Study on the isolation and characterization of rhizobia strains as biofertilizer tools for growth improvement of four grain legumes in Ngaoundéré-Cameroon

Increasing the yield and economical efficiency of grain legumes in the Guinea-Savannah zone of Cameroon is a high researcher priority to assist growers in the rural areas. We report here a two-years study inthe production process of fertilizer containing rhizobia for a sustainable production of grain legumes in the region. To address the issue, nodulation and rhizobia strains characterization were assessed at Dang and Wakwa, two soils different in trapping rhizobia partners for groundnut, bambara groundnut, cowpea and soybean. This was a prerequisite step in the determination of the most efficient rhizobia strains for biofertilizer production. Results indicate that all the four grain legumes differently formed nodules in their roots system in the two experimental soils. Cowpea and soybean demonstrated a highly significant (p ≤ 0.001) potential in fixing atmospheric nitrogen through their nodules than groundnut and bambara groundnut. The dry weight of nodules in groundnut and bambara groundnut was significantly lower (0.0001 < p ≤ 0.038) than that of cowpea and soybean in the two soils. When rhizobia were isolated from root nodules of plant species, the number of isolates ranged from 2 to 4 per grain legumes. All the isolates were convex in elevation, smooth/humid on the surface, with regular edges, except one groundnut colony from wakwa soil. The colonies were either whitish for soybean, whitish/yellowish for cowpea, groundnut and bambara groundnut. The rhizobia biofertilizer produced for each grain legumes were stored in the refrigerator for field tests. This is a step forward for further molecular characterization of isolates to enable production of elite inoculum in the region.