title: Identification of resistance to either paraquat or ALS-inhibiting herbicides in two Western Australian Hordeum leporinum biotypes.
abstract: BACKGROUND
  Hordeum populations are becoming increasingly difficult to control in cropping fields. Two herbicide-resistant H. leporinum populations were identified during a random crop survey after herbicides were applied. The study aimed to determine the herbicide resistance profile of these H. leporinum biotypes to a range of herbicides used for their control.
  
  
  RESULTS
  Based on dose-response studies, one H. leporinum population was very highly resistant to sulfosulfuron and sulfometuron (both sulfonylurea herbicides) and also displayed low-level resistance to imazamox (an imidazolinone herbicide). Reduced sensitivity of the ALS enzyme was identified with in vitro activity assays. Gene sequence analysis revealed a proline-to-threonine substitution at amino acid position 197 of ALS, which is likely to be the molecular basis for resistance in this population. Herbicide screening also revealed a different H. leporinum population with resistance to the bipyridyl herbicide paraquat.
  
  
  CONCLUSIONS
  This study established the first cases of (1) sulfonylurea-to-imidazolinone cross-resistance and (2) field-evolved paraquat resistance in a Hordeum species in Western Australia.
authors.affiliation: Australian Herbicide Resistance Initiative, School of Plant Biology, Institute of Agriculture, University of Western Australia, Crawley, WA, Australia. mechelle.owen@uwa.edu.au
authors.forename: Mechelle J
authors.initials: MJ
authors.lastname: Owen
authors.forename: Danica E
authors.initials: DE
authors.lastname: Goggin
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Powles
mesh_terms: D000095:Acetolactate Synthase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001315:Australia; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D053209:Herbicide Resistance; D006540:Herbicides / Q000494:pharmacology*; D001467:Hordeum / Q000737:chemistry / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D008969:Molecular Sequence Data; D010269:Paraquat / Q000494:pharmacology*; D010940:Plant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D014904:Western Australia
chemical_list: D004791:Enzyme Inhibitors; D006540:Herbicides; D010940:Plant Proteins; D000095:Acetolactate Synthase; D010269:Paraquat