Herbicide resistance and gene flow in wild-oats (Avena fatua and Avena sterilis ssp. ludoviciana)

The process of resistance evolution to fenoxaprop-P-ethyl was investigated in the cereal weeds wild-oats (Avena fatua L. and Avena sterilis ssp. ludoviciana Malzew) at a number of locations in England, including one farm where distinct patches occur within fields. Genetic fingerprints produced using PCR-based techniques provided evidence for hybridisation between the species and that resistance had spread from one patch to others. The proportion of total variation due to differences between populations (G_st) was estimated at 33^2%, and herbicide-resistant patches contained on average less genetic diversity than herbicide-sensitive counterparts: both findings were consistent with a high degree of self-pollination. It was however concluded that cross-pollination occurs both within and possibly between species, and that this can result in the spread of herbicide resistance.