PIWIs’ variation in drought response under semi-controlled conditions 

Context and purpose of the study ‐ Vine balance is a concept describing the relationship between carbon assimilation (usually estimated using a measure of vine vigour, e.g. pruning weight) and its utilisation for fruit production (usually estimated using harvest yield). Manipulating vine balance through leaf area or crop load adjustments affects the proportion of the vine’s total carbohydrate production required to mature the fruit. It is commonly considered that composition of the berry, and resulting wine, is strongly affected by vine balance.

Polyphenols, namely anthocyanins and flavanols, are key compounds for wine color definition and taste perception (astringency and bitterness). During winemaking, several processes could influence the polyphenol composition and, therefore, the organoleptic parameters of wine.

Climate change presents increasing challenges to viticulture, particularly with rising water stress contributing significantly to yield losses and damages. The identification of the MYB60 transcription factor, which regulates stomatal opening and closing in Arabidopsis thaliana and Vitis vinifera, offers potential solutions. Notably, knockout studies in Arabidopsis have shown reduced stomatal opening and increased drought tolerance in myb60 mutants. Additionally, the grapevine ortholog, VviMYB60, can restore the wild-type phenotype of Arabidopsis myb60 mutants. Further investigation of the Arabidopsis promoter region has revealed that mutations in DOF motifs lead to reduced expression of AtMYB60.

The quality of red wine depends on the composition of polyphenols influencing wine color and taste. The question is, how much we must fear over extraction, especially of seed tannins, under cool climate conditions. The extraction of polyphenols from grape skins and grape seeds were investigated for the grape varieties Cabernet Sauvignon and Pinot noir

Understanding how different pedoclimatic conditions interact with vine and berry physiology, and subsequently impact wine quality, is paramount for an good valorization of viticultural terroirs and can help to optimize mitigation strategies in the face of global warming