Investigations on 'Candidatus Phytoplasma Solani' in Western Sicily, Southern Italy

‘Candidatus Phytoplasma solani’, belonging to the 16SrXII-A subgroup, is associated with grapevine Bois Noir (BN). It is usually transmitted by Hyalesthes obsoletus from a wide range of weeds to grapevine, which is considered a dead-end host. Moreover, other alternative vectors can play a role in the epidemiology of the disease. In Sicily, the presence of BN was reported in 1996, both on typical and on newly introduced cultivars. Furthermore, high BN incidence was observed on native grape cultivars grown close to ‘Chardonnay’ vineyards. In summer 2014 and 2015, the spread and the severity of BN were recorded in a 10 year-old vineyard located in San Giuseppe Jato (PA, Western Sicily), grown with cultivars Chardonnay, Nero d'Avola, and Pinot Noir. Preliminary surveys showed the presence of a rich leafhopper fauna and the absence of H. obsoletus. The presence of ‘Ca. P. solani’ in randomly sampled vines from all cultivars was confirmed by amplifying DNA through nested-PCR and RFLP, and no other phytoplasma were found. The percentage of symptomatic grapevines was the lowest in cv Pinot Noir and the highest in cv Chardonnay. Ca. P. solani’ was also detected in some herbaceous plants and in leafhoppers collected inside the rows and at the border of the vineyard. Considering the importance of the disease and the recent finding of Euscelidius variegatus, Neoaliturus fenestratus, and Exitianus taeniaticeps as alternative vectors in vineyards of Eastern Sicily, there is the need to clarify the epidemiology of BN in Western Sicily vineyards to set up appropriate management strategies.