From soil to canopy, the diversity of adaptation strategies  to abiotic constraints in grapevine

The addition of partially dehydrated grapes to enrich must composition for producing complex dry/sweet wines represents a traditional practice in several regions of the world. However, the environmental conditions of dehydration chambers may facilitate the infection of Botrytis cinerea Pers. by promoting disease and provoking large grape losses. B. cinerea attack can induce alterations in the profile of volatile organic compounds (VOCs), which could be detected by sensors specifically trained to detect infection/disease-related compounds. These sensors could facilitate the early detection of the infection, consequently allowing to adjust some dehydration parameters.

Wine is at risk of being labelled as a dangerous health product, based on studies that focus on its alcohol content. However, multiple studies suggest that moderate consumption is healthy. Changing the focus from health impacts to the environmental and socioeconomic impacts that wine companies cause, what can be said?

According to the World Economic Forum and the European Union’s Biodiversity Strategy for 2030, the loss of biodiversity and the collapse of ecosystems are major threats facing humanity in the future.

Acacia senegal gum (Asen) is an edible dried gummy exudate [1] added in young red wines to ensure their colloidal stability, precluding the precipitation of the coloring matter. Asen macromolecules, belonging to the arabinogalactan-protein (AGP) family [2], are hyperbranched, charged and amphiphilic heteropolysaccharides composed especially of sugars (92-96 %) and a small fraction of proteins (1-3 %). Asen is defined as a continuum of macromolecules that could be separated into three fractions by hydrophobic interaction chromatography (HIC) [3-4]. HIC-F1 (85-94 % of Asen), HIC-F2 (6-18 % of Asen) and HIC-F3 (1-3 % of Asen) are named and classified in that order according to their protein content, and then a growing hydrophobicity. The efficiency of Asen towards the coloring matter instability is evaluated according to an “efficacy test” that consists to determine the Asen quantity required to prevent the flocculation by calcium of a colloidal iron hexacyanoferrate solution (International Oenological Codex).

As an essential element for grapevine development and yield, nitrogen is also involved in the winemaking process and largely affects wine composition. Grape must amino nitrogen deficiency affects the alcoholic fermentation kinetics and alters the development of wine aroma precursors. It is therefore essential to control and optimize nitrogen use efficiency by the plant to guarantee suitable grape nitrogen composition at harvest. Understanding the impact of environmental conditions and cultural practices on the plant nitrogen metabolism would allow us to better orientate our technical choices with the objective of quality and sustainability (less inputs, higher efficiency). This trial focuses on the impact of crop limitation – that is a common practice in European viticulture – on nitrogen distribution in the plant and particularly on grape nitrogen composition. A wide gradient of crop load was set up in a homogeneous plot of Chasselas (Vitis vinifera) in the experimental vineyard of Agroscope, Switzerland. Dry weight and nitrogen dynamics were monitored in the roots, trunk, canopy and grapes, during two consecutive years, using a 15N-labeling method. Grape amino nitrogen content was assessed in both years, at veraison and at harvest. The close relationship between fruits and roots in the maintenance of plant nitrogen balance was highlighted. Interestingly, grape nitrogen concentration remained unchanged regardless of crop load to the detriment of the growth and nitrogen content of the roots. Meanwhile, the size and the nitrogen concentration of the canopy were not affected. Leaf gas exchange rates were reduced in response to lower yield conditions, reducing carbon and nitrogen assimilation and increasing intrinsic water use efficiency. The must amino nitrogen profiles could be discriminated as a function of crop load. These findings demonstrate the impact of plant balance on grape nitrogen composition and contribute to the improvement of predictive models and sustainable cultural practices in perennial crops.