Studies on Seed Viability of Some Cowpea Cultivars Inoculated with Single and Mixed Virus Isolates

This research aimed at investigating and examining the effects of virus infections on seed quality of some selected cultivars of cowpea. Thus, a field study was conducted at the Teaching and Research Farm of the Faculty of Agriculture, Ahmadu Bello University (ABU), Zaria, Mokwa Station (090211 N and 50135 E, 201 m above sea level) situated in the Southern Guinea Savanna zone of Nigeria to achieve this. The site was cleared, ploughed, harrowed and ridged at 0.75 m apart then marked out into plots and replications. The trial was a randomized complete block design (RCBD) replicated three times. Three cowpea seeds of each cultivar were sown after dressing with Apron – star (methylthiuram + metalaxyl + carboxin) at the of rate 3.0 kg seed per 10 g of the fungicide. Seeds were sown at an intra and inter–row spacing of 0.30 × 0.75 m along the ridges and later thinned to two per stand at 2 weeks after sowing (WAS). Four independent trials were conducted simultaneously, for single and mixed infections. Twenty-five cultivars of seedlings were injected at 10 days after sowing (DAS) for the single viral infection and at 17 DAS for the mixed virus infection. Seed viability was determined at the Crop Production Laboratory, Department of Crop Production, Federal University of Technology, Minna, Nigeria. The results showed that all the test cultivars were susceptible to single and mixed infections of the two viruses but to different levels. The viability of seeds from single infection with CMeV was slight in some instances, also, test of accelerated ageing for four weeks indicated that seed vigour was seriously impaired as compared to the other three virus treatments even when seeds viability was not much impaired. The test cowpea cultivars also recorded fewer pods with poor seed yield in both single and mixed virus infections.