Optimizing Phosphorus Solubilization Through Rhizosphere-Isolated Fungi

Abstract

Phosphate Solubilizing Microorganisms (PSMs) are capable of solubilizing insoluble forms of soil phosphate to liberate soluble P and make it available to plants. The growth and productivity of many different crops can be enhanced through these PSMs. Thus, introducing PSMs to seeds, crops, and soil is promising for promoting sustainable agriculture without endangering the environment. Hence this study was conducted to isolate and optimize the culture media for effective P solubilizing fungus. All experiments were conducted in laboratory conditions with a Complete Randomized Design (CRD) with three replicates. All the data were statistically analyzed using analysis of variance (ANOVA), and means were separated using Tukey’s HSD test. Four fungal strains were isolated from different plant rhizospheres of rice (1), maize (1), and chilli (2) plants as potential P solubilizers which produced a clear halo appearance. These fungal strains were tested for their capability on P solubilization by using phosphorus solubilizing index (PSI) in plates and the amount of solubilized P in broth cultures to identify the most effective P solubilizer. The selected fungus was further tested for media optimization. Different nitrogen (N), phosphorus (P), carbon (C) sources, and pH levels were optimized under in vitro conditions. One of the fungi isolated from chilli rhizosphere (Fd) was identified as the most effective P solubilizer with an established significantly highest solubilized P (2.54 ppm ± 0.13) and the average highest PSI (1.68). The media optimization study results showed that potassium di-hydrogen phosphate as P source, fructose as the C source, ammonium sulphate as the N source, and neutral pH (pH 7) could maximize the solubilization of P with Fd. Further improvements would be essential to introduce Fd as a P-solubilizing fungal inoculum to the soil.