抗草甘膦杂草的抗性机理研究进展

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.     

杂草对草甘膦的抗性及抗性治理

本文从草甘膦现状、杂草抗性、抗性机制及抗性治理等几方面进行综述．并提出几点看法。力求提高草甘膦管理水平延长其使用年限，促进农业的发展。     

草甘膦在抗除草剂油菜田的应用研究初报

油菜是杂草危害较为严重的作物之一,我国冬油菜区草害面积达45%～48%,中度以上危害的面积达22%～23%,春油菜区危害面积高达80%以上,草害已成为制约我国油菜生产水平提高的重要因素.目前,防治油菜田单子叶类杂草如禾本科杂草,使用稳杀得、盖草能、禾草克等除草剂就能收到较好的防治效果,但对双子叶类的阔叶杂草还没有理想的除草剂.     

草甘膦抗性杂草的田间监测

北京的大兴区北藏村镇巴园子村的苦菜、节节草对草甘膦不敏感,防效仅为40%~60%;顺义区木林镇魏家店村的马唐对草甘膦不敏感,防效仅70%;通州区潞城镇小营村的藜对草甘膦不敏感,防效仅50%;延庆县井庄镇二司村的黄花蒿、刺儿菜、狗尾草、苦荬菜对草甘膦不敏感,防效仅40%~60%;延庆县农场的黄花蒿、刺儿菜、紫花地丁、苦荬菜对草甘膦不敏感,防效仅30%~50%;山东省淄博的铁苋菜对草甘膦不敏感,防效为70%;滕州的小飞蓬、苘麻、葎草对草甘膦不敏感,防效为40%~60%;广西的杂草对草甘膦都比较敏感,防效都在88%以上;其他杂草对草甘膦较敏感。     

沙蚕毒素类杀虫剂作用机制及其抗性的研究进展

本文对沙蚕毒素类杀虫剂的研究历史、对害虫的作用机制、害虫对沙蚕毒素类杀虫剂的抗性及其抗性治理研究进展等作了介绍。     

除草剂面临的挑战及草甘膦复配的意义

除草剂是保证农业高产、稳产的重要工具,在农业现代化进程中发挥着举足轻重的作用。本文对我国除草剂面临的挑战及草甘膦复配等方面的内容进行了综述,并提出相关可行性解决方案。     

除草剂安全剂作用机制研究进展

除草剂安全剂在不影响除草剂对靶标杂草活性的前提下可选择性地保护作物免受除草剂的伤害。本文通过讨论安全剂对植物体内除草剂各种生理生化过程的影响,阐述了安全剂作用机制的研究。     

阿根廷新发现一种抗草甘膦杂草

在阿根廷,一种新的杂草品种Bradley发展出了抗草甘膦除草剂的特性。国家杂草抗性知识网REM已经发出预警,提醒这种多年生的草本植物Bradley已发展出抗药性。据REM称,这是禾本科杂草中出现的第六个抗性品种,其余还包括假高梁（Sorghumhalepense）、多花黑麦草（Loliummultiflorum）、     

What have the mechanisms of resistance to glyphosate taught us?

The intensive use of glyphosate alone to manage weeds has selected populations that are glyphosate resistant. The three mechanisms of glyphosate resistance that have been elucidated are (1) target-site mutations, (2) gene amplification and (3) altered translocation due to sequestration. What have we learned from the selection of these mechanisms, and how can we apply those lessons to future herbicide-resistant crops and new mechanisms of action? First, the diversity of glyphosate resistance mechanisms has helped further our understanding of the mechanism of action of glyphosate and advanced our knowledge of plant physiology. Second, the relatively rapid evolution of glyphosate-resistant weed populations provides further evidence that no herbicide is invulnerable to resistance. Third, as new herbicide-resistant crops are developed and new mechanisms of action are discovered, the weed science community needs to ensure that we apply the lessons we have learned on resistance management from the experience with glyphosate. Every new weed management system must be evaluated during development for its potential to select for resistance, and stewardship programs should be in place when the new program is introduced. Copyright © 2011 Society of Chemical Industry     

Simulating evolution of glyphosate resistance in Lolium rigidum I: population biology of a rare resistance trait

Despite frequent use for the past 25 years, resistance to glyphosate has evolved in few weed biotypes. The propensity for evolution of resistance is not the same for all herbicides, and glyphosate has a relatively low resistance risk. The reasons for these differences are not entirely understood. A previously published two‐herbicide resistance model has been modified to explore biological and management factors that account for observed rates of evolution of glyphosate resistance. Resistance to a post‐emergence herbicide was predicted to evolve more rapidly than it did to glyphosate, even when both were applied every year and had the same control efficacy. Glyphosate is applied earlier in the growing season when fewer weeds have emerged and hence exerts less selection pressure on populations. The evolution of glyphosate resistance was predicted to arise more rapidly when glyphosate applications were later in the growing season. In simulations that assumed resistance to the post‐emergence herbicide did not evolve, the evolution of glyphosate resistance was less rapid, because post‐emergence herbicides were effectively controlling rare glyphosate‐resistant individuals. On their own, these management‐related factors could not entirely account for rates of evolution of resistance to glyphosate observed in the field. In subsequent analyses, population genetic parameter values (initial allele frequency, dominance and fitness) were selected on the basis of empirical data from a glyphosate‐resistant Lolium rigidum population. Predicted rates of evolution of resistance were similar to those observed in the field. Together, the timing of glyphosate applications, the rarity of glyphosate‐resistant mutants, the incomplete dominance of glyphosate‐resistant alleles and pleiotropic fitness costs associated with glyphosate resistance, all contribute to its relatively slow evolution in the field.     

The possible role of quinate in the mode of action of glyphosate and acetolactate synthase inhibitors

BACKGROUND: The herbicide glyphosate inhibits the biosynthesis of aromatic amino acids by blocking the shikimate pathway. Imazethapyr and chlorsulfuron are two herbicides that act by inhibiting branched‐chain amino acid biosynthesis. These herbicides stimulate secondary metabolism derived from the aromatic amino acids. The aim of this study was to test if they cause any cross‐effect in the amino acid content and if they have similar effects on the shikimate pathway. RESULTS: The herbicides inhibiting two different amino acid biosynthesis pathways showed a common pattern in general content of free amino acids. There was a general increase in total free amino acid content, with a transient decrease in the proportion of amino acids whose pathways were specifically inhibited. Afterwards, an increase in these inhibited amino acids was detected; this was probably related to proteolysis. All herbicides caused quinate accumulation. Exogenous application of quinate arrested growth, decreased net photosynthesis and stomatal conductance and was ultimately lethal, similarly to glyphosate and imazethapyr. CONCLUSIONS: Quinate accumulation was a common effect of the two different classes of herbicide. Moreover, exogenous quinate application had phytotoxic effects, showing that this plant metabolite can trigger the toxic effects of the herbicides. This ability to mimic the herbicide effects suggests a possible link between the mode of action of these herbicides and the potential role of quinate as a natural herbicide. Copyright © 2009 Society of Chemical Industry     

Herbicide‐resistant weed management: focus on glyphosate

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. Copyright © 2011 Society of Chemical Industry     

Evolution and spread of glyphosate resistance in Conyza bonariensis in California and a comparison with closely related Conyza canadensis

Glyphosate‐resistant weeds are an increasing problem in perennial cropping systems in the Central Valley of California, USA. To elucidate the evolutionary origins and spatial spread of resistance, we investigated the geographical distribution of glyphosate resistance and the population genetic diversity and structure of Conyza bonariensis and compared the results with previously studied C. canadensis. Thirty‐five populations from orchards and vineyards across the Central Valley were sampled. Population genetic structure was assessed using microsatellite markers. Population‐level resistance was assessed in glasshouse screening of plants grown from field‐collected seed. Bayesian clustering and analyses of multilocus genotypes indicated multiple origins of resistance, as observed in C. canadensis. Pairwise F_ST analysis detected spatial spread of resistance in the south of the Central Valley, also similar to C. canadensis. The results strongly indicate that the southern valley was an environment markedly more suitable than the northern valley for resistance spread and that spread in Conyza species was driven by increased uniformity of strong selection in the southern valley, due to recent regulation on herbicides other than glyphosate. Accordingly, resistant C. canadensis individuals occurred at high frequencies only in the southern valley, but interestingly resistant C. bonariensis occurred at high frequencies throughout the valley. Expression of resistance showed varying degrees of plasticity in C. bonariensis. The lower selfing rate and substantially greater genotypic diversity in C. bonariensis, relative to C. canadensis, indicate greater evolutionary potential over shorter time periods. Interspecific hybridisation was detected, but its role in resistance evolution remains unclear.     

Why have no new herbicide modes of action appeared in recent years?

Herbicides with new modes of action are badly needed to manage the evolution of resistance of weeds to existing herbicides. Yet no major new mode of action has been introduced to the market place for about 20 years. There are probably several reasons for this. New potential products may have remained dormant owing to concerns that glyphosate-resistant (GR) crops have reduced the market for a new herbicide. The capture of a large fraction of the herbicide market by glyphosate with GR crops led to significantly diminished herbicide discovery efforts. Some of the reduced herbicide discovery research was also due to company consolidations and the availability of more generic herbicides. Another problem might be that the best herbicide molecular target sites may have already been discovered. However, target sites that are not utilized, for which there are inhibitors that are highly effective at killing plants, suggests that this is not true. Results of modern methods of target site discovery (e.g. gene knockout methods) are mostly not public, but there is no evidence of good herbicides with new target sites coming from these approaches. In summary, there are several reasons for a long dry period for new herbicide target sites; however, the relative magnitude of each is unclear. The economic stimulus to the herbicide industry caused by the evolution of herbicide-resistant weeds, especially GR weeds, may result in one or more new modes of action becoming available in the not too distant future.     

Resistance to glyphosate in Lolium rigidum

Annual ryegrass (Lolium rigidum) is a widespread and important weed of Australia and populations of this weed have developed resistance to most major herbicides, including glyphosate. The possible mechanisms of resistance have been examined in one glyphosate-resistant Lolium population. No major differences were observed between resistant and susceptible biotypes in respect of (i) the target enzyme (EPSP synthase), (ii) DAHP synthase, the first enzyme of the target (shikimate) pathway, (iii) absorption of glyphosate, or (iv) translocation. Following treatment with glyphosate, there was greater accumulation of shikimate (derived from shikimate-3-Pi) in susceptible than in resistant plants. In addition, the resistant population exhibited cross-resistance to 2-hydroxy-3-(1,2,4-triazol-1-yl)propyl phosphonate, a herbicide which, although structurally similar to glyphosate, acts at an unrelated target site. On the basis of these observations we speculate that movement of glyphosate to its site of action in the plastid is involved in the resistance mechanism. © 1999 Society of Chemical Industry