Current Understanding of PGPR–Plant Interaction under Salt Stress Environment: A Review

Abstract

Soil salinity is a serious environmental problem which affects agricultural production globally, especially in arid and semi-arid areas. Soluble salt accumulation may affect water uptake, induce ionic toxicity, decrease nutrient availability and increase reactive oxygen species (ROS) production that leads to damage to cellular components and affects normal physiological functioning. Traditional breeding has developed salt-tolerant crops, but long breeding cycles, high costs, and genotype–environment interactions limit its efficiency. Plant growth-promoting bacteria (PGPB) offer an eco-friendly alternative for improving crop performance under salinity. They enhance salt tolerance through complementary mechanisms, including phytohormone regulation, osmolyte accumulation, exopolysaccharide production, nutrient acquisition, and balanced Na⁺/K⁺ uptake. PGPB also promote proline and glycine betaine accumulation, supporting osmotic adjustment, membrane stability, and cellular protection. Together, these microbial activities help plants maintain ionic and physiological balance, reduce salt-induced damage, and sustain growth under saline conditions. This review brings together the physiological responses of the crop plants to salinity and discusses both the direct and indirect mechanisms mediating salt tolerance that PGPB provide based on fundamental and contemporary (2020‒2026) literature. Representative plant-bacterium associations are curated in comparative tables to showcase the taxonomic diversity and mechanisms already described, and existing knowledge gaps are highlighted, including at the field-level and in the context of multi-strain consortia. The use of PGPB is proposed as a low-cost, non-toxic, and ecofriendly solution to maintain crop productivity in salinity affected soils, and to help ensure long-term food security in the face of climatic changes.