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Author summary Since the first outbreaks, Flavescence doree epidemics had been associated to the introduction of the North American leafhopper vector Scaphoideus titanus. We hereby show that the associated phytoplasma originated from European alders and that epidemics in grapevine are restricted to some phytoplasma genetic variants pre-existing in this wild asymptomatic plant host. The compatibility of this phytoplasma to the introduced S. titanus insect vector resulted from the adaptation of phytoplasma variable membrane proteins Vmps to leafhoppers of the same subfamily living on alders. Vmps organization is similar to adhesion related proteins (ARP) and seems to allow the duplication of pre-adapted repeated domains. This suggests a key role of the Vmp adhesins in the life-style of phytoplasmas infecting woody hosts that rely on the adaptation to new insect vectors to expand their plant-host range. Flavescence doree (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

A survey of genetic diversity of “flavescence dorée” (FD)-related phytoplasmas in grapevines, alders and clematis as well as alder-feeding leafhoppers was conducted in France, Hungary, Germany, Italy and Serbia. Genotyping was based on the housekeeping gene map and on the vmp genes encoding surface variable membrane proteins. Transmission assays of the phytoplasmas were performed with alder and/or grapevine-feeding leafhoppers. The study demonstrated that European alders constitute an original reservoir of FD phytoplasma by hosting a high diversity of FD-related phytoplasma genotypes, also present in non viticultural areas. The alder phytoplasmas grouping in Vmp-I cluster were transmitted by the Macropsinae O. alni, but were not compatible with the FD phytoplasma vector on grapevine the Deltocephalinae Scaphoideus titanus. The alder phytoplasmas in Vmp-II and -III clusters were transmitted by the Deltocephalinae Allygus spp. and Orientus ishidae. Such pre-existing phytoplasmas were compatible with S. titanus transmissibility and can be responsible for the emergence of FD phytoplasma epidemics in grapevine. VmpA proteins of cluster II better adhered to Euscelidius variegatus and S. titanus insect cells and midguts than those of cluster I. Such adhesins might play a key role in the adaptation to new vectors

During 2010, several maize production areas in Hungary were surveyed for the occurrence of maize redness (MR) disease symptoms associated with stolbur phytoplasma, as well as for the presence of the known vector of the disease, a planthopper Reptalus panzeri (Low). Incidence of maize plants with symptoms of reddening was low in all surveyed areas. Altogether, 25 symptomatic maize plants were collected at 9 localities and tested for phytoplasma presence. In addition, from one locality specimens of cixiids R. panzeri and Hyalesthes obsoletus Signoret were collected and PCR analyzed. Presence of stolbur phytoplasma in MR symptomatic maize plants and stolbur-infected R. panzeri was identified at the single locality Monorierdo in central Hungary. This finding represents the first report of MR presence in Hungary.

During 2010, several maize production areas in Hungary were surveyed for the occurrence of maize redness (MR) disease symptoms associated with stolbur phytoplasma, as well as for the presence of the known vector of the disease, a planthopper Reptalus panzeri (Low). Incidence of maize plants with symptoms of reddening was low in all surveyed areas. Altogether, 25 symptomatic maize plants were collected at 9 localities and tested for phytoplasma presence. In addition, from one locality specimens of cixiids R. panzeri and Hyalesthes obsoletus Signoret were collected and PCR analyzed. Presence of stolbur phytoplasma in MR symptomatic maize plants and stolbur-infected R. panzeri was identified at the single locality Monorierdo in central Hungary. This finding represents the first report of MR presence in Hungary.

In August 2010 potato plants expressing symptoms of phytoplasma infection were collected from three localities in Vojvodina province of Serbia and analyzed for phytoplasma presence. Phytoplasma detection was performed by PCR/RFLP analyzes of 16S rRNA gene and by stolbur-specific PCR amplification with Stol11 primers. Stolbur phytoplasma was detected in all symptomatic potato plants analyzed. This is the first report of molecular detection of stolbur phytoplasma infecting potato in Serbia.

In August 2010 potato plants expressing symptoms of phytoplasma infection were collected from three localities in Vojvodina province of Serbia and analyzed for phytoplasma presence. Phytoplasma detection was performed by PCR/RFLP analyzes of 16S rRNA gene and by stolbur-specific PCR amplification with Stol11 primers. Stolbur phytoplasma was detected in all symptomatic potato plants analyzed. This is the first report of molecular detection of stolbur phytoplasma infecting potato in Serbia.