Physiological characterization of root endophytic Fusarium haematococcum for hydrolytic enzyme production, nutrient solubilization and salinity tolerance

Abstract

Fungal endophytes residing in tissue improve the plant's tolerance against abiotic stresses and produce extracellular enzymes. Previous studies have shown that the root-endophytic fungus, Fusarium haematococcum (=Nectria haematococca) can improve plant growth under normal and stress conditions. In this study, the potentiality of F. haematococcum to produce extracellular enzymes at different pH and incubation period (IP) using various carbon sources, solubilization of insoluble forms of minerals, and tolerance against salinity under in vitro conditions was evaluated. The fungus produced extracellular amylase, cellulase, and protease enzymes. The pH, carbon sources, and IP significantly influenced the enzyme activities. The maximum amylolytic and cellulolytic activity occurred at pH6 on the 12th day of incubation. Maltose and dextrose were the best carbon source for cellulase production, and the former was also best for amylase activity. Amending the paddy straw maximized the production of protease on the 2nd day of incubation. The fungus solubilized insoluble form of zinc, potassium, and phosphorus with an intermediate solubilization index. The antioxidant activities and total phenolic contents of F. haematococcum significantly varied with increasing salinity levels. The present study indicated the ability of F. haematococcum to produce various extracellular enzymes, solubilize minerals, and tolerate salinity through increased antioxidant production. Therefore, formulation of this fungus into bioinoculum could improve plant growth via nutrient solubilization under normal and abiotic stress conditions, and in the production of important extracellular enzymes at industrial levels.