A POLLEN-DISPERSAL EXPERIMENT WITH TRANSGENIC OILSEED RAPE - ESTIMATION OF THE AVERAGE POLLEN DISPERSAL OF AN INDIVIDUAL PLANT WITHIN A FIELD

In order to help establish a basis for the assessment of gene flow ass ociated with the large-scale release of transgenic oilseed rape, we pr eviously designed a method which makes it possible to retrieve the ave rage pollen dispersal of a single plant from that of a large source pl ot. The 'individual' pollen distribution thus obtained is less depende nt on the experimental design than pollen distributions usually publis hed and could therefore be used to model the possible escape of a tran sgene from commercial transgenic crops. In this study we report on a f ield experiment set up to study the pollen dispersal from an herbicide -resistant transgenic variety of oilseed rape and to test the applicab ility of the method on the experimental data. Two techniques were used to determine the individual pollen dispersal, and their outcomes are compared. The results suggest that approximately half of the pollen pr oduced by an individual plant fell within 3m and that the probability of fertilisation afterwards decreased slowly along a negative exponent ial of the distance. Comparison with the global pollen distribution fr om the source plot indicates that pollen-dispersal distributions based on dispersal from whole plots instead of individual plants would have underestimated the proportion of pollen that was dispersed over avera ge or long distances.