Functional diversity of phosphate solubilizing plant growth promoting rhizobacteria isolated from apple trees in the Trans Himalayan region of Himachal Pradesh, India

摘要

A total of 206 phosphate solubilizing bacteria (PSBs) were isolated from rhizosphere soil (RS) (116) and endorhizosphere (90) of apple trees of four locations: Chamba, Shimla, Kinnaur and Kullu of Himachal Pradesh, India. The population count of PSBs was invariably higher in rhizosphere than in root endosphere (ER) of apple. The greatest Shannon diversity indices for PSBs from RS (1.77) and ER (1.69) were obtained from Kinnaur. Polymorphism among 85 PSBs was detected using PCR-RAPD analysis. Sixteen representative PSBs from RAPD groups were identified further by biochemical tests and 16S rRNA gene analysis. Bacillus was the dominant genus represented by six different species, B. subtilis and B. licheniformis followed by B. pumilus, B. methylotrophicus, B. firmus and B.altitudinis suggesting diversity among species of the genus Bacillus. Variation exists in RS and ER PSBs suggesting the hypothesis that root exudates of apple plant exert selective pressure on the proliferation of specific kind of rhizobacteria on the surface of the root as well as within the root. B. methylotrophicus SMa(5)A, B. pumilus ECS(10)A and B. altitudinis ECH(8)A from ER and B. firmus KR(4)A from RS have been reported for the first time as plant growth promoting rhizobacteria from apple trees.