Manipulation of 'Teran' grape composition with severe shoot trimming and cluster thinning

Accelerated grape ripening and high wine alcohol content has become a widespread problem in various grape growing regions worldwide in the recent years. One possibility of adaptation to this situation can be obtained by the use of canopy management practices that decrease the leaf area/yield ratio, in order to reduce sugar concentration in grapes. The purpose of this study was to assess the effects of various leaf area/yield ratios obtained by severe shoot trimming and cluster thinning on yield components and grape composition of Vitis vinifera L. 'Teran' vines. Two different canopy heights (70 and 130 cm), obtained by shoot trimming at the beginning of veraison, were combined with cluster thinning by removing 0 or 35% of clusters. Leaf area/yield ratio differed considerably among treatments, ranging from 0.70 for vines with short canopy and no cluster thinning applied to 1.69 for vines with high canopy and cluster thinning applied. Severe shoot trimming reduced sugar concentration in grapes, while titratable acidity and pH were not significantly influenced by the investigated treatments. Total anthocyanins and total phenolics in grapes were not negatively affected if severe shoot trimming was combined with cluster thinning, while if cluster thinning was not applied, total anthocyanins and total phenolics were reduced by severe shoot trimming. It is concluded that wines with reduced alcohol concentration and unaffected phenolic composition may be obtained by combining severe shoot trimming and cluster thinning, although the economic aspect should be considered in this case concerning the yield loss obtained by cluster thinning.