Identification of phosphate solubilizing fungi isolated from saline-sodic soils (A Case study)

Soil salinity is the main factor in reducing crop yield, especially in arid areas. The availability of Phosphorous (P), is low in salt-affected soils. The purpose of this study was to isolate and identify the phosphate solubilizing fungi from saline-sodic soils and also to investigate phosphate solubilization in the presence of different salt concentrations. For this purpose, twenty soil samples were collected from the rhizosphere of Salicornia persica. Isolation of phosphate solubilizing fungi was done by plate culture technique on National Botanical Research Institute’s phosphate growth medium- Bromo Phenol Blue (NBRIP-BPB) solid media. Phosphate solubilization was tested in the presence of 0, 50, 100, 200, 400, 600, 800, and 1000 mM NaCl during 15 days of incubation on solid media. Thereafter, the phosphate solubilizing potential of isolates was tested in 6-day experiments in broth, and the phosphate solubilizing capability was evaluated in the presence of different concentrations of NaCl. The results showed that all strains produced halo zone until NaCl concentration reached to 200 mM, but with increasing salinity, only KARFUN 1 and KARFUN 2 could solubilize phosphate. Results of the 6-day experiment in broth culture were showed that KARFUN 1 had the highest phosphate solubilization potential, so it was selected for further investigation. Molecular identification indicated that KARFUN 1 isolate had a similarity of 100% with Aspergillus. niger and A. tubingensis species. The results showed that with increasing NaCl concentration, the phosphate solubilization increased and pH decreased. The lowest and the highest phosphorous concentration was observed in 1000 and 0 mM NaCl, respectively. Irrespective of NaCl concentration, results showed that there was an increase in phosphorous solubilization during the incubation time. The maximum phosphate solubilization was achieved (549 mgL-1) after 12 days of incubation and pH reached to 1.19. However, the KARFUN1 strain was able to solubilize inorganic phosphate in different NaClconcentrations as it could release 224 mgL-1 phosphorus at 1000 mM NaCl in broth medium.