Modulation of secondary metabolism in Vitis vinifera through A. nodosum extracts: Effects on vine eco-physiology and grape quality

In most Mediterranean climatic regions, vineyards are subject to periods of high solar radiation, high temperatures and soil water deficit. These conditions accelerate berry ripening processes, resulting in unbalanced wines, with high alcoholic content and low polyphenolic concentrations (Mosedale et al. 2016). For these reasons, this project aimed to investigate the effects of a foliar distribution of a brown macroalga extract (Ascophyllum nodosum) on ecophysiological parameters and secondary metabolites in Vitis vinifera. The experiment was carried out in the 2016 growing seasons in a 1 Ha experimental vineyard (Vitis vinifera cv. Sangiovese), located in “Chianti Classico” Designation of Origin, in Italy. Using an experimental randomized block design with five replication per treatment, the comparison between vines treated with a A. nodusum extract (SWE) and non-treated vines (CTRL) was set up. The extract was applied in two treatments in the ratio of 4mL/L each, 30 and 15 days before harvest. This extract is rich in micro- and macronutrients and amino acids (mainly alanine, phenylalanine and methionine). Weekly, eco-physiological measurements have been taken (leaf gas exchanges, chlorophyll fluorescence, stem water potential) and berry samples were collected to investigate secondary metabolites with HPLC and to analyse soluble solids, titratable acidity and berry weight. SWE showed significantly higher photosynthetic rates, stomatal conductance and pre-dawn water potential, of about 60%, 38% and 26% respectively, if compared to CTRL. Furthermore, with the same berry weight, in SWE soluble solids are significantly lower than CTRL, and statistical differences were observed for flavonoid and anthocyanin concentrations in berries.