Agro-ecological incidence and severity of Pepper veinal mottle virus, genus Potyvirus, family Potyviridae, on cultivated pepper (Capsicum annuum L.) in Nigeria

A survey for the agro-ecological distribution of Pepper veinal mottle virus (PVMV) (Family Potyviridae, genus Potyvirus) its incidence and severity on cultivated pepper was conducted between 2003 to 2005 in six agro-ecological zones in Nigeria, comprising the major pepper producing areas of the humid forest, derived savanna, southern Guinea savanna, mid-altitude, northern Guinea savanna and Sudan savanna The virus was isolated and its physical properties determined. PVMV was confirmed to be present in cultivated pepper fields in the six agro-ecological zones surveyed but with significant difference in disease incidence and severity within the agro-ecological zones. Out of the three thousand suspected viral infected pepper leaves sample collected from the fields in the six agro-ecological zones, 88% were confirmed to be PVMV positive through the serological test while 12% were found to be negative. The Electron micrograph photograph showed antiserum decorated PVMV particles, having flexuous filamentous particles of 750nm in length and 10 nm wide. The thermal inactivation point of the virus was 70C and still infective up to the 12th day, while the dilution end point in which PVMV extract from Capsicum annuum L. was still infective was 10. The incidences of PVMV diseases were observed to be high in the derived savanna and the humid forest compared with the other agro-ecological zones. The percentage PVMV disease incidence ranged between 39.14% with 34.48% severity in the Sudan savanna to 50.12% incidence and 43.85% severity in the derived savanna zone. The high incidence and severity of PVMV in these two agro-ecological zones that are characterized by thick vegetation and warm humid climate, with the presence of many secondary host plants for the virus. suggest that ecological characteristics, climate and vegetation in the different ecological zones appeared to play a major role in determining the incidence and severity of PVMV infection on pepper in the fields.