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 33-42%, 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.