Results from the ‘Epidemiological studies on reservoir hosts and potential vectors of grapevine flavescence dorée and validation of different diagnostic procedures” Project

Grapevine “flavescence dorée” (FD) is a severe grapevine disease of high economic impact for vine growers, nurseries and provincial governments in all European grape growing areas and the associated organism is of quarantine concern in Europe (directive 2000/29 EC). Genetic analysis of FD genome with different molecular markers revealed a population variability and the presence of different FD strains in the 16S rDNA, belonging to subgroups 16SrV-C and 16SrV-D (Martini et al.,1999; Arnaud et al., 2007). The main hosts for this phytoplasma are Vitis vinifera and V. riparia and the known vector is the leafhopper Scaphoideus titanus Ball. However, interest has been focused on several wild species, found infected by FD e.g. Clematis vitalba, Alnus glutinosa (Malembic-Maher et al., 2009), Ailanthus altissima (Filippin et al., 2010) and on some other leafhoppers able to harbor FD phytoplasma e.g. Dictyophara europaea (Filippin et al., 2009) and Orienthus ishidae (Gaffuri et al., 2011; Mehle et al., 2011). The laboratory detection of FD phytoplasma is difficult mainly due to its irregular distribution in the plant tissues, low phytoplasma titer in latently infected plants, seasonal variability in phytoplasma concentration and the presence of other phytoplasmas inducing similar symptoms. The EUPHRESCO GRAFDEPI Project was aimed: i) to increase the knowledge about FD disease epidemiology, with special focus on the role of reservoir hosts of the phytoplasma alternative to grapevine and on presence of other potential insect vectors beside the reported S. titanus; ii) to harmonize the phytoplasma detection protocols within the EU by performing inter-laboratory comparison of the most common diagnostic procedures to verify their reliability towards validation parameters; iii) to provide elements for the development of a more efficient control of the disease.