Chickpea‐mediated effects of Bacillus thuringiensis on Helicoverpa armigera and its larval parasitoid, Campoletis chlorideae

Abstract

AbstractEfforts are underway to express toxin genes from Bacillus thuringiensis (Bt) in chickpea for controlling the pod borer, Helicoverpa armigera. The interaction between Bt toxins, Helicoverpa‐resistant chickpeas, and the parasitoid, Campoletis chlorideae are not fully understood. Therefore, we studied tritrophic interactions between Bt (administered as spray), chickpea genotypes, and the parasitoid, C. chlorideae. Chickpea genotypes resistant to H. armigera exercised a significant reduction in leaf feeding, survival and development of H. armigera, but did not influence the development and survival of the parasitoid, C. chlorideae. Bt sprays on different chickpea genotypes prolonged the larval period, and reduced pupation and adult emergence of C. chlorideae. Weights of H. armigera larvae showed a strong and positive association with C. chlorideae larval period on Bt treated, and a negative association on untreated chickpeas. The Bt‐intoxicated H. armigera larvae also resulted in reduced weight of the cocoons and adults of C. chlorideae, suggesting significant influence of host size on development and survival of the parasitoid. Bt toxins were detected in H. armigera larvae fed on Bt‐sprayed chickpeas, but not in C. chlorideae reared on H. armigera larvae fed on Bt‐treated chickpeas, and in the parasitoid adults fed on honey intoxicated with 0.05%Bt. The adverse effects of Bt on the parasitoid were largely through early mortality of H. armigera larvae or poor quality of the host. This information would be useful for planning appropriate strategies for testing and deployment of Bt‐transgenic chickpea with resistance to H. armigera for sustainable crop production.