The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.
QUIK STATS (last updated Aug 16, 2013 )
NOTES ABOUT THIS BIOTYPE
For the perennial ryegrass populations, we have three separate populations, and the level of resistance in each is 30-fold, 13-fold and 10-fold respectively. The PhD student who is lead author of this paper is currently working on mode of action and genetic studies for these populations, and has just about finished a quick cross-resistance study.
CONTRIBUTING WEED SCIENTISTS
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.
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 14C‐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.
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.