weed resistance

This study evaluates the interaction among developing herbicide resistance, seed size and seed dormancy of ripgut brome, wild oat and hare barley collected from within intensively-managed fields (in-crop) in comparison with populations in surrounding ruderal (non-crop disturbed) areas with no history of exposure to herbicides within the Western Australian grainbelt.

This study shows that the resistance mechanism endowing pyroxasulfone resistance in this Lolium rigidum population is enhanced rates of pyroxasulfone metabolism. This enhanced rate of pyroxasulfone metabolism is associated with over-expression of two glutathione transferases. Thus, the resistance mechanism in this Lolium population of enhanced rates of pyroxasulfone metabolism suggests GST-catalysed increased rates of glutathione conjugation. More work is required for definitive evidence of specific responsible GSTs.

Herbicides classified as synthetic auxins have been most commonly used to control broadleaf weeds in a variety of crops and in non-cropland areas since the first synthetic auxin herbicide (SAH), 2,4-D, was introduced to the market in the mid-1940s.

The incidence of weed species resistant to SAHs is relatively low considering their long-term global application with 30 broadleaf, five grass, and one grass-like weed species confirmed resistant to date.

An understanding of the context and mechanisms of SAH resistance evolution can inform management practices to sustain the longevity and utility of this important class of herbicides.