title: Widespread occurrence of both metabolic and target-site herbicide resistance mechanisms in Lolium rigidum populations.
abstract: BACKGROUND
  Lolium rigidum populations in Australia and globally have demonstrated rapid and widespread evolution of resistance to acetyl coenzyme A carboxylase (ACCase)-inhibiting and acetolactate synthase (ALS)-inhibiting herbicides. Thirty-three resistant L. rigidum populations, randomly collected from crop fields in a most recent resistance survey, were analysed for non-target-site diclofop metabolism and all known target-site ACCase gene resistance-endowing mutations.
  
  
  RESULTS
  The HPLC profile of [(14) C]-diclofop-methyl in vivo metabolism revealed that 79% of these resistant L. rigidum populations showed enhanced capacity for diclofop acid metabolism (metabolic resistance). ACCase gene sequencing identified that 91% of the populations contain plants with ACCase resistance mutation(s). Importantly, 70% of the populations exhibit both non-target-site metabolic resistance and target-site ACCase mutations.
  
  
  CONCLUSIONS
  This work demonstrates that metabolic herbicide resistance is commonly occurring in L. rigidum, and coevolution of both metabolic resistance and target-site resistance is an evolutionary reality. Metabolic herbicide resistance can potentially endow resistance to many herbicides and poses a threat to herbicide sustainability and thus crop production, calling for major research and management efforts.
authors.affiliation: Australian Herbicide Resistance Initiative, School of Plant Biology, University of Western Australia, Crawley, WA, Australia.
authors.forename: Heping
authors.initials: H
authors.lastname: Han
authors.affiliation: Australian Herbicide Resistance Initiative, School of Plant Biology, University of Western Australia, Crawley, WA, Australia.
authors.forename: Qin
authors.initials: Q
authors.lastname: Yu
authors.affiliation: Australian Herbicide Resistance Initiative, School of Plant Biology, University of Western Australia, Crawley, WA, Australia.
authors.forename: Mechelle J
authors.initials: MJ
authors.lastname: Owen
authors.affiliation: School of Plant Biology, University of Western Australia, Crawley, WA, Australia.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Cawthray
authors.affiliation: Australian Herbicide Resistance Initiative, School of Plant Biology, University of Western Australia, Crawley, WA, Australia.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Powles
mesh_terms: D000095:Acetolactate Synthase / Q000037:antagonists & inhibitors* / Q000235:genetics; D000103:Acetyl-CoA Carboxylase / Q000037:antagonists & inhibitors / Q000235:genetics*; D001315:Australia; D005075:Biological Evolution; D055768:Halogenated Diphenyl Ethers / Q000378:metabolism / Q000494:pharmacology; D053209:Herbicide Resistance; D006540:Herbicides / Q000378:metabolism* / Q000494:pharmacology; D008129:Lolium / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D010647:Phenyl Ethers / Q000378:metabolism / Q000494:pharmacology; D010940:Plant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics*; D011422:Propionates / Q000378:metabolism / Q000494:pharmacology
chemical_list: C529887:2-(4-(2,4-dichlorophenoxy)phenoxy)propionic acid; D055768:Halogenated Diphenyl Ethers; D006540:Herbicides; D010647:Phenyl Ethers; D010940:Plant Proteins; D011422:Propionates; C012891:dichlorfop-methyl; D000095:Acetolactate Synthase; D000103:Acetyl-CoA Carboxylase
keywords: Lolium ridigum; diclofop; herbicide metabolism; metabolic resistance; resistance evolution; target-site mutation