Harnessing stress-tolerant plant growth-promoting rhizobacteria for climate-resilient rice agroecosystems

Environmental stresses pose a serious threat to global rice production. Drought, flooding, salinity, heavy metal contamination, and the excessive use of synthetic pesticides are among the major stressors affecting rice production, with some of these pressures being exacerbated by climate change. This review examines the ecological roles, mechanisms, and potential applications of stress-tolerant plant growth-promoting rhizobacteria (PGPR) as a sustainable strategy to enhance the resilience of rice agroecosystems under adverse environmental conditions. Particular emphasis is placed on the ecological responses of the rice rhizosphere microbiome and the molecular and physiological responses of rice plants to abiotic stress, together with the adaptive mechanisms associated with stress-tolerant PGPR activity. These include modulation of stress-responsive genes, enhanced antioxidant responses, osmoprotectant production, exopolysaccharide synthesis, and biofilm formation. The role of bacterial ACC deaminase in modulating stress-induced ethylene accumulation in rice is also reviewed. In addition, the potential contribution of stress-tolerant PGPR to mitigating methane emissions from paddy fields is explored, together with the potential of saline and heavy metal-contaminated soils as reservoirs of novel multi-stress-tolerant PGPR. Finally, recent advances in the bioformulation and delivery of stress-tolerant PGPR are discussed, highlighting their potential to improve bacterial survival, rhizosphere colonization, and field performance and to support more sustainable and climate-resilient rice production.