Effects of foliar applications of methyl jasmonate alone or with urea on anthocyanins content during grape ripening

Anthocyanins, the main phenolic compounds responsible for the color of red grapes and wines, exhibit antioxidant and antimicrobial properties and offer various health benefits for humans. Currently, climate change can affect grape quality by causing a decoupling between the technological and phenolic maturities of the grapes. Foliar application of methyl jasmonate (MeJ) and urea (Ur) can be a tool to mitigate the global warming effects in the vineyard. The aim of this work was to study i) the development of anthocyanin content in 'Tempranillo' grapes along the ripening process, and ii) the effect of foliar application of MeJ and MeJ+Ur on these phenolic compounds over two vintages (2019 and 2020). Overall, in the first vintage, anthocyanins peaked in their concentrations in the pre-harvest or harvest moments; whereas in the second vintage, the highest contents of these phenolic compounds were reached at harvest time, after that, a maintenance or decreased of their concentrations was observed. In both vintages, non-acylated anthocyanins was the most abundant family of anthocyanins. Foliar application of MeJ+Ur was more effective in enhancing anthocyanin biosynthesis than MeJ treatment, which also increased anthocyanin content compared to control grapes. Therefore, MeJ and Ur foliar treatment could present a synergy in anthocyanin biosynthesis by the plant. Moreover, the impact of these applications varied across vintages, and also the content of anthocyanins in grapes, probably due to different climatological conditions. Consequently, the two foliar treatments, MeJ and MeJ+Ur, could be a suitable tool to increase anthocyanins biosynthesis in grapes, and thus improve grape quality.