Effect of pre- and post-veraison water deficit on proanthocyanidin and anthocyanin accumulation during Shiraz berry development

Background and Aims: Water deficit is known to influence berry development as well as flavonoid metabolism. The aim of this study was to investigate the influence of pre- and post-veraison water stress on the proanthocyanidin and anthocyanin accumulation on berry samples selected at comparable physiological maturity, especially after veraison while avoiding sugar influence. Methods and Results: Three irrigation treatments were applied by a drip irrigation system on three rows of 30 vines from an experimental Shiraz vineyard. Pre-veraison water stress had no effect on total proanthocyanidin accumulation but increased accumulation of all anthocyanins except malvidin and p-coumaroylated derivatives, whereas post-veraison water stress enhanced the overall anthocyanin biosynthesis, particularly malvidin and p-coumaroylated derivatives. Conclusions: Pre- and post-veraison water stress affected the anthocyanin composition differently, suggesting a differential regulation of the genes involved in the last steps of anthocyanin biosynthesis pathway. Significance of the Study: The study identifies the effect of pre- and post-veraison water stress while avoiding sugar influence on anthocyanin accumulation which could be maximised since both stresses differently impacted hydroxylation and methylation of anthocyanins