ED Sciences de la Vie et de la Santé
Crossed approaches of oenology and experimental economics concerning the evaluation of products (grapes, wines) from low phytosanitary input vineyard systems
by Marie-Amélie ALAYRAC (Oenologie)
The defense will take place at 9h30 - Amphithéâtre Institut des Sciences de la Vigne et du Vin 210 chemin de Leysotte 33140 Villenave d'orion
in front of the jury composed of
- Philippe DARRIET - Professeur des universités - Université de Bordeaux - Directeur de these
- Cécile COULON-LEROY - Maîtresse de conférences - ESA Angers - Rapporteur
- Foued CHERIET - Professeur - Institut Agro Montpellier - Rapporteur
- Marie BLACKFORD - Chargée de recherche - Agroscope Changins - Examinateur
- Eric GIRAUD-HERAUD - Directeur de recherche - INRAE - Examinateur
- Yann RAINEAU - Ingénieur de recherche - INRAE - CoDirecteur de these
This PhD thesis is set within the context of the agroecological transition of viticulture and the need to reduce the use of plant protection products while maintaining wine quality and typicity. It primarily draws upon oenology and experimental economics to evaluate different strategies aimed at adapting vineyards to current sanitary and environmental challenges. The first part of the thesis focuses on the analysis of oenological impacts associated with the development of grapevine fungal diseases, namely downy mildew and black rot. Experimental vinifications incorporating increasing proportions of disease-affected grapes were carried out to produce wines that were subsequently subjected to sensory evaluation and to the identification of chemical markers reflecting the presence and severity of these fungal alterations. Analyses were performed using gas chromatography–mass spectrometry and ion chromatography, techniques that can be readily implemented in oenological laboratories. The second part concerns the characterization of grapes and wines obtained from breeding progenies resulting from crosses between Bordeaux grape varieties, Cabernet Franc and Petit Verdot, and resistant parental lines carrying resistance genes against downy mildew and powdery mildew. These genotypes were evaluated over several vintages through the study of their agronomic performance, phenological behaviour, and oenological potential. The resulting grapes and wines were subjected to physicochemical analyses and sensory evaluations conducted by expert panels in order to identify the most promising genotypes for the production of wines exhibiting characteristics compatible with the typicity of Bordeaux red and white wines. Finally, the third part investigates consumer perceptions of varietal innovation strategies aimed at reducing pesticide use in viticulture. Two experimental economics protocols combining wine tasting and incentive-compatible preference elicitation mechanisms were conducted with 267 regular Bordeaux wine consumers. The first experiment demonstrates that varietal innovation does not, in itself, constitute a barrier to consumer acceptance of wines. It also shows that information relating to the reduction of plant protection product use increases the economic valuation of wines, whereas the sole argument of varietal tradition does not. The second experiment explores the consequences of a reduction in the availability of conventional wines and reveals consumers' attachment to product diversity. The results further indicate that reducing product availability may constitute an original tool for eliciting consumer preferences and provide new insights into the observed discrepancies between willingness to pay and willingness to accept. Taken together, these studies aim to improve our understanding of the oenological, sensory, and economic consequences of strategies designed to reduce phytosanitary inputs, while supporting the development of innovative solutions that reconcile environmental sustainability, preservation of wine typicity, and consumer acceptance.