Adaptive Capabilities of Two Varieties of Cowpea in Crude Oil-Contaminated and Un-Contaminated Soils

Abstract

Background and Objective: Cowpea (Vigna unguiculata (L.) Walp., is well-adapted to the Northern parts of Nigeria than the Southern Region especially the Niger Delta Region of Nigeria. The aim of this study was to investigate the adaptive capabilities of cowpea in crude oil-contaminated and non-contaminated soils. Materials and Methods: Two varieties of cowpea namely TVU-31 and Aloka bean were planted in crude oil-contaminated and un-contaminated soils in three replicates using the randomized complete block design for a 50 days period. Data was collected for vegetative vigor, agronomic parameters and root nodulation. The fungal species associated with the roots were isolated using Yeast Extract Mannitol Agar (YEMA) media and later subcultured in Potato Dextrose Agar Medium (PDA) media for identification. Results: The two cowpea varieties, had intermediate vegetative vigor and a gradual increase in the plant height, root length, root width and number of nodules. From the root architecture, it was observed, that the cowpea varieties in the contaminated soil had more adventitious roots with smaller diameters, shallower basal roots with longer, denser root hairs and higher root biomass than the varieties in the un-contaminated soil. Seven fungal species namely Penicillium chrysogenum, Botryodiplodia the obromae, Mucor circinelloides, Aspergillus flavus, Aspergillus spp., Neurospora spp. and Aspergillus niger) were identified to associate with the roots of cowpea. Conclusion: This study, therefore, provides preliminary data for further research into the adaptive capabilities of cowpea in Nigeria.