Unraveling the osmotic stress response pathways in cultivated (Fragaria × ananassa Duch.) and wild (Fragaria nubicola Lindl.) strawberries through physiological, transcriptomic and metabolomic analysis

PEG-induced osmotic stress severely restricts strawberry growth and productivity. However, the molecular mechanisms underlying osmotic stress adaptation in wild strawberry germplasm resources remain insufficiently understood. In the present study, we comparatively investigated the physiological, transcriptomic, and metabolomic responses of cultivated octoploid strawberry ( Fragaria × ananassa Duch.) (CS) and wild diploid strawberry ( Fragaria nubicola Lindl.) (WS) collected from Medog County, Tibet, under PEG6000-induced osmotic stress. Physiological analyses demonstrated that osmotic stress markedly reduced net photosynthetic rate ( P n), stomatal conductance ( G s), transpiration rate ( T r), relative water content (RWC), and water use efficiency (WUE), while increasing reactive oxygen species (ROS) accumulation and malondialdehyde (MDA) content in both strawberry species. Compared with the CS, the wild species exhibited more severe wilting, oxidative damage, and membrane lipid peroxidation, indicating greater sensitivity to osmotic stress. Integrated transcriptomic and metabolomic analyses revealed substantial differences in stress-responsive pathways between the two species. In CS, 896, 4591, and 6346 differentially expressed genes (DEGs) were identified under 5%, 10%, and 20% PEG treatments, respectively, whereas 3978, 977, and 1176 DEGs were identified in WS. DEGs were primarily enriched in peroxisome biogenesis, phytohormone signal transduction, glutathione metabolism, oxidative phosphorylation, and secondary metabolite biosynthesis pathways. Metabolomic profiling further demonstrated distinct regulation of phenylpropanoid metabolism, biosynthesis of phenylpropanoids, flavonoid biosynthesis, and the tricarboxylic acid (TCA) cycle. The CS preferentially regulated ABA- and cytokinin-associated signaling pathways, whereas the WS exhibited enhanced ethylene-related responses and stronger accumulation of flavonoid metabolites. Importantly, the contrasting responses observed between the two strawberry species may also reflect differences in genome ploidy. CS likely possesses enhanced transcriptional buffering capacity, metabolic plasticity, and hormonal coordination compared with WS under osmotic stress conditions. Overall, this study provides new insights into the molecular mechanisms underlying osmotic stress adaptation in strawberry germplasm resources and offers valuable information for future drought-resistance breeding programs.