title: Resistance to aryloxyphenoxypropionate herbicides in Amazon sprangletop: Confirmation, control, and molecular basis of resistance.
abstract: Amazon sprangletop is problematic weed of rice in the midsouthern USA. Two biotypes of this species from rice fields approximately 100km apart in Louisiana were unaffected when sprayed with the labeled field rate of cyhalofop-butyl (314g ai ha-1) in 2008. Dose response studies were conducted to confirm the level of resistance to cyhalofop-butyl over a range of doses. Cross-resistance to acetyl-CoA carboxylase (ACCase)-inhibiting herbicides from two different chemical families and multiple herbicide resistance to other mechanisms of action were evaluated. Sequencing using the Illumina Hiseq platform and ACCase gene sequencing revealed two different amino acid substitutions, Trp2027-to-Cys in the first resistant biotype and Asp2078-to-Gly in the second resistant biotype, within the CT domain of the ACCase gene. Two known amino acid substitutions confirmed resistance to cyhalofop-butyl and fenoxaprop-P-ethyl in resistant Amazon sprangletop biotypes. Asp2078-to-Gly amino acid substitution that was detected in one of the resistant biotypes did not result in cross-resistance to clethodim, an ACCase-inhibiting cyclohexandione herbicide which has endowed clethodim resistance in other weed species. Based on this research, both resistant Amazon sprangletop biotypes have evolved target-site resistance to the APP herbicides; yet, alternative herbicides are still active on these plants.
authors.affiliation: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR, USA. Electronic address: ptehranc@uark.edu.
authors.forename: Parsa
authors.initials: P
authors.lastname: Tehranchian
authors.affiliation: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR, USA.
authors.forename: Jason K
authors.initials: JK
authors.lastname: Norsworthy
authors.affiliation: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR, USA.
authors.forename: Nicholas E
authors.initials: NE
authors.lastname: Korres
authors.affiliation: Department of Crop, Soil, and Environmental Sciences, Auburn University, 201 Funchess Hall, Auburn, AL, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: McElroy
authors.affiliation: Department of Crop, Soil, and Environmental Sciences, Auburn University, 201 Funchess Hall, Auburn, AL, USA.
authors.forename: Shu
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Scott
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000037:antagonists & inhibitors / Q000235:genetics*; D019943:Amino Acid Substitution; D002073:Butanes / Q000633:toxicity; D053209:Herbicide Resistance / Q000235:genetics*; D006540:Herbicides / Q000633:toxicity*; D009570:Nitriles / Q000633:toxicity; D010940:Plant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics*; D006109:Poaceae / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D011422:Propionates / Q000633:toxicity*; D017423:Sequence Analysis, RNA
chemical_list: D002073:Butanes; D006540:Herbicides; D009570:Nitriles; D010940:Plant Proteins; D011422:Propionates; C501583:cyhalofop-butyl; D000103:Acetyl-CoA Carboxylase
keywords: ACCase-inhibiting herbicide resistance; Amazon sprangletop; Cross and multiple resistance; Dose response; Gene sequencing; Illumina HiSeq; Leptochloa panicoides