Abstract

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The identification of native rhizobia capable of inducing effective nodulation in legumes is a prerequisite for selection of strains for bioinoculation. The study aimed to characterize and evaluate the symbiotic efficiency of native rhizobia capable of effectively nodulating Bambara groundnut (Vigna subterranean). Greenhouse experiment was conducted in a completely randomized design with five accessions of Bambara groundnut and five replications. The rhizobia strains were isolated from the root nodules and subjected to nodulation test on the host plants. The rhizobial isolates were characterized by morpho-cultural characteristics and 16S rRNA gene sequencing technique. The symbiotic efficiency of the isolates on Bambara groundnut was also evaluated as data on dry shoot weights, nodule number, fresh and dry weights were collected. Of the thirty five rhizobial isolates obtained, only 15 (42.9%) successfully induced effective nodulation in Bambara groundnut plants and the 16S rRNA gene sequencing identified them as strains of Bradyrhizobium, Mesorhizobium, Sinorhizobium and Rhizobium. The results of the symbiotic efficiency of rhizobia showed significant variations in the symbiotic capacities of the strains. The nodule number, fresh and dry weights ranged from 13.67±0.88 to 57.33±2.03 per plant, 0.10±0.01 to 0.33±0.03 g/plant and 8.33±0.67 to 40.00±1.73 mg/plant, respectively. The strains enhanced the dry shoot weights by 36.7% to 121.8% over non-inoculated control. The study therefore revealed the potential of native strains of rhizobia in nodulating Bambara groundnuts and these strains could be considered as potential inoculant strains for sustainable production of Bambara groundnut in Nigeria

Keywords: Rhizobia, Vigna subterranean, nodulation, symbiotic efficiency, inoculant