Origin of unpleasant smelling sulphur compounds during wine fermentation

The biodiversity of cultivated vines has been significantly reduced due to a series of factors that have favoured the cultivation of a limited number of varieties and clones over time. In veneto, since 1980, a series of important actions have been implemented to counter this process. These actions have focused on the conservation of germplasm identified in the territory and the recovery of varieties historically present in the region, which were in danger of being abandoned and disappearing.

Context and purpose of the study. Climate change is affecting wine production and induces a large variability in wine composition between vintages.

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.

Botrytis bunch rot occurrence is one of the most important limitations for the wine industry in humid environments. A positive correlation between grapevine growth and susceptibility to fungal pathogens has been found. In theory the effect of grapevine vegetative growth on bunch rot expression results from direct effects (cluster architecture, nitrogen status among others) and indirect ones (via microclimate). However, a reduction in bunch rot incidence can be achieved in some circumstances without major vine growth reduction. The present study was aimed to test the general hypothesis that bunch rot susceptibility is affected by vine vigor, but other factors associated with grapevine vegetative expression could be even more relevant.

Climate change will increase the frequency of water deficit experienced in certain european regions, due to increased evapotranspiration and reduced rainfall during the growing cycle. We therefore need to find ways of adaption, including the use of more drought-tolerant planting material. In addition to the varieties used as grafts and involved in the wine ypicity of our wines, rootstocks selection is a relevant way of adapting to more restrictive environmental conditions.