Busi Roberto, Girotto Marcelo, Powles Stephen B
Australian Herbicide Resistance Initiative, School of Plant Biology, The University of Western Australia, Crawley, WA, Australia.
Pest Manag Sci. 2016 Mar;72(3):603-8. doi: 10.1002/ps.4032. Epub 2015 May 22.
When applied at the correct plant stage and dose, herbicides are highly toxic to plants. At reduced, low herbicide doses (below the recommended dose) plants can survive and display continuous and quantitative variation in dose-survival responses. Recurrent (directional) selection studies can reveal whether such a phenotypic variation in plant survival response to low herbicide dose is heritable and leads to herbicide resistance. In a common experimental garden study, we have subjected a susceptible population of self-pollinated hexaploid Avena fatua to low-dose recurrent selection with the ACCase-inhibiting herbicide diclofop-methyl for three consecutive generations.
Significant differences in response to low-dose diclofop-methyl selection were observed between the selected progenies and parent plants, with a twofold diclofop-methyl resistance and cross-resistance to ALS-inhibiting herbicides. Thus, the capacity of self-pollinated A. fatua to respond to low-dose herbicide selection is marginal, and it is much lower than in cross-pollinated L. rigidum. Lolium rigidum in the same experiment evolved 40-fold diclofop-methyl resistance by progressive enrichment of quantitative resistance-endowing traits.
Cross-pollination rate, genetic variation and ploidy levels are identified as possible drivers affecting the contrasting capacity of Avena versus Lolium plants to respond to herbicide selection and the subsequent likelihood of resistance evolution at low herbicide dose usage.
当在正确的植物生长阶段和剂量下施用时，除草剂对植物具有高毒性。在降低的低除草剂剂量（低于推荐剂量）下，植物能够存活，并在剂量-存活反应中表现出连续的定量变化。反复（定向）选择研究可以揭示植物对低除草剂剂量的存活反应中的这种表型变异是否可遗传，并导致除草剂抗性。在一项普通实验园研究中，我们对自花授粉的六倍体野燕麦的一个敏感种群连续三代用抑制乙酰辅酶A羧化酶（ACCase）的除草剂禾草灵进行低剂量反复选择。
在所选后代与亲本植物之间观察到对低剂量禾草灵选择的反应存在显著差异，所选后代对禾草灵的抗性提高了两倍，并且对抑制乙酰乳酸合成酶（ALS）的除草剂产生了交叉抗性。因此，自花授粉的野燕麦对低剂量除草剂选择的反应能力有限，远低于异花授粉的硬直黑麦草。在同一实验中，硬直黑麦草通过逐步富集赋予定量抗性的性状，对禾草灵的抗性提高了40倍。
异花授粉率、遗传变异和倍性水平被确定为可能影响燕麦与黑麦草植物对除草剂选择的不同反应能力以及随后在低除草剂剂量使用情况下抗性进化可能性的驱动因素。
