24 research outputs found

    Management strategies for glyphosate-resistant Italian ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot]

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    Glyphosate-resistant (GR) Italian ryegrass has been documented in many different countries around the world and has now become a major problem in row crop production areas of Mississippi. Field experiments were conducted from 2006 to 2008 in the Mississippi Delta to evaluate various herbicide and tillage treatment programs for its control. style=\u27mso-spacerun:yes\u27\u3e Highest level of control and reduction of GR Italian ryegrass biomass was observed with mechanically incorporated as well as surface applied residual herbicides in the fall of the year. style=\u27mso-spacerun:yes\u27\u3e Control of GR Italian ryegrass was 86-95% with surface applications of clomazone at 0.56, 0.84, and 1.12 kg ai/ha, s-metolachlor at 1.79 kg class=SpellE\u3eai/ha and KIH-485 at 0.16 kg ai/ha 171 days after emergence. Using a systems approach, preplant incorporated (PPI) class=SpellE\u3eclomazone and/or s- class=SpellE\u3emetolachlor followed by preemergence (PRE) application of paraquat + linuron+ non-ionic surfactant was also found to control and reduce biomass of GR Italian ryegrass

    Selection of glyphosate resistance in Amaranthus tuberculatus (Mq ex DC) J.D. Sauer and potential for transfer of glyphosate resistance in Conyza

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    Iowa farmers rely on glyphosate (N-(phosphonomethyl) glycine) resistant crops for weed management in row crops. Inconsistent glyphosate control was reported in common waterhemp (Amaranthus tuberculatus (Mq. ex DC) and horseweed (Conyza canadensis (L.) Cronq.) populations. Therefore, an investigation was undertaken to ascertain the potential for selection of glyphosate resistance in common waterhemp and assess the possibility for transfer of glyphosate resistance in two Conyza species.;Rate responses verified that 0.62 kg acid equivalents (ae) of glyphosate ha-1 were required to reduce biomass by 50% ( GR50) in common waterhemp from Everly, Iowa, compared to 0.24 kg ae ha-1 of a pristine population from Paint Creek, Ohio. Recurrent selection was performed to isolate resistant and susceptible plants within the Everly population. Rate responses suggested that the frequency of resistant individuals increased in the first (S1) and second (S2) recurrent generations and that selection reduced the overall population variability to glyphosate. Interestingly, both the S1 and S2 populations selected for glyphosate resistance demonstrated sex ratios skewed towards maleness. Since variability for glyphosate resistance remained in the S2, a three-level selection strategy was used to isolate asexually propagated plants with a homogenous response to glyphosate. This research suggested that resistance can evolve in common waterhemp with a variable response to glyphosate.;Hybridization between the glyphosate resistant horseweed and dwarf fleabane (Conyza ramosissima Cronq.) ranged from 0% to 9% in assisted crosses and \u3e95% in artificial crosses. The interspecific hybrid ( FH1 ) was phenotypically intermediate to both parents, but shared more homology to the dwarf fleabane parent. Stability, heterosis, and absence of reproductive barriers confirmed that the FH1 was fertile. Inheritance of glyphosate resistance in the FH1 followed the hybrid resistance model and the nuclear encoded, incompletely-dominant single gene (R-allele) model in the hybrid progeny ( FH2 ). We argue that adequate fitness and niche differentiation are prerequisites for successful hybrid adaptation in the environment and that hybridization in Conyza may complicate the containment of glyphosate resistance in current agroecosystems

    Relationship between EPSPS copy number, expression, and level of resistance to glyphosate in common waterhemp (Amaranthus rudis) from Kansas

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    Master of ScienceAgronomyMithila JugulamCommon waterhemp (Amaranthus rudis) is a problematic weed species of cropping systems throughout the Midwestern states, including Kansas. Recently, waterhemp populations from Kansas were found to have evolved resistance to the widely used herbicide glyphosate as a result of amplification of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), the enzyme target of glyphosate. The objectives of this research were to 1) perform glyphosate dose-response study and determine the relationship between relative EPSPS genomic copies and EPSPS gene expression in glyphosate-resistant waterhemp, and 2) characterize the genomic configuration and distribution of EPSPS copies using florescence in situ hybridization (FISH) in three glyphosate-resistant waterhemp populations. Waterhemp populations from eastern Kansas were screened with 868 g ae haˉ¹ (field used rate) of glyphosate, and genomic DNA and total RNA was isolated from the survivors to determine the EPSPS genomic copies and EPSPS gene expression relative to the acetolactate synthase (ALS) gene using qPCR. Furthermore, waterhemp specific EPSPS probes were synthesized to perform florescence in situ hybridization (FISH) on these glyphosate-resistant plants. Results of these experiments indicate a positive correlation between level of glyphosate resistance, EPSPS copies, and their expression. As expected, a negative correlation was found between shikimate accumulation and EPSPS copies. Sequencing of the EPSPS gene showed no presence of the proline 106 mutation, which is known to be associated with glyphosate resistance suggesting that an insensitive EPSPS enzyme was not involved in the mechanism of glyphosate resistance. FISH analysis of resistant plants illustrated presence of amplified EPSPS copies on two homologous chromosomes, likely near the centromeric region. . This is the first report demonstrating a positive relationship between EPSPS copies and expressions, as well as chromosome configuration of EPSPS copies in glyphosate- resistant waterhemp from Kansas

    Herbicide Resistance in Plants

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    Today, herbicide-resistant weeds dominate research and development efforts in the discipline of weed science. The incidence, management challenges, and cost of multiple herbicide-resistant weed populations are continually increasing worldwide. Crop varieties with multiple herbicide-resistance traits are being rapidly adopted by growers and land managers to keep ahead of the weed resistance tsunami. This Special Issue of Plants comprises papers that describe the current status and future outlook of herbicide resistance research and development in weedy and domestic plants, with topics covering the full spectrum from resistance mechanisms to resistance management. The unifying framework for this Special issue is the challenge posed to all of the contributing authors: What are the (potential) implications for herbicide resistance management

    Cross- and multiple-resistance of weeds to herbicides

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    La agricultura es una de las principales potencias económicas, produciendo desarrollo y riqueza a nivel mundial. Este sector está afectado por diversos factores, tanto bióticos como abióticos, los cuales se traducen en elevadas pérdidas de rendimiento y costes en los cultivos. Los principales factores bióticos que afectan a la agricultura son las enfermedades, plagas y malas hierbas. Las malas hierbas son plantas que crecen de forma predominante en situaciones alteradas por el hombre, y que no resultan deseables para él en un lugar y momento determinado. Los herbicidas representan en la actualidad un papel imprescindible en el control de malas hierbas, siendo la herramienta más efectiva que se haya desarrollado, controlando alrededor del 99% de malas hierbas. Desafortunadamente, la era dorada de los herbicidas como única herramienta de control se ha visto truncada a causa de la aparición de malas hierbas resistentes a herbicidas por el uso abusivo de estos. El aumento exponencial de malas hierbas con resistencia se produce en una situación en la que durante los últimos 25 años no se han desarrollado nuevos modos de acción. La resistencia a herbicidas es el resultado de la adaptación evolutiva de las malas hierbas a las sucesivas aplicaciones herbicidas, y es sin duda, una de las principales preocupaciones en la agricultura moderna. Desafortunadamente, las malas hierbas pueden desarrollar no solo resistencia a un herbicida, sino que pueden desarrollar resistencia cruzada y/o múltiple. La comunidad centrada en la malherbologia presenta la preocupación de que los agricultores podrían enfrentarse a la perdida de los herbicidas como herramientas eficaces y económicas en las que se basa la agricultura productiva moderna. Este preocupante escenario comienza con la dependencia exclusiva del uso de un solo herbicida, ya sea por ejemplo glifosato en cultivos perennes, o diclofop en cultivos anuales. Ante esta situación, los agricultores cambian de herbicida, pero en muchas ocasiones no cambian de modo de acción, por lo que el problema no es solventado. En otras ocasiones, se cambia de modo de acción pero no es alternado con otros herbicidas en las sucesivas aplicaciones, apareciendo nuevamente la resistencia. Debido a la repercusión que ha ocasionado la resistencia de malas hierbas a herbicidas, así como la aparición de resistencia cruzada y/o múltiple, en este trabajo se han determinado los mecanismos de resistencia involucrados en poblaciones de Lolium rigidum resistente a glifosato en Francia [Capítulo II] y España, así como ofrecer alternativas químicas para obtener un control optimo, y poder controlar la resistencia [Capítulo III]. Además, se caracterizó la tolerancia natural de Avena sterilis a glifosato en el sur de España [Capítulo IV], sirviendo de ejemplo de que algunas malas hierbas no son controladas por glifosato, no por haber desarrollado resistencia sino por ser tolerantes. En el capítulo V se determinó la múltiple resistencia a herbicidas no selectivos en especies del genero Lolium spp. en la Península Ibérica, a causa de no alternar diferentes modos de acción en las sucesivas aplicaciones. Del mismo modo, en el Capítulo VI se caracterizó la resistencia cruzada a herbicidas pertenecientes a los inhibidores de la ACCasa (acetil- CoA carboxilasa) en Cynosurus echinatus procedente de Chile, a causa de utilizar herbicidas de diferentes familias químicas, pero todas ellas pertenecientes al mismo modo de acción. Se determinó el primer caso de resistencia francés en L. rigidum en el que se conocen los mecanismos implicados. Los resultados mostraron que la resistencia a glifosato en la población resistente francesa de L. rigidum se debe en parte a la reducción de absorción y translocación de glifosato en relación con la población susceptible, así como a una mutación en el gen que codifica la EPSPS. Por el contrario, la resistencia a glifosato en la población resistente española de L. rigidum se debe en parte a la reducción de absorción y translocación de glifosato, y no se encontró ninguna mutación en el gen que codifica la EPSPS. Los ensayos de campo determinaron que es posible obtener un control eficaz de L. rigidum utilizando diferentes modos de acción, así como la reducción del banco de semillas resistentes a glifosato. Las prospecciones realizadas mostró resultados homogéneos entre todas las accesiones de A. sterilis recogidas y, por lo tanto, todas ellas tienen el mismo nivel de tolerancia innata al glifosato, siendo los mecanismos fuera del sitio de acción los implicados en la tolerancia innata a glifosato en A. sterilis. Esto es probablemente debido en parte a una menor absorción / translocación del herbicida y metabolismo de glifosato. Estudios moleculares confirmaron que tres especies de malas hierbas de Lolium resistentes a glifosato (L. rigidum, L. perenne, y L. multiflorum) recogidas de cultivos perennes en la Península Ibérica también han desarrollado resistencia múltiple a los herbicidas glufosinato y oxifluorfen. Este estudio identificó el primer caso de resistencia a oxifluorfen en una gramínea. Los ensayos in vitro y de dosisrespuesta de ACCasa determinaron la resistencia cruzada a los herbicidas de las familias químicas APP, CHD y PPZ en C. echinatus. Los estudios de secuenciación de ADN confirmaron que la resistencia cruzada de C. echinatus a los inhibidores de ACCasa ha sido conferida por las mutaciones puntuales Ile-2041-Asn y Cys-2088-Arg.Agriculture is one of the main economic powers, producing development and wealth worldwide. This sector is affected by several factors, both biotic and abiotic, which have resulted in high yield and crop cost losses. The main biotic factors affecting agriculture are diseases, pests, and weeds. Weeds are plants that predominantly grow in situations altered by man, and are not desirable for at any time and given place. To date, herbicides play an essential role in weed control, being the most effective tool developed, controlling about 99% of weeds. Unfortunately, the golden era of herbicides as the only tool has been cut short by the herbicide-resistant weeds due to abusive use. The exponential increase of resistant weeds occurs in a situation where no new action modes have been developed during the last 25 years. Herbicide resistance is the result of the evolutionary adaption of weeds to successive herbicide applications, and it is undoubtedly one of the main concerns in modern agriculture. Unfortunately, weeds can develop not only resistance to one herbicide, but also they can develop cross- and multiple-resistance. The weed research community is concerned that farmers may be faced with the herbicide loss as an effective and economic tool on which modern productive agriculture is based. This worrying scenario begins with the exclusive use of a single herbicide, whether for example glyphosate in perennial crops, or diclofop in annual crops. In this situation, farmers change to another herbicide, but in many cases, they do not change the action mode, so the problem is not solved. At other times, they change the action mode, but it is not alternated with other action modes in the successive applications, exhibiting resistance again. Due to the herbicide-resistant weed impact, as well as the occurrence of cross- and multiple-resistance, this work has determined the mechanisms of resistance involved in glyphosate-resistant populations of Lolium rigidum from France [Chapter II], and Spain, as well as to offer chemical alternatives to control the resistance [Chapter III]. Also, the natural tolerance of Avena sterilis to glyphosate in southern Spain has been characterized [Chapter IV], offering as an example that some weeds are not controlled by glyphosate, not because of developed resistance, but because they are tolerant. In Chapter V, the multiple-resistance to non-selective herbicides in species of Lolium spp. genus from the Iberian Peninsula, due to not alternating different action modes in the successive applications has been reported. In the same way, cross-resistance to herbicides belonging to the ACCase (acetyl-CoA carboxylase)-inhibitors in Cynosurus echinatus from Chile has been characterized in Chapter VI, because of the use of herbicides of different chemical families, but all of them belonging to the same action mode. The first case of French resistance of L. rigidum has been determined in which the mechanisms involved are known. The results showed that glyphosate resistance in the French resistant population of L. rigidum was due in part to the reduction of glyphosate absorption and translocation in relation to the susceptible one, as well as to a mutation in the gene encoding EPSPS. In contrast, glyphosate resistance in the Spanish population of L. rigidum was due to reduced absorption and translocation, and no mutation was found in the gene encoding EPSPS. Field trials determined that it is possible to obtain an effective control of L. rigidum using different action modes, as well as the reduction of the glyphosate resistant seed bank. The surveys carried out showed homogenous results among all of the A. sterilis accessions collected; therefore, all of them have the same level of innate tolerance of glyphosate, being the non-target-site resistance the mechanism involved. This was due in part to a lower absorption and translocation, and glyphosate metabolism. Molecular studies confirmed that three species of glyphosate-resistant Lolium (L. rigidum, L. multiflorum, and L. perenne) collected from perennial crops have also developed multiple-resistance to glufosinate and oxyfluorfen. This study reported the first case of resistance to oxyfluorfen in grass. The in vivo and dose-response assays of ACCase determined the cross-resistance to the herbicides of the APP, CHD, and PPZ chemical families in C. echinatus. DNA sequencing studies confirmed that crossresistance to ACCase-inhibitors in C. echinatus has been conferred by Ile-2041-Asn and Cys-2088-Arg point mutations

    Fitness costs of herbicide resistance traits in common waterhemp (Amaranthus tuberculatus)

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    A three-year multigenerational greenhouse study was conducted to determine the fitness costs of five herbicide resistances (HR) in waterhemp. In the study, a synthetic waterhemp population segregating for five types of HR was subjected to competitive growth conditions in the absence of herbicide selection for six generations. The resistance frequencies of each generation were determined from both whole-plant herbicide treatments (glyphosate, atrazine, 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors) and molecular markers (acetolactate synthase (ALS) and protoporphyrinogen oxidase (PPO) inhibitors). Our result is the first report of the fitness costs for NTR to atrazine and HPPD inhibitors, as well as for the different fitness costs of two EPSPS alterations. Our results indicate that the resistance traits have no fitness costs, with the exception that ALS inhibitor resistance conferred by T574L target-site substitution had a minor fitness cost. Specifically, the relative fitnesses determined from the overall resistance frequency changes were 0.92, 1.02, 1.09, 0.97, and 1.07 for resistances to ALS and PPO inhibitors, atrazine, HPPD inhibitors, and glyphosate, respectively. It was also determined that glyphosate resistance (GR) in the study population was endowed by at least two resistance mechanisms (P106S target-site mutation and amplification of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene). A phenotype-genotype association analysis was conducted to determine if the two GR mechanisms differ in their fitness costs and significance in conferring resistance. No fitness penalty was observed for the P106S substitution, while EPSPS amplification had a significant fitness cost (relative fitness of 1.12 and 0.72, respectively). EPSPS amplification and the P106S mutation did not fully account for glyphosate resistance in the population. The evolution of GR likely is a result of the interplay of different resistance mechanisms, with relative fitness of the mechanisms— both in the presence and absence of glyphosate—playing roles. The results from this novel study add to a growing body of evidence indicating that herbicide rotation is not an effective resistance management strategy because most herbicide resistances lack significant fitness costs

    Cross- and multiple-resistance of weeds to herbicides

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    La agricultura es una de las principales potencias económicas, produciendo desarrollo y riqueza a nivel mundial. Este sector está afectado por diversos factores, tanto bióticos como abióticos, los cuales se traducen en elevadas pérdidas de rendimiento y costes en los cultivos. Los principales factores bióticos que afectan a la agricultura son las enfermedades, plagas y malas hierbas. Las malas hierbas son plantas que crecen de forma predominante en situaciones alteradas por el hombre, y que no resultan deseables para él en un lugar y momento determinado. Los herbicidas representan en la actualidad un papel imprescindible en el control de malas hierbas, siendo la herramienta más efectiva que se haya desarrollado, controlando alrededor del 99% de malas hierbas. Desafortunadamente, la era dorada de los herbicidas como única herramienta de control se ha visto truncada a causa de la aparición de malas hierbas resistentes a herbicidas por el uso abusivo de estos. El aumento exponencial de malas hierbas con resistencia se produce en una situación en la que durante los últimos 25 años no se han desarrollado nuevos modos de acción. La resistencia a herbicidas es el resultado de la adaptación evolutiva de las malas hierbas a las sucesivas aplicaciones herbicidas, y es sin duda, una de las principales preocupaciones en la agricultura moderna. Desafortunadamente, las malas hierbas pueden desarrollar no solo resistencia a un herbicida, sino que pueden desarrollar resistencia cruzada y/o múltiple. La comunidad centrada en la malherbologia presenta la preocupación de que los agricultores podrían enfrentarse a la perdida de los herbicidas como herramientas eficaces y económicas en las que se basa la agricultura productiva moderna. Este preocupante escenario comienza con la dependencia exclusiva del uso de un solo herbicida, ya sea por ejemplo glifosato en cultivos perennes, o diclofop en cultivos anuales. Ante esta situación, los agricultores cambian de herbicida, pero en muchas ocasiones no cambian de modo de acción, por lo que el problema no es solventado. En otras ocasiones, se cambia de modo de acción pero no es alternado con otros herbicidas en las sucesivas aplicaciones, apareciendo nuevamente la resistencia. Debido a la repercusión que ha ocasionado la resistencia de malas hierbas a herbicidas, así como la aparición de resistencia cruzada y/o múltiple, en este trabajo se han determinado los mecanismos de resistencia involucrados en poblaciones de Lolium rigidum resistente a glifosato en Francia [Capítulo II] y España, así como ofrecer alternativas químicas para obtener un control optimo, y poder controlar la resistencia [Capítulo III]. Además, se caracterizó la tolerancia natural de Avena sterilis a glifosato en el sur de España [Capítulo IV], sirviendo de ejemplo de que algunas malas hierbas no son controladas por glifosato, no por haber desarrollado resistencia sino por ser tolerantes. En el capítulo V se determinó la múltiple resistencia a herbicidas no selectivos en especies del genero Lolium spp. en la Península Ibérica, a causa de no alternar diferentes modos de acción en las sucesivas aplicaciones. Del mismo modo, en el Capítulo VI se caracterizó la resistencia cruzada a herbicidas pertenecientes a los inhibidores de la ACCasa (acetil- CoA carboxilasa) en Cynosurus echinatus procedente de Chile, a causa de utilizar herbicidas de diferentes familias químicas, pero todas ellas pertenecientes al mismo modo de acción. Se determinó el primer caso de resistencia francés en L. rigidum en el que se conocen los mecanismos implicados. Los resultados mostraron que la resistencia a glifosato en la población resistente francesa de L. rigidum se debe en parte a la reducción de absorción y translocación de glifosato en relación con la población susceptible, así como a una mutación en el gen que codifica la EPSPS. Por el contrario, la resistencia a glifosato en la población resistente española de L. rigidum se debe en parte a la reducción de absorción y translocación de glifosato, y no se encontró ninguna mutación en el gen que codifica la EPSPS. Los ensayos de campo determinaron que es posible obtener un control eficaz de L. rigidum utilizando diferentes modos de acción, así como la reducción del banco de semillas resistentes a glifosato. Las prospecciones realizadas mostró resultados homogéneos entre todas las accesiones de A. sterilis recogidas y, por lo tanto, todas ellas tienen el mismo nivel de tolerancia innata al glifosato, siendo los mecanismos fuera del sitio de acción los implicados en la tolerancia innata a glifosato en A. sterilis. Esto es probablemente debido en parte a una menor absorción / translocación del herbicida y metabolismo de glifosato. Estudios moleculares confirmaron que tres especies de malas hierbas de Lolium resistentes a glifosato (L. rigidum, L. perenne, y L. multiflorum) recogidas de cultivos perennes en la Península Ibérica también han desarrollado resistencia múltiple a los herbicidas glufosinato y oxifluorfen. Este estudio identificó el primer caso de resistencia a oxifluorfen en una gramínea. Los ensayos in vitro y de dosisrespuesta de ACCasa determinaron la resistencia cruzada a los herbicidas de las familias químicas APP, CHD y PPZ en C. echinatus. Los estudios de secuenciación de ADN confirmaron que la resistencia cruzada de C. echinatus a los inhibidores de ACCasa ha sido conferida por las mutaciones puntuales Ile-2041-Asn y Cys-2088-Arg.Agriculture is one of the main economic powers, producing development and wealth worldwide. This sector is affected by several factors, both biotic and abiotic, which have resulted in high yield and crop cost losses. The main biotic factors affecting agriculture are diseases, pests, and weeds. Weeds are plants that predominantly grow in situations altered by man, and are not desirable for at any time and given place. To date, herbicides play an essential role in weed control, being the most effective tool developed, controlling about 99% of weeds. Unfortunately, the golden era of herbicides as the only tool has been cut short by the herbicide-resistant weeds due to abusive use. The exponential increase of resistant weeds occurs in a situation where no new action modes have been developed during the last 25 years. Herbicide resistance is the result of the evolutionary adaption of weeds to successive herbicide applications, and it is undoubtedly one of the main concerns in modern agriculture. Unfortunately, weeds can develop not only resistance to one herbicide, but also they can develop cross- and multiple-resistance. The weed research community is concerned that farmers may be faced with the herbicide loss as an effective and economic tool on which modern productive agriculture is based. This worrying scenario begins with the exclusive use of a single herbicide, whether for example glyphosate in perennial crops, or diclofop in annual crops. In this situation, farmers change to another herbicide, but in many cases, they do not change the action mode, so the problem is not solved. At other times, they change the action mode, but it is not alternated with other action modes in the successive applications, exhibiting resistance again. Due to the herbicide-resistant weed impact, as well as the occurrence of cross- and multiple-resistance, this work has determined the mechanisms of resistance involved in glyphosate-resistant populations of Lolium rigidum from France [Chapter II], and Spain, as well as to offer chemical alternatives to control the resistance [Chapter III]. Also, the natural tolerance of Avena sterilis to glyphosate in southern Spain has been characterized [Chapter IV], offering as an example that some weeds are not controlled by glyphosate, not because of developed resistance, but because they are tolerant. In Chapter V, the multiple-resistance to non-selective herbicides in species of Lolium spp. genus from the Iberian Peninsula, due to not alternating different action modes in the successive applications has been reported. In the same way, cross-resistance to herbicides belonging to the ACCase (acetyl-CoA carboxylase)-inhibitors in Cynosurus echinatus from Chile has been characterized in Chapter VI, because of the use of herbicides of different chemical families, but all of them belonging to the same action mode. The first case of French resistance of L. rigidum has been determined in which the mechanisms involved are known. The results showed that glyphosate resistance in the French resistant population of L. rigidum was due in part to the reduction of glyphosate absorption and translocation in relation to the susceptible one, as well as to a mutation in the gene encoding EPSPS. In contrast, glyphosate resistance in the Spanish population of L. rigidum was due to reduced absorption and translocation, and no mutation was found in the gene encoding EPSPS. Field trials determined that it is possible to obtain an effective control of L. rigidum using different action modes, as well as the reduction of the glyphosate resistant seed bank. The surveys carried out showed homogenous results among all of the A. sterilis accessions collected; therefore, all of them have the same level of innate tolerance of glyphosate, being the non-target-site resistance the mechanism involved. This was due in part to a lower absorption and translocation, and glyphosate metabolism. Molecular studies confirmed that three species of glyphosate-resistant Lolium (L. rigidum, L. multiflorum, and L. perenne) collected from perennial crops have also developed multiple-resistance to glufosinate and oxyfluorfen. This study reported the first case of resistance to oxyfluorfen in grass. The in vivo and dose-response assays of ACCase determined the cross-resistance to the herbicides of the APP, CHD, and PPZ chemical families in C. echinatus. DNA sequencing studies confirmed that crossresistance to ACCase-inhibitors in C. echinatus has been conferred by Ile-2041-Asn and Cys-2088-Arg point mutations

    Crop Updates 2009 - Weeds

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    This session covers twenty three papers from different authors: Herbicides 1. New pre-seeding grass selective herbicides – How well do they work in zero or no-till systems? Dr Catherine Borgerand Dr Abul Hashem, Department of Agriculture and Food 2. Velocity®—An alternate mode of action for the control of wild radish in cereals, Mike Clarke, Bayer Cropscience Pty Ltd, Dr Aik Cheam, Department of Agriculture and Food, Dr Michael Walsh, WAHRI, University of Western Australia 3. Herbicide tolerance of new barley varieties, Harmohinder Dhammu, Vince Lambert, Chris Roberts and Russell Quartermaine, Department of Agriculture and Food 4. Herbicide tolerance of Desi chickpea – influence of seeding depth and rainfall, Harmohinder Dhammu, and David Nicholson, Department of Agriculture and Food 5. Herbicide tolerance of new wheat varieties, Harmohinder Dhammu, and David Nicholson, Department of Agriculture and Food 6. PARAGON plus Bromicide 200: a triple mode-of-action approach to combating wild radish, Raphanus raphanistrum, Mike Jackson and Bill Campbell, Nufarm Australia Limited 7. Interaction of glyphosate dose, annual ryegrass growth stage and environmental conditions on the performance of glyphosate for control of annual ryegrass, John Moore, Abul Hashem, Mario D’Antuono, Paul Matson and Dave Nicholson, Department of Agriculture and Food 8. Metribuzin pre-sowing of lupins, Peter Newman, Department of Agriculture and Food 9. Wild radish herbicides - you get what you pay for, Peter Newman, Department of Agriculture and Food 10. Glyphosate-the consequences of cutting rates, Sally Peltzer and Dave Minkey, Department of Agriculture and Food, and Australian Herbicide Resistance Initiative 11. Reasons to use only the full label herbicide rate, Stephen B Powles, Qin Yu, Mechelle Owen, Roberto Busi and Sudheesh Manalil, WA Herbicide Resistance Initiative, School of Plant Biology, University of Western Australia 12. Mandelup has reasonable tolerance to atrazine, Leigh Smith and Peter White, Department of Agriculture and Food Herbicide resistance 13. Risk of glyphosate resistance in wide-row lupin cropping systems, Fiona Evans, Abul Hashem and Art Diggle, Department of Agriculture and Food 14. More glyphosate-resistant annual ryegrass populations within Western Australia, Dr Abul Hashem and Dr Catherine Borger, Department of Agriculture and Food 15. Western Australian farmers are sowing herbicide-resistant weed seed into their cropping paddocks! Mechelle Owen1, Pippa Michael2and Stephen Powles1, 1WA Herbicide Resistance Initiative, School of Plant Biology, University of Western Australia, 2Muresk Institute, Curtin University of Technology Integrated Weed Management 16. Inversion ploughing: Effects of long-term deep burial on weed seed reserves, Aik Cheam and Siew Lee, Department of Agriculture and Food 17. How long cam wild radish seeds survive in the soil? Aik Cheam and Siew Lee, Department of Agriculture and Food 18. An economic comparison of IWM tools, Rob Grima, Department of Agriculture and Food 19. Emerging weeds in changing farming systems, Dr Abul Hashem, Department of Agriculture and Food 20. Eight years of IWM smashes ryegrass seed banks by 98 per cent over 31 focus paddocks, Peter Newman, Glenn Adam and Trevor Bell, Department of Agriculture and Food 21. Mouldboard plough - the answer to all the problems with sandplain farming! Peter Newman and Steve Davies, Department of Agriculture and Food 22. Flaxleaf fleabane - coming to a property near you! Sally Peltzer, Department of Agriculture and Food, 23. Trimming weed seed heads and crop-topping reduce seed bank of wild radish, Glen Riethmuller and Abul Hashem, Department of Agriculture and Foo

    Elucidating the Cellular Physiology Associated with the Herbicide (Glyphosate) Resistance and Tolerance in Agricultural Weeds Using Metabolomics Approach

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    Current management practices overemphasizes on herbicides to manage weeds in crop production systems. However, indiscriminate use of herbicides to manage weeds has resulted in the development of resistance in several weed biotypes. Over-application on glyphosate to manage weeds in cropping system that uses RoundUp® Ready™ trait has resulted in the dominance of glyphosate resistant weeds across cropping systems. Glyphosate resistance is an important, economically unviable and rapidly escalating problem across agricultural production systems. To combat herbicide resistance, current recommendations advocate for changes in chemical and cultural practices of weed control, including rotation of herbicide regimen with herbicides with alternate modes of action, and formulation of cultural practices that would penalize the expression of resistance. Some of the bottlenecks in practicing these approaches are the current lack of knowledge about the weed cellular physiology that ensues resistance expression, the potential metabolic cost associated with this resistance expression, and the occurrence of compensatory pathways that could defray the cost of resistance expression. Adopting an alternate herbicide regimen without an understanding of the cellular physiology of resistance expression would result in the development of herbicide cross resistance in weeds, which would further aggravate the problem. To bridge this knowledge-gap, in this studies, metabolomics approach and complementary biochemical analyses were used to track the changes in cellular metabolism in weed species and biotypes that are resistant and naturally tolerant to glyphosate. In Ipomoea lacunosa, non-targeted metabolic profiling captured the differences in metabolic pool levels in two biotypes (WAS and QUI) with contrasting glyphosate tolerance (GR50 = 151 g ae ha-1 and 59 g ae ha-1). Metabolic profiling followed by pathway topological analysis captured innate metabolic differences (22 significantly different metabolites) between WAS and QUI biotypes. Despite the glyphosate dose being half the GR50 rate, shikimic acid accumulation was observed in both the biotypes. However, regardless of EPSPS inhibition, no changes in aromatic amino abundance was observed in the QUI biotype and WAS biotype, indicating their tolerance to the glyphosate. The results from this study implies that though I. lacunosa is tolerant to glyphosate, glyphosate exposure induces cellular metabolic perturbations. The varying tolerance to glyphosate could thus be due to physiological and metabolic adaptations between the different biotypes. Following through, metabolite and biochemical profiling of a susceptible (S) and resistant (R) biotype of Amaranthus palmeri identified physiological perturbations induced by glyphosate in both the biotypes at 8 and 80 hours after treatment (HAT). Compared to the S-biotype, the R-biotype had a 17 fold resistance to the normal field recommended rate of glyphosate. At 8HAT, shikimic acid accumulation in both S- and R-biotypes in response to glyphosate application indicated that the R-biotype was equally susceptible to glyphosate toxicity. The metabolite pool of glyphosate-treated R-biotype was similar to that of the water-treated (control) S and R-biotype, indicating physiological recovery at 80 HAT. A key finding from this study is that despite being resistant to glyphosate, Palmer amaranth biotypes initially sustained metabolic perturbation from glyphosate. However, what differentiates them from the susceptible biotypes is their ability to recover from the glyphosate induced metabolic disruptions. In response to glyphosate, glyphosate-treated R-biotype had lower reactive oxygen species (ROS) damage, higher ROS scavenging activity, and higher levels of secondary compounds of the shikimate pathway, leading to the finding that elevated anti-oxidant mechanisms in A. palmeri complements the resistance conferred due to increased EPSPS copy number. Furthermore, metabolite dynamics in response to glyphosate application studied using stable isotope resolved metabolomics revealed that despite glyphosate toxicity induced decrease in soluble proteins, a proportional increase in both 14N and 15N amino acids was observed in the susceptible plants. This indicates that following glyphosate treatment, a potential increase in de novo amino acid synthesis, coupled with a lower protein synthesis, and higher protein catabolism is observed in the S-biotype. In contrast, the R-biotype, though affected by glyphosate initially, had higher de novo amino acid synthesis without significant disruptions. Moreover, it is to be noted that although the initial assimilation of inorganic nitrogen to organic forms is less affected in the S-biotype than the R-biotype by glyphosate, amino acid biosynthesis downstream of glutamine is disproportionately disrupted. It is thus concluded that the herbicide-induced amino acid abundance in the S-biotype is contributed to by both protein catabolism, and de novo synthesis of amino acids such as glutamine and asparagine. Due to variability in the genetic makeup of populations, each biotype would exhibit different physiological manifestations when exposed to the same rate of glyphosate. Biochemical and metabolic profiling of five different Palmer amaranth biotypes indicated that both the S- and R-biotypes had comparable innate phytochemical profile and similar abundance in flavonoids and phenolic. However, compared to the S-biotypes, the R-biotypes had innately higher anti-oxidant capacity, and the antioxidant capacity was observed to correlate with the GR50 such that antioxidant capacity increased with increasing GR50. Upon treatment with glyphosate, there were significant alterations in the metabolic pool levels across all biotypes. After glyphosate treatment, the content of total phenolic and flavonoids decrease in S-biotypes, whereas the abundance of these metabolites either remained the same, or increased in the R-biotypes. These results indicate that antioxidant capacity is a complementary function aiding in conferring glyphosate resistance and the phytochemistry and the antioxidant capacity is partly induced after glyphosate application, rather than being constitutively expressed. Overall, these study demonstrates that, across biotypes and species, irrespective of their degree of resistance/tolerance, glyphosate not only perturbs shikimate pathway, but also a multitude of other metabolic pathways that are independent of shikimate pathway (secondary toxic effects) as early as eight hours after treatment. While in the susceptible biotypes these metabolic perturbations result in rapid cellular damage, these metabolic perturbations fail to translate to cellular damage in the resistant biotypes. The results indicate that the resistance of A. palmeri biotypes that were used in these studies partially stems from their ability to rapidly induce the production of phenylpropanoids soon after the glyphosate application. This induction of phytochemicals could quench the reactive molecules that are initially produced during the secondary metabolic perturbations, and would thus complement the glyphosate resistance in Amaranthus biotypes conferred by EPSPS gene amplification

    Weed Ecology and New Approaches for Management

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    Satisfying consumer needs through the production of healthy and nutritious agricultural products is a substantial challenge facing modern agriculture. However, agricultural production should be carried out with care for plant health, biological safety of products, and environmental safety while minimizing the risks to human health. Therefore, the implementation of agricultural practices while respecting these principles is very important for improving the quantity and quality of crops. Additionally, ecosystems have been altered as a result of human activities and climate change, resulting in the reduction of biodiversity and creation of new niches where pests can thrive. This is of particular importance in 2020, as the United Nations General Assembly declared this year as the International Year of Plant Health (IYPH), with “protecting plants, protecting life” as a leading subject.This Special Issue promotes the subject of plant health and emphasize the importance of preventing the spread of pests, including weeds, which cause substantial economic losses. Research articles cover topics related to the biology and harmfulness of weeds, particularly in connection with crop health, segetal weed communities and their biodiversity, and integrated methods of weed control. For this Special Issue, we welcome all types of articles, including original research, opinions, and reviews
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