Isolation and characterization of rhizobia from the root nodule of some cultivated legume crops

Biological nitrogen fixation (BNF) as a result of mutual symbiosis between the rhizobia and the cultivated legume have a vital role to balance the nutrient paucity in the soil. Modern researches shows that the BNF can be the important factors regulating and maintaining the defendable agriculture and ensuring food security especially in the developing countries. The use of artificial nitrogen fertilizers to rise crop yield is an internment farming practice, despite its unfavorable effects and hazards to the environment and human population which can be substituted by rhizobial inoculants as a bio-fertilizers. The present study was aimed to isolate and characterize the Rhizobium from the nine different selected legumes. The Rhizobium bacterium was isolated from the nodules of the nine legume plants on YEMA medium which was found to show white translucent, circular convex colonies and characterized by the non-absorption of Congo red dye. The strains were found to be fast growing except for the rhizobial strains isolated from the Soybean and cowpeas (Bradyrhizobium) which were slow growing. The various biochemical tests of the isolated strains like catalase, bromothymol blue, Urea hydrolysis were favorable while Glucose-Peptone Agar (GPA), starch hydrolysis, Citrate utilization were found to be negative. For the ability to utilize the 2% NaCl, the strains TFR showed positive growth, the strains PSR, PhVR, VUR showed the poor tolerance while the rest of the strains showed no tolerance to the 2% NaCl. DOI: http://dx.doi.org/10.5281/zenodo.490625