ED Sciences de la Vie et de la Santé
Exploring varietal diversity as a tool for adapting wine production to climate change, using an ecophysiological, chemical and sensorial approach. Application to the Bordeaux area.
by Marc PLANTEVIN (Ecophysiologie et Génomique Fonctionnelle de la Vigne)
The defense will take place at 9h30 - Amphithéâtre Institut des Sciences de la Vigne et du Vin, 210 Chemin de Leysotte 33140 Villenave d'Ornon
in front of the jury composed of
- Cornelis VAN LEEUWEN - Professeur - Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine - Directeur de these
- Susan BASTIAN - Associate Professor - University of Adelaide - Examinateur
- Marielle ADRIAN - Professeure - Institut Universitaire de la Vigne et du Vin - Rapporteur
- Markus RIENTH - Professeur - Université de Changins - Rapporteur
- Jordi BALLESTER - Maître de conférences - Institut Universitaire de la Vigne et du Vin Jules Guyot - Examinateur
The aim of the PhD is to study the physiological behaviour of a wide range of Vitis vinifera grapevines varieties as well as the typicity of their wines produced in the context of a changing climate in the Bordeaux vineyards. To study those questions, data were mostly collected in an experimental common garden in château La Tour Carnet, belonging to the “Vignobles Bernard Magrez” and planted in the heart of the Bordeaux vineyards. Some data were also sourced from the VitAdapt experiment plot, planted next to the research center “Institut des Sciences de la Vigne et du Vin”. This PhD includes two main parts. The first part is related to physiological assessment of the adaptation potential of the varieties. Phenology dates of 69 varieties from the La Tour Carnet plot were collected over two vintages to classify the varieties on a range from earlier phenology to later phenology. Among those 69 varieties, 25 were selected to study their yield components over one to two vintages. Responses to water deficits were studied for 48 different varieties with δ13C and water potential measurements over multiple vintages taken from the VitAdapt plot. This allowed to characterise the varietal effect on the water use efficiency (WUE). WUE in non-limiting conditions (when considered with phenology) was found to be a potential tool to asses resilience to water deficit for these varieties. Hydroscapes (which where correlated with some of the δ13C metrics) were also drawn using water potential measurements on a subset of 6 varieties for defining the strategies of those varieties in their iso/anisohydricity behavior. Finally, a large study covering 51 varieties over multiple vintages aimed to analyse the varietal effect on the acidic components from veraison to harvest. Varietal differences in malic acid degradation and tartaric acid modulation were characterized. pH was found to be differently impacted by tartaric acid, malic acid and inorganic cations over the course of the ripening period with a strong varietal effect. It helped in identifying varieties that tend to keep a low pH despite a higher malic acid degradation rate or despite increased uptake of K+. The second part of the PhD studied the volatile composition and the sensory profiles of the wines produced from a subset of 25 red varieties. The wines were made in vintages 2018 to 2022, from the experimental vineyard of La Tour Carnet, in similar winemaking conditions. A first analyses questioned the varietal effect on the volatile composition of the wines. By quantifying 52 known volatile compounds on all the wines, a precise assessment of the varietal effect on those compounds was performed, excluding potential vintage/evolution biases. Similarities among varieties were shown by means of a hierarchical clustering analyses (HCA). This HCA also revealed that classical Bordeaux varieties tend to produce wines with some similarities in their volatile composition. All the wines went through sensory analyses with a large panel of wine professionals. By rating their typicity, a classification of the varieties based on the typicity of the wines they produce was made. Classical Bordeaux varieties were found to produce highly typical wines but other varieties not from Bordeaux were also producing very typical wines. Then a Check-All-That-Apply (CATA) was made by the judges to characterize the sensory profiles of the wines. Through statistical treatments, the boundaries of the sensorial space of the Bordeaux typicity were established. Finally, an HCA was made to assess similarities in sensory profiles from the 25 varieties that allowed to identify 5 non-Bordeaux varieties of interest for their potential introduction in the Bordeaux vineyards. Two last sensory analyses were made to assess the impact of those 5 non-Bordeaux varieties in a classical blend that showed that the typicity of the blend was barely impacted, even when new varieties account for 30% in the final blend of the wine.