Advancing Drought and Salinity Stress Tolerance in Plants: Mechanisms, Molecular Tools and Breeding Strategies—A Review

Abstract

Plants are continuously exposed to abiotic stresses such as drought and salinity, which severely impair growth, metabolism and crop productivity. To survive under these adverse conditions, plants have evolved highly coordinated mechanisms for stress perception, early signal transduction and downstream adaptive responses. Stress perception begins at the plasma membrane and subcellular compartments, where osmotic imbalance, ionic toxicity and membrane perturbations are sensed, leading to rapid calcium (Ca 2+ ) influx, reactive oxygen species (ROS) production and activation of mitogen‐activated protein kinase (MAPK) cascades. These early signalling events function as central hubs that integrate environmental cues with phytohormone signalling networks. Among phytohormones, abscisic acid (ABA) plays a pivotal role in mediating drought and salinity responses, whereas jasmonic acid (JA) and brassinosteroids (BR) fine‐tune antioxidant defences, metabolic reprogramming and growth–stress trade‐offs. The convergence of Ca 2+ , ROS, kinase signalling and hormonal pathways ultimately triggers large‐scale transcriptional reprogramming, activating genes involved in osmotic adjustment, ion homeostasis, antioxidant defence and cellular protection. This review comprehensively synthesizes recent advances in abiotic stress perception, signal transduction and hormone‐mediated regulation, highlighting their roles in shaping plant stress tolerance. In parallel, advances in conventional and molecular breeding approaches, including marker‐assisted selection and genomic selection, are highlighted as essential strategies for translating these mechanistic insights into the development of stress‐resilient cultivars. Additionally, an integrated multi‐scale framework is proposed, linking molecular, physiological and breeding‐level processes to provide a holistic understanding of drought and salinity stress tolerance and to guide the development of resilient crop systems. Furthermore, emerging biotechnological strategies, including CRISPR/Cas‐based genome editing, microbiome engineering and integrative systems approaches, are discussed as promising tools for developing climate‐resilient crops.