Possibilità di controllo del mal dell'esca della vite

Esca is a disease affecting woody tissues, where it causes changes in the morphology and in the lymph transport. It is a disease known for several decades, but in recent years has become increasingly important in the vineyard plant disease management. It is manifested by a series of symptoms, associated with a general decline of the plant, that are: leaf deformation and chlorosis, tiger-striped leaves, failure force and vegetation wilting. These symptoms, as regards the manifestation of the chronic form, are attributable to a complex of disorders that may overlap themselves during the life of the plant. That disorders are: dark streaks of young grapevines, Petri disease, white rot, young esca and proper esca. This high variability in symptoms' expression is due to the fact that there are more fungal species involved in the pathogenesis. The main ones are: Phaeoacremonium aleophilum, Phaeomoniella chlamydospora and Fomitiporia mediterranea. In addition to these species, in the wood of the plant there are many other fungi that can interact with the pathogens by substrate competition arrangements. One of these genera is the Trichoderma to which has been attributed the skill to limit the growth of fungi responsible for grape trunk disease. Physiological changes are localized in the xylem where the infection process of the fungus occurs. The mycelium, colonizing the vascular tissue, induces the plant to occlude the xylem vessels to reduce the spread of the pathogen. The series of these occlusions can get to the stop of the flow of lymph from the roots to the leaves, causing the typical leaf necrosis which extend progressively between the main veins. The reaction of plants to this disease is manifested by the production of defense substances such as resveratrol and viniferine (phytoalexins) that have the target of counteracting the development of the fungus even though some species are tolerant to these compounds. The biosynthesis of these stilbenoids occurs after the production, by the plant, of ROS (Reactive Oxygen Species) which are for example: H2O2, O2- and OH-. The other changes that occur, affect the berry, whose phenolic composition is altered more in the skins rather than in the seeds. In particular, there is a different concentration of catechins and epicatechins between healthy berries and sick berries. The anthocyanin content was significantly reduced in the grapes off symptomatic vines. However, the most significant differences are present in the sugar content (which is considerably reduced) and in total acidity (which increases). These remarks are compatible with a failure of the achievement of technological ripeness related to the decrease of the photosynthetic activity. The lower fruity perception, compared with an higher perception of reduced, vegetable and phenolic sensations afterwards the sensorial analysis, is the evidence of the influence of the disease on the final product.