Relationships between exogenous-toxin quantity and increased biomass of transgenic Bt crops under elevated carbon dioxide

Field-OTC experiments were conducted with the goals of ascertaining if increased biomass in Bt transgenic cotton and rice grown under elevated CO 2 results in diminished exogenous-Bt toxin, and assessing the effectiveness of Bt transgenes against lepidopteran pests. Bt cotton responded differently, in terms of Bt-toxin quantity, than Bt rice, and both indicated differences among developmental stages. Dramatic biomass increase significantly diluted Bt-toxin content in 45-DAS (“days after seedling”) petioles and shoots and 90-DAS Bt cotton squares, and in the 50-DAS tissues and 100-DAS leaf sheaths of Bt rice. Moreover, the dilution effect was partially responsible for decreased Bt-toxin in these tissues, but not responsible for significant decreases in Bt-toxin in 90-DAS Bt cotton leaves and bolls. Furthermore, elevated CO 2 significantly affected the fitness and performance of Chilo suppressalis, and the susceptible and resistant colonies of Helicoverpa armigera, although adversely affected Bt-gene expression for the transgenic cotton and rice.