Isolation and Characterization of Phosphate Solubilizing Bacteria from Tomato (Solanum l.) Rhizosphere and Their Effect on the Host Plant under Green House Experiment

A total of eleven phosphate solubilizing bacteria were isolated from rhizosphere soil of tomato (Solanum lycopersicum) plants. Isolates designated as PSB1, PSB2, PSB4, PSB5 and PSB7 were selected out of eleven isolates based on their clear zone diameters. They were characterized to generic level and found to belong to Pseudomonas spp. Tricalcium phosphate (TCP), rock phosphate (RP) and bone phosphate (BP) solubilizing efficiency of these isolates was studied in the laboratory at 5, 10, and 15 days of incubation. All bacterial isolates solubilized significantly (P< 0.05) higher amounts of TCP over uninoculated control. The highest P was release upon 5 days of incubation was recorded from the isolate PSB1 with 7.64 mg/50ml in the medium and the least P release was recorded by isolates PSB4 and PSB5 with a P content of 4.79 mg /. At 10th day of incubation, the highest P release was recorded by isolates PSB2 (8.19 mg/50ml), PSB1 (8.10mg/ 50ml). At 20th days of incubation, the highest P release was recorded by isolate PSB7 (11.77 mg/ 50ml) and PSB2 (11.33 mg/ 50ml) and the least P released was recorded by isolate PSB5 (5.44 mg/ 50ml)). Under RP solubilization, the p released from all isolates upon 5 days of incubation was not significant as compared to the control. At 10th day of incubation, the highest P release was recorded by isolates PSB5 (5.56 mg/50ml), PSB7 (5.02 mg/ 50ml) and the least P release was observed by isolate PSB4 (3.46mg/g). At 20th days of incubation, the highest P release was recorded by isolate PSB7 (7.928 mg/ 50ml) and the least P release was recorded by isolate PSB4 (4.025mg/ 50ml). Regarding BP, The p released from all isolates except isolate PSB7 (3.020mg /50ml) upon 5 days of incubation was not significant as compared to the control. At 10th day of incubation, the highest P release was recorded by isolates PSB5 (7.37 mg/50ml), PSB7 (7.025 mg/ 50ml) and the least P released was observed by isolate PSB2 (5.47 mg/50ml). At 20th days of incubation, the highest P release was recorded by isolate PSB7 (11.09 mg/ 50ml) and the least P release was recorded by isolate PSB4 (9.06 mg/ 50ml). Under greenhouse experiment, root length and shoot length of inoculated plant did not show variation as compared to positive control. In shoot dry weight all inoculated treatments except PSB4+TCP were effective as equal as that of positive control. Upon determination of phosphorus uptake efficiency of the plant, treatments PSB2 (1.17 mg/g), PSB4 (1.09 mg /g) and PSB7 (1.08 mg /g) showed maximum p uptake while isolate PSB1 (0.94 mg/g) showed the least p uptake as compared to the positive control.