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Glyphostate-drift but not herbivory alters the rate of transgene flow from single and stacked trait transgenic canola (Brassica napus L.) to non-transgenic B. napus and B. rapa
Citation:
Londo, J. P., M. A. BOLLMAN, C. L. Sagers, E. LEE, AND L. S. WATRUD. Glyphostate-drift but not herbivory alters the rate of transgene flow from single and stacked trait transgenic canola (Brassica napus L.) to non-transgenic B. napus and B. rapa. NEW PHYTOLOGIST. Blackwell Publishing, Malden, MA, 191:840-849, (2011).
Impact/Purpose:
While transgenic plants can offer agricultural benefits, the escape of transgenes out of crop fields is a major environmental concern.
Description:
While transgenic plants can offer agricultural benefits, the escape of transgenes out of crop fields is a major environmental concern. Escape of transgenic herbicide resistance has occurred between transgenic Brassica napus (canola) and weedy species in numerous locations. In this study we tested the hypotheses that glyphosate herbicide and insect herbivore selective pressures can change the rate of transgene flow between B. napus and weedy species. We constructed plant communities in sunlit outdoor mesocosms that contained single and stacked transgenic B. napus genotypes expressing glyphosate herbicide resistance (CP4 EPSPS), lepidopteran insect resistance (Cry1Ac), or both traits ("stacked"), plus non-transgenic B. napus, B. rapa, and B. nigra. Two different selective pressures, a sub-lethal glyphosate dose and lepidopteran herbivores (Plutella xylostella), were applied and rates of transgene flow and transgenic seed production were measured. The two selective treatments both reduced fitness of some genotypes but differed in ability to affect transgene flow and in the production of transgenic seeds. Most notably, glyphosate increased the incidence of transgenic seeds, presumably by increasing the abundance of pollen with glyphosate resistant genes. The findings of this study indicate that transgenic traits such as herbicide resistance may be transmitted to wild populations and may increase in frequency in weedy populations even without direct selection due to the indirect effects of selection on gene flow.
