The separation distances required to ensure cross-pollination is below specified limits in non-seed crops of sugar beet, maize and oilseed rape

The separation distances used to ensure that harvested crops reach specifie d levels of genetic parity is under review. The existing experimental evide nce has been studied, along with practical experience from, for example, se ed certification schemes, to assess the relationship between distance from pollen sources and cross-pollination levels in adjacent crops. The study ha s covered all production and breeding systems for maize, oilseed rape and b eet. This paper describes the scope of the study, considers the most import ant factors influencing levels of cross-pollination, and recommends separat ion distances needed to achieve off-type thresholds of 0.1 %, 0.5% and 1.0% in commercial non-seed crops. The levels at which wind-borne maize pollen fertilizes adjacent crops is strongly affected by the size of the emitting crop, the strength of the wind and any barriers that intervene. Hence the s eparation distances have been derived from experiments where these factors seem to have been very favourable. Maize grain is the only part of the plan t affected by cross-pollination. Separation of receptor crops intended for silage can be reduced and still keep cross-pollination within specified lev els. For oilseed rape, the levels of cross-pollination between fields decli nes rapidly with distance. where the receptor crop contains male sterile pl ants the levels of cross-pollination are increased compared to conventional varieties. Cross pollination does not affect the produce of non-seed beet craps.