השפעת מועד דילול האשכולות בכרם יין על הגפן, ואיכות הענבים והיין

Abstract

In the current practice among vineyards, it is customary to regulate the vines' crop in order to achieve the required quality. Many studies have shown a correlation between low crop levels and increased grape and wine quality. The aim of this work is to examine the effect of relatively late grape bunch thinning on crop parameters and wine quality, as well as their effect on the expression of genes in the phenylpropenoid pathway. Thinning treatments were executed during (1) an early stage of berry growth, the veraison phase (color change), and (3) the "harvest eve" phase – about two weeks before the harvest. The research work took place for several years at vineyards in Gush Etzion and Mevo Horon, Israel. In this paper, we present the research that took place in 2018 at the Mevo Horon vineyard, using Shiraz and Merlot wine varieties. The results show that there was an improvement in the indices of acid, polyphenols, and color in the thinned plots compared to the non-thinned control plots. In most indices, an improvement was found in grapes treated by late thinning over that of non-thinned. Thus, it may be concluded at this stage that even a thinning treatment conducted 10 days before harvest has a significant positive influence on wine quality compared to the maintenance of high yields until harvest time. An analysis of the expression level of central genes involved in the formation of anthocyanins (color) showed that the early thinning treatments caused an increase in their expression level. The results of this experiment may present the basis for further examination of a new cultivation practice in which high yield will be maintained and thinning will be carried out late in the season. The clusters removed during thinning may be used to produce rose wines, given adequate compensation to the farmer and winery for this costly operation.