Same disease, different response: the case of Flavescence dorée phytoplasma and diverse grapevine cultivars

Flavescence dorée of grapevine (FD) is a phytoplasma-associated disease present in several European countries and transmitted by the nearctic leafhopper Scaphoideus titanus among plants of the genus Vitis. FD causes severe losses to viticulture and spreads through primary infections (from gone-wild vines surrounding the vineyard to cultivated grapevines) and secondary infections (from vine to vine within the vineyard). FD transmission experiments to the main Piedmontese grapevine cultivars (cvs) were carried out with the vector S. titanus, in order to screen for different levels of cv susceptibility to the phytoplasma. Transmission experiments were done both using ex-vitro micropropagated grapevine plants under greenhouse conditions and on grafted cuttings under semi-field conditions. Susceptibility was estimated by measuring, for each cv, the proportion of infected plants and the phytoplasma load, as estimated by qPCR. The research is further developing by investigating the mechanisms underlying susceptibility/tolerance, that are possibly related to the vector fitness/feeding behaviour on the different grapevine genotypes and/or to the plant genetic characteristics.