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.
Highlights
Nitrogen is an essential component of tissues and growth of plant
Strains from Acacia spp. and Albizia lebeck appeared on the culture medium after 5 days whereas Vigna unguiculata strains grown on the medium appeared after 8 days and those of Millettia laurentii after 9 days
The result founded in this study showed that there were among Acacia spp strains both fast and slow-growing strains, they took 3 to 5 days to appear on the yeast extract mannitol agar (YMA) medium
Summary
Nitrogen is an essential component of tissues and growth of plant. This component can be provided by industrial or biological sources. The conventional way of increasing agricultural yield through high inputs of chemical nitrogen, phosphate fertilizers and pesticides is not sustainable because of high costs and concerns about global warming, environmental pollution, and safety concerns. In this context, the use of natural soil microorganisms to increase the yield of food crops is an ecological, cost-effective and sustainable alternative tool to the use of chemical fertilizers and pesticides [6]. Legumes crops become able to access atmospheric di-nitrogen (N2) by the symbiotic relationship with rhizobia that domicile within root nodules [9] These symbioses are important interactions on the ecological level, influencing composition, diversity and succession of communities. The manipulation of plant growth-promoting (PGP) bacteria, for better plant health and betterment of soil, has become one of the captivating approaches for developing sustainable farming systems due to their particular respect for the environment, their production, and low cost and reduced con-
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