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QUIK STATS (last updated Nov 17, 2016 )
NOTES ABOUT THIS BIOTYPE
Crop Protection 78 (2015) 1-4
Glyphosate-resistant Lolium multiflorum and Lolium perenne populations from New Zealand are also resistant to glufosinate and amitrole
Hossein Ghanizadeh a, Kerry C. Harrington a, *, Trevor K. James b
a Institute of Agriculture and Environment, Massey University, PB 11-222, Palmerston North 4442, New Zealand
b AgResearch, Ruakura Research Centre, PB 3123, Hamilton 3240, New Zealand
This study examined if glyphosate-resistant populations of Lolium multiflorum and Lolium perenne from some New Zealand vineyards were still susceptible to glufosinate and amitrole. The response of plants of one glyphosate-resistant population of L. multiflorum, population A, and two glyphosate-resistant L. perenne populations, populations J and O, to glufosinate and amitrole were evaluated and compared to susceptible populations in two dose response experiments. Based on the herbicide rates giving 50% reduction in growth (GR50 values), populations A, J and O were 3.9, 4.5 and 3.8 times more resistant to glufosinate respectively, compared to the susceptible populations in a glufosinate doseeresponse experiment. Populations A, J and O were also found to be 2.9, 5.0 and 13.1 times more resistant to amitrole respectively, in an amitrole dose response experiment. Very similar results were obtained when both dose response experiments were repeated. This is the first confirmed report of weed species that have developed multiple-resistance to glyphosate, glufosinate and amitrole. These are the three main herbicides currently used for weed control in New Zealand vineyards.
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.