Vineyard Landscape in Vale dos Vinhedos: Pressure and Protection

A Syrah/R99 vineyard in the Stellenbosch area was used. The vineyard is vertically trained and spaced 2.75 x 1.5 m in north-south orientated rows on terroir with Glenrosa soil and west-facing slope. Irrigation (to 100% field water capacity) treatments were applied at different development stages [all stages (including berry set stage); pea size; véraison; post-véraison]. Combined effects of water status and ripeness level were investigated. Preliminary results are presented.

Spring freeze events threaten grape production globally. As grape buds emerge from dormancy in spring, freezing temperatures have the potential to damage green tissues, decreasing yield potential and compromising fruit quality by harvest.

This study used climatic and topographic data to characterize the sub-appellations that have been recently delineated in the Niagara Peninsula viticulture area in order to assess their potential for ripening early to late season Vitis vinifera varieties. No major differences were found in the ripening-period mean temperatures, but major differences in the diurnal temperature ranges were observed.

Sulfites (SO2) addition during winemaking is a widespread practice worldwide. This addition is realized at different steps of the winemaking due to the antimicrobial and antioxidant capacity of SO2. In a context of understanding white wines oxidative stability, knowledge about the impact of SO2 on the wine molecular diversity, especially compounds involved in the antioxidant capacity of wine, appears to be very important. In recent years, some studies have shown that SO2 can react with a large number of wine compounds resulting in the formation of numerous adducts. The diversity of compounds involved is important including in particular pyruvic acid, 2-keto-glutaric acid, glyceraldehyde, sugar, phenolics compounds but also amino acids or peptides. Moreover Roullier-Gall et al. have shown using FT-ICR-MS analysis that the molecular composition of wines remains impacted by addition of SO2 to the must (0, 4 and 8 g/hL SO2), several years after winemaking. Indeed, wines made from protected must (8g/hL SO2) contain a larger diversity of CHOS and CHONS compounds than wines made from unprotected must (0 g/hL SO2). The study of the impact of glutathione addition on the sensory oxidative stability has further shown that CHOS and CHONS compounds (amino acids, aromatic compounds and peptides) are markers of the antioxidant metabolome of white wines. This suggests that CHOS and CHONS compounds arise from SO2 adducts formation but also from a protecting effect of SO2 on the antioxidant metabolome of white wines.

This study aims to create an updated, agile viticultural climate index (similar to the Winkler Index) by performing in-depth analyses of current and historical data from industry partners in several major winegrowing regions. The Winkler Index was developed in the early twentieth century based on analysis of various grape-growing regions in California. The index uses heat accumulation (i.e. Growing Degree Days) throughout the growing season to determine which grape varieties are best suited to each region. As viticultural regions are increasingly subject to the complexity and uncertainty of a changing climate, a more rigorous, agile model is needed to aid grape growers in determining which cultivars to plant where. For the first phase of this study, 21 industry partners throughout Napa Valley shared historical phenology, harvest, viticultural practice, and weather data related to their Cabernet sauvignon vineyard blocks. To complement this data, berry samples were collected throughout the 2021 growing season from 50 vineyard blocks located throughout 16 American Viticultural Areas that were then analyzed for basic berry chemistry and phenolics. These blocks have been mapped using a Geographic Information System (GIS), enabling analysis of altitude, vineyard row orientation, slope, and remotely sensed climate data. Sampling sites were also chosen based on their proximity to a weather station. By analyzing historical data from industry partners and data specifically collected for this study, it is possible to identify key parameters for further analysis. Initial results indicate extreme variability at a high spatial resolution not currently accounted for in modern viticultural climate indices and suggest that viticultural practices play a major role. Using the structure of data collection and analyses developed for the first phase, this project will soon be expanded to other wine regions globally, while continuing data collection in Napa Valley.