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GENE FLOW STUDIES BETWEEN BRASSICA NAPUS AND B. RAPA IN CONSTRUCTED PLANT COMMUNITIES
Citation:
SAGERS, C. L., L. S. WATRUD, G. KING, AND E. LEE. GENE FLOW STUDIES BETWEEN BRASSICA NAPUS AND B. RAPA IN CONSTRUCTED PLANT COMMUNITIES. Presented at Botany 2007 Meeting (BSA/ASPB), Chicago, IL, July 07 - 11, 2007.
Description:
The commercial production of genetically modified crops has led to a growing awareness of the difficulties of transgene confinement and of the potential environmental risks associated with the escape of transgenes into naturalized or native plant populations. A potential consequence of an unintended release is an increase in the fitness and invasiveness of weedy non-crop species that have received transgenes. Gene flow and fitness changes could be a particular problem in canola (Brassica napus L.) as F1 hybrids with weedy field mustard (B. rapa L.) show no reproductive costs from transgene introgression. Even though substantial interspecific hybridization and introgression between these two species have occurred, transgenic hybrid productivity and competitiveness have not been well characterized. Using a split-split plot design, we evaluated the effects of a pesticidal Bt cry1Ac transgene on the productivity of transgenic vs. non-transgenic Brassica hybrids. Parental varieties (B. napus, Bt-B. napus, B. rapa) and their hybrids were grown in the presence or absence of insect herbivore (Plutella xylostella (Lepidoptera)) selective pressure, and in competition with B. napus or native ruderals. The studies were carried out in outdoor, sunlit mesocosms equipped with unique filters to prevent the release of pollen to the environment. Tukey-Kramer post hoc analyses of significant (P<0.05) three-way interaction terms demonstrate that fitness effects of the transgene are context-dependent: fitness benefits of the transgene are expressed only in the presence of herbivores under low competition. This outcome suggests that the risks of transgene establishment are likely to vary among B. rapa populations. Our findings suggest that evaluation of the fitness of hybrids that may form between GM crop plants and their wild relatives should be considered in the environmental risk assessment of transgenic crops.