Effect of leaf removal on grapes of Cabernet Sauvignon and Sangiovese coltivated in different Italian environments

The leaf removal is one of the feasible intervention on the vine that most influence the quality of grapes and wine; known are the effects that this practice can be established on the time of technological maturity of the grapes (Percival et al., 1994; Kliewer e Lider, 1968) and on skins and seeds polyphenolic assest (Downey et al., 2006; Kliewer, 1970; Morrison et al., 1990), even if, especially as regards the effect on polyphenolic content, a unique evaluation doesn\u2019t exist. This application must take into account of cultivars, climatic conditions and exposure of the vineyard; leaf-stripping changes the structure of the canopy and influences the microclimate, understood as a set of environmental conditions affecting the surrounding canopy and / or specific organs or areas of the canopy itself (Poni, 2002). Two red grape cultivar, the Cabernet Sauvignon and the Sangiovese, widely cultivated on the Italian territory, were chosen to better investigate the effects that different types of leaf removal, carried out in vineyards with north-south orientation (leaf removal at east side and west side, east side only, west side only, no leaf removal), have on vegetative-productive and qualitative parameters of grapes. In the present study were taken into account five areas, wich are different for geographical location, climate and altitude: Puegnago sul Garda (BS), Scansano (GR) (only for Sangiovese), Bolgheri (LI) (for the single cultivar Cabernet Sauvignon), Brisighella (RA), Montefalco (PG). Data were collected in 2007, 2008, 2009 and 2010 and took into account vegetative-productive parameters and analytical data of musts, as well as the polyphenolic content of grapes (Mattivi et al. , 2002). It can be generally observed from the analysis of data that the two varieties have reacted differently to leaf removal; in fact, considering the average data from all sites, the Sangiovese seems more sensitive than Cabernet Sauvignon to leaf removal, resulting in lower average weights of the bunch in all leaf removal tests and recording higher sugar content, in the case of east side leaf removal test. With regard to the anthocyanins and polyphenolics level this variety shows higer concentration in three leaf removal tests, however with no significant differences; Cabernet Sauvignon seems to react negatively to the leaf removal, in fact the higher content in anthocyanins and total polyphenols is higher in the covered test, although, also in this case, the recorded difference was statistically insignificant. Taking into account differences between the four tests within each site of Sangiovese, the average data in Brisighella shows the higest sugar and anthocyanins content in the east side leaf removal test compared to other test; the vineyard of Puegnago recorded a similar behaviour for the same cultivar, in fact, also in this case, the same test has the highest sugar level. the reaction of this variety in the vineyards of Montefalco and Scansano was different: in the first case it can see how the total leaf removal test and west side leaf removal test show pH value lower than the others; in Scansano the total leaf removal test appears to be the one that best preserves the acidic content. For the vineyard of Cabernet Sauvignon in Brisighella the behaviour is opposite to that observed for the first variety; in fact in this case the east leaf removal test is the one that has a lower sugar content, as it has been observed in Bolgheri for the same test. In Puegnago for Cabernet Sauvignon the covered test produced musts with higher acid levels and lower sugar content than other tests, while in Montefalco these characteristics are common to the covered test and the west side leaf removal test. It\u2019s so clear as this agricultural practice can not be adopted in a general manner, because it leads to different results due to the location and grape