Grapevine is a perennial crop often cultivated by grafting a scion cultivar on a suitable rootstock. Rootstocks influence scions, particularly with regard to water uptake and vigor. Therefore, one of the possibilities to adapt viticulture to the extended drought stress periods is to select rootstocks conferring increased tolerance to drought. However, the molecular mechanisms associated with the ability of rootstock/scion combination to influence grape berry metabolism under drought stress are still poorly understood. The transcriptomic changes induced by drought stress in grape berries (cv. Pinot noir) from vines grafted on either 110R (drought-tolerant) or 125AA (drought-sensitive) rootstock were compared. The experiments were conducted in the vineyard for two years and two grape berry developmental stages (50% and 100% veraison). The genome-wide microarray approach showed that water stress strongly impacts gene expression in the berries, through ontology categories that cover cell wall metabolism, primary and secondary metabolism, signaling, stress, and hormones, and that some of these effects strongly depend on the rootstock genotype. Indeed, under drought stress, berries from vines grafted on 110R displayed a different transcriptional response compared to 125AA-concerning genes related to jasmonate (JA), phenylpropanoid metabolism, and pathogenesis-related proteins. The data also suggest a link between JA and secondary metabolism in water-stressed berries. Overall, genes related to secondary metabolism and JA are more induced and/or less repressed by drought stress in the berries grafted on the drought-sensitive rootstock 125AA. These rootstock-dependent gene expression changes are relevant for berry composition and sensory properties.

No abstract

Background and Aims To successfully use berry sorting in winemaking, it is crucial to understand the interaction of physical and chemical composition of berries. The aim of this study was to investigate the relationship between berry diameter and colour and aspects of wine composition, such as titratable acidity, aroma compounds and phenolic substances of Vitis vinifera L. cv. Riesling. Methods and Results In a first trial, berries were sorted into three berry diameter classes with equal TSS concentration and vinified by 70 mL scale fermentation. In a second trial, berries from each of two diameter classes with equal TSS concentration were sorted by berry colour to obtain samples of low a* value and high a* value berries for the respective diameter class, and vinified. In the first trial, wines from smaller berries had lower titratable acidity and a lower concentration of malic acid. In the second trial, wine obtained from berries with higher a* values showed a higher concentration of free C13‐norisoprenoids as well as free and glycosylated monoterpenes. Wines from smaller berries in this trial showed a higher concentration of norisoprenoids and a lower pH. Conclusions Berry diameter and colour are highly variable within single vineyards, vines and single bunches. Sorting by berry size or colour will lead to wines with a pronounced difference in aroma compounds, acidity and α‐amino nitrogen. Significance of the Study This study shows the relationship between berry diameter or colour and wine quality aspects such as acidity and aroma. Understanding this relationship will assist winemakers to conduct targeted berry sorting.

No abstract

Aims: A better understanding of the relationship between weather conditions and wine quality would provide tools for assessing the impact of climate change and the potential for adaptation. Most studies rely on assessing wine quality by the price per bottle or by an overall ranking and then establishing general relations to weather conditions. However, such an approach may imply the addition of bias by variable winemaking techniques overcoming vintage effects. The aim of our study was therefore to implement a controlled conditions approach using grape samples from a single vineyard and a standardized micro-scale winemaking technique to produce wines in similar conditions for each vintage over more than a decade. We hope that this data will allow new insights into responses to climatic differences.Methods and results: From 2005 to 2015, data was collected from a vineyard of Hochschule Geisenheim University planted with Vitis vinifera L. cv. Pinot Noir grafted on rootstock SO4 in four field replicates. Weather conditions were recorded together with the major phenological stages, yield, infection of the bunches by Botrytis cinerea bunch rot, and pruning weight. Key primary juice compounds were analyzed and berry phenolics in skins and seeds were determined before harvest. Micro-scale winemaking was developed to produce wines in standardized conditions. The repeatability of the method to assess the extraction of anthocyanins and tannins was shown to be 2–10% and 8–12%, respectively, depending on grape maturity stage. Sugar accumulation was coupled to warmer conditions during the maturation period, and high temperatures after véraison decreased the concentration of malic acid in the juice. The accumulation of primary amino acids (N-OPA) in the juices seemed positively related to warmer conditions between bud break and flowering. Increased temperature, especially before véraison, accompanied by a lack of precipitation was related to an accumulation of tannins in fruit and wine, with a higher accumulation in skins than seeds. The temperature-sensitive anthocyanin accumulation in grapes was coupled to warmer conditions after véraison. These differences in anthocyanin concentration could also be observed in the wine.Conclusions: High-quality vintages were linked to warmer than normal growing seasons and below normal precipitation.Significance and impact of the study: The use of a micro-scale winemaking technique represents an innovative tool to provide detailed information in a controlled and reproducible way. A better understanding of the interaction between weather conditions and berry/wine compounds will help with developing improved winemaking techniques and better adapting to future impacts of climate change.