The effects of grapevine trunk diseases (GTDs) on vine physiology

Abstract

Esca disease as well as Botryosphaeria and Eutypa dieback cause considerable economic problems for vineyards worldwide, and currently, no efficient treatment is available to control these diseases. For these three grapevine trunk diseases (GTDs), the main physiological effects reported concern carbohydrate metabolism and defence responses in the different organs of vine. In the trunk, a depletion of starch reserves in woody tissues is associated with fungal colonization; in the leaves, where pathogens are not present, the carbohydrate metabolism is also affected as revealed by a decline of the photosynthetic rate. A consequence of these disturbances is a lower pool of carbon reserves that might contribute to a decrease of plant development and vigour during the subsequent year. Other metabolic activities such as lipid and amino acid metabolism are down regulated. The perturbation of these primary metabolisms is often associated with the induction of defence responses. The development of biochemical barriers resulting from the accumulation of both tyloses and gummosis is observed during the infection of the wood causing blockage of the xylem vessels and thus limiting the fungal invasion. Their progression in the wood is also inhibited by the formation of polyphenol-rich reaction zones and by the accumulation of pathogenesis-related proteins, and the oxidative burst and the production of reactive oxygen species. Additionally, detoxification processes of the vine are involved; this reaction could be linked to the production of extracellular compounds by GTD agents some of which are phytotoxic. As a consequence, the sensory quality of berries and probably the wine made from these berries decrease. This review presents an overview of the physiological modifications described in vines affected by GTDs.