Comparative study on solubilization of tri-calcium phosphate (TCP) by phosphate solubilizing fungi (PSF) isolated from Nsukka pepper plant rhizosphere and root free soil

Abstract

Phosphate solubilizing fungi (PSF) possessing the ability to solubilize insoluble phosphate was isolated from the rhizospheric soil of Nsukka pepper plant. Twelve (12) fungal strains were isolated from both root-free soil (non-rhizosphere) and rhizosphere of Nsukka pepper plant. Of the 12 fungi isolated, 6 strains were from Nsukka pepper plant rhizosphere whereas the other six were from root- free soil. PF isolates were designated to be isolates from the rhizosphere of Nsukka pepper whereas NF isolates were designated to be isolates from non-rhizosphere soil. The former isolates were able to solubilize insoluble phosphate, both in PVK agar and NBRIP broth, whereas the latter isolates were unable to solubilize insoluble phosphate on Pikovskaya (PVK) agar medium but solubilize slightly on NBRIP broth. Fungal phosphate solubilization was analyzed by determining the quantity solubilized using NBRIP broth and calculation of the phosphate solubilization efficiency (E) on PVK agar was estimated using E = solubilization diameter/growth diameter x 100. The highest phosphate solubilization efficiency was demonstrated by PF7 isolate as 240.0% followed by PF2 isolate as 137.5% with 4.12 and 4.06 mg/ml, respectively, as the NBRIP broth analysis, whereas the non-rhizosphere isolates showed no solubilization effect on PVK agar medium but slight solubilization on NBRIP. Key words: Phosphate solubilizing fungi, Pikovskaya, phosphate solubilization efficiency, rhizosphere.