Effects of Seasonal and Agronomical Practices onSkin Anthocyanin Profile of Nebbiolo Grapes

The influence of season and of 50% cluster thinning (CT) and 50% leaf removal (LR) on skin anthocyanin profile was studied on cv. ‘Nebbiolo’ in the production area of Barbaresco wine (North-West Italy). Climatic conditions over two years strongly interacted with treatments: 2000 was hot and rainy; 2001 was cooler and very dry. The leaf area/yield ratio value was higher in 2000 in response to good water availability, and it was optimal only in 2000 LR vines and in 2001 CT vines, which displayed the highest total soluble solid content at harvest. In comparison with control vines, anthocyanin concentration increased only in 2000 CT vines, even if final concentration was not significantly higher, because of its reduction before harvest. The 2001 drought reduced vine vegetative development, sugar production (-8.3%), and total anthocyanin concentration (-20.7%) respective to 2000. Individual anthocyanin concentration varied as a consequence of chemical structure, canopy management practices, and seasonal climatic conditions. Thus, the peonidin-3-glucoside/malvidin-3-glucoside ratio varied on average from 1.9, in 2000, to 1.2 in 2001 and it was higher in treated vines than in control vines. Anthocyanin accumulation can be divided into two distinct phases: an initial phase of rapid increase influenced primarily by vine vegetative conditions, and secondarily by cultural practices and a second ‘finishing’ phase during which climatic conditions played a fundamental role. 3’-Substituted anthocyanin biosynthesis is likely more strongly influenced by climatic conditions and cultural practices if compared with 3’,5’-substituted anthocyanin biosynthesis.