Nine authenticated strains of rhizobia were collected from different All India co-ordinated research centres (AICR) of soybean in India. Rhizobium strains (IND1, IND2, LSBR3, LSER7, LSER8, PANT1, PANT 2) along with reference strains (DS-1, SB-271) were characterized on the basis of morphological, phenotypical and physiological characteristics. Phenotypic characteristics studies included colony morphology, resistance to antibiotics, phosphate solubilising activity, Bromothymol blue (BTB) agar activity and hydrogenase activity. It was observed that the colonies were circular, light pink, convex, rod shaped, aerobic, motile and non spore former. Out of nine strains, 5 strains were identified as slow grower Bradyrhizobium strains and 4 strains as fast grower Ensifer strains on Yeast extract mannitol agar YEMA (BTB) medium. Significantly high IAA was recorded with LSER8 (25.75µg ml-1) in the presence of L-tryptophan (0.01%). In qualitative screening of hydrogenase activity 2 Bradyrhizobium and 3 Ensifer strains showed red coloration on YEMA media amended with 0.01% TTC dye. In qualitative screening of phosphate solubilization 80% of isolates produced halo zone on Pikovaskaya’s and NBRIP media. These rhizobial strains can be explored as future biofertilizer to promote growth and yield in soybean.
Biofertilizer, Phenotypic characteristics, Rhizobium, Soybean
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