Assessment of the response of fifteen cowpea [Vigna unguiculata L. (Walp.)] genotypes to infestation by Callosobruchus maculatus Fab. (Coloeptera: Bruchidae)

Abstract

AbstractStorage of cowpea [Vigna unguiculata L. (Walp)] is constrained by the cowpea seed bruchid pest, Callosobruchus maculatus. However, in Ghana, little is known of the responses of cowpea genotypes to infestation by C. maculatus. Hence, the assessment of responses of fifteen cowpea genotypes to C. maculatus infestation in vitro. Forty seeds of each of the cowpea genotype were weighed and inoculated with five pairs of C. maculatus. The cultures were incubated for 40 days at 29 ± 1 °C. Three replicates of each cowpea genotype were arranged in a randomized complete block design and the mean seed weight loss, and bruchid development among others were subjected to analysis of variance and the means distinguished with the Fisher’s Least Significant Difference. The mean development period (egg to adult emergence) ranged from 21–28 days and the severity of seed damage was between 2.86 and 7.01. The susceptibility index ranged from 19–22 and seed weight loss was above 60% for all genotypes. Oviposition rate, percentage of seed weight loss, and severity of seed damage were significantly different (P < 0.05) among the cowpea genotypes. Percentage seed weight loss significantly (p < 0.05) correlated with the mean C. maculatus development period (r = 0.62) and number of F1 progeny (r = 0.56). The damage to cowpea seeds by C. maculatus infestation and the loss in seed weight can be reliably controlled by exploiting resistant genes to improve cowpea immunity to the pest.

Keywords

• Cowpea genotypes
• Callosobruchus maculatus
• Susceptibility