The Potential for Evolution of glyphosate resistance in UK weeds
Glyphosate is currently the worlds most commonly used herbicide, due to its high effectiveness and also its high toxicological and environmental safety. Glyphosate is a non-selective herbicide usually used in UK agricultural situations to remove weeds before crop seeding and as a result of this selection pressure for resistance is generally low, as only a small proportion of the population is exposed.
However, in countries where genetically modified crops have been adopted, glyphosate is used in conjunction with genetically modified glyphosate resistant crops, as the main or sole weed control method. Glyphosate is also used on a frequent basis between rows of tree, nut and vine crops and for roadside weed control and in these situations selection pressure is greater. This continual use of glyphosate imposes a greater selection pressure for glyphosate resistance evolution and has led to a shift towards glyphosate resistant individuals.
Even though glyphosate generally imposes low selection pressure, in 1998, 24 years after it was first marketed, the first case of glyphosate resistance was reported in Australia. Glyphosate resistance has now been reported in 21 species across 14 countries, although none is currently found in the UK.
(Severe blackgrass (left) and Italian ryegrass (right) problem)
Many resistance studies focus on resistance once it has already evolved. This project, however, aims to investigate the potential for glyphosate resistance evolution in the UK. As glyphosate use and selection pressure increases in the UK there is an excellent opportunity to investigate the evolutionary processes and potential for glyphosate resistance before it evolves.
This will be achieved through investigation of the variability in glyphosate susceptibility in important UK weed species and using glasshouse selection experiments to test the hypothesis that standing genetic variation can be enriched in these species. Differences in susceptibility to glyphosate in UK blackgrass (Alopecurus myosuroides) and Sterile brome (Anisantha sterilis) populations will be related to previous glyphosate use history and variation in glyphosate sensitivity will also be tested in Arabidopsis thaliana. Fitness costs and tradeoffs related to glyphosate resistance or increased tolerance will also be investigated. The results from these investigations will be collated to assess the potential for glyphosate resistance evolution in the UK.
Dr Paul Neve
p dot neve at warwick dot ac dot uk
Blackgrass (Alopecurus myosuroides)
Italian ryegrass (Lolium multiflorum)