Efficient Phosphate Solubilization by Fungal Strains Isolated from Rice-rhizosphere Soils for the Phosphorus Release.

Out of 42 fungal strains, twelve efficient strains of phosphate solubilizing fungi were isolated, screened and characterized from paddy soils of southern peninsular region of Tamil Nadu, India. Mineral phosphate solubilizing (MPS) activities of twelve isolates were tested in tricalcium phosphate medium by analyzing the possible phosphorus release and phosphatase activity, from 3rd, 5th , 7th, 9th, 11th and 13th day of incubation Maximum phosphorus content was recorded on 9th day after incubation for all the fungal strains ranging between 393.9-4701.8 ^g/ml. The highest peak of phosphatase activity in culture filtrates in between the strains were observed from 3rd to 9th day of incubation ranging from 172.4 - 315.5 U. These fungal strains isolated were found to be much efficient in solubilization and mineralization of insoluble phosphate (tricalcium phosphate) and the phosphorus content released into the culture medium depends upon the efficiency of the phosphatase on its substrate. The results suggest that some strains (TI-3 and K-1) produced more amount of phosphatase activity but it released less amount of phosphorus which is due to the non-specific binding activity of the phosphatase. The phosphate solubilizing fungi isolated from rice rhizospere soil showed higher solubilization of phosphate and released more amount of phosphorus and phosphatase when compared with other fungal strains isolated from different field soils.