Ultrastructural and chemical analysis of berry skin from two Champagne grapes varieties and in relation to Botrytis cinerea susceptibility

Since the approval in 2019 of the use of high-power ultrasound (US) in winemaking to support extractive processes from grape to must, the study of this technology in red winemaking has increased significantly, with laboratory and semi-industrial scale studies.

The sustainability certification ‘nachhaltig austria’ (www.sustainableaustria.com) has been offered to austrian wineries in an online version for 10 years and over 25% of the austrian wine-growing area is now certified. Since the 2022 harvest, ‘nachhaltig austria’ has automatically calculated the carbon footprint for each winery, per hectare of vineyard, per litre of bulk wine and per 0.75-litre bottle (poelz, w. And rosner, f.g. 2023). In last year’s publications and numerous presentations at national and international level, topics such as refilling glass bottles, lightweight glass bottles, renewable energy, … Etc.

The increasing frequency of heat waves during grape ripening presents challenges for the production of high-quality wine grapes. This underscores the significance of developing effective irrigation and canopy management techniques to optimize both yield and grape quality.
A field experiment was carried out during 2021 and 2022 using Manto negro wine grapes to study the effect of two irrigation strategies and different light exposure levels on grape quality. In a four-block experimental vineyard at Bodega Ribas in Mallorca, two irrigation treatments—moderate and severe deficit irrigation—were implemented. Within each irrigation plot, three light exposure treatments were randomly assigned, encompassing exposed clusters from pea size, non-exposed clusters, and shaded clusters after softening.

A large varietal collection including over 1700 varieties was maintained in Conegliano, ITA, since the 1950s. Phenological data on a subset of 400 grape varieties including wine grapes, table grapes, and raisins were acquired at bud break, flowering, veraison, and ripening since 1964. Despite the efforts in maintaining and acquiring data over such an extensive collection, the data set has varying degrees of missing cases depending on the variety and the year. This is ubiquitous in phenology datasets with significant size and length. In this work, we evaluated four state-of-the-art methods to estimate missing values in this phenological series: k-Nearest Neighbour (kNN), Multivariate Imputation by Chained Equations (mice), MissForest, and Bidirectional Recurrent Imputation for Time Series (BRITS). For each phenological stage, we evaluated the performance of the methods in two ways. 1) On the full dataset, we randomly hold-out 10% of the true values for use as a test set and repeated the process 1000 times (Monte Carlo cross-validation). 2) On a reduced and almost complete subset of varieties, we varied the percentage of missing values from 10% to 70% by random deletion. In all cases, we evaluated the performance on the original values using normalized root mean squared error. For the full dataset we also obtained performance statistics by variety and by year. MissForest provided average errors of 17% (3 days) at budbreak, 14% (4 days) at flowering, 14.5% (7 days) at veraison, and 17% (3 days) at maturity. We completed the imputations of the Conegliano dataset, one of the world’s most extensive and varied phenological time series and a steppingstone for future climate change studies in grapes. The dataset is now ready for further analysis, and a rigorous evaluation of imputation errors is included.

‘Mavrodafni’ (Vitis vinifera L.) is considered one of the oldest grapevine cultivars indigenous to the Greek vineyard, with western Peloponnese being its primary center of cultivation. ‘Renio’ is considered to be either a variant of ‘Mavrodafni’ or an altogether different cultivar. Both ‘Mavrodafni’ and ‘Renio’ can be found in the vineyards of the centers of cultivation, since ‘Renio’ is considered to be more productive compared to ‘Mavrodafni’, and for this reason, it has gradually replaced ‘Mavrodafni’ from cultivation over the course of time. The aim of the present study was to assay the mechanical properties, the polyphenolic content and the antioxidant capacity of skin extracts and must of berries coming from ‘Mavrodafni’ and ‘Renio’, cultivated in the same vineyard as well as in the different regions of cultivation of the PDO Mavrodafni Patras.