EVALUATION OF ORGANIC ACID PRODUCTION POTENTIAL OF PHOSPHATE SOLUBILIZING FUNGI ISOLATED FROM SOILS IN OKINAWA, JAPAN

Abstract

Deficiency of available phosphorous (P) in soil is one of the major factors that limit plant growth and yield. Microorganisms play an important role to improving available P status in soil by solubilization. Although phosphate solubilizing mechanism is not clearly understood, organic acid production seems to be the main mechanism of P solubilizing. Therefore, present study evaluated the organic acid production potentials of 16 P solubilizing fungal strains (2 Aspergillus floccosus, 3 Aspergillus niger, 2 Aspergillus niveus, 2 Penicillium oxalicum, 5 Penicillium spp. and 2 Talaromyces pinophilus isolates) isolated from soils in Okinawa, Japan to select outstanding strains that could facilitate the P solubilization process. Results revealed that both type and quantity of microbial organic acids production depend on the P sources and fungal strains. The highest quantity of organic acids was found when Ca3(PO4)2 was used as substrate followed by FePO4 and AlPO4. Based on the organic acids production potential, A. niger (SI-12URAgr) considered as outstanding P solubilizing fungi regardless of substrates followed P. oxalicum (SI-6URAgr, SI-16URAgr) and A. niger (SI-10URAgr). These strains could have great potential as promising bioresource for efficient P utilization in agricultural production.