EFFECTS OF DIFFERENT PRUNING TYPES ON CHARENTE UGNI BLANC GRAPE AND WINE QUALITY

Abstract

Since the use of sodium arsenite was banned in 2001, Grapevine Trunk Diseases (GTDs) have become even more widespread increasing (1).To avoid pathogen entry, pruning, an age-old practice, is increa- singly coming to the fore. As the vine is a liana (2), any excessive woody proliferation has to be stopped. This can preserve grapevine life, provided it does not damage the diaphragm.

Our trial concerned two Ugni blanc parcels planted in 2006 and 2015, in vineyards managed by JAS HENNESSY & CO, at Juillac-le-Coq and Saint-Preuil in Charente. The parcels were set out in double Guyot-Poussard. Starting in 2018, two different types of pruning quality were used in both parcels. Short pruning damaged the diaphragm, whereas high pruning ensured a desiccation cone to keep the diaphragm safe. The aim of our work was to measure over three years the different impacts of these two types of pruning on grape and wine quality.

From 2020 to 2022, weight and quality of grapes were analysed at harvest. Microvinification was then carried out. On both musts and wines, several chemical analyses were performed: (i) amino acids, to de- termine the nitrogen status of future wine quality; (ii) ester and higher alcohol aroma wine markers; (iii) methyl salicylate, a specific GTDs plant marker. Triangular wine tasting was carried out on six-month- old wines.

Amino acid results tended to differ with pruning quality. This was not the case for the ester and higher alcohol results, which only showed differences between the vintages. The methyl salicylate level was low in wines, thereby confirming the findings of Xavier Poitou (3) for the Ugni blanc cultivar. Although the wine tasting analyses did detect differences between short and high pruning for the young parcel, it was more difficult to do so for the older one.

The present study confirms the interest of applying high pruning on a long-term basis. It can have an indirect effect on the plant’s physiological functioning, keeping the vines safer and preserving the grape quality.