Assessment of resistance status in cowpea genotypes and demographic parameters of cowpea aphid (Aphis Craccivora KOCH)

Abstract

Cowpea, a crucial legume in Nigeria, faces significant challenges from various biotic and abiotic stresses, with the Cowpea Aphid (Aphis crassivora Koch) being the most detrimental pest affecting yield. Despite breeding efforts to develop resistant varieties, emerging aphid biotypes have compromised this resistance. The research aimed to ascertain the resistance status of cowpea genotypes and detail the demographic parameters of the cowpea aphid. Eighteen cowpea genotypes were evaluated phenotypically in insect-proof cages within a screen house, using a completely randomized design with three replications. The parameters measured included the pre-reproductive period, reproductive period, life span, total offspring, intrinsic rate of natural increase, and mean relative growth rate of cowpea aphids. The study found varying levels of resistance among the genotypes, with SAC-20KTE-11 and Sampea 14 showing the highest resistance, while Dan Misra and Aloka Local exhibited the highest susceptibility. The pre-reproductive period of aphids was prolonged by the resistant genotypes compared to the susceptible ones. The resistant genotypes also shortened the reproductive period, life span, total offspring, intrinsic rate of increase, and mean relative growth rate of aphids compared to the susceptible genotypes. SAC-20KTE-11 and Sampea 14 displayed antibiosis-type resistance, indicating their potential to reduce aphid reproductive rates. These genotypes could be selected for inclusion in cowpea breeding programs aimed at developing improved resistant lines against aphids.