Modeling the effect of gene flow on the evolution of resistance to transgenic crops in developing countries

Transgenic crops producing Bacillus thuringiensis (Bt) toxins are increasingly being adopted by developing countries. In these countries, planting of farm-saved seed, as opposed to purchased seed, is a traditional practice. As gene flow readily occurs between Bt and non-Bt crops, contamination could accumulate in both Bt and non-Bt seed lots when seed from small farms is replanted year after year. Here, we used a simulation model to examine the potential for such contamination to affect the evolution of insect resistance to Bt crops. Sensitivity analyses were used to outline how biological, environmental, and operational factors (i.e., agricultural landscape attributes, agronomic practices, degree of gene flow, pest feeding behavior) affected the evolution of resistance. We discuss potential methods to delay resistance in areas with farm-saved seed where contamination between Bt and non-Bt crops is likely to occur.