Engineering saline-alkali-tolerant apple rootstock by knocking down MdGH3 genes in M9-T337.

Soil salinization and alkalization have become an increasingly severe global issues, significantly limiting both the yield and quality of apples (Malus × domestica). M9-T337 is a widely used apple dwarfing rootstock; however, it is sensitive to saline-alkali stress. Therefore, developing saline-alkali tolerant apple rootstocks is essential. In this study, we utilized RNAi (RNA interference) technology to knock down GH3 genes in the M9-T337 background, aiming to engineer a dwarfing and stress-tolerant apple rootstock. We found that MdGH3 RNAi plants exhibited superior morphology compared to M9-T337 under saline-alkali stress conditions, characterized by more robust root systems, increased plant height, a lower Na⁺/K⁺ ratio, and enhanced photosynthetic and antioxidant capacities. Moreover, when MdGH3 RNAi plants were used as rootstocks, the GL-3/MdGH3 RNAi plants also displayed greater plant height, root vitality, photosynthetic ability, and antioxidant capacity compared to GL-3 grafted onto M9-T337 rootstock. Taken together, our study constructed a saline-alkali-tolerant apple rootstock by knocking down MdGH3 genes.