title: Mechanisms of glyphosate resistance in two perennial ryegrass (Lolium perenne) populations.
abstract: BACKGROUND
  Perennial ryegrass (Lolium perenne) has developed resistance to glyphosate within New Zealand vineyards following many years of herbicide application. The objectives of this work were to confirm resistance within two populations obtained from affected vineyards, and to determine the mechanism of resistance to glyphosate.
  
  
  RESULTS
  Population O was confirmed to have a 25-fold resistance to glyphosate, whereas population J had a sevenfold resistance. Results of genotyping assays demonstrated a single nucleotide substitution at codon 106 of 5-enolpyruvylshikimate-3-phosphate synthase in population O but not population J. Glyphosate-resistant and glyphosate-susceptible populations did not differ in glyphosate absorption. However, in both resistant populations, much more of the absorbed (14) C-glyphosate remained in the treated leaf than occurred in the susceptible population. Significantly more glyphosate was found in the pseudostem region of susceptible plants compared with resistant plants.
  
  
  CONCLUSIONS
  Both target-site and non-target-site mechanisms of glyphosate resistance were found in the perennial ryegrass population with 25-fold resistance, whereas only the non-target-site mechanism of resistance was found in the population with sevenfold resistance. This is the first study of the mechanism of glyphosate resistance in perennial ryegrass.
authors.affiliation: Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand.
authors.forename: Hossein
authors.initials: H
authors.lastname: Ghanizadeh
authors.affiliation: Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand.
authors.forename: Kerry C
authors.initials: KC
authors.lastname: Harrington
authors.affiliation: AgResearch, Ruakura Research Centre, Hamilton, New Zealand.
authors.forename: Trevor K
authors.initials: TK
authors.lastname: James
authors.affiliation: Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand.
authors.forename: David J
authors.initials: DJ
authors.lastname: Woolley
authors.affiliation: AgResearch Grasslands, Palmerston North, New Zealand.
authors.forename: Nicholas W
authors.initials: NW
authors.lastname: Ellison
mesh_terms: D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase / Q000235:genetics*; D005838:Genotype; D005998:Glycine / Q000031:analogs & derivatives* / Q000378:metabolism; D053209:Herbicide Resistance; D006540:Herbicides / Q000378:metabolism; D008129:Lolium / Q000737:chemistry / Q000201:enzymology / Q000235:genetics*; D009520:New Zealand; D018515:Plant Leaves / Q000737:chemistry; D017422:Sequence Analysis, DNA; D000097797:Glyphosate
chemical_list: D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase; D005998:Glycine; D006540:Herbicides; D000097797:Glyphosate
keywords: New Zealand; glyphosate; herbicide resistance; perennial ryegrass; resistance mechanism