Levels of trans-resveratrol in leaves of vines affected with “esca”
Abstract: A survey was carried out on esca symptomatic vines, diseased asymptomatic vines andhealthy vines in vineyards previously inspected for more than 15 years. The levels of trans-resveratrolwere determined on leaves with different symptoms severity and on leaves ofasymptomatic vines, and compared with what assessed on leaves from healthy plants, at threedifferent phenological growth stages. Moreover, in the laboratory, leaves collected from healthyvines were immersed in cultural filtrates of Phaeomoniella chlamydospora (Pch) or in sterileliquid growth medium and then in a suspension of trans-resveratrol or distilled water to assessthe possible effects. The levels of trans-resveratrol in symptomatic leaves were particularly highat pre-bunch closure but also at harvest, increasing with the severity of foliar symptoms. Atveraison, a dramatic decrease in trans-resveratrol content was observed and no differences werenoticed among the different leaf groups or subgroups. In the laboratory test trans-resveratrol didnot show any kind of effect on cut leaves previously immersed in Pch filtrates compared to whatwas observed for distilled water. The response of the plant to foliar symptoms as trans-resveratrolproduction varied in different phenological stages probably in relation to specificphysiological conditions occurring at these stages. The correlation between trans-resveratrollevels and severity of symptoms on the leaf surface noticed at pre-bunch closure and at harvestbut not at veraison as well as the lack of effects on cut leaves allowed us to hypothesize thattrans-resveratrol is not involved in the control of foliar symptoms. However, taking into accountthe current hypothesis on the origin of foliar symptoms, trans-resveratrol may be considered asan important factor to better understand the plant response to symptoms expression.