title: Characterization of multiple-herbicide-resistant Italian ryegrass (Lolium perenne spp. multiflorum).
abstract: BACKGROUND
  Multiple-herbicide resistance in Lolium perenne spp. multiflorum has evolved in many areas in Oregon. To manage the resistant populations, the resistance patterns must be determined. In this study, a population (CT) suspected to be resistant to sulfometuron and hexazinone was collected from a Christmas tree plantation.
  
  
  RESULTS
  The CT population is resistant to at least six herbicides with four different mechanisms of action: atrazine (>16-fold), diuron (2.4-fold), glyphosate (7.4-fold), hexazinone (3.1-fold), imazapyr (1.8-fold) and sulfometuron (>16-fold). Two mutations, Trp-591-Leu and Ser-264-Gly, were identified in the acetolactate synthase (ALS) and psbA gene respectively. No previously reported mutation in the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene was found. Less shikimic acid accumulated in the CT plants than in the susceptible plants after treatment with glyphosate at 0.6 kg AE ha(-1) .
  
  
  CONCLUSIONS
  This study suggests that the multiple resistance patterns of Lolium perenne spp. multiflorum populations can be complex, but that chemical control options to manage these populations exist. These remaining chemical options should be integrated with non-chemical management strategies to slow the spread of multiple-resistant biotypes in agroecosystems.
authors.affiliation: Department of Crop and Soil Science, Oregon State University, Corvallis, OR, USA.
authors.forename: Mingyang
authors.initials: M
authors.lastname: Liu
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Hulting
authors.forename: Carol A
authors.initials: CA
authors.lastname: Mallory-Smith
mesh_terms: D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase / Q000235:genetics / Q000378:metabolism; D000095:Acetolactate Synthase / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D053209:Herbicide Resistance; D006540:Herbicides / Q000494:pharmacology*; D008129:Lolium / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D009922:Oregon; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D058728:Weed Control
chemical_list: D006540:Herbicides; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D000095:Acetolactate Synthase; D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase
keywords: Lolium multiflorum; dose-response studies; herbicide resistance