Influence des tanins condensés du tégument de fèves (Vicia faba) sur le développement larvaire de Callosobruchus maculatus

Des tanins condenses sont extraits et isoles a partir du tegument de Vicia faba var. ‘Geante Portugaise’. Quatre polymeres sont quantifies et identifies a quatre fractions: A, B, C et D. Ces fractions sont incorporees, en melange ou separees a differentes concentrations, dans un milieu nutritif favorable au developpement de Callosobruchus maculatus (F.) (Coleoptera, Bruchidae). Les composes phenoliques provoquent la mortalite d'une partie de la population et retardent le developpement des survivants. La mortalite observee varie suivant les fractions, leurs doses et le stade de developpement de la bruche. La barriere constituee par le tegument des feves est bien de nature chimique et concerne les tanins condenses. Dans un systeme de production agricole, l'utilisation des cultivars de feves riches en tanins faiblement condenses pourrait permettre de reduire les taux d'infestation des graines de V. faba par C. maculatus. Summary Effect of condensed tannins of horse bean husks on larval development of Callosobruchus maculatus Condensed tannins were extracted and isolated from the integument of Vicia faba var. ‘Geante Portugaise’. Four polymers were quantified and identified, as fractions A, B, C and D. Together they represent about 5% of the dry weight of the husk. The four fractions were incorporated, in mixtures or separately in different concentrations, into a larval diet of C. maculatus. These experiments have shown the depressive effect of phenolic compounds on the bruchid development. The condensed tannins cause mortality of a part of the experimental population and delay the development of survivors. The mortality observed varies between tannic fractions and developmental stages. At natural concentrations or higher ones, fractions C and D are more depressive to C. maculatus than the A and B ones. The highest mortality is observed in the fourth larval instar, and the males are more sensitive than the females. We conclude that the barrier of the husk is chemical. It consists of condensed tannins. In an agricultural pest management system, the use of cultivar of horse beans rich in weakly condensed tannins could cause a decrease of infestation rate of V. faba by C. maculatus.