Phenotypic and Biochemical Characterization of Rhizobia Associated with Medicagopolymorpha Growing in Rajasthan

In present study, a total of 15rhizobial isolates were isolated from the root nodules of Medicagopolymorphagrowing in Jaipur and were characterized for their phenotypic, biochemical and plant growth promoting activities. The root nodules of M. polymorpha were elongated, branched and indeterminate. All isolated rhizobia were highly diverse in their physiological traits. Based on colony morphology, all isolates were categorized into six groups. Major group containing 6 isolates (MP1, MP3, MP9, MP10, MP11 and MP13) showed white, opaque, raised, smooth edges, non-gummy, and mucilaginous characteristics. Four rhizobia strains MP3, MP4, MP9, and MP15 showed salt-tolerance up to 3% and were well adapted to high alkaline conditions and exhibited growth in extremely alkaline media (pH 10). Majority of strains showed positive result for IAA production, nitrate reductase and catalase activity. In addition, citrate utilization, ammonia production, phosphate solubilization and cellulase activity were observed in few isolates. In present study, some rhizobia isolates like MP3, and MP15 were very versatile rhizobia that showed high plant growth promoting activities (IAA production and phosphate solubilization) and were also tolerant to high pH and salt concentration. Such type of superior rhizobia can be part of biofertilizers to enhance legume crop productivity in an ecofriendly manner without application of chemical fertilizers. Our study suggested that rhizobia isolates associated with Medicagopolymorpha were significantly diverse in their physiological and biochemical parameters