Isolation of Rhizobium strains: Cultural and biochemical characteristics

Abstract

Out of 157 pure isolates of Rhizobium obtained from 6 common pulses grown in 6 different places of Assam, only 15 were found to be nodulation positive. The cells of all the isolates were rod shaped, motile and Gram negative varying within the range of 0.6–0.8 × 1.6–2.5 m in size. Considerable variation of cultures in respect of configuration, margin, elevation and colour was observed. The physiological and biochemical characterisation of the isolates confirmed the purity of the isolates. A differential pattern of carbohydrate utilization by the rhizobial isolates was also observed. The growth of the isolates in bromothymol blue enriched YEMA medium showing an alkaline reaction confirmed the isolates to be slow growing Bradyrhizobium.