strains of H. aegyptius examined, 15 had a type 1 protein profile, and 3 had a type 2 profile, whereas the 5 strains of H. influenzae biotype III examined had three other protein profile types. All Haemophilus strains examined had 31- and 76-kilodalton (kDa) proteins and minor proteins with molecular...

  14. Weed control changes and genetically modified herbicide tolerant crops in the USA 1996–2012

    Science.gov (United States)

    Brookes, Graham

    2014-01-01

    Crops that have been genetically modified (GM) to be tolerant to herbicides have been widely grown in the USA since 1996. The rapid and widespread adoption of this technology reflects the important economic and environmental benefits that farmers have derived from its use (equal to $21.7 billion additional farm income and a 225 million kg reduction in herbicide active ingredient use 1996–2012). During this time, weed control practices in these crops relative to the ‘conventional alternative’ have evolved to reflect experience of using the technology, the challenges that have arisen and the increasing focus in recent years on developing sustainable production systems. This paper examines the evidence on the changing nature of herbicides used with these crops and in particular how farmers addressed the challenge of weed resistance. The evidence shows that use of the technology has resulted in a net reduction in both the amount of herbicide used and the associated environmental impact, as measured by the EIQ indicator when compared to what can reasonably be expected if the area planted to GM HT crops reverted to conventional production methods. It also facilitated many farmers being able to derive the economic and environmental benefits associated with switching from a plough-based to a no tillage or conservation tillage production system. In terms of herbicide use, the technology has also contributed to a change the profile of herbicides used. A broad range of, mostly selective herbicides has been replaced by one or 2 broad-spectrum herbicides (mostly glyphosate) used in conjunction with one or 2 other (complementary) herbicides. Since the mid-2000s, the average amount of herbicide applied and the associated environmental load, as measured by the EIQ indicator, have increased on both GM HT and conventional crops. A primary reason for these changes has been increasing incidence of weed species developing populations resistant to herbicides and increased

  15. Weed control changes and genetically modified herbicide tolerant crops in the USA 1996-2012.

    Science.gov (United States)

    Brookes, Graham

    2014-01-01

    Crops that have been genetically modified (GM) to be tolerant to herbicides have been widely grown in the USA since 1996. The rapid and widespread adoption of this technology reflects the important economic and environmental benefits that farmers have derived from its use (equal to $21.7 billion additional farm income and a 225 million kg reduction in herbicide active ingredient use 1996-2012). During this time, weed control practices in these crops relative to the 'conventional alternative' have evolved to reflect experience of using the technology, the challenges that have arisen and the increasing focus in recent years on developing sustainable production systems. This paper examines the evidence on the changing nature of herbicides used with these crops and in particular how farmers addressed the challenge of weed resistance. The evidence shows that use of the technology has resulted in a net reduction in both the amount of herbicide used and the associated environmental impact, as measured by the EIQ indicator when compared to what can reasonably be expected if the area planted to GM HT crops reverted to conventional production methods. It also facilitated many farmers being able to derive the economic and environmental benefits associated with switching from a plough-based to a no tillage or conservation tillage production system. In terms of herbicide use, the technology has also contributed to a change the profile of herbicides used. A broad range of, mostly selective herbicides has been replaced by one or 2 broad-spectrum herbicides (mostly glyphosate) used in conjunction with one or 2 other (complementary) herbicides. Since the mid-2000s, the average amount of herbicide applied and the associated environmental load, as measured by the EIQ indicator, have increased on both GM HT and conventional crops. A primary reason for these changes has been increasing incidence of weed species developing populations resistant to herbicides and increased awareness of

  16. Distinguishing suitable biotypes of Dactylopius tomentosus (Hemiptera: Dactylopiidae) for biological control of Cylindropuntia fulgida var. fulgida (Caryophyllales: Cactaceae) in South Africa.

    Science.gov (United States)

    Mathenge, C W; Holford, P; Hoffmann, J H; Zimmermann, H G; Spooner-Hart, R; Beattie, G A C

    2009-12-01

    Cylindropuntia fulgida (Engelmann) F.M. Knuth var. fulgida (Engelmann) F.M. Knuth (Cff) (Caryophyllales: Cactaceae) is native to Mexico and Arizona and was introduced into South Africa for ornamental purposes. It subsequently became highly invasive, necessitating control. The cochineal insect, Dactylopius tomentosus (Lamarck) (Hemiptera: Dactylopiidae), was selected as a potential biological control agent based on its restricted host range among Cylindropuntia species and previous success in controlling C. imbricata (DC.) F. Knuth (Ci). Eight D. tomentosus provenances (Cholla, Cholla E, Fulgida, Mamillata, Imbricata, Tunicata U, Tunicata V and Rosea) from Cylindropuntia species in their native ranges were reared on Cff, whilst Cholla and Imbricata were also reared on Ci. Large differences were found in the development and survival of crawlers, and in the reproductive capacity of females. Three subjective categories of provenance interaction with host plants were identified based on a fitness index (FI) calculated from data relating to crawler survival, female development time and fecundity: (i) thriving (FI > or = 1) - insects had shorter developmental times, high crawler survival and highly fecund females (Cholla); (ii) surviving (FI0) - insects had extended development times, low crawler survival and low fecundity (Imbricata, Fulgida and Mamillata); and (iii) dying (FI = 0) - insects died before or at the second instar (Rosea, Tunicata U and Tunicata V). Cholla, therefore, is highly suitable for biological control of Cff in South Africa. In addition, Cholla thrived on Cff but only survived on Ci whilst, in contrast, Imbricata thrived on Ci but only survived on Cff. This differential ability of provenances to thrive or survive on different host plants demonstrated that host adapted biotypes of D. tomentosus exist; therefore, biotypes should be taken into account when considering this species as a biological control agent of cactus weeds.

  17. Effect of Cultural Practices in Night on Weed Density and Weed Dry Matter

    Directory of Open Access Journals (Sweden)

    M.H Rashed Mohasel

    2011-01-01

    Full Text Available Abstract In order to evaluate the response of weed seeds to light, two experiments, at two different locations were conducted at Ferdowsi university of Mashhad in 2009. At the first experiment, field was ploughed in day and night. Weed density was evaluated 70 d after plough, with 1×1 quadrate. At the second experiment, at night treatment, ploughing, potato planting and weeding with cultivator were done at night. Weed sampling was done twice at 43 and 130 days after planting with 1×1 quadrate and weeds were identified and counted. Result showed pigweed (Amaranthus retroflexus L., sowthistle (Sonchus oleraceus L., crabgrass (Digitaria sanguinalis (L. scop, jimsonweed (Datura stramonium L. and mallow (Hibiscus trionum L. did not observed at night plough, in contrast, night plough has no significance influence on common lambsquarters (Chenopodium album L., and black nightshade (Solanum nigrum L.. Only common lambsquarters had similar appearance in two treatments, indicating insusceptibility of this weed to time of plough. Interestingly, at the second experiment, result was very similar. Potato yield was higher at night treatment, but not significant. This research showed that some cultural practice like plough, planting and weeding with cultivator in night can reduce weed density and weed dry matter. Keywords: Germination, Time of plough, Sustainable weeds management, Light

  18. Adapting weed management in rice to changing climates

    NARCIS (Netherlands)

    Rodenburg, J.; Meinke, H.B.

    2011-01-01

    This paper provides some of the scientific background on how projected environmental conditions could affect weeds and weed management in rice in Africa. Elevated CO2 levels may have positive effects on rice competitiveness with C4 weeds, but these are generally outnumbered by C3 species in weed pop

  19. Competitive oats for integrated weed management and organic rotations

    OpenAIRE

    Fradgley, Nick

    2014-01-01

    Using a competitive crop like oats is essential for integrated management of weed problems. Oats can compete well with weeds through efficient nutrient uptake, allelopathy and canopy cover shading. Weeds are suppressed by the crops tillering ability and varieties with good canopy cover. Some varieties can tolerate weeds better by having both good canopy cover and height.

  20. A rotational framework to reduce weed density in organic systems

    Science.gov (United States)

    Weeds are a major obstacle to successful crop production in organic farming. Producers may be able to reduce inputs for weed management by designing rotations to disrupt population dynamics of weeds. Population-based management in conventional farming has reduced herbicide use 50% because weed den...

  1. Weed Garden: An Effective Tool for Extension Education

    Science.gov (United States)

    Beck, Leslie; Patton, Aaron J.

    2015-01-01

    A weed garden was constructed to quantify and improve identification skills among clientele. The garden was planted with over 100 weed species based on surveys on problematic weeds. The weed garden proved useful for introducing additional hands-on learning activities into traditional lecture-based seminars. Through seminar and field day attendee…

  2. Delivering the barebones for designing more weed suppressive crop rotations

    NARCIS (Netherlands)

    Bastiaans, L.; Berghuijs, H.N.C.

    2011-01-01

    Even though crop rotation is often regarded as an important component of weed management, tools for optimising the weed-suppressive character of crop rotations are lacking. The long-term character of this strategy and the variety of weed-promoting and weed-suppressing conditions and events that are

  3. Weed Garden: An Effective Tool for Extension Education

    Science.gov (United States)

    Beck, Leslie; Patton, Aaron J.

    2015-01-01

    A weed garden was constructed to quantify and improve identification skills among clientele. The garden was planted with over 100 weed species based on surveys on problematic weeds. The weed garden proved useful for introducing additional hands-on learning activities into traditional lecture-based seminars. Through seminar and field day attendee…

  4. Clinical Considerations on the Root Coverage of Gingival Recessions in Thin or Thick Biotype.

    Science.gov (United States)

    Kahn, Sergio; Almeida, Renato Alves da Rocha; Dias, Alexandra Tavares; Rodrigues, Walmir Júnior; Barceleiro, Marcos Oliveira; Taba, Mario

    2016-01-01

    Gingival biotype is a clinical term used to describe the thickness of the gingiva. It has been classified as being thick or thin and may be related to the clinical outcome of root coverage procedures. This study evaluated the impact of gingival biotype on the clinical outcome of root coverage procedures following subepithelial connective tissue graft plus coronally positioned flap. A total of 19 patients, 10 with thin and 9 with thick gingival biotype, were treated for localized Miller Class I or II gingival recessions. After 6 months, 14 patients achieved complete root coverage, 7 from each group. The overall mean pooled root coverage rate was 90.93%. The thin biotype cases yielded a reduced mean root coverage of 88.51% compared with 93.63% for patients who had the thick biotype classification. Although the thin gingival biotype may impair the clinical outcome of root coverage procedures, this limitation does not appear to have a strong influence on the success of the root coverage therapy when subepithelial connective tissue graft was associated with the coronal positioning of the flap.

  5. Characterization of Yersinia enterocolitica biotype 1A strains isolated from swine slaughterhouses and markets.

    Science.gov (United States)

    Paixão, Renata; Moreno, Luisa Zanolli; Sena de Gobbi, Débora Dirani; Raimundo, Daniele Cristine; Hofer, Ernesto; Matté, Maria Helena; Ferreira, Thais Sebastiana Porfida; de Moura Gomes, Vasco Tulio; Costa, Barbara Leticia Pereira; Moreno, Andrea Micke

    2013-01-01

    Yersinia enterocolitica is an important foodborne pathogen that causes illness in humans and animals. Y. enterocolitica is also the most heterogeneous species of the genus and is divided into distinct serotypes and over six biotypes. Y. enterocolitica biotype 1A strains are classically considered as nonpathogenic; however, some biotype 1A isolates have been considered as causative of gastrointestinal disease, yielding symptoms indistinguishable from those produced by pathogenic biotypes. Even after decades of isolation of clinical strains, the pathogenic mechanisms of these isolates are still not fully understood. In the present study, 122 Yersinia enterocolitica biotype 1A strains isolated from swine slaughterhouses and meat markets in Sao Paulo, Brazil, were characterized according to the presence of the virulence genes ail, virF, and ystA. A total of 94 strains were positive to at least one virulence gene (77.05%), and 67 were positive to all of them (54.92%). Twenty-two strains were submitted to PFGE genotyping resulting in 22 distinct pulsotypes, varying from 50% to 84% of genetic similarity. Any clustering tendency among pulsotypes related to origin, isolation site, or even virulence profile was not observed. The present study reports an important contamination of the environment in swine slaughterhouses, meat markets, and pork, by potentially virulent Y. enterocolitica biotype 1A.

  6. Characterization of Yersinia enterocolitica Biotype 1A Strains Isolated from Swine Slaughterhouses and Markets

    Directory of Open Access Journals (Sweden)

    Renata Paixão

    2013-01-01

    Full Text Available Yersinia enterocolitica is an important foodborne pathogen that causes illness in humans and animals. Y. enterocolitica is also the most heterogeneous species of the genus and is divided into distinct serotypes and over six biotypes. Y. enterocolitica biotype 1A strains are classically considered as nonpathogenic; however, some biotype 1A isolates have been considered as causative of gastrointestinal disease, yielding symptoms indistinguishable from those produced by pathogenic biotypes. Even after decades of isolation of clinical strains, the pathogenic mechanisms of these isolates are still not fully understood. In the present study, 122 Yersinia enterocolitica biotype 1A strains isolated from swine slaughterhouses and meat markets in Sao Paulo, Brazil, were characterized according to the presence of the virulence genes ail, virF, and ystA. A total of 94 strains were positive to at least one virulence gene (77.05%, and 67 were positive to all of them (54.92%. Twenty-two strains were submitted to PFGE genotyping resulting in 22 distinct pulsotypes, varying from 50% to 84% of genetic similarity. Any clustering tendency among pulsotypes related to origin, isolation site, or even virulence profile was not observed. The present study reports an important contamination of the environment in swine slaughterhouses, meat markets, and pork, by potentially virulent Y. enterocolitica biotype 1A.

  7. Susceptibility of MED-Q1 and MED-Q3 Biotypes of Bemisia tabaci (Hemiptera: Aleyrodidae) Populations to Essential and Seed Oils.

    Science.gov (United States)

    Samuel Fogné, Drabo; Olivier, Gnankine; Bassolé, Imael H N; Nébié, Roger Charles; Laurence, Mouton

    2017-06-01

    Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a major pest of many agricultural and ornamental crops in tropical and subtropical regions causing damages that result in important economic losses. Insecticides are commonly used in greenhouses or fields to control B. tabaci populations leading to rapid evolution of resistance that render treatments inefficient. Therefore, and for environmental and human health concerns, other approaches must be developed for this pest management. In the present study, we compare, using the leaf dip method, the toxicity of three essential oils (Cymbopogon citratus, Ocimum americanum, and Hyptis spicigera) and three seed oils (Lannea microcarpa, Lannea acida, and Carapa procera) with three chemical insecticides (acetamiprid, deltamethrin, and chlorpyrifos-ethyl) on adults. Two B. tabaci biotypes (MED-Q1 and MED-Q3) belonging to the Mediterranean species and collected in Burkina Faso were used. Essential oils were analyzed by gas chromatography-mass spectrometry and gas chromatography-flame ionization detector. We showed that these two biotypes have different levels of resistance to the three insecticides, MED-Q3 being more sensitive than MED-Q1. Moreover, they differ in the frequency of resistance alleles to insecticides, especially for organophosphates, as these alleles are almost fixed in MED-Q1. On the other hand, the two biotypes prove to be more susceptible to the plant extracts than to insecticides except for chlorpyrifos-ethyl, with essential oils that showed the highest insecticidal activities. Monoterpenes content were the most abundant and showed the highest insecticidal activities. Our results indicated that essential oils, but also seed oils, have the potential to constitute an alternative strategy of pest management. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  8. Vaccine Induced Specific Protection Against Enteric Red Mouth Disease (ERM) Caused by Yersinia Ruckeri Serotype 1 Biotype 2

    DEFF Research Database (Denmark)

    Deshmukh, Sidharta; Raida, Martin K.; Dalsgaard, Inger;

    2011-01-01

    In European fish farms there is evidence of enteric red mouth disease (ERM) outbreaks in previously vaccinated farmed fish. It has been suggested that the occurrence of a Yersinia ruckeri variant (biotype 2) may explain this situation. Recent development of commercial vaccines has included both......) developed against ERM was investigated following intraperitoneal (IP) challenge with Yersinia ruckeri serotype1 biotype 2. Fish were immersion vaccinated for 30 s and challenged 2, 4 and 6 months post vaccination. The onset and severity of various pathological lesions along with their disappearance during...... biotype 1 and 2. In this study, the specificity of immune protection extended by three commercial vaccines viz; AQUAVAC ERM® Intervet Schering Plough (based on biotype 1 only), ERMOGEN VET® Novartis (based on biotype 1 only) and AQUAVAC RELERA® Intervet Schering Plough (based on both biotype 1and 2...

  9. Community structure affects annual grass weed invasion during restoration of a shrub-steppe ecosystem

    Science.gov (United States)

    Phil S. Allen; Susan E. Meyer

    2014-01-01

    Ecological restoration of shrub-steppe communities in the western United States is often hampered by invasion of exotic annual grasses during the process. An important question is how to create restored communities that can better resist reinvasion by these weeds. One hypothesis is that communities comprised of species that are functionally similar to the invader will...

  10. Biological weed control with soil fungi? Antagonistic effects of arbuscular mycorrhizal fungi on the growth of weeds

    NARCIS (Netherlands)

    Veiga, R.

    2012-01-01

    Excessive weed growth represents one of the major threats to crop production especially when reliance on herbicides is reduced. Biological weed control is an alternative, environmentally-sound method that, combined with other weed control practices, can contribute to an effective weed management in

  11. [Effects of weeding methods on weed community and its diversity in a citrus orchard in southwest Zhejiang].

    Science.gov (United States)

    Yao, He-Jin; Jin, Zong-Lai; Yang, Wei-Bin; Zhao, Jian-Hua; Zhang, Fan

    2010-01-01

    By using the research methods of ecological community, the effects of different weed management strategies including chemical weeding, manual weeding, and their combination on the weed community and its diversity in a citrus chard of main orange producing region in Quzhou City, Zhejiang Province were studied from June 2005 to May 2008. In control plots, there were 75 species and 25 families of weeds; after chemical weeding, manual weeding, and their combination, there were 46 species and 17 families, 59 species and 20 families, and 51 species and 18 families of weeds, respectively. The Margalef's species richness index, Shannon's diversity index, and Shannon's evenness index were the lowest after chemical weeding, but the highest after manual weeding, suggesting that chemical weeding had the greatest effects on the weed diversity in the citrus orchard. It was suggested that to sufficiently control the weeds while to maintain the weed diversity in the orchard weeds in southwest Zhejiang, the combination of chemical and manual weeding would be the best management strategy.

  12. Soil solarization for weed control in carrot

    Directory of Open Access Journals (Sweden)

    MARENCO RICARDO ANTONIO

    2000-01-01

    Full Text Available Soil solarization is a technique used for weed and plant disease control in regions with high levels of solar radiation. The effect of solarization (0, 3, 6, and 9 weeks upon weed populations, carrot (Daucus carota L. cv. Brasília yield and nematode infestation in carrot roots was studied in São Luís (2º35' S; 44º10' W, MA, Brazil, using transparent polyethylene films (100 and 150 mm of thickness. The maximum temperature at 5 cm of depth was about 10ºC warmer in solarized soil than in control plots. In the study 20 weed types were recorded. Solarization reduced weed biomass and density in about 50% of weed species, including Cyperus spp., Chamaecrista nictans var. paraguariensis (Chod & Hassl. Irwin & Barneby, Marsypianthes chamaedrys (Vahl O. Kuntze, Mitracarpus sp., Mollugo verticillata L., Sebastiania corniculata M. Arg., and Spigelia anthelmia L. Approximately 40% of species in the weed flora were not affected by soil mulching. Furthermore, seed germination of Commelina benghalensis L. was increased by soil solarization. Marketable yield of carrots was greater in solarized soil than in the unsolarized one. It was concluded that solarization for nine weeks increases carrot yield and is effective for controlling more than half of the weed species recorded. Mulching was not effective for controlling root-knot nematodes in carrot.

  13. A study of weeding policies in eleven TALON resource libraries.

    Science.gov (United States)

    Goldstein, C H

    1981-01-01

    A study was made of the weeding policies and practices of eleven TALON resource libraries. The results indicated that although weeding, or collection evaluation as it is also known, was performed by most of the libraries, few had a written policy. The reasons for weeding and the types of weeding done by the libraries are described. A discussion of the prevalent means of disposition of withdrawn materials and of the obstacles to cooperative weeding is included. PMID:7248594

  14. A study of weeding policies in eleven TALON resource libraries.

    Science.gov (United States)

    Goldstein, C H

    1981-07-01

    A study was made of the weeding policies and practices of eleven TALON resource libraries. The results indicated that although weeding, or collection evaluation as it is also known, was performed by most of the libraries, few had a written policy. The reasons for weeding and the types of weeding done by the libraries are described. A discussion of the prevalent means of disposition of withdrawn materials and of the obstacles to cooperative weeding is included.

  15. A study of weeding policies in eleven TALON resource libraries.

    OpenAIRE

    Goldstein, C H

    1981-01-01

    A study was made of the weeding policies and practices of eleven TALON resource libraries. The results indicated that although weeding, or collection evaluation as it is also known, was performed by most of the libraries, few had a written policy. The reasons for weeding and the types of weeding done by the libraries are described. A discussion of the prevalent means of disposition of withdrawn materials and of the obstacles to cooperative weeding is included.

  16. Critical period of weed control In cumin (Cuminum cyminum)

    OpenAIRE

    azade hoseyni; alireza koochaki; mehdi nassiri mahalati

    2009-01-01

    In order to evaluate the critical period of weed control in Cumin, an experiment with Complete Randomized Block Design and three replications was conducted in experimental field of Faculty of Agriculture, Ferdowsi University of Mashhad, During 2004-2005 growing season. Treatments included different combinations of weed free and weed infested periods (20, 30, 40 and 80 days after germination) plus weedy check and weed free check. Critical period weed control was evaluated with Gompertz and Log...

  17. Research on the development of weed-suppressing rice varieties

    Institute of Scientific and Technical Information of China (English)

    Shaochuan ZHOU; Decheng LU; Hong LI; Daoqiang HUANG; Ruowei MIAO

    2009-01-01

    This study was conducted to develop weed-suppressing rice varieties in a weed-suppressing nursery by specific secondary metabolite markers of allelopathic potential. Weed-suppressing rice variety Feng-Hua-Zhan was screened out by a specific secondary metabolite marker of allelopathic potential. Weed-suppressing rice No. 1, a new rice line with good quality, was also developed using this method. The genetic backgrounds and research directions of weed-suppressing rice varieties are discussed in this paper.

  18. Nutritional Value and Toxins in Various Noxious Weeds

    OpenAIRE

    Burritt, Beth; Hart, Rae Ann

    2014-01-01

    Teaching animals to eat noxious weeds may be a solution to reducing noxious weeds. Grazing animals often avoid eating weeds due to novelty even though weeds are often as nutritious as many of our planted pasture and rangelands species. This fact sheet provides livestock producers with the nutritive values of many common weeds. These values were summarized from a variety of peer-reviewed journal articles.

  19. Combining a weed traits database with a population dynamics model predicts shifts in weed communities

    DEFF Research Database (Denmark)

    Storkey, Jonathan; Holst, Niels; Bøjer, Ole Mission;

    2015-01-01

    A functional approach to predicting shifts in weed floras in response to management or environmental change requires the combination of data on weed traits with analytical frameworks that capture the filtering effect of selection pressures on traits. A weed traits database (WTDB) was designed......, populated and analysed, initially using data for 19 common European weeds, to begin to consolidate trait data in a single repository. The initial choice of traits was driven by the requirements of empirical models of weed population dynamics to identify correlations between traits and model parameters....... These relationships were used to build a generic model, operating at the level of functional traits, to simulate the impact of increasing herbicide and fertiliser use on virtual weeds along gradients of seed weight and maximum height. The model generated ‘fitness contours’ (defined as population growth rates) within...

  20. On the Parable of Weeds and Wheat

    Institute of Scientific and Technical Information of China (English)

    HUANG Wei

    2013-01-01

    This paper probes on one of the famous parables of Jesus-the Wheat and Weeds, and demonstrates some implied meaning and morals connoted in it. Through an interesting contrast between the calm restraint of the householder and high anxi-ety of his slaves, this parable suggests that people should stay calm and learn from God to be tolerate and lenient religiously to“let wheat and weeds grow together until the harvest”. Meanwhile, God drops a subtle hint to seed wheat positively in stead of sug-gesting people to remove weeds negatively.

  1. The Evaluation and the Comparison of the Effect of Mechanical Weeding Systems on Rice Weed

    Directory of Open Access Journals (Sweden)

    Fazlollah Eskandari Cherati

    2012-08-01

    Full Text Available In order to study the influence of different methods of controlling weeds such as mechanical weeding and mechanical weeder efficiency analysis in mechanical cultivation conditions, in farming year of 2011 an experiment was done in a farm in coupling and development of technology center in Haraz, Iran. The treatments consisted of (I control treatment: where no weeding was done, (II use of mechanical weeding without engine and (III power mechanical weeding. Results showed that experimental treatments had significantly different effects (p = 0.05 on yield traits and number of filled grains per panicle, while treatments had the significant effects on grain weight and dry weight of weeds in the first, second and third weeding methods at 1% of confidence level. Treatment (II had its most significant effect on number of filled grains per panicle and yield performance standpoint, which was 3705.97 kg/ha in its highest peak. Treatment (III was ranked as second influential with 3559.8 kg/ha. In addition, under (I treatments, 2364.73 kg/ha of yield produced. The minimum dry weights of weeds in all weeding methods were related to the treatment (II, (III and (I, respectively. The correlation coefficient analysis showed that total yield had a significant positive correlation with the panicle grain yield per plant (r = 0.55* and the number of grains/panicle (r = 0.57* and the number of filled grains (r = 0.63*. Total rice yield also had negative correlation of r = -0.64* with weed dry weight at second weed sampling time (17 DAT. The weed dry weight at third and fourth sampling times (24 and 40 DAT had negative correlations of -0.65** and r = -0.61* with rice yield, respectively.

  2. Effects of host, temperature and relative humidity on competitive displacement of two invasive Bemisia tabaci biotypes [Q and B

    Institute of Scientific and Technical Information of China (English)

    Dong Chu; Yun-Li Tao; You-Jun Zhang; Fang-Hao Wan; Judith K Brown

    2012-01-01

    Bemisia tabaci shifted unexpectedly in China from a predominance of B biotype to Q biotype during 2005-2008.This observation stimulated an interest in investigating whether environmental factors,including host,temperature and relative humidity (RH) could possibly explain the observed shift in biotypes distribution.Results indicated that all three parameters examined influenced biotype survivability.The percentage of B biotype,when reared together on pepper plants with the Q biotype,decreased significantly from 66.7% in the founder population,to 13.6% and 3.7% in the first and second generations,respectively.When the B (founder at 66.7%) and Q (founder at 33.3%) biotypes were reared together on eggplant alone,or on pepper-plus-eggplant combination,the population size of the B biotype either remained constant,or increased somewhat in the first and second generations.On eggplant,the effects of RH and temperature on the competitiveness between the Q and B biotypes (3 pairs of Q and 6 pairs of B) were not significant.

  3. 4.8%甲氧咪草烟·咪唑乙烟酸水剂防除抗除草剂向日葵品种田杂草效果及安全性评价%Control efficacy and safety assessment of 4.8%Imazamox-Imazethapyr (AS) against weeds in herbicide resistant sunflower fields

    Institute of Scientific and Technical Information of China (English)

    白全江; 赵存虎; 程玉臣; 云晓鹏; 杜磊; 魏海明

    2016-01-01

    The occurrence of weeds in sunflower field brings severe yield loss and quality deterioration to sunflower seeds product. In practice, artificial weeding need more labor and higher cost, and there is no suitable foliar-applied herbicide for annual weeds in sunflower fields. In 2007, we introduced an herbicide resistant sunflower hybrid--Jaguar, and used 4.8%Imazamox-Imazethapyr (AS) as foliar-applied herbicide on it. In this study, the test herbicide was sprayed at the dosage between 66.7 mL/667m2 and 200 mL/667m2.Results showed that the control efficacies of test herbicide were from 88.1% to 99.9% 40 days after spraying. When applying dosage were 83.3 mL/667m2 and 100 mL/667m2, it kept effective and safe to sunflower.%向日葵田杂草危害,严重影响其产量和品质,人工防除费工费时,而且劳动成本高,生产中没有理想的茎叶处理防除向日葵田一年生单双子叶杂草的药剂。2007年引进国外抗咪唑啉铜类除草剂向日葵品种———美洲虎,应用甲氧咪草烟·咪唑乙烟酸4.8%AS 66.7 mL/667m2~200 mL/667m2茎叶喷雾处理。施药后40 d调查,结果表明,该药剂对田间一年生单双子叶杂草综合株防效达88.1%~99.9%,其中83.3 mL/667m2、100 mL/667m2用药量处理对供试向日葵既安全,又具有较好防效。

  4. Using simulation models to investigate the cumulative effects of sowing rate, sowing date and cultivar choice on weed competition.

    Science.gov (United States)

    Andrew, Izzadora K S; Storkey, Jonathan

    2017-05-01

    With the increasing pressure on crop production from the evolution of herbicide resistance, farmers are increasingly adopting Integrated Weed Management (IWM) strategies to augment their weed control. These include measures to increase the competitiveness of the crop canopy such as increased sowing rate and the use of more competitive cultivars. While there are data on the relative impact of these non-chemical weed control methods assessed in isolation, there is uncertainty about their combined contribution, which may be hindering their adoption. In this article, the INTERCOM simulation model of crop/weed competition was used to examine the combined impact of crop density, sowing date and cultivar choice on the outcomes of competition between wheat (Triticum aestivum) and Alopecurus myosuroides. Alopecurus myosuroides is a problematic weed of cereal crops in North-Western Europe and the primary target for IWM in the UK because it has evolved resistance to a range of herbicides. The model was parameterised for two cultivars with contrasting competitive ability, and simulations run across 10 years at different crop densities and two sowing dates. The results suggest that sowing date, sowing density and cultivar choice largely work in a complementary fashion, allowing enhanced competitive ability against weeds when used in combination. However, the relative benefit of choosing a more competitive cultivar decreases at later sowing dates and higher crop densities. Modeling approaches could be further employed to examine the effectiveness of IWM, reducing the need for more expensive and cumbersome long-term in situ experimentation.

  5. Integrated weed management systems with herbicide-tolerant crops in the European Union: lessons learnt from home and abroad.

    Science.gov (United States)

    Lamichhane, Jay Ram; Devos, Yann; Beckie, Hugh J; Owen, Micheal D K; Tillie, Pascal; Messéan, Antoine; Kudsk, Per

    2017-06-01

    Conventionally bred (CHT) and genetically modified herbicide-tolerant (GMHT) crops have changed weed management practices and made an important contribution to the global production of some commodity crops. However, a concern is that farm management practices associated with the cultivation of herbicide-tolerant (HT) crops further deplete farmland biodiversity and accelerate the evolution of herbicide-resistant (HR) weeds. Diversification in crop systems and weed management practices can enhance farmland biodiversity, and reduce the risk of weeds evolving herbicide resistance. Therefore, HT crops are most effective and sustainable as a component of an integrated weed management (IWM) system. IWM advocates the use of multiple effective strategies or tactics to manage weed populations in a manner that is economically and environmentally sound. In practice, however, the potential benefits of IWM with HT crops are seldom realized because a wide range of technical and socio-economic factors hamper the transition to IWM. Here, we discuss the major factors that limit the integration of HT crops and their associated farm management practices in IWM systems. Based on the experience gained in countries where CHT or GMHT crops are widely grown and the increased familiarity with their management, we propose five actions to facilitate the integration of HT crops in IWM systems within the European Union.

  6. Genetically modified organisms : herbicide-resistance

    OpenAIRE

    Sánchez Retuerta, Violeta

    2014-01-01

    Pòster Due to the overgrowth of weeds, and the fact that herbicides cannot differentiate between crops and weeds, herbicide-resistant crops have been developed. This kind of genetically modified organisms (GMO) allows farmers to eliminate all weeds in a unique implementation of the herbicide meaning: less spraying, less “traffic” in the field and lower operating costs. However, this, like any other innovation, has generated much controversy

  7. The benefits of herbicide-resistant crops.

    Science.gov (United States)

    Green, Jerry M

    2012-10-01

    Since 1996, genetically modified herbicide-resistant crops, primarily glyphosate-resistant soybean, corn, cotton and canola, have helped to revolutionize weed management and have become an important tool in crop production practices. Glyphosate-resistant crops have enabled the implementation of weed management practices that have improved yield and profitability while better protecting the environment. Growers have recognized their benefits and have made glyphosate-resistant crops the most rapidly adopted technology in the history of agriculture. Weed management systems with glyphosate-resistant crops have often relied on glyphosate alone, have been easy to use and have been effective, economical and more environmentally friendly than the systems they have replaced. Glyphosate has worked extremely well in controlling weeds in glyphosate-resistant crops for more than a decade, but some key weeds have evolved resistance, and using glyphosate alone has proved unsustainable. Now, growers need to renew their weed management practices and use glyphosate with other cultural, mechanical and herbicide options in integrated systems. New multiple-herbicide-resistant crops with resistance to glyphosate and other herbicides will expand the utility of existing herbicide technologies and will be an important component of future weed management systems that help to sustain the current benefits of high-efficiency and high-production agriculture.

  8. Comparative Genomic Analysis of Clinical and Environmental Vibrio Vulnificus Isolates Revealed Biotype 3 Evolutionary Relationships

    Directory of Open Access Journals (Sweden)

    Yael eKotton

    2015-01-01

    Full Text Available In 1996 a common-source outbreak of severe soft tissue and bloodstream infections erupted among Israeli fish farmers and fish consumers due to changes in fish marketing policies. The causative pathogen was a new strain of Vibrio vulnificus, named biotype 3, which displayed a unique biochemical and genotypic profile. Initial observations suggested that the pathogen erupted as a result of genetic recombination between two distinct populations. We applied a whole genome shotgun sequencing approach using several V. vulnificus strains from Israel in order to study the pan genome of V. vulnificus and determine the phylogenetic relationship of biotype 3 with existing populations. The core genome of V. vulnificus based on 16 draft and complete genomes consisted of 3068 genes, representing between 59% and 78% of the whole genome of 16 strains. The accessory genome varied in size from 781 kbp to 2044 kbp. Phylogenetic analysis based on whole, core, and accessory genomes displayed similar clustering patterns with two main clusters, clinical (C and environmental (E, all biotype 3 strains formed a distinct group within the E cluster. Annotation of accessory genomic regions found in biotype 3 strains and absent from the core genome yielded 1732 genes, of which the vast majority encoded hypothetical proteins, phage-related proteins, and mobile element proteins. A total of 1916 proteins (including 713 hypothetical proteins were present in all human pathogenic strains (both biotype 3 and non-biotype 3 and absent from the environmental strains. Clustering analysis of the non-hypothetical proteins revealed 148 protein clusters shared by all human pathogenic strains; these included transcriptional regulators, arylsulfatases, methyl-accepting chemotaxis proteins, acetyltransferases, GGDEF family proteins, transposases, type IV secretory system (T4SS proteins, and integrases. Our study showed that V. vulnificus biotype 3 evolved from environmental populations and

  9. Importance of isolation and biotypization of Gardnerella vaginalis in diagnosis of bacterial vaginosis.

    Science.gov (United States)

    Numanović, Fatima; Hukić, Mirsada; Nurkić, Mahmud; Gegić, Merima; Delibegović, Zineta; Imamović, Alma; Pasić, Selma

    2008-08-01

    The natural habitat of Gardnerella vaginalis is a vagina since it could be located among 69% of women who have no signs of vaginal infection and in the vagina of as many as 13.5% girls. G. vaginalis is almost certainly identified among women diagnosed with bacterial vaginosis as well as in the urethra of their sexual partner. The inc