The Experts below are selected from a list of 43389 Experts worldwide ranked by ideXlab platform
Stephen B. Powles - One of the best experts on this subject based on the ideXlab platform.
-
cytochrome p450 cyp81a10v7 in lolium rigidum confers metabolic resistance to herbicides across at least five modes of action
Plant Journal, 2021Co-Authors: Heping Han, Roland Beffa, Susana Gonzalez, Frank Maiwald, Jing Wang, Stephen B. PowlesAbstract:Rapid and widespread evolution of multiple herbicide resistance in global Weed species endowed by increased capacity to metabolize (degrade) herbicides (metabolic resistance) is a great threat to herbicide sustainability and global food production. Metabolic resistance in the economically damaging Crop Weed species Lolium rigidum is well known but a molecular understanding has been lacking. We purified a metabolic resistant (R) subset from a field evolved R L. rigidum population. The R, the herbicide susceptible (S) and derived F2 populations were used for candidate herbicide resistance gene discovery by RNA sequencing. A P450 gene CYP81A10v7 was identified with higher expression in R vs. S plants. Transgenic rice overexpressing this Lolium CYP81A10v7 gene became highly resistant to acetyl-coenzyme A carboxylase- and acetolactate synthase-inhibiting herbicides (diclofop-methyl, tralkoxydim, chlorsulfuron) and moderately resistant to hydroxyphenylpyruvate dioxygenase-inhibiting herbicide (mesotrione), photosystem II-inhibiting herbicides (atrazine and chlorotoluron) and the tubulin-inhibiting herbicide trifluralin. This wide cross-resistance profile to many dissimilar herbicides in CYP81A10v7 transgenic rice generally reflects what is evident in the R L. rigidum. This report clearly showed that a single P450 gene in a cross-pollinated Weed species L. rigidum confers resistance to herbicides of at least five modes of action across seven herbicide chemistries.
-
intensive Cropping systems select for greater seed dormancy and increased herbicide resistance levels in lolium rigidum annual ryegrass
Pest Management Science, 2015Co-Authors: Mechelle J Owen, Danica E Goggin, Stephen B. PowlesAbstract:BACKGROUND: Lolium rigidum (annual ryegrass) is a widespread annual Crop Weed that has evolved high levels of resistance to selective herbicides. Anecdotal evidence suggests that intensive Cropping also leads to higher seed dormancy in L. rigidum. This was quantified by measuring dormancy levels in L. rigidum populations collected from paired sites (one with nil to low Cropping intensity, the other intensively Cropped) located throughout the Western Australian grain belt. RESULTS: Populations from non-Cropped fields or those with low Cropping intensity showed higher and faster germination than populations from fields with a medium- or high-intensity Cropping regime. Resistance to selective herbicides was also higher in the medium- and high-intensity Cropping fields than in the low-intensity Cropping fields. CONCLUSION: High-intensity Cropping systems are likely to impose greater selection pressures for seed dormancy and selective herbicide resistance, because late-emerging seedlings avoid preplanting Weed control practices (tillage and non-selective herbicide application) but are exposed to selective in-Crop herbicides. © 2014 Society of Chemical Industry
-
metabolism based herbicide resistance and cross resistance in Crop Weeds a threat to herbicide sustainability and global Crop production
Plant Physiology, 2014Co-Authors: Qin Yu, Stephen B. PowlesAbstract: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.
-
glyphosate a once in a century herbicide
Pest Management Science, 2008Co-Authors: Stephen O Duke, Stephen B. PowlesAbstract:Since its commercial introduction in 1974, glyphosate [N-(phosphonomethyl)glycine] has become the dominant herbicide worldwide. There are several reasons for its success. Glyphosate is a highly effective broad-spectrum herbicide, yet it is very toxicologically and environmentally safe. Glyphosate translocates well, and its action is slow enough to take advantage of this. Glyphosate is the only herbicide that targets 5-enolpyruvyl-shikimate-3-phosphate synthase (EPSPS), so there are no competing herbicide analogs or classes. Since glyphosate became a generic compound, its cost has dropped dramatically. Perhaps the most important aspect of the success of glyphosate has been the introduction of transgenic, glyphosate-resistant Crops in 1996. Almost 90% of all transgenic Crops grown worldwide are glyphosate resistant, and the adoption of these Crops is increasing at a steady pace. Glyphosate/glyphosate-resistant Crop Weed management offers significant environmental and other benefits over the technologies that it replaces. The use of this virtually ideal herbicide is now being threatened by the evolution of glyphosate-resistant Weeds. Adoption of resistance management practices will be required to maintain the benefits of glyphosate technologies for future generations. Copyright © 2008 Society of Chemical Industry
-
management strategies for herbicide resistant Weed populations in australian dryland Crop production systems
Weed Technology, 2007Co-Authors: Michael J Walsh, Stephen B. PowlesAbstract:In most world Crop-production areas, the evolution of herbicide-resistant Weeds is becoming a major issue. This problem has become most severe across the Australian dryland Crop-production region, where herbicide-resistant Weed populations are threatening Crop-production profitability and sustainability across 20 million ha. Widespread herbicide resistance has forced changes in agronomic and herbicide practices. This problem is particularly evident in Western Australia, where the frequency and distribution of herbicide-resistant Weed populations appear to be greater than anywhere else in the world. Judicious use of herbicide mixtures and rotations can reduce the selection pressure for evolved resistance to any one specific herbicide. Additionally, agronomic practices, such as the double knockdown (preseeding sequential application of nonselective herbicides), increased seeding rates, and targeting of Weed seed production to prevent seedbank inputs, are needed to reduce the selection pressure on all herbicides by reducing in-Crop Weed populations. However, these techniques are not without problems or limitations, and their Weed control efficacy is inferior to that of most in-Crop selective herbicides. The adoption by Australian farmers of the current limited technology is clear evidence of the value placed on the use of these alternate Crop Weed-control practices. The continued evolution of herbicide resistance more than justifies continuing research and development efforts to produce integrated strategies and smarter herbicide use so as to achieve sustainable Weed management.
Bao-rong Lu - One of the best experts on this subject based on the ideXlab platform.
-
reduced Weed seed shattering by silencing a cultivated rice gene strategic mitigation for escaped transgenes
Transgenic Research, 2017Co-Authors: Lei Li, Xiaoqi Jiang, Jia Fang, Jun Su, Feng Wang, Bao-rong LuAbstract:Transgene flow form a genetically engineered (GE) Crop to its wild relatives may result in unwanted environmental consequences. Mitigating transgenes via introducing a gene that is disadvantageous to wild relatives but beneficial to Crops, and is tightly-linked with the target transgenes, may provide a promising solution to limit the spread of transgenes in wild/Weedy populations. Here we demonstrate a novel system with significantly reduced seed shattering in Crop-Weed hybrid descendants by partially silenced expression of the seed-shattering gene SH4 in cultivated rice, using artificial microRNA and antisense RNA techniques. Accordingly, fewer seeds were found in the soil of the field plots where transgenic hybrid lineages were grown. However, no differences in productivity-related traits were detected between GE and non-GE cultivated rice. To silence seed-shattering genes provides a useful strategy to reduce the potential environmental impacts caused by transgene flow from commercial GE rice to Weedy rice, in addition to the control of Weedy rice.
-
a novel 5 enolpyruvoylshikimate 3 phosphate epsp synthase transgene for glyphosate resistance stimulates growth and fecundity in Weedy rice oryza sativa without herbicide
New Phytologist, 2014Co-Authors: Wei Wang, Jun Su, Feng Wang, Xiao Yang, Ting Xu, Hong Jiang Si, Allison A Snow, Bao-rong LuAbstract:Summary � Understanding evolutionary interactions among Crops and Weeds can facilitate effective Weed management. For example, gene flow from Crops to their wild or Weedy relatives can lead to rapid evolution in recipient populations. In rice (Oryza sativa), transgenic herbicide resistance is expected to spread to conspecific Weedy rice (Oryza sativa f. spontanea) via hybridization. � Here, we studied fitness effects of transgenic over-expression of a native 5-enolpyruvoylshikimate-3-phosphate synthase (epsps) gene developed to confer glyphosate resistance in rice. Controlling for genetic background, we examined physiological traits and field performance of Crop–Weed hybrid lineages that segregated for the presence or absence of this novel epsps transgene. � Surprisingly, we found that transgenic F2 Crop–Weed hybrids produced 48–125% more seeds per plant than nontransgenic controls in monoculture- and mixed-planting designs without glyphosate application. Transgenic plants also had greater EPSPS protein levels, tryptophan concentrations, photosynthetic rates, and per cent seed germination compared with nontransgenic controls. � Our findings suggest that over-expression of a native rice epsps gene can lead to fitness advantages, even without exposure to glyphosate. We hypothesize that over-expressed epsps may be useful to breeders and, if deployed, could result in fitness benefits in Weedy relatives following transgene introgression.
Nathalie Colbach - One of the best experts on this subject based on the ideXlab platform.
-
assessing innovative sowing patterns for integrated Weed management with a 3d Crop Weed competition model
European Journal of Agronomy, 2014Co-Authors: Nathalie Colbach, Alban Collard, Sebastien H M Guyot, Delphine Meziere, Nicolas MunierjolainAbstract:Weed dynamics models are needed to design innovative Weed management strategies. Here, we developed a 3D individual-based model called FlorSys predicting growth and development of annual Weeds and Crops as a function of daily weather and Cropping practices: (1) Crop emergence is driven by temperature, and emerged plants are placed onto the 3D field map, depending on sowing pattern, density, and emergence rate; plants are described as cylinders with their leaf area distributed according to height; (2) Weed emergence is predicted by an existing submodel, emerged Weed seedlings are placed randomly; (3) plant phenology depends on temperature; (4) a previously developed submodel predicts available light in each voxel of the canopy; after emergence, plant growth is driven by temperature; when shaded, biomass accumulation results from the difference between photosynthesis and respiration; shading causes etiolation; (5) frost reduces biomass and destroys plants, (6) at plant maturity, the newly produced seeds are added to the soil seed bank. The model was used to test different sowing scenarios in an oilseed rape/winter wheat/winter barley rotation with sixteen Weed annuals, showing that (1) Crop yield loss was negatively correlated to Weed biomass averaged over the Cropping season; (2) Weed biomass was decreased by scenarios allowing early and homogenous Crop canopy closure (e.g. reduced interrows, increased sowing density, associated or undersown Crops), increased summer fatal Weed seed germination (e.g. delayed sowing) or, to a lesser degree, cleaner fields at cash Crop sowing (e.g. sowing a temporary cover Crop for “catching” nitrogen); (3) the scenario effect depended on Weed species (e.g. climbing species were little affected by increased Crop competition), and the result thus varied with the initial Weed community (e.g. communities dominated by small Weed species were hindered by the faster emergence of broadcast-sown Crops whereas taller species profited by the more frequent gap canopies); (4) the effect on Weed biomass of sowing scenarios applied to one year was still visible up to ten years later, and the beneficial effect during the test year could be followed by detrimental effects later (e.g. the changed tillage dates accompanying catch Crops reduced Weed emergence in the immediately following cash Crop but increased seed survival and thus infestation of the subsequent Crops). This simulation showed FlorSys to predict realistic potential Crop yields, and the simulated impact of Crop scenarios was consistent with literature reports.
-
a 3d model for light interception in heterogeneous Crop Weed canopies model structure and evaluation
Ecological Modelling, 2013Co-Authors: Nicolas Munierjolain, Sebastien H M Guyot, Nathalie ColbachAbstract:Abstract Models predicting photosynthetically active radiation (PAR) in heterogeneous canopies are an essential component of process-based Weed dynamics models for assessing integrated Weed management strategies. Most existing light availability models either consider only homogeneous canopies or are based on optical principles that are too complex for multi-annual and large-scale simulations required for evaluating Weed dynamics. The TROLL model adopted a simpler approach, discretizing the canopy into cubic volume cells (“voxels”) and successively calculating PAR transmitted between voxel layers as a function of leaf area and extinction coefficient in each voxel. The present study aimed at developing at a simple, generic individual-based 3D model predicting light availability and interception in heterogeneous canopies for subsequent introduction into a Weed dynamics model called FlorSys . In a first step, TROLL was adapted to Crop:Weed canopies for arable Crops in temperate latitudes by (1) developing a new function adapted to annuals for describing plant morphology, (2) accounting for lateral light transmission as a function of solar angle, and (3) predicting the variation in lateral transmission with season and latitude. In the second step, the predictions produced by the FlorSys light availability model were compared to PAR measurements in heterogeneous Crop stands. The model was shown to rank situations correctly and to predict incident PAR satisfactorily. A sensitivity analysis of FlorSys identified the voxel size optimizing prediction quality. In the last step, simulations were run to evaluate the potential of biological Weed regulation via Crop:Weed competition for light. The present model will be connected to emergence, growth and development models in further studies.
Wei Wang - One of the best experts on this subject based on the ideXlab platform.
-
ambient insect pressure and recipient genotypes determine fecundity of transgenic Crop Weed rice hybrid progeny implications for environmental biosafety assessment
Evolutionary Applications, 2016Co-Authors: Hui Xia, Feng Wang, Hongbin Zhang, Wei Wang, Xiao Yang, Hanbing Xia, Xingxing CaiAbstract:Transgene introgression into Crop Weedy/wild relatives can provide natural selective advantages, probably causing undesirable environmental impact. The advantages are likely associated with factors such as transgenes, selective pressure, and genetic background of transgene recipients. To explore the role of the environment and background of transgene recipients in affecting the advantages, we estimated the fitness of Crop-Weed hybrid lineages derived from crosses between marker-free insect-resistant transgenic (Bt/CpTI) rice with five Weedy rice populations under varied insect pressure. Multiway anova indicated the significant effect of both transgenes and Weedy rice genotypes on the performance of Crop-Weed hybrid lineages in the high-insect environment. Increased fecundity was detected in most transgene-present F1 and F2 hybrid lineages under high-insect pressure, but varied among Crop-Weed hybrid lineages with different Weedy rice parents. Increased fecundity of transgenic Crop-Weed hybrid lineages was associated with the environmental insect pressure and genotypes of their Weedy rice parents. The findings suggest that the fitness effects of an insect-resistant transgene introgressed into Weedy populations are not uniform across different environments and genotypes of the recipient plants that have acquired the transgene. Therefore, these factors should be considered when assessing the environmental impact of transgene flow to Weedy or wild rice relatives.
-
a novel 5 enolpyruvoylshikimate 3 phosphate epsp synthase transgene for glyphosate resistance stimulates growth and fecundity in Weedy rice oryza sativa without herbicide
New Phytologist, 2014Co-Authors: Wei Wang, Jun Su, Feng Wang, Xiao Yang, Ting Xu, Hong Jiang Si, Allison A Snow, Bao-rong LuAbstract:Summary � Understanding evolutionary interactions among Crops and Weeds can facilitate effective Weed management. For example, gene flow from Crops to their wild or Weedy relatives can lead to rapid evolution in recipient populations. In rice (Oryza sativa), transgenic herbicide resistance is expected to spread to conspecific Weedy rice (Oryza sativa f. spontanea) via hybridization. � Here, we studied fitness effects of transgenic over-expression of a native 5-enolpyruvoylshikimate-3-phosphate synthase (epsps) gene developed to confer glyphosate resistance in rice. Controlling for genetic background, we examined physiological traits and field performance of Crop–Weed hybrid lineages that segregated for the presence or absence of this novel epsps transgene. � Surprisingly, we found that transgenic F2 Crop–Weed hybrids produced 48–125% more seeds per plant than nontransgenic controls in monoculture- and mixed-planting designs without glyphosate application. Transgenic plants also had greater EPSPS protein levels, tryptophan concentrations, photosynthetic rates, and per cent seed germination compared with nontransgenic controls. � Our findings suggest that over-expression of a native rice epsps gene can lead to fitness advantages, even without exposure to glyphosate. We hypothesize that over-expressed epsps may be useful to breeders and, if deployed, could result in fitness benefits in Weedy relatives following transgene introgression.
-
conspecific Crop Weed introgression influences evolution of Weedy rice oryza sativa f spontanea across a geographical range
PLOS ONE, 2011Co-Authors: Hanbing Xia, Hui Xia, Wei Wang, Wei ZhaoAbstract:Background Introgression plays an important role in evolution of plant species via its influences on genetic diversity and differentiation. Outcrossing determines the level of introgression but little is known about the relationships of outcrossing rates, genetic diversity, and differentiation particularly in a Weedy taxon that coexists with its conspecific Crop.
Nicolas Munierjolain - One of the best experts on this subject based on the ideXlab platform.
-
assessing innovative sowing patterns for integrated Weed management with a 3d Crop Weed competition model
European Journal of Agronomy, 2014Co-Authors: Nathalie Colbach, Alban Collard, Sebastien H M Guyot, Delphine Meziere, Nicolas MunierjolainAbstract:Weed dynamics models are needed to design innovative Weed management strategies. Here, we developed a 3D individual-based model called FlorSys predicting growth and development of annual Weeds and Crops as a function of daily weather and Cropping practices: (1) Crop emergence is driven by temperature, and emerged plants are placed onto the 3D field map, depending on sowing pattern, density, and emergence rate; plants are described as cylinders with their leaf area distributed according to height; (2) Weed emergence is predicted by an existing submodel, emerged Weed seedlings are placed randomly; (3) plant phenology depends on temperature; (4) a previously developed submodel predicts available light in each voxel of the canopy; after emergence, plant growth is driven by temperature; when shaded, biomass accumulation results from the difference between photosynthesis and respiration; shading causes etiolation; (5) frost reduces biomass and destroys plants, (6) at plant maturity, the newly produced seeds are added to the soil seed bank. The model was used to test different sowing scenarios in an oilseed rape/winter wheat/winter barley rotation with sixteen Weed annuals, showing that (1) Crop yield loss was negatively correlated to Weed biomass averaged over the Cropping season; (2) Weed biomass was decreased by scenarios allowing early and homogenous Crop canopy closure (e.g. reduced interrows, increased sowing density, associated or undersown Crops), increased summer fatal Weed seed germination (e.g. delayed sowing) or, to a lesser degree, cleaner fields at cash Crop sowing (e.g. sowing a temporary cover Crop for “catching” nitrogen); (3) the scenario effect depended on Weed species (e.g. climbing species were little affected by increased Crop competition), and the result thus varied with the initial Weed community (e.g. communities dominated by small Weed species were hindered by the faster emergence of broadcast-sown Crops whereas taller species profited by the more frequent gap canopies); (4) the effect on Weed biomass of sowing scenarios applied to one year was still visible up to ten years later, and the beneficial effect during the test year could be followed by detrimental effects later (e.g. the changed tillage dates accompanying catch Crops reduced Weed emergence in the immediately following cash Crop but increased seed survival and thus infestation of the subsequent Crops). This simulation showed FlorSys to predict realistic potential Crop yields, and the simulated impact of Crop scenarios was consistent with literature reports.
-
a 3d model for light interception in heterogeneous Crop Weed canopies model structure and evaluation
Ecological Modelling, 2013Co-Authors: Nicolas Munierjolain, Sebastien H M Guyot, Nathalie ColbachAbstract:Abstract Models predicting photosynthetically active radiation (PAR) in heterogeneous canopies are an essential component of process-based Weed dynamics models for assessing integrated Weed management strategies. Most existing light availability models either consider only homogeneous canopies or are based on optical principles that are too complex for multi-annual and large-scale simulations required for evaluating Weed dynamics. The TROLL model adopted a simpler approach, discretizing the canopy into cubic volume cells (“voxels”) and successively calculating PAR transmitted between voxel layers as a function of leaf area and extinction coefficient in each voxel. The present study aimed at developing at a simple, generic individual-based 3D model predicting light availability and interception in heterogeneous canopies for subsequent introduction into a Weed dynamics model called FlorSys . In a first step, TROLL was adapted to Crop:Weed canopies for arable Crops in temperate latitudes by (1) developing a new function adapted to annuals for describing plant morphology, (2) accounting for lateral light transmission as a function of solar angle, and (3) predicting the variation in lateral transmission with season and latitude. In the second step, the predictions produced by the FlorSys light availability model were compared to PAR measurements in heterogeneous Crop stands. The model was shown to rank situations correctly and to predict incident PAR satisfactorily. A sensitivity analysis of FlorSys identified the voxel size optimizing prediction quality. In the last step, simulations were run to evaluate the potential of biological Weed regulation via Crop:Weed competition for light. The present model will be connected to emergence, growth and development models in further studies.