Sardinia terroir and Cannonau: a zoning approach to discover an ancient tradition

Aims: Microscopic bud dissection is a common tool used to assess grapevine bud fertility and therefore to predict the yield of the following season

Wine is one of the most representative components of Mediterranean diet. Moderate wine intake together with food, has been positively correlated with reduced risk of many chronic diseases. This beneficial effect seems to be ascribed to elevated polyphenolic content of wine [1]. Traditional approaches for the identification of wine biomarkers consumption include targeted metabolomics that focuses on the quantification of well-defined metabolites, losing a valuable information about a massive number of compounds. On the other hand, untargeted metabolomics can disclose a large quantity of signals corresponding to potential biomarkers in a single analysis with high sensitivity and resolution.

Global warming and increased frequency and/or severity of drought events are among the most threatening consequences of climate change for agricultural crops. In response to drought, grapevine (as many other plants) exhibits osmotic adjustment through active accumulation of osmolytes which in turn shift the leaf turgor loss point (TLP) to more negative values, allowing to maintain stomata opened at lower water potentials1. We investigated the capacity of Pinot noir leaves to modulate their osmotic potential as a function of: (i) time (seasonal osmoregulation), (ii) growing temperatures, and (iii) drought events, to enhance comprehension of the resilience of grapevines in drought conditions. We performed trails under semi-controlled field conditions, and in two different greenhouse chambers (20/15 °C vs 25/20 °C day/night). For two consecutive vegetative seasons, grafted potted grapevines (Pinot noir/SO4) were subjected to two different water regimes for at least 30 days: well-watered (WW) and water deficit (WD).

Volatile thiols play a key role in the aromatic expression of white wines, contributing to notes such as passion fruit, grapefruit, and herbal nuances [1]. These compounds, present as non-volatile precursors in grapes, require enzymatic activation to be released and realize their aromatic potential.

Measurement of carbon isotope discrimination in berry juice sugars at maturity (δ13C) provides an integrated assessment of water use efficiency (WUE) during the period of berry ripening, and when collected over multiple seasons can be used as an indication of drought stress response. Berry juice δ13C measurements were carried out on 48 different varieties planted in a common garden experiment in Bordeaux, France from 2014 through 2021 and were paired with midday and predawn leaf water potential measurements on the same vines in a subset of six varieties. The aim was to discriminate a large panel of varieties based on their stomatal behaviour and potentially identify hydraulic traits characterizing drought tolerance by comparing δ13C and hydroscapes (the visualisation of plant stomatal behaviour as a response to predawn water potential). Cluster analysis found that δ13C values are likely affected by the differing phenology of each variety, resulting in berry ripening of different varieties taking place under different stress conditions within the same year. We accounted for these phenological differences and found that cluster analysis based on specific δ13C metrics created a classification of varieties that corresponds well to our current empirical understanding of their relative drought tolerances. In addition, we analysed the water potential regulation of the subset of six varieties (using the hydroscape approach) and found that it was well correlated with some δ13C metrics. Surprisingly, a variety’s water potential regulation (specifically its minimum critical leaf water potential under water deficit) was strongly correlated to δ13C values under well-watered conditions, suggesting that base WUE may have a stronger impact on drought tolerance than WUE under water deficit. These results give strong insights on the innate WUE of a very large panel of varieties and suggest that studies of drought tolerance should include traits expressed under non-limiting conditions.