An Effective Method for Screening and Testing the True Phosphate-Solubilizing Fungus That Enhances Corn Growth

The effect of large-scale application of phosphate-solubilizing microorganisms (PSMs) on the promotion of crop growth varies. Usually the solubilization of tricalcium phosphate is considered as the standard for screening most PSMs. This study aimed to establish a common method for screening and testing true PSMs. The isolated fungus’s phosphate-solubilizing ability, adaptation to corn root exudates, organic acids secreted, and colonization ability were analyzed. And the microorganism’s diversity and ability to promote corn growth were also tested through plot experiment. The isolated fungus Aspergillus niger H1 (A-H1) was isolated and identified from plant rhizosphere that could solubilize phosphate, utilize corn root exudates as sources, and propagate well in vitro and soil. Lactic acid was excreted and reached 377.9 ?g mL-1 at 30 h in culture by A-H1, which decreased the pH of culture to 1.73. The amount of A-H1 increased by 41-fold in 28 d and was maintained for 49 d. PSM showed selectivity on the transformation of different forms of P.However, a wide range of insoluble phosphates, such as Ca8H2(PO4)6·5H2O, AlPO4, FePO4, and Ca10(PO4)6(OH)2, was converted to soluble CaHPO4 in soil.CaHPO4 was also inhibited from being converted into insoluble phosphate by A-H1. Corn yield increased by 10.71% that remarkable higher than the control after A-H1inoculation. Data show that A-H1 could propagate well, solubilize phosphate in soil, and promote corn growth. A common method was created to screen and test a true phosphate-solubilizing fungus that enhances plant growth.