Gene ow in the European corn borer Ostrinia nubilalis: implications for the sustainability of transgenic insecticidal maize

Strategies proposed for delaying resistance to Bacillus thuringiensis toxins expressed by transgenic maize require intense gene £ow between individuals that grew on transgenic and on normal (referred to as refuges) plants. To investigate gene £ow in the European corn borer, Ostrinia nubilalis (HÏbner), the genetic variability at 29 sampled sites from France was studied by comparing allozyme frequencies at six polymorphic loci. Almost no deviations from Hardy^Weinberg expectations occurred, and a high stability of allelic distribution was found among samples collected in the same site over two or three di¡erent generations, indicating a high stability of the genetic structure over time. The overall genetic di¡erentiation was low at the region and whole country level, suggesting a high and homogeneous gene £ow. These results are discussed in relation to the sustainability of transgenic insecticidal maize