Quantifying gene movement from oilseed rape to its wild relatives using remote sensing

The potential environmental risks due to gene flow from genetically modifie d (GM) crops into wild plant populations are currently of great concern. Of particular interest is gene flow from GM oilseed rape (Brassica napus) int o its wild parental species B. rapa and B. oleracea, with which it forms sp ontaneous hybrids. The rate of hybridization is best determined empirically under a wide variety of field conditions. A procedure for quantifying hybr id formation using remote sensing over a large area of southern England is described. Satellite sensor images were used to identify localities where g ene flow was most likely by searching for oilseed rape fields adjacent to r egions where the parent plants occur, namely rivers and cliff-tops. These s ites were visited and screened for hybrids. A single hybrid was observed in an area of over 16 000 km(2). We use these data to suggest a strategy to m inimise gene flow following commercial scale release of GM B. napus across Europe and propose a procedure that may allow post-release containment.