Long-distance dispersal of oilseed rape seeds: The role of grain trailers.

In agroecosystems, anthropogenic activities can modify the natural dispersal capacity of crops and their capacity to establish feral populations. In the case of oilseed rape (OSR), seed spillage from grain trailers during harvest was first quantified by an in situ scientific study (Selommes, Loir-et-Cher, France). Demographic analysis of seeds collected from 85 traps set on road verges suggested that OSR dispersal distance due to seed spillage from grain trailers can be up to 400m. In the present study, we used SSR markers to genotype seeds collected from trap-sites and from surrounding OSR fields to precisely estimate the distances between traps and fields. Trailer directions on each road were also considered. Few seeds (5.8%) were not linked to a field in the studied area, while most of the seeds (59.2%) were linked to a field situated over 400 m away. The overall mean dispersal distance was 1250 m. It ranged from 308 m to 1392 m for one-lane roads, and from 1048 m to 1404 m for two-lane roads. Events of seed dispersal at greater distances (> 5 km) were rare but still possible. It thus follows that OSR seed dispersal due to spillage from grain trailers should be carefully considered in the context of genetically modified plant cultivation.