Evaluation of indigenous rhizobial isolates in search for candidate strain for commercial production

High cost of Nitrogen (N) fertilizer coupled with its potential deleterious effect on soil properties necessitates the need for alternative sources. Grain legumes in association with rhizobia contribute immensely in nitrogen accrual to agricultural system by fixing N from the atmosphere. An essential component for increasing the use of grain legumes is research leading to the selection and development of effective strains of rhizobia for commercial use. Fifty (50) indigenous rhizobial strains were collected from the gene bank of Soil Microbiology Laboratory at Institute for Agricultural research (IAR), Ahmadu Bello Zaria and screened for their symbiotic effectiveness. The test crop was Soybean variety TGx 1448-2E grown in 3 kg pot in screenhouse at the same Institute. Treatments included the 50 different strains, 3 commercial strains and 2 controls (-N and +N controls). Nodulation and dry biomass production were used to assess the performances of the inoculants vis-a-vis the commercial ones and the controls. The result showed that 70% of the strains outperformed the controls and commercial strains in terms of nodule number, 74% nodule dry weight while 18% recorded higher dry matter yield over control. However only 14%, 26% and 1% recorded significantly higher nodule number, nodule dry weight and dry matter yield respectively over the controls and commercial strains. Outstanding strains include SAMFIX036, SAMFIX074, SAMFIX113, SAMFIX306, SAMFIX369, SAMFIX381 and SAMFIX221. Hence, further characterization and field evaluation across multiple locations need to be carried out on these strains, as they may be suitable candidates for commercial production.Keywords: Candidate strain, Dry-biomass, Nodulation, Rhizobia isolates, SAMFIX