Solubilization of inorganic phosphate by rhizospheric fungi isolated from soil cultivated with Sorghum bicolor L.

Abstract

Three zinc-phosphate-solubilizing fungi (ZPSF) were isolated from rhizospheric soil cultivated with Sorghum bicolor L. The fungal isolates were identified as Aspergillus chevalieri, Fusarium moniliforme, and Trichoderma harzianum. The results showed that halo zone formation by ZPSF on Pikovskaya (PVK) agar medium plates was an indicator of zinc phosphate (ZP) solubilization. The lowest in pH of the inoculated medium containing ZP was observed with A. chevalieri, followed by T. harzianum, followed by F. moniliforme, compared with the initial pH (6.5) of the non-inoculated medium. ZP solubilization processes at different temperatures (10 °C, 20 °C, 30 °C, and 40 °C) were conducted using ZPSF at different doses of ZP (0.5 g/L, 1 g/L, and 2 g/L). The released P, to P2O5, was monitored during the solubilization process. The released phosphorus increased as the temperature increased, with the greatest values of phosphorus obtained with F. moniliforme, A. chevalieri, and T. harzianum being 11.54 mg/L, 24.40 mg/L, and 28.40 mg/L, at 30 °C and a dose of 2 g/L of ZP, respectively. In contrast, the smallest values of phosphorus were 11.89 mg/L, 8.2 mg/L, and 7.97 mg/L, at 10 °C and a dose of 0.5 g/L of ZP, with F. moniliforme, A. chevalieri, and T. harzianum, respectively.