Symbiotic effectiveness and ecologically adaptive traits of native rhizobial symbionts of bambara groundnut (Vigna subterranea L. Verdc.) in Africa and their relationship with phylogeny.
Ibny, Fadimata Y.I. Jaiswal, Sanjay K. Mohammed, Mustapha Dakora, Felix D.
Ibny, Fadimata Y.I.
Jaiswal, Sanjay K.
Mohammed, Mustapha
Dakora, Felix D.
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Abstract
Bambara groundnut (Vigna subterranea L. Verdc.) is an indigenous, drought-tolerant, underutilized African food legume, with the ability to fx atmospheric N2 in symbiosis with soil bacteria called rhizobia. The aim of this study was to assess the morpho-physiological, symbiotic and phylogenetic characteristics of rhizobia nodulating Bambara groundnut in Ghana, Mali and South Africa. The morpho physiologically diverse isolates tested were also found to exhibit differences in functional efficiency and phylogenetic positions. Based on Enterobacterial Repetitive Intergenic Consensus (ERIC)-PCR banding patterns, the isolates were grouped into eight major clusters. The concentrations of Ca, Na and K in soils had a significant (p≤0.01) effect on the distribution of rhizobia. Though many isolates were symbiotically very effective, the effectiveness index varied markedly (p≤0.05) among them. Moreover,
the isolates also exhibited tolerance to a wide range of NaCl (0.5–7%), streptomycin (50–500µg.ml−1), and kanamycin (25–150µg.ml−1) concentrations. Additionally, these isolates could produce 0.02 to 69. 71µg.ml−1 of indole-3-acetic acid (IAA) in tryptophan-supplemented medium, as well as solubilize tri-calcium phosphate. Phylogenetic analysis of these rhizobial isolates using 16S rRNA, atpD, glnII, gyrB, recA and symbiotic (nifH and nodC) gene sequences revealed distinct and novel evolutionary lineages related to the genus Bradyrhizobium, with some of them being very close to Bradyrhizobium vignae, B. kavangense, B. subterraneum, B. elkanii and B. pachyrhizi.
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2019-08-13
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Nature Research
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Keywords
Bambara groundnut, Drought-tolerant, Food legume, Bradyrhizobium, Morpho-physiological