A total of sixty five strains of Beijerinckia were isolated in the present study from rhizosphere, endorhizosphere and non-rhizosphere soil samples collected from different forest ecosystems of Western Ghats, Karnataka. Representative colonies were purified and microscopic, morphological and biochemical studies were performed. The strains were tentatively ascribed to two species of Beijerinckia, namely, B. derxii and B. mobilis. In order to explore the functional PGPR potential of these strains, all the strains were tested for indole acetic acid and gibberelic acid production. All the strains produced IAA and GA in the range of 6.2 to 99.9 mg /ml and 0.02 to 0.3 mg /ml respectively. Considering the high amount of IAA obtained in the colorimetric assays and ambiguity of the test reagent to react with a range of indole and its derivatives produced by the organism along the pathway, the specific production of indole acetic acid of six strains producing over 75 µg/ ml of IAA, was further analysed by its extraction and detection through HPLC. It was seen that the strain MDBeijXXVIIR321c produced a maximum of 385.7µg/ ml IAA in tryptophan supplemented broth over an incubation period of 7 days with agitation. It can be concluded that the potential strains could be used in raising crop productivity.
Plant growth promoting rhizobacteria, Indole acetic acid, Beijerinckia
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