Assessing the risks of transgene escape through time and crop-wild hybrid persistence


  • J. Schmitt's general interests are plant population biology and ecological genetics. Research topics in her lab include the measurement of natural selection, seed ecology, maternal effects, the evolution of phenotypic plasticity, and the ecological impact of transgenic plants. C. R. Under is a PhD candidate in the Department of Ecology and Evolutionary Biology at Brown University. He studies the ecological determinants of fitness of crop-wild hybrids and applies the results to assessing the fate of transgenes in the environment. He is also interested in using molecular techniques to advance plant population biology and quantitative generics.

Department of Ecology and Evolutionary Biology, Box G-W108, Brown University, Providence, RI 02912, USA. Tel. (401) 863–2789; Fax. (401) 863–2166; e-mail st402774@brownvm.bitnet; st402774@


Transgenes introduced into crops can escape in time, as well as space, via the seed bank. For annual plants, especially ruderals, seed bank behaviour may be the most important factor determining population persistence. Crop seeds may exhibit some dormancy and germination cueing in the soil but are expected to be less able to persist than their wild relatives, which often have considerable dormancy and longevity, as well as effective germination cueing responses. Crop-wild hybrids may have seed bank characteristics more suited to persistence, and maternal effects may favour persistence of hybrids having wild plants for their female parent. Escape of transgenes via crop-wild hybrids presents unique concerns not present for crops. Hybrids can undergo natural selection and may back-cross with wild plants. We suggest methods that can be used in conjunction with evaluation of the relative fitness of crop-wild hybrids that will determine the likelihood of back-crossing. Accurate assessment of escape in time and transgene persistence via crop-wild hybrids requires proper plant materials. We emphasize the use of null segregants as controls for transgenic crops and for generating crop-wild hybrid controls for transgenic hybrids. Since good empirical and theoretical understanding of how individual genes influence the fate of plants in different environments is lacking, evaluation of escape in time and the persistence of transgenes via crop-wild hybrids should be on a case-by-case basis.