Testing root length bioassay for assessment of herbicide resistance in wild oat (Avena fatua L.)

Non-Peer Reviewe

Control of gene-stacked canola by alternative herbicides

Non-Peer ReviewedUnintentional herbicide resistance gene stacking in canola may alter the sensitivity of volunteers to herbicides of alternative modes of action commonly used for their control. Greenhouse experiments were conducted to investigate the dose response of three single herbicide-resistant (HR) cultivars (glyphosate, glufosinate, imidazolinone), one non-HR cultivar, and seven multiple (double or triple) HR experimental lines treated at the two- to three-leaf stage to 2,4-D (amine and ester), MCPA ester, and metribuzin; and of one non-HR and four HR cultivars (glyphosate, glufosinate, imidazolinone, bromoxynil) to 2,4-D amine applied at two growth stages (two to three, and five to six leaves). All canola cultivars or lines treated at the two- to three-leaf stage responded similarly to increasing doses of the three herbicides. At the five- to six-leaf stage, however, the bromoxynil HR cultivar was less sensitive to 2,4-D than the other cultivars. The results of this study suggest that canola with multiple herbicide resistance traits does not differ from cultivars that are non-HR or single HR in its sensitivity to herbicides commonly used to control volunteers. All volunteers, whether non-HR, single HR, or multiple HR, should be treated when plants are most sensitive to herbicides (two- to four-leaf stage) to reduce their interference against crops and their perpetuation of gene flow

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

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

Genetic load and transgenic mitigating genes in transgenic Brassica rapa (field mustard) × Brassica napus (oilseed rape) hybrid populations

<p>Abstract</p> <p>Background</p> <p>One theoretical explanation for the relatively poor performance of <it>Brassica rapa </it>(weed) × <it>Brassica napus </it>(crop) transgenic hybrids suggests that hybridization imparts a negative genetic load. Consequently, in hybrids genetic load could overshadow any benefits of fitness enhancing transgenes and become the limiting factor in transgenic hybrid persistence. Two types of genetic load were analyzed in this study: random/linkage-derived genetic load, and directly incorporated genetic load using a transgenic mitigation (TM) strategy. In order to measure the effects of random genetic load, hybrid productivity (seed yield and biomass) was correlated with crop- and weed-specific AFLP genomic markers. This portion of the study was designed to answer whether or not weed × transgenic crop hybrids possessing more crop genes were less competitive than hybrids containing fewer crop genes. The effects of directly incorporated genetic load (TM) were analyzed through transgene persistence data. TM strategies are proposed to decrease transgene persistence if gene flow and subsequent transgene introgression to a wild host were to occur.</p> <p>Results</p> <p>In the absence of interspecific competition, transgenic weed × crop hybrids benefited from having more crop-specific alleles. There was a positive correlation between performance and number of <it>B. napus </it>crop-specific AFLP markers [seed yield vs. marker number (r = 0.54, P = 0.0003) and vegetative dry biomass vs. marker number (r = 0.44, P = 0.005)]. However under interspecific competition with wheat or more weed-like conditions (i.e. representing a situation where hybrid plants emerge as volunteer weeds in subsequent cropping systems), there was a positive correlation between the number of <it>B. rapa </it>weed-specific AFLP markers and seed yield (r = 0.70, P = 0.0001), although no such correlation was detected for vegetative biomass. When genetic load was directly incorporated into the hybrid genome, by inserting a fitness-mitigating dwarfing gene that that is beneficial for crops but deleterious for weeds (a transgene mitigation measure), there was a dramatic decrease in the number of transgenic hybrid progeny persisting in the population.</p> <p>Conclusion</p> <p>The effects of genetic load of crop and in some situations, weed alleles might be beneficial under certain environmental conditions. However, when genetic load was directly incorporated into transgenic events, e.g., using a TM construct, the number of transgenic hybrids and persistence in weedy genomic backgrounds was significantly decreased.</p

Broad Resistance to ACCase Inhibiting Herbicides in a Ryegrass Population Is Due Only to a Cysteine to Arginine Mutation in the Target Enzyme

BACKGROUND: The design of sustainable weed management strategies requires a good understanding of the mechanisms by which weeds evolve resistance to herbicides. Here we have conducted a study on the mechanism of resistance to ACCase inhibiting herbicides in a Lolium multiflorum population (RG3) from the UK. METHODOLOGY/PRINCIPAL FINDINGS: Analysis of plant phenotypes and genotypes showed that all the RG3 plants (72%) that contained the cysteine to arginine mutation at ACCase codon position 2088 were resistant to ACCase inhibiting herbicides. Whole plant dose response tests on predetermined wild and mutant 2088 genotypes from RG3 and a standard sensitive population indicated that the C2088R mutation is the only factor conferring resistance to all ten ACCase herbicides tested. The associated resistance indices ranged from 13 for clethodim to over 358 for diclofop-methyl. Clethodim, the most potent herbicide was significantly affected even when applied on small mutant plants at the peri-emergence and one leaf stages. CONCLUSION/SIGNIFICANCE: This study establishes the clear and unambiguous importance of the C2088R target site mutation in conferring broad resistance to ten commonly used ACCase inhibiting herbicides. It also demonstrates that low levels "creeping", multigenic, non target site resistance, is not always selected before single gene target site resistance appears in grass weed populations subjected to herbicide selection pressure

Gene Flow in Genetically Modified Wheat

Understanding gene flow in genetically modified (GM) crops is critical to answering questions regarding risk-assessment and the coexistence of GM and non-GM crops. In two field experiments, we tested whether rates of cross-pollination differed between GM and non-GM lines of the predominantly self-pollinating wheat Triticum aestivum. In the first experiment, outcrossing was studied within the field by planting “phytometers” of one line into stands of another line. In the second experiment, outcrossing was studied over distances of 0.5–2.5 m from a central patch of pollen donors to adjacent patches of pollen recipients. Cross-pollination and outcrossing was detected when offspring of a pollen recipient without a particular transgene contained this transgene in heterozygous condition. The GM lines had been produced from the varieties Bobwhite or Frisal and contained Pm3b or chitinase/glucanase transgenes, respectively, in homozygous condition. These transgenes increase plant resistance against pathogenic fungi. Although the overall outcrossing rate in the first experiment was only 3.4%, Bobwhite GM lines containing the Pm3b transgene were six times more likely than non-GM control lines to produce outcrossed offspring. There was additional variation in outcrossing rate among the four GM-lines, presumably due to the different transgene insertion events. Among the pollen donors, the Frisal GM line expressing a chitinase transgene caused more outcrossing than the GM line expressing both a chitinase and a glucanase transgene. In the second experiment, outcrossing after cross-pollination declined from 0.7–0.03% over the test distances of 0.5–2.5 m. Our results suggest that pollen-mediated gene flow between GM and non-GM wheat might only be a concern if it occurs within fields, e.g. due to seed contamination. Methodologically our study demonstrates that outcrossing rates between transgenic and other lines within crops can be assessed using a phytometer approach and that gene-flow distances can be efficiently estimated with population-level PCR analyses

Crop Updates 2010 - Crop Specific

This session covers twenty four papers from different authors: PLENARY 1. Challenges facing western Canadian cropping over the next 10 years, Hugh J Beckie, Research Centre, Agriculture and Agri-Food Canada, Saskatoon, Saskatchewan CROP SPECIFIC Breeding 2. The challenge of breeding canola hybrids – new opportunities for WA growers, Wallace Cowling, Research Director, Canola Breeders Western Australia Pty Ltd 3. Chickpea 2009 crop variety testing of germplasm developed by DAFWA/CLIMA/ICRISAT/COGGO alliance. Khan, TN1,3, Adhikari, K1,3, Siddique, K2, Garlinge, J1, Smith, L1, Morgan, S1 and Boyd, C1 1Department of Agriculture and Food, Western Australia (DAFWA), 2Insititute of Agriculture, The University of Western Australia (UWA), 3Centre for Legumes in Mediterranean Agriculture (CLIMA), The University of Western Australia 4. PBA Pulse Breeding Australia – 2009 Field Pea Results, Ian Pritchard1, Chris Veitch1, Colin Boyd1, Stuart Morgan1, Alan Harris1 and Tony Leonforte2, 1Department of Agriculture and Food, Western Australia, 2Department of Primary Industries, Victoria 5. PBA Pulse Breeding Australia – 2009 Chickpea Results, Ian Pritchard1, Chris Veitch1, Colin Boyd1, Murray Blyth1, Shari Dougal1 and Kristy Hobson2 1Department of Agriculture and Food, Western Australia, 2Department of Primary Industries, Victoria Decision Support 6. A tool for identifying problems in wheat paddocks, Ben Curtis and Doug Sawkins, Department of Agriculture and Food 7. DAFWA Seasonal Forecast for 2010, Stephens, D, Department of Agriculture and Food, Western Australian, Climate and Modelling Group Disease 8. Enhancement of black spot resistance in field pea, Kedar Adhikari, T Khan, S Morgan and C Boyd, Department of Agriculture and Food, 9. fungicide management of yellow spot in wheat, Ciara Beard, Kith Jayasena, Kazue Tanaka and Anne Smith, Department of Agriculture and Food 10. Resistance to infection by Beet western yellows virus in four Australian canola varieties, Brenda Coutts and Roger Jones, Department of Agriculture and Food 11. Yellow spot carryover risk from stubble in wheat-on-wheat rotations, Jean Galloway, Pip Payne and Tess Humphreys, Department of Agriculture and Food 12. Fungicides for the future: Management of Barley Powdery Mildew and Leaf Rust, Kith Jayasena, Kazue Tanaka and William MacLeod, Department of Agriculture and Food 13. 2009 canola disease survey and management options for blackleg and Sclerotinia in 2010, Ravjit Khangura, WJ MacLeod, M Aberra and H Mian, Department of Agriculture and Food 14. Impact of variety and fungicide on carryover of stubble borne inoculum and yellow spot severity in continuous wheat cropping, Geoff Thomas, Pip Payne, Tess Humphreys and Anne Smith, Department of Agriculture and Food 15. Limitations to the spread of Wheat streak mosaic virus by the Wheat curl mite in WA during 2009, Dusty Severtson, Peter Mangano, Brenda Coutts, Monica Kehoe and Roger Jones, Department of Agriculture and Food 16. Viable solutions for barley powdery mildew, Madeline A. Tucker, Australian Centre for Necrotrophic Fungal Pathogens, Murdoch University Marketing 17. The importance of varietal accreditation in a post-deregulation barley marketing environment, Neil Barker, Barley Australia 18. Can Australia wheat meet requirements for a new middle east market? Robert Loughman, Larisa Cato, Department of Agriculture and Food, and Ken Quail, BRI Australia VARIETY PERFORMANCE 19. Sowing rate and time for hybrid vs open-pollinated canola, Mohammad Amjad and Mark Seymour, Department of Agriculture and Food 20. HYOLA® National Hybrid vs OP Canola Hybrid F1 vs Retained Seed Generation Trial Results and recommendations for growers, Justin Kudnig, Mark Thompson, Anton Mannes, Michael Uttley, Chris Fletcher, Andrew Etherton, Nick Joyce and Kate Light, Pacific Seeds Australia 21. HYOLA® National Hybrid vs OP Canola Sowing Rate Trial Results and plant population recommendations for Australian growers, Justin Kudnig, Mark Thompson, Anton Mannes, Michael Uttley, Andrew Etherton, Chris Fletcher, Nick Joyce and Kate Light, Pacific Seeds Australia; Peter Hamblin, Agritech Research Young, NSW, Michael Lamond, Agrisearch, York, Western Australia 22. Desi chickpea agronomy for 2010, Alan Meldrum, Pulse Australia and Wayne Parker, Department of Agriculture and Food 23. New wheat varieties – exploit the benefits and avoid the pitfalls, Steve Penny, Sarah Ellis, Brenda Shackley, Christine Zaicou, Shahajahan Miyan, Darshan Sharma and Ben Curtis, Department of Agriculture and Food 24. The influence of genetics and environment on the level of seed alkaloid in narrow-leafed lupins, Greg Shea1, Bevan Buirchell1, David Harris2 and Bob French1, 1Department of Agriculture and Food, 2ChemCentr