Evaluation of phosphate solubilizing microorganisms (PSMs) from rhizosphere soil of different crop plants and its antagonistic activity.

Indigenous rhizosphere soil samples were collected during study period (October 2011 – March 2012) of different crop plant from Thiruvannamalai District, Tamilnadu, India for the enumeration of Phosphate solubilizing microorganisms (PSMs). Efficient phosphate solubilizing bacteria, fungi and heterotrophic bacteria were enumerated. Maximum heterotrophic bacterial populations (19.4 X105), phosphate solubilizing bacteria (4.7 X 105) were recorded in the month of February and phosphate solubilizing fungi (3.9 X 102) were documented in the month of December in rhizosphere soil of ground nut. Minimum bacterial populations (14.3 X 105) were observed in rhizosphere soil of chilli in the month of March. Lowest phosphate solubilizing bacteria (1.2 X105) and phosphate solubilzing fungi (1.2 X 102) were observed in rhizosphere soil of paddy during the month of October. Phosphate solubilizing bacteria Pseudomonassp. - BS1, Bacillus sp. – BS2, Micrococcus sp. – BS3 and fungi Aspergillus sp. – FS1, Penicillium sp. – FS2.and Trichoderma sp. – FS3 were identified. Pseudomonas sp. - BS1. exhibited maximum solubilizing efficiency (SE) and solubilizing index (SI) of 300.0 and 4.0 respectively. In fungi Aspergillus sp. – FS1 showed a maximum solubilizing efficiency (SE) and solubilizing index(SI) of 283.3 and 3.8 respectively. Antagonistic activity of P-solubilizing Pseudomonassp. - BS1 was deliberated against selected fungal plant pathogens. Among pathogens studied Aspergillus sp. showed a maximum inhibition activity (16 mm) and minimum activity (12 mm) was observed against Fusarium sp. Moreover inhibition efficiency (IE) and inhibition index (II) of Pseudomonas sp. - BS1. also calculated base on the antagonistic activity. Aspergillus sp. exhibited highest inhibition efficiency and inhibition index of 166.6 and 3.6 respectively.