Effect of certain climatic variables on the phenolic and aromatic composition of two red grape varieties (Merlot and Cabernet-Sauvignon) grown in the Mancha region (Spain)

Between 2002 and 2004 we studied the behaviour of two red grape varieties – Merlot and Cabernet Sauvignon – within the scope of an experimental protocol encompassing 14 plots, 7 of which had not been cultivated, situated in geographically distant locations representing different terroirs of Castilla-La Mancha. A brief geopedological characterisation was performed of the different plots (geological stratum, topography, geomorphology, type of soil…). The agronomic characteristics of the plots were also determined (crop age, planting density, vegetation growth control, fertilisation…). The most significant climatological variables for wine production, IS (Dryness Index), IH (Heliothermal Index) and IF (Cool Night Index), the dates of the four most representative phenological states in vines (shooting, semi-flowering, semi-veraison and ripening), the importance of plant cover (LAI: Leaf Area Index) and phenolic composition (phenolic ripening parameters) and aromatic composition (GC/MS: gas-phase chromatography combined with mass spectrometry) of ripe grapes were some of the parameters monitored in these years. The results obtained show that the thermal regime during the vegetative cycle and ripening, as well as certain cropping practices (particularly those that influence vine architecture and fruit characteristics and weight), bear an important influence on the phenolic and aromatic composition of grapes during ripening, even in the semi-arid conditions of La Mancha.