Blackeye cowpea mosaic virus (BlCMV) is a major virus, infecting legumes with attendant huge losses. Cultivation of resistant varieties is the most effective and sustainable control strategy. Therefore, some groundnut (Arachis hypogaea) cultivars were evaluated against BlCMV in Minna, Southern Guinea savanna zone of Nigeria.

The response of cowpea (Vigna unguiculata) inoculated with Blackeye cowpea mosaic virus (BlCMV), Cowpea aphid-borne mosaic virus (CABMV), and BlCMV+CABMV was investigated under screenhouse conditions, using completely randomised design with six replications. Seedlings of the cowpea line TVU 76 were mechanically inoculated at 10 days after sowing. Uninoculated cowpea plants served as controls. Disease incidence, severity and yield parameters were recorded. Virus concentration in leaf samples was determined using Antigen Coated Plate-Enzyme Linked Immunosorbent Assay (ACP-ELISA). One hundred percent infection was obtained at two weeks post inoculation regardless of the virus combination. CABMV and BlCMV+CABMV elicited the highest symptom score of 4 while the lowest score of 2.8 was observed in BlCMV-inoculated plants. Mixed infections enhanced the highest virus concentration (1.7). The virus titre value in plants infected with CABMV (0.8) was relatively higher than in the BlCMV-inoculated plants (0.5). The seeds from uninoculated plants gave the highest (2.1 g) weight. Mixed infections with BlCMV+CABMV resulted in the lowest seed weight per plant (0.4 g), followed by single infection with CABMV (0.7 g), whereas the value was 0.8 g in the BlCMV-infected plants. Adoption of cowpea cultivars with genetic resistance against multiple virus infections is recommended in order to guard against complete crop failure.Keywords: Disease incidence and severity; seed weight; Vigna unguiculata; virus concentration

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Groundnut (Arachis hypogaea) is a major legume crop with diverse uses in Nigeria. Its productivity is however threatened by Cowpea aphid-borne mosaic virus (CABMV) in most groundnut producing areas, resulting in huge losses. This study was conducted to determine the resistance of some commercial groundnut cultivars under CABMV disease. The experiment was conducted in Minna, Southern Guinea Savanna agro-ecological zone of Nigeria. Twenty groundnut cultivars were evaluated separately as healthy and CABMV infected trials. The experiment was laid out in randomised complete block design with three replications. Seedlings were infected with the virus by mechanical inoculation at 10 days after sowing. The plants were observed for disease incidence, growth and yield attributes. The data collected were subjected to analysis of variance, principal component and cluster analyses at p≤0.05. One hundred percent infection was found regardless of the cultivar. The healthy plants exhibited significantly (p<0.05) higher morphological and yield parameters than infected plants. Principal component analysis revealed that 100-seed weight accounted for the greatest variability in healthy (eigen vector = 0.6239) and CABMV infected (eigen vector = 0.6005) plants. Cluster analysis showed that 18 (90 %) cultivars formed cluster 1, whereas one cultivar each was found in cluster 2 and 3. The top three cultivars for 100-seed weight: "SAMNUT 23" (56.0 g), "SAMNUT 25" (50.5 g) and "SAMNUT 26" (50.9 g) were the most tolerant to CABMV, whereas "ICG-92267" was identified as the best cultivar for dry matter production (24.0 g/plant). Planting of these tolerant cultivars is recommended in order to mitigate the stresses imposed by CABMV.