Characterization of plant growth promoting rhizobia from root nodule of <i>Crotolaria pallida</i> grown in Assam

Abstract

From five different sites of Assam, 22 bacterial strains were isolated from the root nodules of <i>Crotolaria pallida</i>. The isolates were subjected to morphological and physiological characterization, and compared with reference strains <i>Rhizobium</i> <i>leguminoserum</i> MTCC-99, <i>Bradyrhizobium japonicum</i> MTCC-120 and <i>Mesorhizobium thiogangeticum</i> MTCC-7001. Although isolates showed close similarity in their morphological features, they had wide variation in their physiological features. All the 10 selected isolates were found to be potent phosphate solubilizer and the isolate DCP1 showed the highest phosphate solubilization efficiency (PSE; 187%). IAA production was detected in 8 isolates with the highest production (66 µg/mL) by MKCP1. The isolates also showed wide variation in their pH and salt tolerance ability. <i>NifH</i> gene analysis revealed the presence of <i>nifH</i> gene in 6 isolates. The result of PCR-RFLP grouped the isolates into three different 16S rDNA types; 2 isolates were related to <i>B. japonicum</i> MTCC-120, 6 isolates were related to <i>R. leguminoserum</i> MTCC-99 and 2 isolates were related to <i>M. thiogangeticum</i> MTCC-7001.