Stomatal restrictions to photosynthesis in grapevine cultivars grown in a semiarid environment

The chemical composition of grape berries at harvest is one of the most important factors that should be considered to produce high quality wines. Among the different chemical classes which characterize the grape juice, the polyphenolic compound, such as flavonoids, contribute to the final taste and color of wines. Recently, an innovative non-destructive method, based on chlorophyll fluorescence, was developed to estimate the phenolic maturity of red grape varieties through the evaluation of anthocyanins accumulated in the berry skin. To date, only few data are available about the application of this method on white grape varieties.

AIM: the aim of this study was to develop a method for fine-scale temperature zoning. The effect of temperature variability on vine phenology and grape composition was assessed in the production area of Saint-Emilion

High concentration of sugars in grapes and alcohol in wines is one of the consequences of climate change on viticulture production in several wine-growing regions. In order to investigate the possibilities of adaptation of vineyard management practices aimed to reduce the accumulation of sugar during the maturation phase without reducing the accumulation of anthocyanins in grapes, a study with severe shoot trimming, shoot thinning, cluster thinning and date of harvest was conducted on Merlot variety in Istria region (Croatia), under the Mediterranean climate. Four factors which may affect grape maturation and its composition at harvest were investigated in a two-years experiment; severe shoot trimming applied at veraison when >80% of berries changed colour (in comparison to untreated control), shoot thinning (0 and 30%), cluster thinning (0 and 30%), and the date of harvest (early and standard harvest dates). Shoot thinning had no significant impact on berry composition, despite the obtained reduction in yield per vine. Lower Brix in grapes were obtained with earlier harvest date and if no cluster thinning was applied, although at the same time a reduction in the concentration of anthocyanins in berries was observed in these treatments. On the other hand, if severe shoot trimming was applied when >80% of berries changed colour, a reduction of Brix was obtained without a negative impact on berry anthocyanins concentration. We conclude that in cases when undesirably high sugar concentrations at harvest are expected, severe shoot trimming at 80% veraison may effectively be used in order to obtain moderate sugar concentration in berries together with the adequate phenolic composition.

L’objectif de l’étude était de connaître le rôle du climat sur les aspects phénologiques du cépage « Moscato bianco » dans les différentes zones de production du vin Moscato d’Asti aocg en Piemonte (Italie) et ses effets sur l’époque de vendange. La représentation cartographique ( échelle 1 :25000) de exposition, altitude, climat, index

White wines are commonly stabilised by removing the heat unstable proteins through adsorption by bentonite, an effective but inefficient wine processing step. Alternative absorbents are thus sought and zirconium dioxide (zirconia) is recognised as a promising candidate.