ED Sciences de la Vie et de la Santé
Assessement of the impact of vine dieback diseases on yield, berry composition, and the sensory profile of wines. The case of esca and grapevine fanleaf
by Coralie DEWASME (Ecophysiologie et Génomique Fonctionnelle de la Vigne)
The defense will take place at 9h00 - Amphithéâtre ISVV ISVV, 210 chemin de Leysotte, 33882 Villenave d'Ornon
in front of the jury composed of
- Grégory GAMBETTA - Professeur - Bordeaux Sciences Agro - Directeur de these
- Florence FONTAINE - Professeure - Université de Reims Champagne-Ardenne - Rapporteur
- Jean-Sébastien REYNARD - Chargé de recherche - Agroscope - Rapporteur
- Cécile COULON-LEROY - Maîtresse de conférences - Ecole Supérieure des Agricultures (ESA) - Examinateur
- Martin TEICHMANN - Professeur - Inserm - Examinateur
- Jörg SCHAFER - Professeur des universités - Université de Bordeaux - Examinateur
Wine production involves finding the optimal balance between yield and grape quality depending on the final product. Achieving these objectives is influenced, in particular, by a range of abiotic and biotic factors. Abiotic factors have been extensively studied and, among the biotic factors, much work has focused on pests that do not attack the perennial parts of the vine, such as downy mildew or powdery mildew. However, data on the harmful effects of dieback diseases, including yield losses, changes in berry composition, and wine profiles, are more scarce. Among the various dieback diseases, the work carried out in this thesis focuses on esca and fanleaf based on data collected in the Bordeaux region at different scales, ranging from the vine, to the parcel, and to the appellation (a small area of a few thousand hectares). The work has led to methodological improvements and wealth of quantitative data for studying the impact of these two diseases. Our work has shown that the prevalence of grapevine fanleaf virus was underestimated in the region. According to our study, at least 83 % of parcels have at least one infected vine, regardless of age or grape variety. Yield losses in vines affected by esca and those infected with grapevine fanleaf virus were measured over a period of five to seven years. Depending on the disease and the history or appearance of the symptoms, these yield losses range from 28 % to 97 % compared to healthy vines. In addition, the quality potential of the berries was assessed and the results reveal slight differences between healthy vines and those affected by esca or grapevine fanleaf virus. However, the study of a broad panel of wines highlighted differences in the evolution of the sensory profiles of those from vines affected by esca during aging. The negative impact of esca on wines is slight or absent in young wines, but increases with storage time. During aging, wines made from grapes from vines that showed symptoms of esca in the year of harvest show a more rapid evolution in color, as well as a decrease in fruitiness, complexity, tannic intensity and quality of tannins. Finally, our study showed the difficulty of exclusively linking the mortality observed in the vineyard to any of the diseases studied. In order to address this issue, close monitoring of the various diseases on the same parcels over a long period of five to ten years could help determine the cause of mortality. The methodologies used in this thesis could be applied to other grape varieties in other French regions in order to obtain a more representative view of the impact of these diseases on a national scale or even other viral infections. The results obtained already make it possible to improve the recommendations made to vinegrowers in terms of both vine management, grape selection, and their final destination. More broadly, the results obtained could serve as a basis for a technical and economic study of the levers for managing these dieback processes.