Regional patterns of gene flow and its consequence for GM oilseed rape

The imminent commercialisation of genetically modified oilseed rape varieti es requires accurate quantification of transgene movement via pollen within realistic agricultural contexts. This study measured gene flow on a region al and local scale. A 70 square km area west of Dundee was used, in which o ilseed rape crops were common, but no GM OSR was grown. Fifty-two sites wer e selected at distances between zero m and 4000 m from the nearest non-GM s pring oilseed rape crop. At each site male-sterile bait plants were placed for a 14 day period and airborne pollen density measured. Pollination occur red at all sites, even those at the greatest distance from flowering oilsee d rape fields. Although airborne OSR pollen was recorded at all sites, the density declined rapidly with distance from source. There was also evidence that bees may be important pollen vectors over a range of distances. Addit ional sites 100 to 900 m from a GM spring oilseed rape crop in a second stu dy area were also investigated. Despite the predominance of non-GM OSR crop s in the immediate locality, all sites were pollinated by a mixture of GM a nd non-GM sources. The results suggest that the farm to farm spread of OSR transgenes will be widespread.