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A total of 102 bacterial strains isolated from nodules of three Bambara groundnut and one soybean cultivars grown in nineteen soil samples collected from northern Ghana were characterized using multilocus gene sequence analysis. Based on a concatenated sequence analysis (glnII-rpoB-recA-gyrB-atpD - dnaK), 54 representative strains were distributed in 12 distinct lineages, many of which were placed mainly in the Bradyrhizobium japonicum and Bradyrhizobium elkanii supergroups. Twenty-four of the 54 representative strains belonged to seven putative novel species, while 30 were conspecific with four recognized Bradyrhizobium species. The nodA phylogeny placed all the representative strains in the cosmopolitan nodA clade III. The strains were further separated in seven nodA subclusters with reference strains mainly of African origin. The nifH phylogeny was somewhat congruent with the nodA phylogeny, but both symbiotic genes were mostly incongruent with the core housekeeping gene phylogeny indicating that the strains acquired their symbiotic genes horizontally from distantly related Bradyrhizobium species. Using redundancy analysis, the distribution of genospecies was found to be influenced by the edaphic factors of the respective sampling sites. In general, these results mainly underscore the high genetic diversity of Bambara groundnut-nodulating bradyrhizobia in Ghanaian soils and suggest a possible vast resource of adapted inoculant strains. [ABSTRACT FROM AUTHOR]

Low soil phosphorus levels in savanna soils of Ghana limit cowpea response to inoculation. A two-year experiment was carried out on 2 soil types of the Guinea and Sudan savanna zones of Ghana based on the hypothesis that Bradyrhizobia inoculant (BR3267) in combination with phosphorus and potassium fertilizer will significantly increase cowpea root nodulation, growth and yield. The study aimed to determine the effect of phosphorus and potassium fertilizer on cowpea response to Bradyrhizobia inoculant. The treatments were laid out in Randomized Complete Block Design, replicated four times. The plot size was 8 × 3 m, with the sowing distance of 60 × 20 cm. The treatment comprises of commercial Bradyrhizobia inoculant, phosphorus (0, 30, 40 kg P2O5 ha−1) and potassium (0, 10, 20, 30 K2O ha−1). Application of Bradyrhizobia inoculant with 30 kg P2O5 ha−1 and 20 kg K2O ha−1 gave the highest grain yield (1.68 and 1.86 tons ha−1) at both soils which did not differ from the yield obtained from BR-40-30 kg ha−1 P2O5 and K2O ha−1 on the Ferric Lixisol and BR-40-20 kg ha−1 P2O5 and K2O on the Ferric Luvisol. The same treatment also gave the highest nodule number and nodule dry weight. The results of this study have shown that the application of Bradyrhizobia inoculant followed by P and K fertilizer was effective for cowpea growth in field conditions. [ABSTRACT FROM AUTHOR]