Influence of methyl jasmonate foliar application to vineyard on grape volatile composition over three consecutive vintages

Abstract

An alternative to improve grape quality is the application to the vineyard of elicitors. Although these compounds were first used to increase resistance of plants against pathogens, it has been found that they are also able to induce mechanisms involved in the synthesis of phenolic compounds and some amino acids. However, researches about the influence of elicitors on grape volatile composition are scarcely. Therefore, the aim of this work was to study the influence of methyl jasmonate (MeJ) foliar application on grape aroma composition over three consecutive vintages. MeJ was applied to Tempranillo grapevines at a concentration of 10 mM in 2013, 2014, and 2015 years. Control plants were sprayed with water. The treatments were applied to grapevine twice, at veraison and one week later, and for each application, 200 mL/plant were sprayed over leaves. The treatments were carried out in triplicate and were arranged in a complete randomized block design. Grape volatile composition (terpenes, C13 norisoprenoids, esters, benzenoids, and C6 compounds) was determined by HS-SPME-GC-MS. The statistical analysis was performed by ANOVA, considering grape volatile compounds as dependent variables and treatment and vintage as categorical factors. The results showed that the grape volatile content was different for each year. Regarding treatment factor, in the first year of study, foliar application of MeJ positively affected the presence of p-cymene, methyl jasmonate, and hexanal, and negatively to the content of 2-hexen-1-ol acetate, (z)-3-hexen-1-ol, and n-hexanol; the rest of the compounds were unaffected by the treatment. However, in the second year, the application of MeJ to grapevine showed a greater influence on the presence of volatile compounds in grape. The formation of all terpenes, with the exception of p-cymene, was negatively affected by the MeJ foliar application. For C13 norisoprenoids, the effect of the treatment was also negative for
norisoprenoids was unaffected by the MeJ treatment. Likewise, the grape level of esters and benzenoids was also negatively affected by the MeJ treatment. Finally, the MeJ treatment increased the presence of n-hexanol while (z)-3-hexen-1-ol was reduced; for the remaining C6 compounds no effect of the MeJ treatment was observed. It is noteworthy that the influence of the MeJ foliar application was positive for the grape volatile composition in the third year of study. The foliar application of MeJ favoured the synthesis of ten volatile compounds that are considered positive for grape aroma, while the rest of the positive compounds were unaffected, with the exception of geranyl acetone. In conclusion, grape volatile content and the effect of MeJ foliar application on it were dependent on the vintage.