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Ecological effects of transgene persistence on plant communities in the presence and absence of drift levels of glyphosate herbicide
Citation:
WATRUD, L. S., G. KING, R. COLASANTI, AND E. LEE. Ecological effects of transgene persistence on plant communities in the presence and absence of drift levels of glyphosate herbicide. Presented at Botany 2008 Meeting, Vancouver, BC, CANADA, July 26 - 30, 2008.
Impact/Purpose:
In 2005, plant communities were constructed in outdoor sunlit chambers that contained 3 round tubs having a surface area of 1.2 m2 and a depth of 0.6 m. Six plant types were planted in triplicate using the same spatial arrangement in each tub.
Description:
In 2005, plant communities were constructed in outdoor sunlit chambers that contained 3 round tubs having a surface area of 1.2 m2 and a depth of 0.6 m. Six plant types were planted in triplicate using the same spatial arrangement in each tub. Three of the six plant types were sexually compatible Brassica spp: F1 glyphosate resistant hybrids created by pollinating conventional Brassica napus cultivar Sponsor with pollen from GM glyphosate-resistant B. napus cultivar RaideRR that contained the CP4 EPSSP gene, Sponsor and weedy B. rapa. Additional plant community members included Panicum capillare, Digitaria sanguinalis and Lapsana communis. In 2006 and 2007, 5% of the seeds produced by each genus during the previous year were resown in the tubs. At the time of Brassica flowering in 2006 and 2007, two of the five mesocosms were sprayed with glyphosate at 10% of the field application rate to simulate spray drift. In 2006, no significant differences in Brassica biomass or seed production were observed between treated and control chambers. In 2007, Brassica biomass and seed production in chambers exposed to the drift level of glyphosate were significantly greater than in control chambers; in treated chambers Brassica constituted 54% of the total biomass as compared to 34% in the controls. The frequency of Brassica expressing CP4 EPSPS in the control chambers increased from the initial 33% at planting to 60% in 2006 and 2007; under drift herbicide selective pressure, the frequency of Brassica seedlings with the CP4 EPSPS gene increased to 81% in 2006 and 96% in 2007. Biomass of P. capillare and L. communis were unaffected by glyphosate while D. sanguinalis biomass decreased with glyphosate treatment. Our results suggest that glyphosate drift selective pressure can confer competitive advantage to feral Brassica with the CP4 EPSPS gene and result in plant community changes.