Oenological and productive results of the application of different cluster thinning alternatives and different wintry pruning intensities in Vitis vinifera L. cv Tannat

Abstract

The effect of the different treatments on the production of grape and wood, and the characteristics of the wines produced in a vineyard of Tannat variety, situated in the south region of Uruguay, were studied during 4 years (1997-2000). The experimental design was in parcels at random, with 30 plants per treatment. The plants were
conducted in high trellis, with double Guyot pruning. The treatments were 6: manual cluster thinning at 50% in setting or veraison, chemical cluster thinning (Etephon applications) at the same moments, and pruning at 4 and 6 bud for rod, being this last one considered as witness. 80 kilos of red grape per treatment were wine-made, with identical conditions of elaboration for all the cases. A month after the alcoholic fermentation was finished, the wines were analysed and the oenological classic parameters, the phenolic composition and the colour were determined. There were significant differences in the behaviour of the different treatments in the different years. There were statistical differences between the treatments for all the parameters considered in each year. The highest contents of alcohol in the wines were obtained with the chemical cluster thinning in settings and with the cluster thinning in veraison. However, the highest contents of total polyphenols, anthocyanins, flavanols and proanthocyanidins, and therefore the higher colour intensities of the wines, were obtained with the application of Etephon in veraison. This treatment had no effect of cluster thinning itself, so it did not have any incidence on the production, which was similar to the witness for all the years. The other treatments determined a significant decrease of the production with regard to the 6-bud pruning.