DEVELOPMENT OF CALLOSOBRUCHUS-CHINENSIS (L) AND C-MACULATUS (F) (COLEOPTERA, BRUCHIDAE) IN SEEDS OF VICIA-FABA L DIFFERING IN THEIR TANNIN,VICINE AND CONVICINE CONTENTS

The seeds of the tested genotypes of Vicia faba L. differed by the pre sence or absence of tannins in the seed coat and in the level of vicin e and convicine in the cotyledons. In vertebrates, these two glycoside s can be transformed into divicine and isouramil which influence the e nzymatic activity of glucose-6-phosphate dehydrogenase (G-6-PDH). Call osobruchus chinensis (L.) develops in V. faba seeds and causes high lo sses during storage. C. maculatus (F.) is less able to develop in the seeds of V. faba. For both bruchids the seed coat represents a barrier that only 45-60% of larvae overcome. The presence of tannins did not affect the perforation rate. The texture of the seed coat, its hardnes s or the presence of other toxic compounds could explain these results . The larvae of C. chinensis were able to develop in the seeds of V. f aba whatever their vicine and convicine contents and the survival rate during the post-embryonic development was higher than 70%. The larvae of C. maculatus could only develop well in seeds poor in vicine and i n convicine. The L1 larvae died as soon as they began to consume the c otyledons of the seeds containing high levels of glycosides. The prese nce of vicine in the seeds seemed to be the main mortality factor for C. maculatus larvae. Variations in the convicine content had a more li mited influence. The enzymatic activity of G-6-PDH in haemolymph depen ded on the seed vicine and convince contents and the bruchid species. This activity was low when larvae developed in seeds rich in vicine an d convicine. Whatever the genotype of the seeds, the enzymatic activit y of the G-6-PDH was always higher in C. chinensis adults than in C. m aculatus adults. Varietal selection, through the reduction of the vici ne and convicine content of the seeds, can favour the colonization of V. faba by other phytophagous insects such as C. maculatus.