Insights on insect vector-plant-phytoplasma interactions: the Flavescence dorée of grapevine

Background. Flavescence dorée of grapevine (FD) is a phytoplasma-associated disease transmitted by the leafhopper Scaphoideus titanus. The disease spreads through primary infections (from gone-wild vines surrounding the vineyard to cultivated grapevines) and secondary infections (from vine to vine within the vineyard). To start looking for disease resistance in grapevine, FDp transmission experiments to the main Piedmontese cultivars were carried out with the vector S. titanus. Susceptibility was estimated by measuring the proportion of infected plants and the phytoplasma load, as estimated by qPCR. PhD research project. The research will address the possibility that susceptibility/tolerance would possibly be related to the vector fitness/feeding behaviour on the different grapevine genotypes and/or to the plant genetic characteristics. For this, Electric Penetration Graph (EPG) studies will be conducted on the most susceptible and tolerant cultivars, and vector fitness will be described by measuring S. titanus adult longevity and female prolificacy on the same cultivars. Moreover, the possibility of manipulating vector-FDp interactions using RNA interference will be investigated. For this purpose, dsRNA complementary to insect genes presumably involved in phytoplasma transmission will be produced and delivered to the leafhoppers by injection and feeding. Gene silencing and its effect on vector transmission ability will be evaluated. The expected results, together with the ones obtained by plant physiologists on the identification of grapevine genetic traits possibly involved in resistance, will greatly enhance the comprehension of the epidemiology of FD and open new control perspectives.