From Rhizosphere to Endosphere: Conserved and Specialised Mechanisms of Plant Growth‐Promoting Bacteria in Mediating Salt Tolerance

Soil salinization, a growing global issue threatening sustainable agriculture, can be mitigated by Plant Growth-Promoting Bacteria (PGPB) as a green strategy. PGPB primarily consist of plant growth-promoting rhizobacteria (PGPR) and plant growth-promoting endophytes (PGPE). Numerous studies have demonstrated that both types of bacteria can enhance plant performance under salt stress through various mechanisms that help maintain ion homoeostasis, improve osmotic adjustment, and enhance antioxidant defence. Although PGPR and PGPE share highly conserved core mechanisms, their distinct colonisation niches lead to functional divergence in efficacy, stability, and ecological roles. This review systematically summarises these conserved mechanisms for enhancing plant salt tolerance. Furthermore, it elaborates on their functional differences across various ecological niches and discusses the major challenges and future directions for the field application of these PGPB. Ultimately, this review aims to provide a theoretical foundation for the scientific deployment of PGPB in saline agroecosystems.