Adaptation of a Callosobruchus maculatus strain to Vicia faba, as its new host plant

Abstract

Callosobruchus maculatus (F.) is a bruchid beetle developing in the seeds of 14 leguminous species (Delobel & Tran, 1993). In West Africa, the cowpea Vigna unguiculata is its main host plant. The females lay their eggs on the seed coat and postembryonic development is completed entirely within the seeds. Although this bruchid is oligophagous, its capacity for development in the seeds of the broad bean Vicia faba (L.) is very limited (Hoffmann et al., 1962). Desroches et al. (1995) demonstrated that the presence of two pyrimidic glucosides, vicine and convicine in the cotyledons was the main mortality factor for C. maculatus larvae. In the gut of the C. maculatus larvae β-glucosidases have been found (Gatehouse & Anstee, 1983). These enzymes can hydrolyse the glucosides to produce the highly reactive free radical generating compounds, divicine and isouramil, as observed in vertebrates (Marquardt, 1989).