Crop Adaptation to Combined Abiotic Stresses: Mechanisms and Microbial Partners (Review)

Abstract Combined abiotic stresses (CAS) (drought, salinity, heat, heavy metal toxicity, etc.) pose a significant threat to global food security under climate change, as they induce complex and non-additive plant responses. The present comprehensive review, incorporates a meta-analysis of recent studies, reveals that these combined effects generate unique, often synergistic physiological outcomes that cannot be extrapolated from studies of individual stresses. This review systematizes current knowledge on the types of CAS, their interactions, and their impacts on plant physiological, molecular, and microbiological processes. Particular attention is given to how CAS alter the structure and function of rhizosphere and endosymbiotic microbiomes, and how plants actively recruit beneficial microorganisms through the “cry for help” mechanism. The potential of microbial bioinoculants as a sustainable strategy for enhancing plant tolerance to CAS was analyzed. Although direct evidence of microbial efficacy under CAS conditions remains limited, this review extrapolates from established mechanisms, such as improved photosynthesis, osmolyte production, enhanced antioxidant activity, and hormonal modulation, to propose how microbes may mitigate combined stresses. Our analysis highlights that the role of microbial communities and their application as bioinoculants is critically underexplored in CAS research. Finally, we address the translational gap between laboratory study and field application, advocating for the use of omics technologies to guide the rational design of synthetic microbial consortia tailored to real-world multi-stress conditions.