Genetic diversity of phytoplasmas associated with flavescence dorée at vineyard scale on the Ischia Island (Campania, Italy)

Flavescence dorée (FD) is the most important grapevine yellows, constituting a great threat in all major viticultural areas in Europe. The FD causal agent is an incidentally cited phytoplasma species termed ‘Candidatus Phytoplasma vitis’ (FDp), listed as a quarantine organism in Europe and mainly transmitted from vine to vine by the monophagous leafhopper Scaphoideus titanus. In the present study, the genetic variability of FDp identified in symptomatic plants located in a vineyard cv. Biancolella on the Ischia Island (Campania, Italy) was investigated. Our results unveiled for the first time the presence of FDp strains belonging to the subgroup 16SrV–C with a low genetic variability within map and rp genetic markers, reflecting an homogeneous genetic lineage of phytoplasma population examined in the present study. Phylogeny and nucleotide sequence analyses can also suggest the possible involvement of other insect vectors and plant hosts in the FD epidemiology on the Island. Further investigation to ascertain the presence of putative vectors and plant hosts representing inoculum sources should be carried out to reinforce the preliminary results obtained in the present study.