A direct regional scale estimate of transgene movement from genetically modified oilseed rape to its wild progenitors

One of the major environmental concerns over genetically modified (GM) crop s relates to transgene movement into wild relatives. The pattern of hybridi zation ultimately affects the scale and rapidity of ecological change and t he feasibility of containment. A new procedure for quantifying hybrid forma tion over large areas is described. Remote sensing was used to identify pos sible sites of sympatry between Brassica napus and ifs progenitor species a cross 15 000 km(2) of south-east England in 1998. Two sympatric populations with B. rapa and one with B. oleracea were found over the entire survey ar ea. Every newly recruited plant in these populations in 1999 was screened f or hybrid status using now cytometry and molecular analyses. One hybrid was observed from the 505 plants screened in the B. rapa populations but none of the nine B. oleracea recruits were hybrids. Measures to minimize gene no w are suggested, and a procedure for the post-release evaluation and contai nment of GM cultivars is proposed.