Preliminary results on distribution and diversity of grapevine yellows in Tuscany.

Grapevine yellows (GY) are an important threat to grapevine industry in Europe. In Italy, GY are mostly represented by Flavescence dorée (FD) and Bois noir (BN), respectively associated with infection by 16SrV and 16SrXII phytoplasma ribosomal groups. In the frame of a regional strategy aimed to monitor GY presence, an extensive survey was carried out covering the ten provinces of the Tuscany region, and collecting 585 leaf-samples in the commercial vineyards inspected in summer 2009. Preference was given to samples showing discoloration, downward rolling and symptoms referable to GY diseases. In order to allow tracking of FD positive samples for uprooting, all the plants were marked and localised by “Global Positioning System-GPS”. DNA was extracted and amplified, firstly in a classical nested-PCR reaction and successively with dual-labelled probes specific to FD, BN and grapevine chaperonin gene in a Real-time PCR reaction. Results indicated that BN is largely the most important GY in Tuscany with an ubiquitous distribution; it was present in almost all surveyed vineyard with an overall incidence of 70% (418 out of 585 sample tested). Alarming presence of FD was recorded in 23 samples distributed in 5 provinces including: Arezzo, Massa-Carrara, Florence, Siena and Lucca. Molecular characterization performed with PCR/RFLP analysis on 16S ribosomal and on SecY genes confirmed the presence of either FD-C and FD-D subgroups, this latter is reported for the first time in Tuscany and it is identical to the strain described earlier in France and in Veneto region. On the basis of this results, further investigations on insect vectors, natural reservoirs and molecular characterization of grapevine infecting phytoplasma are needed in order to monitor and understand the epidemiology GY diseases in Tuscany.