New insights on "bois noir" epidemiology in the Chianti Classico area (Tuscany, Central Italy)

Bois noir (BN), a disease of the grapevine yellows complex associated with 'Candidatus Phytoplasma solani' (CaPsol), represents a great threat in wine growing areas worldwide. Several studies revealed that BN epidemiology is complex, including multiple insect vectors and plant hosts. In the present work, a survey on putative CaPsol insect vectors along with molecular typing of CaPsol strains was conducted in a BN-affected vineyard in the Chianti Classico area (Tuscany region). No Hyalesthes obsoletus specimens were captured, while Neoaliturus fenestratus and Reptalus artemisiae were found infected by CaPsol strains. Molecular typing evidenced that R. artemisiae and N. fenestratus were infected by CaPsol strains carrying mainly the stamp sequence variant St10 and St5, respectively. Other insects (Philaenus spumarius, Dictyophara europaea, Psammotettix spp.), were found less frequently infected by CaPsol strains carrying mainly the stamp sequence variant St5. Results obtained in the present study are in accordance with previous evidences reporting the prevalence of R. artemisiae in a vineyard located in the same geographical area and allowed to identify the possible active role of other insect species in the spreading of genetically different 'CaPsol' strains. Further studies are necessary to investigate the role of weeds in CaPsol transmission routes to grapevine, clarify if grapevine could act as reservoir plant for CaPsol acquisition for these putative vectors.