Aplicación foliar en el viñedo de un extracto del alga Ascophyllum nodosum como herramienta para mejorar la composición nitrogenada, fenólica y aromática de la uva y del vino de las variedades Tempranillo y Tempranillo Blanco

Résumé

Different studies suggest that seaweed extracts may behave as elicitors in horticulture, triggering the synthesis of certain secondary metabolites, mainly of phenolic compounds in several crops and woody species, including grapevines. However, the studies about the effects of foliar applications of seaweeds to grapevines are mainly focused on their effects on plant physiology, productivity, physicochemical parameters of musts and wines and the synthesis of certain phenolic compounds. On the other hand, Tempranillo Blanco grapevine variety originated spontaneously from a natural mutation of a Tempranillo grapevine, which was discovered in 1988. Its cultivation has recently been authorized by the D.O.Ca. Rioja. Currently, the oenological characteristics of this variety have been little studied. The aims of this Doctoral Thesis were to study the effect of foliar applications of a commercial extract elaborated from the Ascophyllum nodosum alga to Tempranillo Blanco (Vitis vinifera L.) and Tempranillo (Vitis vinifera L.) grapevines on the phenolic, nitrogen and volatile composition of grapes and wines in 2017 and 2018 seasons, as well as to characterize the phenolic, nitrogen and volatile composition of grapes and wines of Tempranillo Blanco grapevine variety. The applications of these treatments, as well as a control, were carried out twice and in two different dosages; a low (0.25 % v/v) and high (0.5 % v/v) dosages, when the grapevines reached the phenological stage of veraison and one week later. The results showed that catechin was the most abundant phenolic compound in grapes and wines of Tempranillo Blanco variety. Additionally, the grapevines of this variety behaved as arginine accumulators. The C6 compounds were the most abundant volatile compounds in Tempranillo Blanco musts, while (E)-�-damascenone was the most abundant varietal volatile compound in the musts of this variety. In Tempranillo Blanco grapevine variety, the concentration of catechin and flavonols in grapes increased after the application of the high dosage of the seaweed to the grapevines in both seasons. This treatment increased also the concentration of several amino acids in the musts in 2017, while the application of both dosages of the seaweed extract to grapevines barely affected amino acids content in musts in 2018. Phenylalanine, a precursor of several phenolic and volatile compounds in plant tissues increased its content in the musts in both seasons after the application of the high dosage of the seaweed application. The application of this treatment to the grapevines tended to increase the concentration of certain C6 compounds in musts in both seasons, while the application of the low dosage of the seaweed extract to the grapevines tended to decrease the content of 2-phenylethanol and 2-phenylethanal in musts. The season factor affected the content of most of the amino acids and volatile compounds in musts due to the differences in rainfall and relative humidity of both seasons. The concentration of hydroxycinnamic and hydroxybenzoic acids in wines was affected by the winemaking process, probably due to oxidation reactions, while the stilbene content in wines was affected by the effect of cryptogamic diseases in grapes. Yeast assimilable nitrogen in musts seems to have impacted the concentration of most of the amino acids and volatile compounds in wines. In Tempranillo grapevine variety, the low dosage of the seaweed extract applied to the grapevines increased the concentration of most of the phenolic compounds in grapes and the amino acids in musts in 2017 season, while the high dosage of the seaweed extract increased the content of certain flavonols in the grapes in 2017. Both dosages of the seaweed commercial extract applied to Tempranillo grapevines allowed to increase the content in the trans-piceid and total stilbenes in grapes in both seasons. The treatments barely affected the content of phenolic compounds in grapes in 2018 season, however, the high dosage of the seaweed extract increased the content in musts of 6 several individual terpenes, C13 norisoprenoids, esters, benzenoids, alcohols, carbonyl compounds and C6 compounds. Generally, a high content of yeast assimilable nitrogen in the musts allowed to reach a high concentration of amino acids and volatile compounds in wines. The concentration of anthocyanins and flavonols in wines decreased as the duration of malolactic fermentation and volatile acidity increased, while the content of hydroxybenzoic acids and stilbenes in wines had the opposite effect. Therefore, seaweed applications to the grapevines increased the content of most of the analyzed compounds in grapes, depending mostly on the climatic conditions of the season, the dosage of the extract applied to grapevines and the selected variety.