XYLELLA FASTIDIOSA: A PLASMA APPROACH FOR THE RACE FOR THE CURE

The quarantine bacterium Xylella fastidiosa occurred for the first time in the open field in Europe in 2013, in southern Apulia (Italy), posing a serious threat to the agriculture economy and the biodiversity of the whole area. Infections caused by the subspecies pauca strain "De Donno" of this bacterium turned to be extremely aggressive on olive, causing leaf scorching and desiccation symptoms, a disease named Olive Quick Decline Syndrome. Research efforts were devoted to gain basic knowledge of the genetic and epidemiology of the olive strain (e.g. host pathogenicity and range, insect vector(s), and fundamental drivers of its epidemics), in order to find strategies to control its spread or mitigate symptoms [1]. In this contest we explored the feasibility of using low temperature plasma to kill bacterial cells. Low temperature plasma is an environment rich of reactive oxygen and nitrogen species (ROS and RNS) efficient in the decontamination, sterilization, and chemical modification of surfaces. Moreover it presents numerous potential advantages over conventional methods, such as its nontoxic nature, low process operational costs, short treatment time at low temperatures.[2] Preliminary experiments were conducted in vitro to test the biocidal effect of plasma roduced by a surface dielectric barrier discharge on the bacteria. The results were quite encouraging showing that plasma reached high decontamination rate also on biofilm protected colonies of Xylella growing on solid media. Plasma application to trees will require developing protocols and tools able to reach the bacterium, which localizes and replicates in the xylem vessels. Thus, we explored the possibility to administer the plasma cure via water. The rationale was to use the plasma to activate water [3] as a biocidal agent that could freely move inside the xylem system. Preliminary results in liquid culture medium show a complete inactivation of Xylella cells, paving the way to test on model plants in confined conditions.