RECENT ADVANCES ON THE CONTROL OF XYLELLA FASTIDIOSA AND ITS VECTORS IN OLIVE GROVES: STATE OF THE ART FROM THE ONGOING EUROPE'S HORIZON 2020 RESEARCH PROGRAM

Search for therapeutic solutions to suppress the development of diseases caused by strains of Xylella fastidiosa in infected plants has been, since the last century, one of the most challenging objective in several applied research programs developed in the Americas, and more recently this topic is of high priority in the European research programs. Likewise other vector-borne diseases, tools for control are directed to both the pathogen in the host plant(s) and the insect vector(s). A wide range of sustainable approaches are included in the multidisciplinary research workplan funded by the European Commission to tackle, in particular, the severe disease associated with the infections of X. fastidiosa subsp. Pauca, ST53, in olives. Search for olive varietal resistance or tolerance is currently one of the main focus, with a large panel of olive cultivars under screening in greenhouse and open field. Bacterial population size, phenotypic response and expression level of candidate genes involved in the host response are the main experimental parameters evaluated. Applications of antimicrobial formulations and use of antagonists are also at an advanced stage (i.e. in planta and under field conditions), that while confirming the difficulties to counteract the impact of X. fastidiosa in susceptible olives, provide some encouraging evidence to be further implemented and investigated (i.e. attenuation of symptoms upon N-acetylcysteine endotherapic applications; colonization of olives by Paraburkholderia phytorfirmans, previously shown to be effective in grapes). Control of the vector populations is a complementary research task, aiming on one side to elucidate the feeding 19ehavior toward setting strategies for disrupting the transmission events, on the other side by testing organic or inert compound to suppress juveniles and adults. The implications of having strategies for mitigating Xylelladisease are particularly relevant for those European territories (demarcated areas) where the bacterium has established and containment strategies are in place