Phosphate Solubilizing Bacterial Diversity From The Rhizospheric Soils of Sub-Temperate Region of Himachal Pradesh

In the present study, a total of 92 phosphate solubilizing bacterial strains were isolated from the rhizospheric soil of Zea mays grown in Solan (H.P), India out of which 11 isolates showed more then 5 mm zone of solubilization. These 11 isolates were subjected for quantification of phosphate solubilization in NBRIP broth. From these 11 strains, isolate MZPSB58 showed highest solubilization (621.49 μg P/ml) followed by isolate MZPSB16 (571.24 μg P/ml) whereas, standard strain of Pseudomonas putida showed 547.89 μg P/ml of phosphate solubilization. These 11 isolates were further tested for the production of IAA, ammonia and siderophore and eight, ten and seven isolates were found to produce these compounds respectively. The isolates MZPSB16 and MZPSB58 produced 74.95 μg/ml, 86.39 μg/ml of IAA respectively, which was significantly higher than the standard strain (62.83 μg/ml). Antifungal activity against Fusarium oxysporum and Rhizoctonia solani was observed only in five isolates out of 11. Isolate MZPSB16 showed more zone of inhibition as compared to isolate MZPSB58. These two isolates were also tested for the production of hydrolytic enzymes when MZPSB58 and MZPSB16 were found positive for chitinase and protease activity but standard strain was found negative. The ACC deaminase activity of isolates MZPSB16 and MZPSB58 were tested and MZPSB16 showed 1.14 μm αKB mg⁻¹ h⁻¹ enzyme activity whereas the isolate MZPSB58 showed 1.82 μm αKB mg⁻¹ h⁻¹ enzyme activity. The standard strain also showed 1.02 μm αKB mg⁻¹ h⁻¹ enzyme activity. On the basis of 16S rRNA gene sequencing the isolate MZPSB16 was identified as Bacillus subtilis whereas, isolate MZPSB58 was identified as Pseudomonas putida. These native isolates will be more useful as bio-fertilizer and in biological control.