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Crops absorb phosphorous in the form of soluble orthophosphate ion. The solubility of phosphate is inhibited by the presence of iron and aluminium in acidic soils and calcium in neutral and alkaline soils. This leads to fixation of phosphorous, making it not available to crop plants. The phosphate solubilizing bacteria (phosphobacteria) secretes some kinds of organic acids which act on insoluble phosphates and convert the same into soluble form, thus providing phosphorous to plant. An experiment was conducted to enumerate the population density of phosphobacteria in the rhizosphere soils of brinjal, chilly, cotton, green grain, groundnut, maize, paddy, ragi, sorghum and turmeric using Ketznelson and Bose medium following dilution plate technique. Efforts have been made to isolate phosphobacteria from these soils and isolated strains were inoculated in specific media containing specific substrates to produce growth regulating substances such as IAA and GA3 and phosphatase enzyme. The result showed that the population levels of phosphobacteria were higher in the rhizosphere soil of groundnut plant. Further, all the strains of phosphobacteria were able to produce phytohormones and phosphatase enzyme under in vitro conditions.
Keywords: In vitro, phosphobacteria, growth regulators