Review on Phosphate Solubilizing Fungi

Phosphorus (P) is the second important nutrient after nitrogen. In plants, phosphorous increases the strength of cereal straw, promotes flower formation and fruit production, stimulates root development and essential for seed formation. Mobility of phosphate ions in the soil is very low due to their high retention in soil. In this regard, P supply through biological systems is considered a viable alternative, and inoculation of Phosphate solubilizing microorganisms, especially fungi to soil, is a reliable source for increasing soluble P in soil. Though phosphorus is found to be a limiting factor in many soils, application of PSMs as biofertilizers or bioconverters for solubilizing fixed phosphorus has not yet been successfully practiced. Many fungal species can solubilize rock phosphate, aluminum phosphate and tricalcium phosphate, such as Aspergillus niger, Aspergillus tubingensis, Aspergillus fumigatus, Aspergillus terreus, Aspergillus awamor, Penicillium italicum, Penicillium radicum, Penicillium rugulosum, Fusarium oxysporum, Curvularia lunata, Humicola sp., Sclerotium rolfsii, Pythium sp., Aerothecium sp., Phoma sp., Cladosporium sp, Rhizoctonia sp., Rhizoctonia solani, Cunninghamella spp., Rhodotorula sp., Candida sp., Schwanniomyces occidentalis, Oideodendron sp., Pseudonymnoascus sp. The soil yeasts Candida tropicalis, Geotrichum candidum, Geotrichum capitatum, Rhodotorula minuta and Rhodotorula rubra solubilized insoluble phosphate(Birhanu et al., 2017). Yeast belonging to genus Saccharomyces, Hansenula, Klockera, Rhodotorula and Debaryomyces spp. were phosphate solubilizing yeasts. For application of phosphate solubilizing fungi to seeds, the seeds should be surface sterilized, rinsed with sterile water and dried. The surface disinfected seeds can be coated by soaking seeds in liquid culture medium of phosphate solubilizing fungi for 2 hr. While inoculation of the seed using plant and both Aspergillus niger + Penicillium notatum is recommended. Thus the application of P solubilizing fungi is recommended as a sustainable way for increasing crop yield.