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Studies on isolation, characterization and in-vitro screening of plant growth promoting rhizobacteria from Rhizospheric soil of chrysanthemum (Dendranthema grandiflora Tzvelev.)

A total of forty rhizosphere soil samples were collected from different locations of Bengaluru urban district, Karnataka and used for isolation of PGPRs by standard dilution plate method. Seventy bacterial isolates were selected, purified and were examined for morphological characters like colony morphology, cell shape, Gram reaction. Isolates were diverse in their morphology ranging from dull to milky white, rough to smooth margins, viscous, small to large, non-spreading and spreading. Among them twenty seven and seventeen isolates were identified as N2 fixers and as Phosphate solubilizers by initial screening respectively. Further, the selected PGPR isolates were biochemically characterized and identified as Azotobacter spp. Bacillus spp. and Pseudomonas sp. The isolates screened qualitatively and quantitatively for plant growth promotion activities like N2 fixation, phosphate solubalization and growth hormone production (IAA). The amount of nitrogen fixed in Waksman No.77 nitrogen free broth ranged from 4.52 to 19.33 mg per g of C utilized and highest fixed by isolate PGPR-24. Phosphate solubalization efficiency and phosphate solubilization activity in Pikovskaya’s medium was ranged from 102.8 % to 168.7 % and 8.56 %to 14.32% respectively and more phosphate solubilization activity showed by isolatePGPR-9. Indole acetic activity (IAA) production ranged between 4.54 to 25.12 μg per ml. | Studies on isolation, characterization and in-vitro screening of plant growth promoting rhizobacteria from Rhizospheric soil of chrysanthemum (Dendranthema grandiflora Tzvelev.)