Impact of dual-gene Bt transgenic cauliflower plants on non-target organisms

Advances in transgenic plants expressing Bacillus thuringiensis (Bt) insecticidal gene(s) have offered a promising alternative to traditional insecticides for control of lepidopteran pests on cole crops. A private-public partnership, Collaboration on Insect Management for Brassicas in Asia and Africa (CIMBAA), was formed in 2005 with the goal of developing dual-gene Bt cauliflower and cabbage for Asia and Africa to replace the use of broad spectrum, traditional insecticides. Our previous results demonstrated cry1Ba2+cry1Ca4 dual-gene cauliflower plants were very effective against lepidopteran insect pests collected from India, Indonesia, Taiwan, the United States and Australia. In order to address its biosafety concerns before the dual-gene Bt plant is released to farmers in India and Africa, we evaluated the impact of purified Cry1Ba2 toxin, Cry1Ca4 toxin and the dual-gene cauliflower plants on several selected non-target species: cabbage maggot (Delia radicum), cabbage aphids (Brevicoryne brassicae), flea beetles (Phyllotreta cruciferae), Coleomegilla maculata, and Hippodamia convergens in comparison to a common chemical insecticide, pyrethroid. Fitness parameters tested (such as longevity and fecundity) of D. radicumb, B. brassicae, and P. cruciferae were not significantly different between Bt and non-Bt treatments. Our results also indicated that the purified toxins and dual-gene cauliflower plants did not negatively affect the longevity and mortality of the predators, C. maculata and H. convergens, compared to the non-Bt controls. However, the synthetic insecticide significantly increased the mortality of C. maculata and H. convergens when fed on pyrethroid-treated resistant aphids. Our first-tier tests demonstrated that the dual-gene Bt cauliflower plant has negligible impact on non-target species tested.