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Xylella Fastidiosa Active Containment Through a multidisciplinary-Oriented Research Strategy

Periodic Reporting for period 3 - XF-ACTORS (Xylella Fastidiosa Active Containment Through a multidisciplinary-Oriented Research Strategy)

Reporting period: 2019-11-01 to 2021-04-30

XF-ACTORS has been the first international research project in Europe entirely devoted to develop a multidisciplinary research program on the bacterium Xylella fastidiosa. The consortium involved 30 Partners and Research Institutions, including 4 non-European research centers from USA, Brazil, Costa Rica and Taiwan, countries where the pathogen is known to be present since a long time.
The project aimed to address the urgent need to improve prevention strategies, early detection and control of Xylella fastidiosa in Europe. The overall objective was to develop a global strategy for the integrated management of serious diseases associated with Xylella fastidiosa, with the intention of preventing its further spread or introduction in Xf-free areas, and to mitigate the economic, environmental and social impacts.
The knowledge generated by XF-ACTORS research aimed to improve capacity of farmers to manage the disease and prevent further economic losses in crops; enhance capacity and competence of plant health authorities to strengthen the EU plant health regime; generate positive impact towards the improvement of EU prevention measures (legislative provisions, technical procedures, means of disease control, etc.).
The stakeholders’ interests were an important driver of XF-ACTORS. Therefore, an intense program of dissemination and interactions with stakeholders has been implemented, with the participation of representatives of international and national Plant Protection and quarantine services, policy makers at the EU level, growers, producers and nurserymen organizations and extension services.
XF-ACTORS allowed to establish in Europe, for the first time, a multidisciplinary research program to fight this harmful pathogen. A network has been estabhlished with fruitful exchange of knowledge among different experts and disciplines: biology, genetics, bioinformatics, entomology, epidemiology and modeling, etc. We know that finding a therapy against Xylella is a long term and ambitious objective, however XF-ACTORS shed light on several aspects of the EU outbreaks: from the aggressiveness to the host range of the different EU strains; from the disease spread patterns to the epidemiology in the different agro-ecosystems; knowledge on the insect vectors playing a crucial role in the spread of the infections. All these scientific information were extremely important for the EU Commission to build up legislative provisions/measures to protect and implement preventive strategies.
Indeed, all the small piece of scientific knowledge gathered in the different project tasks have been exploited by the team of modelers working on developing models predicting the most risky locations and the forecasting the spread of the pathogen once an outbreak is detected. All the biological information for example have been used to fine tune the parameters of the models, in order to implement models as much as possible close to the real disease scenarios.
The activities and the knowledge gathered in the framework of XF_ACTORS have inspired and driven the workplan of other research projects that built their research program benefiting from the background developed in XF-ACTORS: i.e. BIOVEXO, CURE-XF E ERC-MULTIX projects. Several other national and international research initiative have requested the collaboration and the support of XF-ACTORS members. XF-ACTORS has been the leading consortium on this phytosanitary emergence with an intense activities of networking at diffenrent levels (international, national and regional).

Ensured public visibility and impact of the project results: transfer of knowledge to EU agencies (EFSA and EU Commission); sharing knowledge with the scientific community (more than 100 peer reviewed papers pubhlished in open access; supporting stakeholder awareness by publishing practice abstracts.
• We know better our enemy: the large genomic sequence campaign we have now scientific-based information on the origin of the Xylella in Europe and we know that actually Xylella in Europe makes a longer history than we thought. We also have elucidated some aspects related to its fastidious nature; we know that some strains are less aggressive of the other, and so measures to control the impact of the infections should be tailored on the specific scenarios occurring in the different EU outbreaks.
• We know better how the plants counteract the infections: Advances have been made deciphering the mechanisms and the components of the hosts immune system responding to Xylella infection, opening for new routes for future breeding programs and long term sustainable management approaches.
• We know better how it interacts with the other “co-habitants” in the plants, we have explored the microbial communities to look for pockets of resistance and for natural antagonists. Although results have not identified yet any potential good antagonists, the analysis allowed to have a snapshot of what happens in the infected plants, for example we demonstrated that Xylella suppress the other microbes becoming the predominant microorganism in the microbial community.
• We know better the European insect vectors: investigations in laboratories and under field conditions have unraveled several features of the EU insects vectors (what species they prefer to feed on, what is their life cycle, when/in which stage during their life cycle they became effective carriers of the bacterium from plant to plant, which is the feeding behaviors of this insects and thus gathering insights in the mechanisms underlining the acquisition and transmission of the bacterium. In conclusion, more knowledge on the insect vectors means more targeted interventions to reduce their population and capability of being carrier of the bacterium, then less environmental impact for vectors' control.

• We have developed models to predict the pathogen spread: allowing to identify the most vulnerable sites to prioritize in the inspections, we introduced innovations for the detection of the bacterium, and therefore tools to improve the surveillance program.
Infected trees under field conditions, showing different susceptibility (olive and almond)