Differential physiological responses of grafted cabernet sauvignon grapes to salt and saline–alkali stress: The dual role of VvGAD1 in GABA-mediated tolerance

Saline–alkali stress inflicts more severe damage on grapevines compared to salt stress alone. Grafting onto stress-tolerant rootstocks represents a key strategy for improving crop resilience, making it essential to understand how such rootstocks modulate scion responses to these distinct stresses. However, the molecular mechanisms underlying their differential tolerance remain largely elusive. Here, we compared self-grafted (CS/CS) and hetero-grafted (CS/1103 P) Cabernet Sauvignon under salt and saline–alkali stress using morphophysiological and transcriptomic analyses. Saline–alkali stress led to more severe membrane lipid peroxidation, chloroplast ultrastructural damage, reactive oxygen species accumulation, and photosynthetic inhibition compared with salt stress alone. Rootstock 1103 P markedly enhanced stress tolerance in grafted plants, as evidenced by lower H 2 O 2 and MDA levels, higher antioxidant enzyme activities, and scion-specific upregulation of VvGAD1 , which promoted γ-aminobutyric acid (GABA) accumulation. Functional validation assays showed that VvGAD1 overexpression increased callus antioxidant capacity, stabilized ion homeostasis, enhanced organic acid metabolism, and elevated the expression of stress-responsive genes under both salt and saline–alkali stress. Exogenous GABA further induced endogenous GABA biosynthesis and mitigated stress injury. Collectively, these results indicate that VvGAD1 primarily confers salt stress tolerance by maintaining ion balance and strengthening antioxidant defenses, while also contributing to organic acid metabolism and pH homeostasis under saline–alkali conditions. These findings have important implications for the breeding of stress-resistant grape cultivars. • The rootstock 1103 P enhances scion tolerance by upregulating VvGAD1 expression. • The VvGAD1 gene promotes GABA accumulation to counteract multiple stresses. • VvGAD1 plays a dual role in GABA-mediated tolerance mechanisms.