Distribution of Virus Symptoms and Viruses Infecting Field-Grown Cucurbit Crops Under Natural Tropical Conditions Within a Humid Rainforest Transition Agro-Ecology in Nigeria

Abstract

Farmers’ fields where cucurbit crops were grown in seven Local Government Areas (LGA) of Ogun state were surveyed in 2009 and 2010 for incidence and severity of virus symptoms and the identity of the viruses infecting the crops were determined using DAS-ELISA. Six viruses including Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV), Papaya ringspot virus (PRSV), Cucumber green mottle mosaic virus (CGMMV), Cucumber mosaic virus (CMV), and Melon necrotic spot virus (MNSV) were indexed for in the leaf samples. A total of 14 farms were visited and 130 leaf samples were collected. The incidences of virus symptoms on the field were between 41.0 and 100.0% while the mean severity score were between 1 (apparently healthy) and 5 (severe symptoms and death) in some locations. The incidences of virus symptoms such as mottle, chlorosis and yellowing, mosaic, leaf distortion, puckering, vein banding and vein clearing were 20.0, 19.2, 18.5, 16.2, 11.5, 3.1 and 3.1%, respectively in the collected leaf samples. However, 8.5% of the leaf samples were apparently healthy. Serological analysis of the leaf sample showed the presence of ZYMV, PRSV, WMV, CMV, MNSV, and CGMMV. The most widely distributed virus was MNSV which occurred in 9 out of 14(64.3%)of the locations. This was followed by WMV and CGMMV occurring in 8 out of 14 (57.0%) of the locations. PRSV and CMV occurred in 50.0% of the locations. ZYMV occurred in 5 out of 14 (35.7%) of the locations. The viruses detected are among the viruses reported to limit the production of cucurbit crops world-wide.