SYMP 1-7 - Hybridization, genetic hitchhiking, and the ecology of transgenes in feral Brassica

Monday, August 8, 2011: 4:00 PM
Ballroom E, Austin Convention Center
Jason P. Londo1, Mike Bollman2, Cynthia L. Sagers3, E. Henry Lee4 and Lidia Watrud2, (1)Biological Sciences, University of Arkansas, Fayetteville, AR, (2)Western Ecology Division, US Environmental Protection Agency/NHEERL, Corvallis, OR, (3)Biology, University of Arkansas, Fayetteville, AR, (4)NHEERL/Western Ecology Division, USEPA, Corvallis, OR

Escape and persistence of transgenes from agricultural crops are issues of concern to stakeholders in the environmental safety of transgenic crops.  That is, whether transgenes that confer resistance to biotic or abiotic stresses may benefit weedy or native species outside of agriculture and over time, result in ecological changes in plant communities.  Using a constructed plant community approach, we examined the potential ecological effects of transgene escape from transgenic Brassica napus L. (canola) to feral non-transgenic B. napus and the weedy compatible species, B. rapa L.  Homozygous stacked and single transgene sibling genotypes of B. napus were selected from a segregating F2 population to compare the costs and benefits of transgene resistance to glyphosate herbicide and to lepidopteran insects.  Growth, reproduction, and transgene (CP4 EPSPS and Bt cry1A) movement were evaluated under two different selection pressures, glyphosate-drift and a lepidopteran herbivore, the diamondback moth (Plutella xylostella L.). 


Results demonstrate that stacking of different, unlinked transgenic traits can be costly to canola crop genotypes. However, selection pressure can alleviate fitness costs and contribute to changes in the community seed bank via genetic hitchhiking of unselected transgenes.  Additionally, exposure to sub-lethal glyphosate pressure can alter gene movement in the plant community by contributing to changes in flowering phenology, and by causing transient male sterility of sensitive genotypes.  These results suggest that indirect glyphosate selection pressure can influence the ecological and evolutionary dynamics of plant communities and may contribute to increased transgene persistence in weedy communities.

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