Salinity and Sodicity Tolerance in Rice: Physiological, morpho-anatomical, Molecular and Hormonal Mechanisms with special Reference to Traditional Landraces

Abstract

Soil salinity and sodicity are critical abiotic stresses severely affecting global rice production by causing osmotic stress, ionic toxicity, oxidative damage and nutrient imbalance, collectively impairing plant growth and yield. This review highlights the physiological, morpho-anatomical, molecular and hormonal mechanisms involved in salt tolerance, with special focus on traditional landraces as reservoirs of adaptive genetic diversity. Tolerant mechanisms include osmotic adjustment via compatible osmolytes, antioxidant defense system, ion homeostasis through SOS, NHX and HKT transporters, root apoplastic barrier by lignin and suberin deposition and aerenchyma mediated sodium sequestration. The contributions of stress responsive genes, transcription factors, and QTLs, with particular emphasis on the Saltol QTL, in governing salt tolerance are comprehensively discussed. The role of key hormonal regulators, including abcisic acid, auxin, gibberellins, cytokinins, ethylene, melatonin, jasmonic acid and salicylic acid in mediating stress adaptationare also elaborated. Additionally, the efficacy of exogenous ameliorants such as silicon, biochar and microbial biostimulants in alleviating salt- induced damage is evaluated. The remarkable adaptive potential of traditional landraces and wild rice species is highlighted as a crucial genetic resource for breeding stress- resilient cultivars, offering a comprehensive framework for advancing salt tolerance research and ensuring food security in increasingly salt-affected agricultural environments.