Does salicylic acid alleviate the impacts on growth, development and productivity of “flavescence dorée” in Portuguese “Vinhos Verdes” grapevines?

“Flavescence dorée” (FD) is a quarantine disease of great concern to the stability and sustainability of the wine industry, due to drastic harvest losses and death of infected plants. Previous studies have suggested that salicylic acid (SA) may improve the plant resistance against grapevine diseases, but no studies have been carried out for FD. The effect of 25 mM SA applied at the flowering stage to healthy and FD infected grapevines cultivar Loureiro was evaluated in a field trial. The evaluation of development and productivity (percentage of budburst, fertility index, time to veraison, and chlorophyll content) and grape quality parameters (degree Brix and titrable acidity) was carried out. Fertility index and chlorophyll content were significantly lower in infected plants and SA partly reduced the FD symptoms, since at veraison these plants did not show significant differences when compared to healthy plants for those parameters. However the productivity was significantly lower in the infected plants, with no significant effect of SA application. The berry quality was no significantly different comparing healthy and infected plants or SA-treated and untreated plants.