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Alteration of Photosynthesis in Grapevines Affected by Esca

First, second, fourth, and fifth authors: Laboratoire de Stress, Défenses et Reproduction des Plantes, URVVC UPRES EA 2069, Université de Reims Champagne-Ardenne, UFR Sciences, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2, France; and third author: Moët et Chandon Company, 6 rue Croix de Bussy, 51200 Epernay, France

To further understand the development of esca disease in grapevine, its physiological impact on plants grown in the vineyard was characterized, focusing mainly on photosynthesis. For this purpose, the state of the photosynthetic apparatus was evaluated in symptomatic and asymptomatic leaves in esca-infected grape plants, and wood carbohydrates stored in annual canes were assayed. In symptomatic leaves, esca greatly affected grapevine physiology. Foliar symptoms were associated with both stomatal closure and alteration of the photosynthetic apparatus as revealed by (i) a decrease in CO₂ assimilation, transpiration, and a significant increase in intercellular CO₂ concentration; (ii) a strong drop in both the maximum fluorescence yield and the effective Photosystem II quantum yield; and (iii) a reduction of total chlorophyll but a stable carotenoid content. On symptomatic canes, all these variables were affected more on leaves with symptoms than without symptoms, suggesting a gradation in photosynthesis disruptions in the plant according to the degree of symptom severity. In addition, canes of symptomatic plants had reduced carbohydrate reserves during the winter rest, whether they exhibit symptoms or not. The following year, the lower pool of reserves may contribute to a significant decrease in plant development, as well as a global loss in plant vigor.

Additional keywords: Vitis vinifera .