Influence of rootstock on endogenous hormones and color change in Cabernet Sauvignon grapes

Different rootstocks for grapes can significantly affect fruit color and quality, possibly by affecting hormone contents, related genetic pathways, and fruit coloring mechanisms in peels. ‘Cabernet Sauvignon’ were grafted to ‘5BB’, ‘SO4’, ‘140R’, ‘CS’, ‘3309M’ and ‘ Vitis riparia’ rootstocks, with self-rooting seedlings as the control (CS/CS), and sampled from the early stage of color transformation to the ripening stage. The effects of rootstock on the contents of gibberellin (GA 3 ), auxin (IAA), and abscisic acid (ABA) in grape peels were determined alongside the expression levels of eight anthocyanin synthesis related genes using real-time fluorescence quantitative PCR methods. The rootstock cultivars exhibited accelerated fruit color change, and the CS/140R cultivar had much greater color change than the control group in the same period. With the development of fruit, the IAA and GA 3 contents in the peels of different rootstock combinations showed trends of increasing initially, then decreasing, while the ABA content decreased initially and then increased. During the fruit color change period (28 July), the various ‘Cabernet Sauvignon’ rootstock combinations exhibited varying degrees of increases in GA 3 , ABA, and IAA contents; correlation analysis showed that, at the start of veraison, the expression levels of the anthocyanin synthesis-related genes VvCHS , VvDFR , and VvUFGT had strong positive correlations with hormone contents, which indicated they are key genes involved in the endogenous hormone responsive anthocyanin biosynthesis pathway. The results of this study showed that rootstock grafting regulates the fruit coloring process by influencing the metabolism level of peel hormones in the ‘Cabernet Sauvignon’ grape.