Germination and longevity of some cowpea cultivars affected by single and mixed virus infections in Niger State, Nigeria

Abstract

Cowpea being a dependable source of protein for human growth and development is widely cultivated in sub-Saharan Africa including Nigeria. In spite of its numerous uses, infection by viruses constitutes serious problems to its productivity and once plants are infected, there is no remedy as is with other pathogens such as bacteria, fungi and nematodes. A field trial was conducted to investigate the reactions of twenty five cowpea cultivars to single and mixed infections with two unrelated viruses: Blackeye cowpea mosaic virus (BlCMV) and Cowpea mottle virus (CPMoV) on seed germination and longevity. The trial was conducted at the Teaching and Research Farm of the Ahmadu Bello University (ABU), Zaria, Mokwa Station and set up in a randomized complete block design (RCBD) with three replicates. For the single virus infection, seedlings of the twenty five cultivars were inoculated at 10 days after sowing (DAS), while for the mixed virus infections, seedlings were inoculated at 10 and 17 DAS. Results showed that all the cultivars were susceptible to single and mixed infections but to seemingly different extents. Germination of seeds was generally high before storage but was short lived indicating that conservation of infected seeds of the cultivars was impaired. Seeds of cultivars IT04K-267-8 and IT07K-222-2 recorded germination percentages of 54.6 and 53.7% respectively, while cultivars IT96D-610 and IT04K-291-2 had germination values of 52% which did not differ from each other. Viability of seeds amongst the 25 test cowpea cultivars from single infection with CPMoV alone and BICMV alone did not differ in some instances. Percent germination in cultivars IT98K-205-M8, IT90K-277-2 and IT07K-222-2 inoculated with BICMV + CPMoV were not much affected. Test of accelerated ageing germination (AAG) percentage for four weeks showed that seed vigour was greatly impaired in cultivars IT07K-292-2-10, IT06K-124 and IT90K-277-2 infected with BICMV + CPMoV compared to the lowest AAG percentage of 31.6 recorded in seeds of cultivar IT99K-377- 1. Constant monitoring of legume fields through regular field sanitation and disease surveys to identify new and emerging viruses as facts obtained from this study are good starting point for legume virus diseases diagnosis.