title: First report of resistance to acetolactate-synthase-inhibiting herbicides in yellow nutsedge (Cyperus esculentus): confirmation and characterization.
abstract: BACKGROUND
  Yellow nutsedge is one of the most problematic sedges in Arkansas rice, requiring the frequent use of halosulfuron (sulfonylurea) for its control. In the summer of 2012, halosulfuron at 53 g ha(-1) (labeled field rate) failed to control yellow nutsedge. The level of resistance to halosulfuron was determined in the putative resistant biotype, and its cross-resistance to other acetolactate synthase (ALS) inhibitors from four different herbicide families. ALS enzyme assays and analysis of the ALS gene were used to ascertain the resistance mechanism.
  
  
  RESULTS
  None of the resistant plants was killed by halosulfuron at a dose of 13 568 g ha(-1) (256× the field dose), indicating a high level of resistance. Based on the whole-plant bioassay, the resistant biotype was not controlled by any of the ALS-inhibiting herbicides (imazamox, imazethapyr, penoxsulam, bispyribac, pyrithiobac-sodium, bensulfuron and halosulfuron) tested at the labeled field rate. The ALS enzyme from the resistant biotype was 2540 times less responsive to halosulfuron than the susceptible biotype, and a Trp574 -to-Leu substitution was detected by ALS gene sequencing using the Illumina HiSeq.
  
  
  CONCLUSIONS
  The results suggest a target-site alteration as the mechanism of resistance in yellow nutsedge, which accounts for the cross-resistance to other ALS-inhibiting herbicide families.
authors.affiliation: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR, USA.
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: Crop Production Systems Research Unit, United States Department of Agriculture, Agricultural Research Service, Stoneville, MS, USA.
authors.forename: Vijay
authors.initials: V
authors.lastname: Nandula
authors.affiliation: Department of Crop, Soil, and Environmental Sciences, Auburn University, Auburn, AL, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: McElroy
authors.affiliation: Department of Crop, Soil, and Environmental Sciences, Auburn University, Auburn, AL, USA.
authors.forename: Shu
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Crop, Soil and Environmental Sciences, Lonoke, AR, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Scott
mesh_terms: D000095:Acetolactate Synthase / Q000037:antagonists & inhibitors* / Q000235:genetics; D001131:Arkansas; D029786:Cyperus / Q000187:drug effects* / Q000201:enzymology; D053209:Herbicide Resistance / Q000235:genetics*; D006540:Herbicides / Q000494:pharmacology*; D009154:Mutation; D020641:Polymorphism, Single Nucleotide; D013453:Sulfonylurea Compounds / Q000494:pharmacology*
chemical_list: D006540:Herbicides; D013453:Sulfonylurea Compounds; C532033:halosulfuron methyl; D000095:Acetolactate Synthase
keywords: ALS assay; ALS gene sequencing; Cyperus esculentus; Illumina HiSeq; herbicide resistance mechanism; yellow nutsedge