Calcium, methyl jasmonate and their combined foliar applications: Influence on Tempranillo grape amino acids composition over two seasons

BACKGROUND: Climate change is currently affecting chemical grape composition and, consequently, grape quality. The foliar application of biostimulants has emerged as a promising approach to mitigate these effects. This study investigated the effects of foliar applications of calcium (Ca), methyl jasmonate (MeJ), and their combination (Ca + MeJ) on the enological parameters and amino acid composition of Tempranillo grapes over two successive growing seasons (2022 and 2023). The effect of applying the treatments once or twice at post-veraison and 1 week later was also evaluated. RESULTS: Foliar applications showed season-dependent effects on Tempranillo musts, generally increasing pH, malic acid, and total phenol content. Differences between seasons were attributed to climatic variability. In all samples, arginine was the predominant amino acid in grapes, followed by proline and glutamine. All foliar treatments modified the amino acid profile, although the effects varied between seasons. The observed increases in asparagine, glutamine, valine, methionine, isoleucine, ornithine, and leucine following foliar calcium application suggest stimulation of nitrogen assimilation and amino acid biosynthesis pathways. In 2022, Ca + MeJ1 and MeJ2 were the most effective treatments, whereas in 2023, MeJ1 and Ca2 produced the highest amino acid content in musts. CONCLUSION: Foliar application of these biostimulants may represent a useful strategy to improve grape nitrogen composition and mitigate the effects of climate change. The observed increase in amino acid content may also contribute to improved yeast assimilable nitrogen (YAN), supporting yeast metabolism and potentially improving fermentation performance.