Impact of a Novel W2027L Mutation and Non-Target Site Resistance on Acetyl-CoA Carboxylase-Inhibiting Herbicides in a French Lolium multiflorum Population

Abstract

Herbicides that inhibit acetyl-CoA carboxylase (ACCase) are among the few remaining options for the post-emergence control of Lolium species in small grain cereal crops. Here, we determined the mechanism of resistance to ACCase herbicides in a Lolium multiflorum population (HGR) from France. A combined biological and molecular approach detected a novel W2027L ACCase mutation that affects aryloxyphenoxypropionate (FOP) but not cyclohexanedione (DIM) or phenylpyraxoline (DEN) subclasses of ACCase herbicides. Both the wild-type tryptophan and mutant leucine 2027-ACCase alleles could be positively detected in a single DNA-based-derived polymorphic amplified cleaved sequence (dPACS) assay that contained the targeted PCR product and a cocktail of two discriminating restriction enzymes. Additionally, we identified three well-characterised I1781L, I2041T, and D2078G ACCase target site resistance mutations as well as non-target site resistance in HGR. The non-target site component endowed high levels of resistance to FOP herbicides whilst partially impacting on the efficacy of pinoxaden and cycloxydim. This study adequately assessed the contribution of the W2027L mutation and non-target site mechanism in conferring resistance to ACCase herbicides in HGR. It also highlights the versatility and robustness of the dPACS method to simultaneously identify different resistance-causing alleles at a single ACCase codon.

Differential Resistance to Acetyl-CoA Carboxylase Inhibitors in Rice: Insights from Two Distinct Target-Site Mutations

“…To date, resistance has unveiled approximately 20 distinct ACCase amino acid substitutions across seven key loci within the CT domain of the plastidic ACCase in Alopecurus myosuroides, associated with herbicide resistance. These substitutions include Ile-1781-Leu/Thr/Val, Trp-1999-Cys/Leu/Ser, Trp-2027-Cys/Leu/Ser, Ile-2041-Asn/Val, Asn-2078-Glu/Gly, Cys-2088-Arg, and Gly-2096-Ala/Ser. ,− Among these, Ile-1781-Leu is notably prevalent, demonstrating robust resistance across three chemical families of ACCase inhibitor herbicides. Conversely, the Gly-2096-Ser mutation predominantly confers resistance to APP herbicides, with limited exceptions, such as in Phalaris paradoxa, where resistance extends to the CHD herbicide pinoxaden. − In this study, three stably inherited herbicide-resistant mutants were identified within three distinct rice EMS mutant populations.…”

Molecular Mechanisms of Herbicide Resistance in Weeds

“…Among grasses, Echinochloa ssp. is reported in two articles [ 9 , 14 ] and L. multiflorum in one [ 8 ]; among dicots, two articles reported on the global invasive weed species A. palmeri [ 10 , 13 ]. All these weeds are acknowledged to be among the top 10 weed species resistant to most SoAs globally [ 19 ].…”

“…Three articles reported mechanisms of TSR nature covering most of the known types: point mutations [ 8 , 9 ], codon deletion [ 10 ], and altered expression patterns [ 9 ].…”

“…Resistance to ACCase- and ALS-inhibiting herbicides conferred by point mutations in the gene were among the first cases reported as TSR decades ago. Two contributions reported point mutations conferring resistance to ACCase and ALS inhibitors in Lolium multiflorum [ 8 ] and Echinochloa ssp. [ 9 ], respectively.…”

“…Surprisingly, there are still recent discoveries regarding ACCase-inhibiting herbicides. Kaudun et al [ 8 ] found a novel mutation in position 2027 of the ACCase gene, leading to the amino acid change Tryptophan by Leucine. This W2027L change, together with three well-characterized I1781L, I2041T, and D2078G changes also found in the study, endowed resistance to aryloxyphenoxypropionates, phenylpyraxolines, and cyclohexanediones, as well as unidentified NTSR.…”