Natural seed coats provide protection against penetration by Callosobruchus maculatus (Coleoptera: Bruchidae) larvae

The seed coat is the first host or non-host tissue contacted by bruchids, suggesting its participation in the evolutionary adaptation of bruchids to favor legume seeds. In the present work, we studied the influence of seed coat on the ability of Callosobruchus maculatus (Coleoptera: Bruchidae F.) larvae to penetrate, develop in and survive on seeds. Our results showed that the oviposition, larval eclosion and adult emergence of C. maculatus were drastically reduced in some seeds and that the time necessary for the surviving larvae to perforate the seed coat increased by up to 100% in these seeds. The surviving larvae that crossed the Phaseolus vulgaris (Leguminosae B.) seed coat reached only 55.6% of the mass of a normal larva. The seed coat of some seeds was very toxic to insect larval development. Despite individual variations, seed coats were generally highly restrictive to the development and survival of the bruchid. The study of the seed coat efficiency as a protection tissue against penetration of insects can provide an important tool for new strategies for crop protection. The strengthening of the seed coat defense mechanisms may represent an efficient strategy because the seed chemical defense barrier would be moved to the outer structures and damage to the embryo would be minimized or avoided.

► Seed coat interfered in the Callosobruchus maculatus larvae capacity to penetrate, develop and survive on non-host seeds.
► The time necessary for the C. maculatus surviving larvae to perforate completely the seed coat increased of up to 100%.
► The surviving larvae that crossed the Phaseolus vulgaris seed coat reached only 55.6% of the mass of a normal larva.
► Seed coats flours from non-host seeds were toxic to C. maculates larvae.