Assessing potential risks of transgene escape from fiber plantations

Woody crops such as trees pose difficult obstacles for genetic risk analysi s because of their long generation times, large size, and potential for lon g distance dispersal of pollen and seed. This necessitates reliance on esta blished stands for retrospective studies of gene flow, and simulation model s to assess the consequences of introducing new genes into the environment. We are using these approaches to assess potential risks of large-scale cul tivation of transgenic hybrid poplar (Populus spp.). To predict gene flow f rom hybrid plantations, it is necessary to understand both the dynamics of gene movement within and between populations, and the ability of hybrid tre es to produce fit progeny. We have found that up to 3.8% of progeny of wild females growing near hybrid poplar plantations were fathered by hybrid mal es. Also, hybrid seedlings established and grew at about the same rate as w ild seedlings. Data from these field studies will be integrated in a spatia l simulation model which is currently under development. The model will be used to identify the genetic and ecological parameters most important for p redicting the spread of herbicide- and insect-resistance transgenes over sp ace and time. Potential economic and agronomic significance of transgene sp read will also be assessed.