Busi R, Powles S B
Western Australian Herbicide Resistance Initiative, School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Crawley, Western Australia, Australia.
Heredity (Edinb). 2009 Oct;103(4):318-25. doi: 10.1038/hdy.2009.64. Epub 2009 Jun 3.
The majority of the documented cases of field-evolved herbicide-resistant weed biotypes established that single major genes confer glyphosate resistance. However, the contribution of minor genes endowing substantial plant survival at sublethal herbicide doses may be a potential complementary path to herbicide resistance evolution in weed populations under selection. Here, we subjected a number of susceptible individuals of Lolium rigidum to recurrent glyphosate selection to test the potential for sublethal glyphosate doses to additively select for glyphosate resistance. After 3-4 cycles of glyphosate selection in two distinct environments, the progenies of the initially susceptible population were shifted toward glyphosate resistance. The results indicate progressive enrichment of minor gene trait(s) contributing toward plant survival in the glyphosate-selected progenies. After three generations of selection, the estimated LD(50) values were doubled compared with the original population and up to 33% plant survival was obtained in the glyphosate-selected progeny at the recommended glyphosate label rate. This level of resistance probably was the maximum shift achievable with sublethal glyphosate dose selection in this small population. Cross-pollination was a crucial factor enabling the rapid rate of accumulation of minor glyphosate resistance gene trait(s) that are likely to be present at a relatively high frequency in a small susceptible population. The mechanistic basis of the moderate glyphosate resistance level selected by sublethal glyphosate doses remains unknown and warrants future research. Studying the main factors influencing the evolution of resistant weed populations is crucial for understanding, predicting and managing herbicide resistance.
大多数已记录的田间进化出除草剂抗性的杂草生物型案例表明，单个主要基因赋予了草甘膦抗性。然而，在亚致死除草剂剂量下赋予植物显著存活能力的次要基因，可能是杂草种群在选择压力下除草剂抗性进化的一条潜在补充途径。在此，我们对多株黑麦草易感个体进行了反复的草甘膦选择，以测试亚致死草甘膦剂量对草甘膦抗性进行累加选择的潜力。在两个不同环境中经过3 - 4轮草甘膦选择后，最初易感种群的后代向草甘膦抗性转变。结果表明，在草甘膦选择的后代中，有助于植物存活的次要基因性状逐渐富集。经过三代选择，与原始种群相比，估计的半数致死剂量（LD50）值翻倍，并且在推荐的草甘膦标签剂量下，草甘膦选择的后代中获得了高达33%的植物存活率。在这个小种群中通过亚致死草甘膦剂量选择所能达到的最大抗性转变可能就是这种水平。异花授粉是一个关键因素，它使得在小的易感种群中可能以相对高频率存在的次要草甘膦抗性基因性状能够快速积累。亚致死草甘膦剂量所选择的中等草甘膦抗性水平的作用机制尚不清楚，值得未来进行研究。研究影响抗性杂草种群进化的主要因素对于理解、预测和管理除草剂抗性至关重要。
