Comparative Susceptibility of some Cowpea [Vigna unguiculata (L.) Walp.] Accessions, Breeding Lines and Winged Bean to the Cowpea Bruchid, Callosobruchus maculatus (F.) {Coleoptera: Bruchidae}.

Abstract

Some cowpea [Vigna unguiculata (L.) Walp.] accessions, from different locations in Nigeria, and advanced breeding lines obtained from the International Institute of Tropical Agriculture (UTA), as well as winged bean [Psophocarpus tetragonolobulus (L.DC.) ] were screened for resistance to the cowpea bruchid, Callosobrucus maculatus (F.). IT90K-277-2 and IT90K-76 were the resistant standards while Ife Brown was the susceptible standard. The seed lots (20 g each) were infested with three pairs of newly emerged adults and the number of eggs laid was counted at 5 days post-infestation. F1 progeny were counted and from the values and the median developmental period, susceptibility indices were calculated. The number of emerged adults was also expressed as a percentage of the total number of eggs laid. The winged bean lines EM-WB-l, KC- 02E-l, and KC-02E-3 showed antibiosis (evidenced by low F1 progeny and low susceptibility index) at levels stronger than or comparable to those of the resistant standards. No cowpea line matched IT90K-277-2 and IT90K-76 in resistance to cowpea bruchid but three lines (ENU-AB-6, ENU-MB-8, and ENU-OG-4) were as susceptible as Ife Brown.