An aspartate to glycine change in the carboxyl transferase domain of acetyl CoA carboxylase and non-target-site mechanism(s) confer resistance to ACCase inhibitor herbicides in a Lolium multiflorum population.
BACKGROUND
The increasing use of ACCase-inhibiting herbicides has resulted in evolved resistance in key grass weeds infesting cereal cropping systems worldwide. Here, a thorough and systematic approach is proposed to elucidate the basis of resistance to three ACCase herbicides in a Lolium multiflorum Lam. (Italian rye grass) population from the United Kingdom (UK24).


RESULTS
Resistance to sethoxydim and pinoxaden was always associated with a dominant D2078G (Alopecurus myosuroides Huds. equivalent) target-site mutation in UK24. Conversely, whole-plant herbicide assays on predetermined ACCase genotypes showed very high levels of resistance to diclofop-methyl for all three wild DD2078 and mutant DG2078 and GG2078 ACCase genotypes from the mixed resistant population UK24. This indicates the presence of other diclofop-methyl-specific resistance mechanism(s) yet to be determined in this population. The D2078G mutation could be detected using an unambiguous DNA-based dCAPS procedure that proved very transferable to A. myosuroides, Avena fatua L., Setaria viridis (L.) Beauv. and Phalaris minor Retz.


CONCLUSIONS
This study provides further understanding of the molecular basis of resistance to ACCase inhibitor herbicides in a Lolium population and a widely applicable PCR-based method for monitoring the D2078G target-site resistance mutation in five major grass weed species.
Kaundun
Shiv Shankhar
SS
Syngenta, Jealott's Hill International Research Centre, Bracknell, Berkshire, UK. deepak.kaundun@syngenta.com
D000103:Acetyl-CoA Carboxylase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics; D019943:Amino Acid Substitution; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D053209:Herbicide Resistance / Q000235:genetics*; D006540:Herbicides / Q000494:pharmacology*; D008129:Lolium / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
D004791:Enzyme Inhibitors; D006540:Herbicides; D000103:Acetyl-CoA Carboxylase