Varietal Resistance of Cowpea (Vigna unguiculata (L.) Walp.) to Attack by Callosobruchus maculatus (Fabricius, 1775) (Coleoptera: Chrysomelidae) During Post-Harvest Storage in Mali

Abstract

Cowpea (Vigna unguiculata (L.) Walp.) is a tropical legume of major economic, nutritional and agronomic value, but its production is severely constrained by post-harvest losses, mainly caused by the cowpea weevil Callosobruchus maculatus. An experimental study was conducted at the Entomology-Parasitology Laboratory of FST/USTTB (November 2023–February 2024) to assess the susceptibility of forty cowpea varieties, grown under irrigated and water-stress conditions, to damage by C. maculatus during three months of storage. Sterilized seeds (30 g per 500-mL jar) were infested with three pairs of newly emerged (0-24 h) C. maculatus adults, using a completely randomised design with three replicates (360 jars in total). Varietal susceptibility was assessed through the median development period (MDP), damage rate, adult mortality, weight loss and susceptibility index (SI). Five varieties (KT2-23-5, CZ16-3-71, IT13K-1424-12, FAKSON, IT15K-2386-1) were resistant under water-stress conditions and five others (SIMBO, KVX78-6PLANT-1, CZ16-1-1-91, TILIGREPLANT-6, KVX61-1) under irrigated conditions. The combined analysis confirmed the resistance of three varieties: KT2-23-5, TILIGREPLANT-6 and KVX61-1. Damage was positively and significantly correlated with MDP, weight loss and SI, whereas adult mortality was not significantly associated with observed losses. These findings suggest that post-harvest control strategies should target reproduction and immature stages rather than adult mortality alone, and identify KT2-23-5, TILIGREPLANT-6 and KVX61-1 as promising parental lines for a cowpea resistance breeding programme against C. maculatus.