Susceptibility to esca of various grapevine (Vitis vinifera) cultivars grafted on different rootstocks in a vineyard in the province of Siena (Italy).

One vineyard at Castelnuovo Berardenga in the province of Siena (Italy) was surveyed from 1995 to 1999 to determine the incidence of esca. The vineyard had been established in 1982 using various cultivars (17) and rootstocks (6). In July and September of each year 19 columns, comprising 44% of the total number of vines, were inspected for esca, and symptom severity of diseased vines was recorded. At the end of the survey period, maps showing the cumulative incidence of esca were drawn and the incidence for each cultivar and for each cultivar/ rootstock combination was calculated. Data expressed on a binomial scale were analysed with the c2 goodness of fit test. Esca incidence differed significantly among cultivars (P<0.001). The statistical analysis showed that the 17 vine cultivars fell into 4 groups with varying susceptibility to esca. The most susceptible cultivar was Semillon, the least susceptible Roussanne. A possible indirect role of the rootstock in determining cultivar susceptibility to esca also emerged from the surveys.