Costs and benefits of target-site herbicide resistance endowing mutations in the ACCase gene

VILA AIUB, MM; HAN, H; YU, Q; POWLES, SB

Conferencia; Global Herbicide Resistance Challenge Conference; 2013

Australian Herbicide Resistance Initiative

Herbicide resistance evolution is a function of fitness traits endowed by resistance alleles in both the presence (resistance benefit) and absence (resistance cost) of herbicides. Resistance cost and benefit associated with resistance-endowing alleles (Ile-1781-Leu, Asp-2078-Gly and Cys-2088-Arg) in the ACCase gene in Lolium rigidum were evaluated. Resistance cost associated with each specific ACCase resistance allele was estimated after evaluation of various growth responses. The resistance benefit conferred by each specific allele was estimated by comparing plant survival and growth response in herbicide (clethodim) treated vs. non-treated plants (i.e. resistance decay). Plants with the 1781-Leu resistance allele showed no resistance cost and moderate resistance decay (30%). The 2078-Gly allele endowed both a significant resistance cost (RGR-based 30%) and decay (60%). Plants possessing the 2088-Arg resistance allele showed a moderate resistance cost (RGR-based 13%) in the absence of clethodim but significant decay (50%) when exposed to the herbicide. The origin of resistance costs and benefits are discussed within the context of pleiotropic effects of each specific resistance allele on ACCase activity and kinetics as well as new insights into the understanding of herbicide resistance evolution.