Isolation and Biochemical Characterization of Rhizobium Leguminosarum bv. Trifolii and Sinorhizobium Meliloti using API 20 NE and API 20 E

Abstract

The present study was carried out to isolate and to investigate biochemical characteristics of twenty rhizobacteria strains from red clover (Rhizobium trifolii) and alfalfa (Sinorhizobium meliloti). The result of the study showed a low diversity in morphological, physiological and symbiotic properties among the rhizobial strains. Phenotypically all isolated strains had the same colony morphology conical with a smooth margin, the color and texture was watery to translucent. The isolates were fast-growing and failed to absorb Congo red. API 20NE and API 20E showed a negative reaction for the reduction of nitrate in RtS1, RtR2, and positive for SmM1, SmM2. The reaction was positive for β-galactosidase, β-glucosidase and negative for urease, arginine dihydrolase, for all rhizobial isolates. Carbon sources: glucose, arabinose, mannose,mannitol, maltose, were also positive for all strains. Rhizobial strains utilized a wider range of carbohydrates and this may be a helpful tool for the characterization of the isolates.