What type of Bt corn is suitable for a region with diverse lepidopteran pests: A laboratory evaluation

Transgenic crops that produceBacillus thuringiensis(Bt) toxins are effective tools for controlling lepidopteran pests. However, the degree of susceptibility to Bt toxins differs among various pest species due to relatively narrow spectrum and high selectivity of such toxins. Bt corn hybrids for Chinese market were designed to target Asian corn borerOstrinia furnacalis(Guenee), while their efficacy against other lepidopteran pests are not well defined, such asConogethes punctiferalis(Guenee),Helicoverpa armigera(Hubner),Agrotis ypsilon(Rottemberg), andMythimna separata(Walker), which are also important lepidopteran pests on corn in the Huang-Huai-Hai Summer Corn Region of China. To determine what type of Bt corn is suitable for this region, the efficacy of five Bt toxins, i.e., Cry1Ab, Cry1Ac, Cry1F, Cry2Ab, and Vip3A, to these five lepidopteran species was evaluated in laboratory. BothO. furnacalisandC. punctiferalisshowed similar high susceptibility to all five Bt toxins.A. ypsilonandM. separatewere less sensitive to Cry1Ab and Cry1Ac than the other species.H. armigera, A. ypsilonandM. separatewere less sensitive to Cry1F thanO. furnacalisandC. punctiferalis. H. armigerawas more sensitive to Cry2Ab than other tested species. All five species were equally sensitive to Vip3A, though their LC(50)s were all relatively higher. These findings suggest that the first generation Bt corn expressing single Cry1 toxin should not be the first choice because of the potential risk of control failure or less efficacy againstH. armigera, A. ypsilonorM. separate. The second-generation Bt corn expressing Cry1 and Cry2 toxins, or the third generation Bt corn expressing Cry1, Cry2 and Vip3A toxins might produce better protection of corn in the Huang-Huai-Hai Summer Corn Region of China.