Increasing global temperature could severely affect the quality of grape berries and ultimately that of the wine as it disrupts the balance between sugars, acids, polyphenol concentration and colour intensity. Aiming to alleviate these effects on wine composition, late pruning was applied to maintain optimal photosynthetic activity during ripening. Field trials were carried out on Vitis vinifera cv. Malbec and cv. Syrah grafted on 110 Richter rootstock at an experimental vineyard located at Ayalon Valley, Israel. Grape samples from late pruning treatments showed lower pH and higher titratable acidity due to increments of both tartaric and malic acids concentrations. Fifty-one metabolites were detected and unequivocally annotated employing a UPLCMS-based metabolite profiling protocol. Integrating the data using HCL showed a significant effect of late pruning treatments on berry must and wine. For example, later pruning treatments (LSP3 and LSP1) were clearly separated from the control pruning treatments (WP+T and WP) in two different groups. The most affected metabolite classes were anthocyanins and stilbenes. Syrah metabolite profiles were characterized by a general trend of higher metabolite content in the late pruning treatments, while Malbec profiles did not show a consistent trend along with the late pruning treatments. The combined effect of treatment, cultivar, and vintage was noticed in most metabolic classes except for hydroxycinnamic acids and flavanols. In summary, our results indicate that late pruning exerts a significant effect though varietal specific- on must and wine quality-related metabolites, which should be taken into consideration when planning mitigating strategies in warm climates.
Abbreviations: LSP3, pruning after 3 weeks of bud-break; LSP2, pruning after 2 weeks of bud-break; LSP1, pruning after 1 week of bud-break; W+T, winter pruning and cluster thinning; WP, winter pruning.