Flavescence doré e (FD) is a European quarantine grapevine disease transmitted by the Deltocephalinae leafhopper Scaphoideus titanus. Whereas this vector had been introduced from North America, the possible European origin of FD phytoplasma needed to be challenged and correlated with ecological and genetic drivers of FD emergence. For that purpose, a survey of genetic diversity of these phytoplasmas in grapevines, S. titanus, black alders, alder leafhoppers and clematis were conducted in five European countries. Out of 132 map genotypes, only 11 were associated to FD outbreaks, three were detected in clematis, whereas 127 were detected in alder trees, alder leafhoppers or in grapevines out of FD outbreaks. Most of the alder trees were found infected, including 8% with FD genotypes M6, M38 and M50, also present in alders neighboring FD-free vineyards and vineyard-free areas. The Macropsinae Oncopsis alni could transmit genotypes unable to achieve transmission by S. titanus, while the Deltocephalinae Allygus spp. and Orientus ishidae transmitted M38 and M50 that proved to be compatible with S. titanus. Variability of vmpA and vmpB adhesin-like genes clearly discriminated 3 genetic clusters. Cluster Vmp-I grouped genotypes only transmitted by O. alni, while clusters Vmp-II and-III grouped genotypes transmitted by Deltocephalinae leafhoppers. Interestingly, adhesin repeated domains evolved independently in cluster Vmp-I, whereas in clusters Vmp-II and-III showed recent duplications. Latex beads coated with various ratio of VmpA of clusters II and I, showed that cluster

A survey was conducted over several years in Italy and the Balkans in order to gain an understanding of the relationship between the Flavescence dorée (FD) phytoplasma isolates found in clematis and grapevine. A total of 399 clematis and 107 grapevine samples were analyzed. The results showed that 36% of the Clematis vitalba plant samples were infected by phytoplasmas which, in grapevine, are associated with FD, a quarantine disease in Europe. Infected clematis plants were also found in areas where FD phytoplasma had never previously been reported to infect grapevine, such as Macedonia, Croatia and some areas of Italy and Serbia. Molecular data from three phytoplasma genomic fragments showed the presence of different FD phytoplasma isolates, all belonging to the 16SrV-C subgroup, including the Italian FD-C isolate, the isolate found in Serbia, an isolate similar to the French FD2000 and a new isolate typical of central Italy. A few clematis plants were infected with single nucleotide polymorphism, insertion or deletion mutants of the FD-C isolate. Of all the potential Hemipteran vector species surveyed in Italy and Serbia, only 18 of 527 Dictyophara europaea individuals tested proved to be infected with the FD phytoplasma. Preliminary transmission experiments showed that this species is able to transmit the FD phytoplasma from clematis to grapevine. The presence of FD-infected clematis and of D. europaea could, therefore, constitute a risk for FD epidemics in the European viticultural regions.

The present work was carried out in order to verify the possible association between a new grapevine disease, characterized by leaf mottling and deformation, and the genetic variability and concentration of Grapevine Pinot gris virus (GPGV), a recently identified virus tentatively associated with the pathology. After vineyard surveys and the establishment of real-time qPCR assays, characterization of GPGV isolates and evaluation of GPGV titre were assessed in more than 100 samples of grapevine Glera, collected from plants regardless of whether or not they showed the symptomatology. Results showed that there was an important association between the GPGV variants and manifestation of the symptoms, and that grapevines with symptoms harboured significantly higher GPGV titre than symptomless vines. Moreover, an interesting relationship among the phylogenetic clustering of the isolates originating from plants with symptoms and some epidemiological characteristics of the disease was found. The current study confirmed the role of GPGV in the emergent disease characterized by grapevine leaf mottling and deformation.

2CRA -Centro di ricerca per la viticoltura, 26 viale XXVIII Aprile 31015, Conegliano (TV), ItalyIn addition to the grapevine flavescence doré e phytoplasmas, other members of taxonomic group 16SrV phytoplasmas infect grapevines, alders and species of the genera Clematis and Rubus in Europe. In order to investigate which phytoplasmas constitute discrete, species-level taxa, several strains were analysed by comparing their 16S rRNA gene sequences and a set of five housekeeping genes. Whereas 16S rRNA gene sequence similarity values were .97.5 %, the proposed threshold to distinguish two 'Candidatus Phytoplasma' taxa, phylogenetic analysis of the combined sequences of the tuf, rplV-rpsC, rplF-rplR, map and uvrB-degV genetic loci showed that two discrete phylogenetic clusters could be clearly distinguished. The first cluster grouped flavescence doré e (FD) phytoplasmas, alder yellows (AldY) phytoplasmas, Clematis (CL) phytoplasmas and the Palatinate grapevine yellows (PGY) phytoplasmas. The second cluster comprised Rubus stunt (RS) phytoplasmas. In addition to the specificity of the insect vector, the Rubus stunt phytoplasma contained specific sequences in the 16S rRNA gene. Hence, the Rubus stunt phytoplasma 16S rRNA gene was sufficiently differentiated to represent a novel putative taxon: 'Candidatus Phytoplasma rubi'.Phytoplasmas are plant-pathogenic bacteria belonging to the class Mollicutes, a group of cell wall-less microorganisms phylogenetically related to Gram-positive bacteria with a low DNA G+C content (Weisburg et al., 1989). Phytoplasmas are still unavailable in culture. They are responsible for hundreds of crop diseases worldwide (Lee et al., 2000) and are transmitted from plant to plant by sap-sucking hemipteran insects (Weintraub & Beanland, 2006). Flavescence dorée (FD) of grapevine, a quarantine disease first reported in the 1950s in south-western France (Caudwell, 1957) is now present in southern Europe (Batlle et al., 1997;Belli et al., 1985;Boudon-Padieu, 2002;Duduk et al., 2003). The causal agent of FD was shown to be a phytoplasma (Caudwell et al., 1971) that is transmitted by a grapevine leafhopper of north American origin, Scaphoideus titanus (Ball.) (Schvester et al., 1961). The FD phytoplasma belongs to the 16SrV taxonomic group (Lee et al., 1998). Members of this group share high 16S rRNA gene sequence similarity (Davis & Dally, 2001), but the group consists of phytoplasmas with an important variety of biological niches restricted to woody perennial hosts. 'Candidatus P. ulmi' in the 16SrV-A subgroup is responsible for yellows of elm species in North America and Europe (Lee et al., 2004) and 'Candidatus P. ziziphi' in the 16SrV-B subgroup is the agent of jujube witches'-broom and cherry lethal yellows in Asia (Jung et al., 2003;Lee et al., 2004). In Europe, other phytoplasmas in the 16SrV group mainly infect grapevines (Maixner et al., 1994), alder (Lederer & Seemüller, 1991; Mäurer et al., 1993), blackberry (de Fluiter & van der Meer, 1953; Mäurer & Seemüller, 1995), species of the genu...

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