CLONAL SELECTION OF VERMENTINO GRAPEVINE VARIETY IN THE TUSCAN COASTAL AREA

The importance of the cv. ‘Vermentino’ in the production of white wine in the Tuscan coastal area, has increased during the past few years, as indicated by its use as a main variety for the production of four IGT and twelve D.O.C. white wines, eight of which are varietal wines. This led to a initiate a clonal selection work, which was performed following the current method on twenty-one vineyards. The ELISA tests performed on 115 candidate clones revealed a low percentage of infection for nepovirus while the presence of leafroll associated closterovirus was low for GLRaV1 and high for GLRaV3. An intermediate situation was observed for GVA and GFKV. Vines chosen were free from fanleaf, while leafroll symptoms were observed on 22 % of plants tested. Elevated presence of the rugose wood complex RSP and KSG were also found, while LN33 stem grooving and corky bark (GCB) were absent. At the end of plant health tests twelve candidate clones proved to be free from the main viruses are thus suitable for homologation. Ampelographic and bioagronomic observations, conducted from the 1995 to 1999 growing season showed that 11 candidate clones of ‘Vermentino’ differed in cluster size, yield, time of ripening, berry sugar content and titratable acidity. Wines obtained from microvinification of single clones, were subjected to sensory analysis using a non parametric structured sheet which was built up from a panel using thirteen descriptors. The standardized data were subjected to factorial analysis, thereby obtaining 5 new complex variables (factors), which accounted for around 61% of total variability. Using a multiple linear regression, a correlation between overall appreciation and the 5 factors was found. This made it possible to estimate overall appreciation mathematically from the evaluations of panel descriptors. The results obtained from this work suggest that the homologation of new clones of ‘Vermentino’ having different characteristics could allow viticulturists to broaden the choice of clones with the aim of satisfying specific climatic, agronomic and enological requirements.