Single and combined effects of pre-veraison treatments with 1-naphthaleneacetic and salicylic acids on harvest date and quality potential of Verdejo wine grapes

The progressive increase in temperature due to climate change is resulting in a shorter vine growing season, with earlier and unbalanced grape maturation which negatively affects the quality of the wine. One of the possible techniques to mitigate these effects is the application of plant growth regulators capable of delaying ripening, making it more balanced at lower temperatures. In this context, the objective of this study was to evaluate the usefulness of 1-naphthaleneacetic acid (NAA, 100 mg/L) and salicylic acid (SA, 1 and 5 mM), applied to clusters before veraison, to delay ripening and improve the composition of white wine grapes. For these, a two-year field trial was carried out in a Verdejo/110R vineyard. The results showed that NAA treatment delayed the harvest date by around 17 days compared to control producing, for a same soluble solids content, musts with higher total acidity and lower polyphenol and yeast assimilable nitrogen contents. SA single treatment did not significantly affect the harvest date and had a different impact on grape composition depending on the dose applied. The combined application of NAA with 5 mM SA produced a delayed harvest by 12 days compared to the single NAA treatment, without affecting the vigour of the plants, maintained the acidity levels in the must and enhanced its polyphenol content. The study provides novel insights into the use of NAA and SA in Verdejo variety, and demonstrates the interest of combined application of both bioregulators to mitigate the adverse effects of climate change on grape quality potential. • NAA treatment delays harvest, increases berry weight and total acidity of the must. • Applications of 5 mM SA can improve the polyphenol content of the grapes. • In combined application, 5 mM SA reinforces the effect of NAA on delaying ripening. • NAA and SA combination could improve must quality under summer stress conditions.