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Genetically modified (GM) cowpea seeds expressing αAI-1, an α-amylase inhibitor from the common bean, have been shown to be immune against several bruchid species. Effective control of such pests by growing GM cowpea could promote the spread of bruchid species that are αAI-1 tolerant. Consequently, the sustainability of bruchid pest control could be increased by combining GM seeds and hymenopteran parasitoids. However, there are concerns that αAI-1 could interfere with the biological control provided by parasitoids. Here, we assessed the impact of GM cowpea seeds expressing αAI-1 on the αAI-1-tolerant bruchid Zabrotes subfasciatus and its parasitoid Dinarmus basalis. αAI-1 in cowpea seeds did not increase resistance to Z. subfasciatus or affect the mortality rate of Z. subfasciatus larvae. Parasitism of Z. subfasciatus by D. basalis and fitness of D. basalis offspring were not affected by the presence of αAI-1. Thus, αAI-1-expressing cowpeas and parasitoids should be compatible for the control of bruchid pests.

Genetically modified (GM) legumes expressing the α-amylase inhibitor 1 (αAI-1) from Phaseolus vulgaris L. or cysteine protease inhibitors are resistant to several bruchid pests (Coleoptera: Chrysomelidae). In addition, the combination of plant resistance factors together with hymenopteran parasitoids can substantially increase the bruchid control provided by the resistance alone. If the strategy of combining a bruchid-resistant GM legume and biological control is to be effective, the insecticidal trait must not adversely affect bruchid antagonists. The environmental risk assessment of such GM legumes includes the characterization of the targeted enzymes in the beneficial species and the assessment of the in vitro susceptibility to the resistance factor. The digestive physiology of bruchid parasitoids remain relatively unknown, and their susceptibility to αAI-1 has never been investigated. We have detected α-amylase and serine protease activities in all five bruchid parasitoid species tested. Thus, the deployment of GM legumes expressing cysteine protease inhibitors to control bruchids should be compatible with the use of parasitoids. In vitro inhibition studies showed that sensitivity of α-amylase activity to αAI-1 in the parasitoids was comparable to that in the target species. Direct feeding assays revealed that harmful effects of α-amylase inhibitors on bruchid parasitoids cannot be discounted and need further evaluation.