Transgenic cowpea (Vigna unguiculata) seeds expressing a bean α-amylase inhibitor 1 confer resistance to storage pests, bruchid beetles

Cowpea is one of the important grain legumes. Storage pests, Callosobruchus maculatus and C. chinensis cause severe damage to the cowpea seeds during storage. We employ a highly efficient Agrobacterium-mediated cowpea transformation method for introduction of the bean (Phaseolus vulgaris) alpha-amylase inhibitor-1 (alpha AI-1) gene into a commercially important Indian cowpea cultivar, Pusa Komal and generated fertile transgenic plants. The use of constitutive expression of additional vir genes in resident pSB1 vector in Agrobacterium strain LBA4404, thiol compounds during cocultivation and a geneticin based selection system resulted in twofold increase in stable transformation frequency. Expression of alpha AI-1 gene under bean phytohemagglutinin promoter results in accumulation of alpha AI-1 in transgenic seeds. The transgenic protein was active as an inhibitor of porcine alpha-amylase in vitro. Transgenic cowpeas expressing alpha AI-1 strongly inhibited the development of C. maculatus and C. chinensis in insect bioassays.