Hudaib. European Journal of Biomedical and Pharmaceutical Sciences www.ejbps.com 33 THE ROLE OF SEED COAT THICKNESS IN RESISTANCE/SUSCEPTIBILITY OF LEGUMES TO COWPEA BEETLE (CALLOSOBRUCHUS MACULATUS) INFESTATION Taghread Hudaib* University of Lincoln, School of Pharmacy, Brayford Pool, Lincoln, LN6 7TS. Article Received on 30/01/2019 Article Revised on 20/02/2019 Article Accepted on 13/03/2019 1. INTRODUCTION Physical characteristics of seed coat including the thickness are important factors in the resistance or susceptibility of legume seeds to the cowpea beetle C. maculatus infestations. Nwanze et al. (1975) examined the oviposition preference of C. maculatus across different areas of the host-bean seed-coat and found that textural differences affected the oviposition decisions; females did not lay eggs on the spongy seed hilum. This study concluded that C. maculatus prefer to lay eggs on smooth varieties of beans. Edde and Amatobi (2003) indicate that seed coat thickness has no effect on bean resistance to C. maculatus infestation. They came to this conclusion after rearing the cowpea beetles C. maculatus on two groups of beans; one group was the normal coated beans and the other with beans that have their seed coat removed. They suggested that the seed coat has no value in cowpea defence against C. maculatus attacks. Other researchers have suggested that the role of seed coat thickness in bean resistance is considerable; as example, Kitch et al. (1991) suggested that the seed coat thickness was highly correlated with the resistance of V. unguiculata beans to the cowpea beetle C. maculatus. Resistance was measured as larval mortality following egg-hatch and before penetration (Pre M) of the seed coat compared to larval mortality after penetrating the seed coat (post M). Thirty varieties of cowpea were examined, ten of them revealed a mortality (from egg hatch to adult emergence) of greater than 95%. The range of mortality within the Pre M larvae was 57.9% to 99.4% and the range within the post M was 6.7%, to 82.6%., which showed the high correlation of seed-coat thickness with V. unguiculata resistance to C. maculatus. 2. MATERIALS AND METHODS To explore the effect of seed coat thickness on egg-to- adult survival of C. maculatus, V. unguiculata beans were soaked in distilled water for 15 minutes and the seed coat removed. Decoated seeds were then individually wrapped in 1 to 4 of the still wet and sticky, previously removed seed coats and then wrapped in aluminium foil. A single 5mm diameter hole was created in the foil to expose a constant surface area of seed coat to ovipositing females. An additional treatment was established by soaking P. vulgaris beans that are highly resistant to the cowpea beetle C. maculatus (Huesing et al. 1991) in distilled water for 30 to 45 minutes and a single layer of wet seed coat wrapped around the decoated V. unguiculata beans, before being wrapped in aluminium foil into which a 5mm diameter hole had been created as previously described by Hudaib et al. (2010). In this experiment the control was the decoated V. unguiculata beans wrapped in aluminium foil as described above. Thirty seeds of each group were placed into separate containers and 4 non-virgin C. maculatus females (24 hours from eclosion) added to oviposit for 2h (females SJIF Impact Factor 4.918 Research Article ejbps, 2019, Volume 6, Issue 4, 33-35. European Journal of Biomedical AND Pharmaceutical sciences http://www.ejbps.com ISSN 2349-8870 Volume: 6 Issue: 4 33-35 Year: 2019 *Corresponding Author: Dr. Taghread Hudaib University of Lincoln, School of Pharmacy, Brayford Pool, Lincoln, LN6 7TS. ABSTRACT The role of seed coat thickness in the resistance/susceptibility of V. unguiculata (black-eyed beans, Cultivar: Black-eyed peas) against infestation by the bruchid beetle C. maculatus (F.), was investigated. Decoated V. unguiculata beans were individually coated in one to four of previously removed seed coats or one layer of Phaseolus vulgaris (Red Kidney Beans-British Type) seed coat, before being offered to non-virgin C. maculatus females to oviposit on. Following incubation for several weeks, the total adult emergence was then used to determine egg-adult survival and the seed coat thickness for both types of beans was measured. The seed coat of P. vulgaris was approximately three times thicker than that of V. unguiculata. The survival of larvae in the four coats V. unguiculata treatment was similar to that of P. vulgaris seed coat, which showed the high correlation of seed coat thickness with V. unguiculata beans resistance to C. maculatus. KEYWORDS: Bruchid beetle, Infestation, Seed coat, Thickness.