Evaluation of Phosphate Solubilizers from Soils of North Bengal and Their Diversity Analysis

Four hundred isolates obtained from soil samples collected from forest, river basin, agricultural fields and rhizosphere of plantation crops of North Bengal were screened for phosphate solubilizing activity on Pikovskaya’s agar medium. Among the screened isolates, ninety showed phosphate solubilizing activity. Out of these, ten isolates belonging to Aspergillus niger, A. melleus and A. clavatus were selected for further studies. In vitro evaluation of phosphate solubilization by the different isolates using tricalcium phosphate (TCP) and rock phosphate (RP) revealed that the isolates could solubilize TCP better than RP. Selected isolates were mass multiplied using farm-yard manure (FYM) and were tested in vivo for their growth promoting activity in soybean. While all the isolates promoted growth, A. niger RSP-14 was found to be most effective. While the soil P content decreased due to the activity of the PSFs, root phosphate content showed an increase. These isolates were further analyzed for genetic variability. Genomic DNA from the fungal isolates were obtained and purified. UPGMA cluster analysis divided the ten isolates into two groups with the genetic similarity ranging from 0.350.61. One group consisted of four isolates of A. niger and five isolates of A. melleus, while the other group had one isolate of A. clavatus.