Yu Qin, Cairns Andrew, Powles Stephen
Western Australian Herbicide Resistance Initiative, School of Plant Biology, University of Western Australia, Crawley, Perth, WA, Australia.
Planta. 2007 Jan;225(2):499-513. doi: 10.1007/s00425-006-0364-3. Epub 2006 Aug 12.
Glyphosate is the world's most widely used herbicide. A potential substitute for glyphosate in some use patterns is the herbicide paraquat. Following many years of successful use, neither glyphosate nor paraquat could control a biotype of the widespread annual ryegrass (Lolium rigidum), and here the world's first case of multiple resistance to glyphosate and paraquat is confirmed. Dose-response experiments established that the glyphosate rate causing 50% mortality (LD(50)) for the resistant (R) biotype is 14 times greater than for the susceptible (S) biotype. Similarly, the paraquat LD(50 )for the R biotype is 32 times greater than for the S biotype. Thus, based on the LD(50 )R/S ratio, this R biotype of L. rigidum is 14-fold resistant to glyphosate and 32-fold resistant to paraquat. This R biotype also has evolved resistance to the acetyl-coenzyme A carboxylase (ACCase) inhibiting herbicides. The mechanism of paraquat resistance in this biotype was determined as restricted paraquat translocation. Resistance to ACCase-inhibiting herbicides was determined as due to an insensitive ACCase. Two mechanisms endowing glyphosate resistance were established: firstly, a point mutation in the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene, resulting in an amino acid substitution of proline to alanine at position 106; secondly, reduced glyphosate translocation was found in this R biotype, indicating a co-occurrence of two distinct glyphosate resistance mechanisms within the R population. In total, this R biotype displays at least four co-existing resistance mechanisms, endowing multiple resistance to glyphosate, paraquat and ACCase herbicides. This alarming case in the history of herbicide resistance evolution represents a serious challenge for the sustainable use of the precious agrochemical resources such as glyphosate and paraquat.
草甘膦是世界上使用最广泛的除草剂。在某些使用模式下，除草剂百草枯是草甘膦的一种潜在替代品。经过多年的成功使用，草甘膦和百草枯都无法控制广泛分布的一年生黑麦草（硬直黑麦草）的一种生物型，在此确认了世界上首例对草甘膦和百草枯的多重抗性。剂量反应实验表明，导致抗性（R）生物型50%死亡率（LD50）的草甘膦剂量比对敏感（S）生物型高14倍。同样，R生物型的百草枯LD50比对S生物型高32倍。因此，基于LD50的R/S比值，这种硬直黑麦草的R生物型对草甘膦具有14倍抗性，对百草枯具有32倍抗性。这种R生物型还对乙酰辅酶A羧化酶（ACCase）抑制型除草剂产生了抗性。该生物型对百草枯的抗性机制被确定为百草枯转运受限。对ACCase抑制型除草剂的抗性被确定是由于ACCase不敏感。确定了赋予草甘膦抗性的两种机制：第一，5-烯醇丙酮酸莽草酸-3-磷酸合酶（EPSPS）基因中的一个点突变，导致第106位的脯氨酸被丙氨酸取代；第二，在这种R生物型中发现草甘膦转运减少，表明在R群体中同时存在两种不同的草甘膦抗性机制。总体而言，这种R生物型至少表现出四种共存的抗性机制，赋予了对草甘膦、百草枯和ACCase除草剂的多重抗性。除草剂抗性进化史上的这一惊人案例对草甘膦和百草枯等宝贵农用化学品资源的可持续利用构成了严峻挑战。
