Submitted to: Environmental Biosafety Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2008
Publication Date: 4/20/2008
Citation: Hueberger, S., Yafuso, C, DeGrandi-Hoffman, G., Tabashnik, B. 2008. Outcrossed cottonseed and adventitious Bt plants in Arizona refuges. Environmental Biosafety Research 7:87-96. Interpretive Summary: The widespread use of transgenic crops has caused concern about contamination of conventional crops by transgenes. We examined non-transgenic (i.e. conventional) cotton for the presence of seeds containing transgenes for the production of a toxin from Bacillus thuringiensis (Bt). Seeds from conventional cotton planted in field plots and directly from unopened seed bags were examined. We found about 2 percent of the seeds from border rows of conventional cotton planted adjacent to Bt cotton contained transgenes for Bt. In our experimental plots, 7.5 - 8.1 percent of the conventional cotton plants had evidence of Bt transgenes. We also detected Bt contaminated seeds in bags of conventional cotton seed at a level of about 1 percent of the seed. Though a rate of 1 percent contamination might appear insignificant, it translates into approximately 1000 Bt plants per hectare in fields of conventional cotton. Future studies will be directed at mechanisms responsible for the contamination of conventional cotton particularly the role that pollinators might play in the cross-pollination of conventional cotton with pollen from Bt plants.
Technical Abstract: Understanding how transgenes enter and perpetuate in conventional fields is an important step towards reducing transgene contamination. Here we report hemizygous (Bt/non-Bt) and homozygous (Bt) cotton plants in non-Bt fields, and rogue transgenes in seed bags of conventional cotton. Our results provide evidence that outcrossing between Bt and non-Bt plants played an important role in transgene introgressions into the seed supply, either as the initial source of rogue transgenes, or through perpetuating previous contamination.