Abstract
This study investigated anthocyanin accumulation, sugar contents, and endogenous hormone contents in the berry skin, as well as the expression of genes related to anthocyanin and abscisic acid (ABA) synthesis and metabolism, using grafted ‘Ruby Roman’ berries on the rootstocks of ‘Kober 5BB’ [5BB(2x), a semidwarf rootstock], ‘Hybrid Franc’ [HF(2x), a vigorous rootstock], and their colchicine-induced autotetraploids [5BB(4x) and HF(4x)]. Rootstock had significant effects on the total content, but not on the composition, of anthocyanins. The berries on 5BB(4x) rootstock, where the grapevine showed less vegetative growth, had higher anthocyanin content during the ripening process, and also had higher sugar and ABA contents around véraison. ABA, indole acetic acid (IAA), and cytokinins showed synchronous changes during berry development: they had the lowest levels at pre-véraison, and their metabolic pathways were accelerated after véraison. Furthermore, they all tended to be higher on 5BB(4x) than on the other rootstocks. Since the expression levels of most of the ABA biosynthesis-related genes did not show a corresponding increase with the contents of ABA and ABA-glucosyl ester (ABA-GE), it is considered that the increase in ABA content after véraison may be mainly due to the decrease in catabolism and/or exogenous import from other organs. This study provides an overview showing the dynamic changes and relationship of three phytohormones during the ripening of grape berries grafted on different rootstocks, and explores the mechanisms regulating ripening.
