Salt-tolerant phosphorus-solubilizing fungi enhance plant nutrition and stress resilience in saline soils through organic acid–mediated P mobilization, antifungal metabolite production, and adaptive physiological mechanisms, highlighting their potential as biofertilizers pending field validation.
Keywords: Phosphorus nutrition, Phosphorus solubilizing fungi, Plant growth, Plant promoting traits, Responsiveness, Salinity, Salt tolerance
Soil fungi are key determinants of ecosystem function, contributing to nutrient cycling, plant growth promotion, and soil health through a range of biochemical mechanisms. In this study, scientists from ICAR-Central Soil Salinity Research Institute found that phosphorus-solubilizing fungi (PSF) isolated from saline soils exhibited strong capacities to modify their surrounding environment via secretion of organic acids, siderophores, ammonia, HCN, and IAA. These secretions enhanced the solubilization of P and Zn, reflecting metabolic adjustments such as altered tricarboxylic acid cycle activity under nutrient and salinity stress. The composition and quantity of extracellular metabolites were shaped by both genetic factors and environmental conditions, including phosphorus deficiency and salt stress. Sorghum inoculated with these PSFs showed variable responses across salinity levels, supporting the idea that fungal adaptive strategies—such as organic acid–mediated P release and improved micronutrient availability—enhanced plant growth. Penicillium oxalicum emerged as particularly effective, demonstrating strong nutrient-mobilization traits and consistent growth-promoting effects.
In addition to nutrient mobilization, the isolates displayed several stress-tolerance mechanisms. High butyric acid production indicated antifungal activity that may provide competitive advantages in the rhizosphere. The accumulation of polyphosphate granules and the presence of genes such as ppk and phoD underscored their capacity to withstand osmotic, cationic, and oxidative stress while maintaining phosphorus acquisition pathways. Although P solubilization declined at higher salinity due to reduced microbial and plant biomass, the isolates—especially Penicillium and Talaromyces species—retained measurable activity through acidolysis, proton release, and organic acid–mediated chelation, contributing to increased Olsen P. Their demonstrated resilience and nutrient-mobilizing ability suggest strong potential for use as biofertilizers in salt-affected agroecosystems, though field-scale validation is still required.
Reference:
Chandra P, Rai AK, Basak N, Sundha P, Prajapat K, Singh A, Mann A, Yadav RK. Phosphorus-solubilizing fungi improve growth and P nutrition in sorghum at variable salinity levels. Environ Microbiome. 2025 Sep 29;20(1):124. PMID: 41024202. doi: 10.1186/s40793-025-00716-3. Read more