Isolation and Characterization of Native Rhizobium Strains Nodulating Some Legumes Species in South Brazzaville in Republic of Congo

Abstract

Actually, in Republic of Congo, rhizobia have poorly phenotypically and biochemically characterized. This study aimed to characterize native rhizobia. Rhizobia strains were isolated using nodule roots collected on Milletia laurentii, Acacia spp., Albizia lebbeck, and Vigna unguiculata. The strains isolated were characterized microbiologically, biochemically, physiologically, and molecularly identified using 16S rRNA method. The results reported in this study are only for six strains of all 77 isolated: RhA1, RhAc4, RhAc15, RhAc13, RhW1, and RhV3. All native strains were positive to urease activity, negative to cellulase and pectinase activity except for one isolate that showed a positive cellulase activity. Moreover, isolates have grown at 12% of NaCl. On different effects of temperatures, isolates were able to grow up to 44°C and showed good growth at pH from 7 to 9 and the ability to use ten different carbon hydrates sources. The strains were identified as Rhizobium tropici, Rhizobium sp., Mesorhizobium sp. Bradyrhizobium yuanmingense and Bradyrhizobium elkanii. The phylogenetically analysis of the 16S rRNA genes, using a clustering method, allowed us to have a history that is both ancient and stable of four clades among genes with similar patterns. Expanding our awareness of the new legume-rhizobia will be a valuable resource for incorporating an alternative nitrogen fixation approach to consolidate the growth of legumes. These germs can be used in Congolese agriculture to improve yield of crops.