Screening of calcium- and iron-targeted phosphorus solubilizing fungi for agriculture production

The average efficiency of phosphorus fertilizer is relatively low around the world because the plant-available phosphorus can be readily immobilized by the soil minerals, such as iron, aluminum, and calcium, when phosphorus fertilizer is applied to the field. Phosphorus solubilizing microorganisms can release phosphorus from insoluble phosphorus and help plant grow. This study screened phosphorus solubilizing fungi (PSF) from 153 fungi species by Pikovskayas Agar media and National Botanical Research Institute's phosphate growth medium broth. There were 47 Ca-targeted PSF, and among them, 34 PSF could dissolve FePO₄. Epicoccum dendrobii (B-27) was the best Ca-targeted PSF with the released free phosphorus of 35.49 ± 2.11s% in 4-day incubation, while Aspergillus sp. (A-5) was the best Fe-targeted PSF with 28.75 ± 6.43% of Fe–P dissolved. Besides, Penicillium sp. (Sarita-12) was superior in dissolving both Ca₃(PO₄)₂ and FePO₄ with 34.43 ± 2.22% and 24.27 ± 4.09% released in the supernatant, respectively. The growth kinetic experiments showed that except B-27, all the pH of the selected PSF inoculated media decreased during the incubation, indicating that inorganic/organic acids might be metabolized to dissolve the insoluble phosphorus. The results suggested that the phosphorus solubilizing capability of the selected PSF was different with Ca–P and Fe–P substrates. The screened Sarita-12 strain has great potential to be used as phosphorus-solubilizing bio-fertilizer in calcareous alkaline soils and acidic soils to enhance phosphorus assimilation by plants and improve the phosphorus fertilizer efficiency.