Phytoalexyns dinamic in GLSD affected grapevines (Esca Complex)

Grapevine leaf stripe disease (GLSD), a disease of grapevine within the esca complex, is the cause of reduction in the production and longevity of vineyards. The relationship between the development of the leaves symptoms - a typical interveinal necrosis with a yellow or red margin - and the production and accumulation of phytoalexins like stilbenic substances was investigated. We extracted and identified in the leaves of grapevines affected by GLSD: resveratrol, pterostilbenes, ?, ?, and ?-viniferin. The leaf content of such detected substances was evaluated during different phenological stages. In most of the cases all phytoalexins showed a higher level in symptomatic leaves compared to the asymptomatic leaves of infected or apparently healthy vines. Resveratrol showed to be the stilbene with a higher concentration, reaching the highest values in pre-bunch closure, often with high values also of pterostilbenes and/or ?-viniferin. In all types of leaves a decrease in the level of the different substances at colour change and in the first stages of ripening was recorded, together with a general increase at harvest time. In the whole, the formation of phytoalexins showed to be strictly related with the phenological phases, but also to be different in the symptomatic and the asymptomatic leaves. The development of the leaf symptoms during the growth season in relation with the phytoalexins concentration and the different phenological stages is discussed.