Detection and distribution of seed-borne viruses on commercial cowpea (Vigna unguiculata (L.) Walp) cultivars in Ado-odo Ota, Ogun Sate, Nigeria

Abstract

Cowpea is a major source of dietary protein in the nutrition of people in sub-Saharan Africa. Many viruses have been reported to cause economic reduction in cowpea productivity in Nigeria. However, their current distribution is not well documented while most farmers source their seeds from local markets. This study investigated the detection and distribution of seed-transmitted viruses on commercial cowpea cultivars in Ado-odo Ota Local Government area (LGA) of Ogun State. Cowpea seed samples were collected from eleven markets in the LGA. Coordinates of the locations were recorded with Geographical Positioning System (GPS). Thirty cowpea seeds from each market were sowed in planting pots under screenhouse conditions and seedlings were observed weekly for visible virus symptoms. Four-week old seedlings were tested for viruses using Antigen Coated Plate-Enzyme-Linked Immunosorbent Assay (ACP-ELISA) and Reverse Transcription Polymerase Chain Reaction (RT-PCR). Samples were tested for seven seed-transmitted viruses namely Blackeye cowpea mosaic virus (BlCMV), Cowpea aphidborne mosaic virus (CABMV), Cucumber mosaic virus (CMV), Southern bean mosaic virus (SBMV), Cowpea mottle virus (CMeV), Cowpea yellow mosaic virus (CYMV) and Cowpea mild mottle virus (CPMMV). Seed germination rates ranged from 63.3±15.3% of seeds from Joju to 96.7 ±5.8% for Atan and Iju markets. All samples tested negative to ELISA and were confirmed negative by RT-PCR. These findings suggest absence of seedtransmitted cowpea viruses in the study area as at the time of sampling. Periodic detection survey is recommended to assure the virus-free status of the area.

Keywords: ACP-ELISA, Cowpea viruses, Diagnostics, RT-PCR, Seed transmission