Application of Methyl Jasmonate and Methyl Jasmonate + Urea in Tempranillo Vines: Influence on Grape Phenolic Compounds

Background and goals The aim of this work was to study, for the first time, the influence of foliar application of methyl jasmonate (MeJ) and methyl jasmonate plus urea (MeJ+Ur) on Tempranillo grape phenolic composition over two seasons.

Methods and key findings This work examined grape phenolic compounds using high-performance liquid chromatography-diode array detection. In 2019, both treatments increased the total anthocyanins, but the MeJ+Ur treatment had a stronger effect than the MeJ treatment. MeJ foliar application decreased total flavonols, total flavanols, and total hydroxycinnamic acids in the grapes, while MeJ+Ur significantly decreased total flavonols, but did not affect total flavanols or hydroxycinnamic acids. Neither of the foliar treatments affected total stilbenes. However, in 2020, the effect of treatments was different: foliar treatments did not affect the anthocyanins, flavonols, hydroxycinnamic acids, or stilbenes, but increased the flavanol content in the grapes.

Conclusions and significance The effect of foliar treatments was season-dependent, which can be explained by the differences in preharvest rainfall between vintages. The influence of season on grape phenolic compounds was greater than that of the treatments. The results offer information about the response of grapevine to foliar application under different climate conditions.