Interactions of viruses in cowpea: effects on growth and yield parameters

The study was carried out to investigate the effects of inoculating three cowpea cultivars: OLO II, OLOYIN and IT86D-719 with three unrelated viruses: Cowpea aphid-borne mosaic virus (CABMV), genus Potyvirus, Cowpea mottle virus (CMeV), genus Carmovirus and Southern bean mosaic virus (SBMV), genus Sobemovirus singly and in mixture on growth and yield of cultivars at 10 and 30 days after planting (DAP). Generally, the growth and yield of the buffer inoculated control plants were significantly higher than those of the virus inoculated plants. Inoculation of plants at an early age of 10 DAP resulted in more severe effect than inoculations at a later stage of 30 DAP. The average values of plant height and number of leaves produced by plants inoculated 30 DAP were higher than those produced by plants inoculated 10 DAP. Most of the plants inoculated 10 DAP died and did not produce seeds. However, OLOYIN cultivar was most tolerant and produced reasonable yields when infected 30 DAP. The effect of single viruses on growth and yield of cultivars showed that CABMV caused more severe effects in IT86D- 719, SBMV had the greatest effect on OLO II while CMeV induced the greatest effect on OLOYIN. Yield was greatly reduced in double infections involving CABMV in combination with either CMeV or SBMV in OLOYIN and OLO II, however, there was complete loss in yield of IT86D-719. Triple infection led to complete yield loss in all the three cultivars.