Evaluation of Host Resistance in Cowpea Genotypes to Cowpea Mosaic Virus in Katsina State, North West Nigeria

Cowpea Mosaic Virus (CPMV) is a comovirus with bipartite RNA genome that causes severe mosaic, chlorosis, and yield reduction in cowpea across Northern Nigeria. In Katsina State, where cowpea forms a major dietary and cash crop, viral disease management through host resistance represents the most economically viable and environmentally sustainable control strategy. This study evaluated the response of 25 cowpea genotypes to CPMV inoculation under both greenhouse and field conditions at the Katsina State University experimental farm during 2023 and 2024. Mechanical inoculation was performed at the cotyledon and first trifoliate leaf stages, and disease response was scored at 7, 14, and 21 days post-inoculation using a 1-9 severity scale. Virus titre in inoculated plants was quantified by enzyme-linked immunosorbent assay to differentiate tolerance from resistance. Three genotypes, IT97K-556-6, IT00K-1263, and a local cultivar designated KST-22, displayed systemic resistance across both evaluation environments, with virus titres below detection thresholds in leaf tissue. Eight genotypes classified as tolerant showed moderate virus titres but minimal yield impact. The remaining fourteen genotypes were classified as susceptible. Field evaluations under natural inoculum pressure confirmed greenhouse findings in 91 percent of cases. Aphid transmission efficiency tests showed that Aphis craccivora transmitted CPMV to susceptible controls in all trials. The study recommends deployment of IT97K-556-6 and KST-22 in Katsina cowpea production and their inclusion in regional certified seed multiplication programmes. Keywords: cowpea, CPMV, host resistance, genotype evaluation, Katsina State.