Roles and mechanisms of halophilic/salt-tolerant microorganisms in mitigating plant salt stress and promoting growth

Abstract

Soil salinization is a major constraint on global agricultural productivity and food security, largely because excess salts disrupt osmotic balance, nutrient acquisition, ion homeostasis, and redox stability in plants. Halophilic and salt-tolerant microorganisms, including plant growth-promoting rhizobacteria, endophytes, and fungi, have emerged as promising biological tools for improving crop performance in saline environments. This review synthesizes current evidence on how these microorganisms mitigate salt stress and promote plant growth across diverse crop systems. The major mechanisms include modulation of phytohormone homeostasis, especially through auxin production and ACC deaminase activity; enhanced nutrient acquisition via nitrogen fixation, phosphate solubilization, and siderophore production; maintenance of ionic balance through reduced Na+ toxicity and improved K+/Na+ homeostasis; reinforcement of antioxidant defense systems; stimulation of osmolyte accumulation; and effective rhizosphere colonization through exopolysaccharide secretion and biofilm formation. Representative studies in rice, wheat, maize, tomato, soybean, cucumber, chickpea, common bean, quinoa, and banana consistently show improvements in germination, biomass, physiological resilience, and, in some cases, yield under salinity stress. However, important challenges remain, including strain specificity, inconsistent field performance, limited mechanistic resolution, ecological safety concerns, and the difficulty of translating laboratory strains into stable commercial products. Future progress will depend on multi-omics-guided mechanism dissection, precision microbiome engineering, improved formulation and delivery systems, and rigorous long-term field validation. Overall, halophilic/salt-tolerant microorganisms represent a promising strategy for saline agriculture and sustainable crop production.