Isolation, characterization and selection of salt tolerant rhizobia nodulating Acacia catechu and A-nilotica

Bacterial strains were isolated from root nodules of two tree legumes, Acac ia catechu and A. nilotica, growing in barren soils in the sub-Himalayan tr act. Their morphology, physiology and biochemistry was studied according to the description given for the family Rhizobiaceae in Bergey's Manual of Sy stematic Bacteriology (Jordan, 1984). Morphology, biochemistry and physiolo gy of the strains was similar and indicated that they belong to the species Rhizobium loti, which has now been assigned to Mesorhizobium loti (Jarvis et. al., 1997). Strains MTCC 2379 (isolated from A. catechu) and MTCC 2381 (isolated from A. nilotica) were highly salt-tolerant. There was marked dif ference in nodule number, root length, shoot length, average nodule weight, plant dry weight and nitrogenase activity between salt-tolerant and salt-s ensitive strains. In saline conditions salt-tolerant strains were much more effective.