ABA and Etephon Affect Berry Color Intensity and Hue Assisted by Anthocyanin-Flavonol Copigmentation

High Resolution Image Download MS PowerPoint Slide Exogenous applications of plant growth regulators are interesting ways to modulate berry ripening as well as to investigate the role of phytohormones in the regulation of plant processes. In this experiment, the berries of “Tempranillo” fruit-bearing cuttings were treated at the onset of veraison either with abscisic acid (ABA) or ethephon (ETE, an ethylene releasing compound). Berries were periodically sampled to monitor their ripening and the accumulation of phenolic compounds and nano-scale vinifications were performed on ripe berries. ETE induced the accumulation of sugars and degradation of organic acids, accompanied by an improved phenolic content in grape skins. ABA and, especially, ETE induced lower concentrations of total amino acids, aroma precursor amino acids, and yeast assimilable nitrogen (YAN). ETE strongly altered the anthocyanin profile, increasing the relative abundance of cyanidins and peonidins and decreasing malvidins. ETE induced a smaller relative abundance of glutamine and higher glutamic acid and several terminal amino acids. ETE improved the color properties of the wine, such as color intensity (CI), total polyphenol index (TPI; A 280 ), A 520, A 620, and blue hue ( A 620 /A 520 ). Although ABA induced similar trends regarding anthocyanin and flavonol accumulation, in most cases, these were not statistically significant. Increased berry flavonol biosynthesis, which is often overlooked, was pointed out by partial least squares regression as the main driver of the increase in blue hue. ETE had a stronger and more consistent impact on anthocyanin profiles, wine color, and amino acids, while ABA showed transient effects on acylation. Applications of growth regulators on vineyards aiming for higher color should consider the possibility of these side effects.