Grapevine Flavescence dorée: still a threat to European viticulture

Flavescence dorée (FD) is one of the most important quarantine diseases of grapevine. It is associated with phytoplasmas and is transmitted by the grapevine-feeder Scaphoideus titanus. FD induces severe symptoms leading to fruit abortion up to plant death. The disease is a major problem of viticulture in several European countries, and Piedmont is the most affected Italian region. FD management is based on mandatory insecticide treatments and replacement of infected grapevines with certified heat-treated plants. A continuous research effort is directed to study host/pathogen interactions, mechanisms of phytoplasma infection, host response and plant defense mechanisms, to find alternative and sustainable control strategies. No genetic resistance to FD is known so far, and recent studies have shown different degrees of disease susceptibility among varieties of cultivated grapevines and rootstocks. The role of the spontaneous symptom remission (recovery) in FD epidemiology has been addressed, as well as the feasibility of its exploitation as a management strategy in heavily infected areas. On the other hand, genetic variability of FD phytoplasma isolates has been identified through an in depth analyses of several infection sites, and the epidemic outcomes of the possible competition between strains are under study. Recent monitoring has evidenced high vector populations within the wild compartments, pointing at the role of primary infections in the late year epidemics, despite compulsory insecticide treatments of the vineyards. The existence and possible application of virus infection of S. titanus to complement insecticide treatments is object of a recent H2020 funded project