Effect of late pruning on yield and wine composition in monastrell wines

Abstract

Global warming is shifting vine phenology, resulting in a decoupling of phenolic and technological berry ripening. This is altering the balance of fruit traits, which is key relevance to winegrowers, particularly in arid and semi-arid areas. Our aim was to test late pruning as an useful tool to delay grape ripening and to assess the effects of this technique on the yield and wine composition, looking mainly to reduce the wine alcoholic content without reducing phenolic composition of the wines. A trial was established in a commercial vineyard comparing, in 2020 season, two vine training system (double cordon and goblet), two moments of pruning:

(i) winter (Control) and

(ii) before the basal bud burst (BBCH 07)(late-pruning, LP) and two harvest dates (12°and 14°Baumé).

In 2019, only goblet and harvest at 14°Baumé was tested. In 2019, and although there was a sharp decrease in yield, the composition of wine improve significantly (total acidity, colour intensity, anthocyanin and tannin), therefore we conducted the experiment in 2020 and this year late pruning were tested in two training system (goblet and double cordon) and two moments of harvest (12°and 14°Baume). When grapes were harvested at 12°Baumé, yield was not affected in both training system and late pruning slightly reduced alcohol content and increase total acidity, colour intensity, anthocyanin and tannin in the wines from both vineyards. When harvest was done when grapes reached 14° Baumé, late pruning significantly reduced yield, there was no effect on alcohol content and total acidity but LP increased colour intensity and anthocyanins in the wines of both vineyards. The effect of late pruning on harvest date were negligible for both training system (goblet and double cordon). However, if we compared the chromatic composition of LPT 12º wines with control wines made with 14ºBaume grapes, we could observed that they were similar but alcohol was 20% lower in LP 12º wines. Therefore, late pruning could be an useful tool to improve phenolic composition of wines, allowing a reduction of their alcohol content. It is clear that delayed pruning is a simple and cost-effective technique that may allow the semi-arid regions winegrowers to adapt to global warming, harvesting the grapes with lower sugar content without harming the quality of the wines.