Zonage du terroir viticole en Vallée d’Aoste

In a preliminary phase of the zoning project 85 reference vineyards were selected all along the different areas involved in the valley viticulture and considered representative of the different growing conditions. They were composed as follows: Petit rouge, 33 vineyards; Pinot noir, 31; Moscato bianco, Nebbiolo, 8; Prié blanc, 5. Each vineyard was characterized from the pedological (landscape and soil) and the viticultural (phenology, yield and vigor) point of view. Potential photosynthetically active radiation (PPAR) and Winkler index (growing degree summation on base 10°C during the vegetative period) were estimated along all the valley viticultural areas. Per three years (1999-2001) rates of technological and phenolic ripening have been analyzed by maturation curves. Grapes from reference vineyards have been chemically analyzed and processed by microvinification. Wines were chemically analyzed and sensorially evaluated by trained panel. The effects of the environmental and cultural factors and technological and phenolic maturation have been tested by statistical linear models (ANOVA/ANCOVA and multiple regression) for Petit rouge and Pinot noir. Site elevation resulted to be the most important factor for both the varieties only at the condition to divide vineyards into two o three groups according to the different relative precocity (i.e. different precocity at the same elevation); for Petit rouge these groups resulted to be the S. Pierre area (relatively early vineyards), the western part of the valley and the eastern part of the valley (relatively later). For both the varieties the sensorial analysis confirmed the higher suitability of the relatively earlier vineyards, which wines resulted statistically higher in agreeability, structure and fruity notes. Results completely validated the higher suitability of the classic Petit rouge production areas (Torrette, Enfer d’Arvier).