Gene Flow Between Rapeseed Fields: A Meta-analysis of Available Data

Summary

1. The probability distribution that seeds of organically farmed oilseed rape (Brassica napus L.) are pollinated by pollen grain produced in a neighbouring field of genetically modified oilseed rape is calculated based on a meta-analysis of available gene-flow data.
2. The probability of foreign pollination is modelled as functions of the width of the pollen receiving field and the distance to the pollen donor fields.
3. The significance of using a buffer zone (i.e. a 1-5 m broad border of the organic field, which is excluded from the harvest) to reduce GM-pollination of the crop, is quantified and discussed.
4. Quantitative estimates of the probability of foreign GM-pollination are relevant to organic and conventional farmers in order to suggest minimum isolation distances and other management strategies to keep GM-pollination below threshold values for fields situated near conspecific GM-crops. A 95% credibility level of the gene dispersal from a GM oilseed rape into another rape field is calculated as a function of e.g. the isolation distance between fields. Analysis of different management strategies shows that an increasing isolation distance is more effective to reduce GM pollen dispersal than the use of a buffer zone, especially for small organic fields. If the width of the organic and conventional field can be increased, this has the overall largest effect in reducing the level of GM-pollination from pollen.