Abstract
BackgroundKnowledge of the mechanisms of herbicide resistance is important for designing long term sustainable weed management strategies. Here, we have used an integrated biology and molecular approach to investigate the mechanisms of resistance to acetyl-CoA carboxylase inhibiting herbicides in a UK black-grass population (BG2).Methodology/Principal FindingsComparison between BG2 phenotypes using single discriminant rates of herbicides and genotypes based on ACCase gene sequencing showed that the I1781L, a novel I1781T, but not the W2027C mutations, were associated with resistance to cycloxydim. All plants were killed with clethodim and a few individuals containing the I1781L mutation were partially resistant to tepraloxydim. Whole plant dose response assays demonstrated that a single copy of the mutant T1781 allele conferred fourfold resistance levels to cycloxydim and clodinafop-propargyl. In contrast, the impact of the I1781T mutation was low (Rf = 1.6) and non-significant on pinoxaden. BG2 was also characterised by high levels of resistance, very likely non-target site based, to the two cereal selective herbicides clodinafop-propargyl and pinoxaden and not to the poorly metabolisable cyclohexanedione herbicides. Analysis of 480 plants from 40 cycloxydim resistant black grass populations from the UK using two very effective and high throughput dCAPS assays established for detecting any amino acid changes at the 1781 ACCase codon and for positively identifying the threonine residue, showed that the occurrence of the T1781 is extremely rare compared to the L1781 allele.Conclusion/SignificanceThis study revealed a novel mutation at ACCase codon position 1781 and adequately assessed target site and non-target site mechanisms in conferring resistance to several ACCase herbicides in a black-grass population. It highlights that over time the level of suspected non-target site resistance to some cereal selective ACCase herbicides have in some instances surpassed that of target site resistance, including the one endowed by the most commonly encountered I1781L mutation.
Highlights
Black-grass (Alopecurus myosuroides Huds.) is one of the most problematic weeds in North Western Europe [1]
In Poaceae, acetyl-CoA carboxylase is homomeric with the biotin carboxyl carrier protein (BCCP), biotin carboxylase (BC) and carboxyl transferase a and b subdomains located on a single polypeptide
We have investigated the molecular basis of cycloxydim resistance in a black-grass population from the UK and determined its cross resistance to a number of commonly used acetyl-CoA carboxylase (ACCase) herbicides, paying particular attention to estimating the level of resistance conferred by the different target site mutations and non-target site resistance mechanisms contained in this population
Summary
Black-grass (Alopecurus myosuroides Huds.) is one of the most problematic weeds in North Western Europe [1]. The ACCase herbicides are classified into aryloxyphenoxypropionates (FOPs), cyclohexanediones (DIMs) and phenylpyrazolin (DEN) based on their chemical structures [5,6] In all cases they bind to the carboxyltransferase domain of chloroplastic ACCase of most grass weeds with little to no action on the cytoplasmic isoform [7]. In so doing they inhibit the formation of malonylCoA, depleting the cells of important fatty acids, leading to rapid necrosis and plant death [8,9]. We have used an integrated biology and molecular approach to investigate the mechanisms of resistance to acetyl-CoA carboxylase inhibiting herbicides in a UK black-grass population (BG2)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
