Fungal Inoculants for Native Phosphorus Mobilization

Abstract

More than 96% of the total native phosphorus present in any agriculturalsoils is in unavailable inorganic or organic forms. They may be utilized by the plantsthrough the activity of efficient fungi which are secreting/producing/releasing hugeamount of acid phosphatase, alkaline phosphatase, phytase, and organic acids. Theimportant fungi capable of doing the job are in the groups of Aspergillus,Emericella,Gliocladium,Penicillium,Trichoderma, and Chaetomium besides some AM fungilike Glomus and Gigaspora. The three efficient fungi already used as inoculums areChaetomium globosum,Penicillium purpurogenum, and Emericella rugulosa. Seedinoculation using these fungi is mobilizing 45–60 kg P and 16–25% increase in yieldof different crops. They are mainly exploiting from labile and moderately labilefractions of phosphorus. Minimum concentration of organic acid of fungal originrequired to solubilize P was found between 0.2 and 0.5 mM. In fungal-inoculatedplants, microbial contribution was more than the plant contribution. Fungal extra-cellular enzymes were more efficient than their intracellular counterpart. P uptakeoccurs around the root tip into epidermal cells with their associated root hairs andinto cells in the outer layers of the root cortex. Phosphate can also be taken up bytransfer from mycorrhizal fungi to root cortical cells.