Isolation of both fast and slow growing rhizobia effectively nodulating a medicinal legume, Mucuna pruriens

Strains of root nodulating bacteria were isolated from the root nodules of a medicinal legume plant, Mucuna pruriens (Kaunch), growing wildly in the f oothills of Himalayas. The strains were morphologically, physiologically an d biochemically characterised according to the Bergey's Manual of Determina tive Bacteriology (Holt et al., 1994). According to their generation time t he strains were both fast and slow growers. Both fast and slow growing stra ins showed marked differences in morphology, physiology and biochemical cha racteristics. Morphological, cultural, biochemical characters, G+C mole per cent and in vivo infectivity on their original host and other plants confir med that the fast growing isolates were Rhizobium meliloti while the slow g rowers belong to the Bradyrhizobium sp. (Mucuna). The fast growing strains were highly salt tolerant being able to tolerate 850 mM NaCl concentration in vitro. Slow growing strains showed growth at wide temperature range, bei ng tolerant up to 45 degreesC.