The Effect of Rootstock on the Activity of Key Enzymes in Acid Metabolism and the Expression of Related Genes in ‘Cabernet Sauvignon’ Grapes

Abstract

The types and contents of organic acids in wine grapes determine wine quality. To explore the effects of different rootstocks on the acid metabolism of ‘Cabernet Sauvignon’ grapes, various perennial rootstock–scion combinations were used as experimental materials. High-performance liquid chromatography (HPLC) was used to determine citric acid, tartaric acid, and malic acid contents during fruit development. Succinic acid and oxalic acid contents and the activity of related enzymes were measured using spectrophotometry. The expression levels of related genes were measured using a real-time fluorescence quantitative method. The results showed that all four rootstock types significantly reduced oxalic acid and citric acid contents in the grapes, while increasing succinic acid content to varying degrees. Employing 110R, SO4, and Kangzhen3 rootstocks increased tartaric acid and malic acid contents. Enzyme activity analysis revealed that 110R, SO4, and Kangzhen3 rootstocks increased the NAD-MDH enzyme activity, which positively correlated with malic acid content. Simultaneously, these rootstocks reduced the NADP-ME enzyme activity level. NAD-MDH and PEPC gene expression levels were higher in ‘Cabernet Sauvignon’ grapes grafted with 110R, SO4, and Kangan3 rootstocks compared to control self-rooted seedlings. Grafting these three rootstocks enhanced malic acid accumulation in ‘Cabernet Sauvignon’ grapes.