Survey of Bean Common Mosaic Virus on Cowpea (Vigna unguiculata) in Edo State, South South Nigeria

Cowpea (Vigna unguiculata) is grown extensively across Edo State for household consumption and local market sales in the South South zone. Bean Common Mosaic Virus (BCMV), a seed-transmitted potyvirus vectored by aphids, has been associated with significant yield losses in legume systems across West Africa. This survey investigated the incidence of BCMV in cowpea fields across four local government areas of Edo State during the 2023 growing season. Systematic field transects were applied across 55 farms, and symptomatic plant samples displaying mosaic, mottle, and pod distortion were collected for serological and molecular analysis. BCMV was confirmed through reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay tests in 61 percent of tested symptomatic samples. Mixed infections with Cowpea Aphid-Borne Mosaic Virus were detected in 18 percent of BCMV-positive samples, suggesting synergistic interactions contributing to severe symptom expression. Aphid vector populations, including Aphis craccivora, were documented on all farms and showed seasonal peaks in the early rainy season coinciding with highest virus incidence. Most growers used undifferentiated local seed lots with unknown virus status. The study recommends sourcing of BCMV-tested seed from certified institutions and the adoption of early reflective mulching to reduce aphid colonisation rates. Keywords: cowpea, Bean Common Mosaic Virus, aphid, Edo State, disease incidence.