Topics of researchIn line with the EU Plant Health Law approach, the BeXyl Project aims to strengthen the two pillars of plant protection: prevention and control
New outbreaks risk assessment
Identifying the main drivers of the establishment and spread of the quarantine bacterium Xylella fastidiosa (Xf) in Europe is crucial to prevent and to control the outbreaks. Although research has improved the knowledge in that domain, high uncertainty still exists, especially for the strains isolated in the EU.
The BeXyl project aims to fill this gap to give policy-makers tools for a robust risk assessment on new introductions of Xf in Europe, considering climate change scenarios. Researchers investigate Xf strains’ plant host range and pathogenicity relevant to the Mediterranean Basin’s main crops, ornamentals, and landscape forestry trees. The impact of climate change in the Mediterranean region will be severe. Thus, the BeXyl project works toward identifying Xf genetic traits associated with climate and host adaptation and effects of current and future changing climate on the interactions among the host, the bacterium and the vector, building maps of relative risk to Xf for selected areas in the EU.
Detection and Surveillance
In the EU, surveillance programs for the quarantine plant bacterium Xylella fastidiosa (Xf) are mandatory. However, the large extension of some EU outbreaks makes early detection still a significant challenge. The EU-funded research project XF-ACTORS (2016-21) developed several propagation models based on data for plant species level.
The BeXyl project aims to reduce this uncertainty by integrating a surveillance data-based propagation model with the detailed genetic information of Xf. The researchers engaged in the BeXyl project will develop new accurate and fast methods to characterize the genetic profile of Xf both in plants and vectors. The project explores the potential of sentinel plant species and sentinel plots to provide an early warning of Xf presence in given areas. An essential part of the BeXyl work on surveillance and detection is putting in place a new and efficient trapping method to monitor vector abundance and use them as early warning sentinels for Xf presence. Research in XF-ACTORS demonstrated that remote sensing Xf detection through airborne hyperspectral imagery works. BeXyl aims to scale up to commercial satellite systems, which can cover much larger geographic areas than airplanes. In doing this, research focuses on new techniques to determine differences in the phenotype of plants infected by Xf with no symptoms. BeXyl researchers also assess the potential applications of dogs’ sense of smell in the asymptomatic phases of Xf infections.
Safe plant material exchange
In Europe, the plant nursery sector plays an essential economic and ecologic role in forestry and agriculture. The quarantine plant pest Xylella fastidiosa (Xf) outbreaks are a severe threat to that balance, as the measures to prevent the spread of the pathogen imply the disruption of the free movement of plants. The thermal treatment of plant material is a known solution to ensure a safe trade. Still, approved protocols exist for vines only, and more information on the effectiveness of other Xf host plants is needed.
The BeXyl project aims at developing new thermal treatment schedules for planting and propagating materials. That implies identifying, testing, and evaluating the effectiveness of applying different temperatures, time combinations, and cycles on various plant species and planting materials. The goal is to develop nursery certification systems and make them available for the nursery sector and national plant protection organizations (NPPOs) to ensure safe plant trade.
Host plants resistance
Plant host resistance to infection is one of the most effective ways to neutralize the effects of diseases caused by plant pests. The quarantine plant bacterium Xylella fastidiosa (Xf) makes no exception. In Europe, olive and almond are the most severely affected and threatened crops by Xf-driven diseases caused by strains of the subspecies “pauca” and “multiplex” respectively. The EU-funded research projects POnTE and XF-ACTORS supported studies to understand the genetics of resistance to the former subspecies, while information concerning resistance to the latter needs to be substantially improved. Exploiting the results to increase the number of the available resistant genotypes requires further research and investments.
One of the goals of the BeXyl project is to identify new Xf-resistant host genotypes in main perennial crops and to unravel the mechanisms of resistance to Xf, mainly on olives and almonds. That will provide new tools for genomics-assisted breeding and selecting long-term resistant olive and almond plants.
Several species of sap-sucking insects, mainly “spittlebugs”, are known to be vectors of the quarantine plant bacterium Xylella fastidiosa (Xf). The control of their population is essential to manage the Xf threat. However, some actions to pursue this objective, such as the massive use of synthetic insecticides, can be detrimental to ecosystems.
Former EU-funded research projects provided knowledge on the life cycle, host-plant association, dispersal, transmission biology, feeding behavior and control of spittlebug vectors of Xf in Europe. The BeXyl project goes beyond. Research focuses on new innovative biological tools and nature-derived insecticides (from plants and microbes) to control Xf vector populations and reduce its transmission efficiency. Biological control agents, such as new natural enemies, fungi and viruses pathogenic to spittlebugs, are examples of the investigation in that area.
Control in the plants
No chemical or organic pesticide can fully treat the quarantine plant bacterium Xylella fastidiosa (Xf). In recent years research has focused on the plant microbiome to find micro-organisms able to eliminate or reduce the Xf population in the plant vessels. Other solutions of Xf control in the host plants involve mineral nutrients, botanical extracts, or microbial strains. Each of them, however, has yet to succeed.
The BeXyl project interacts with other EU projects, Life Resilience and BIOVEXO, to develop new methodologies of plant disease control. The goal is to use microbiome modification, the application of new antimicrobials and bacteriophages to attain the production of plants at the nursery scale with increased resilience to Xf infection.
Control on the ground
Outbreaks of the quarantine plant bacterium Xylella fastidiosa (Xf) may have harsh economic, social, and ecological consequences. Thus, there is an urgent need to provide farmers, nurseries, and national plant protection organizations with effective Integrated Pest Management (IPM) solutions to mitigate the impacts of infections. Those must take into consideration the stakeholders’ needs and perspectives.
In this respect, the BeXyl project investigates and validates sustainable solutions. Firstly, setting up integrated modeling tools for risk assessment at different spatial and temporal scales and in different agroecosystems. In the second stage, experimental trials will test and validate the disease control options for different crops and agroecosystems. The tests will include best agronomic practices for tolerant/resistant cultivars in infected areas and innovative solutions developed within BeXyl for controlling the vector populations. In the framework of the project, a plots’ network will contribute to demonstrating innovative tools for managing Xf. All the data and information collected will provide a comparative evaluation of management solutions for Xf in specific contexts.
ECOLOGY AND SOCIETY
Plant disease control measures, such as tree felling or chemical insecticides application, may have undesirable repercussions on public opinion. When a local community rejects the management measures, the pest containment action may be compromised. That has been the case for the quarantine plant pest Xylella fastidiosa (Xf) and the social reaction to the first outbreaks in Europe.
The BeXyl Project wants to provide social, ecological, and economic evidence enabling policy and decision-makers to design effective and socially acceptable interventions. To that aim, researchers will draw lessons from the EU and national strategies to tackle Xf outbreaks, outlining innovative plans for plant health management in future outbreaks. BeXyl will identify potential barriers preventing the adoption of Integrated Pest Management schemes and support their adoption by providing an economic analysis of the implementation of those schemes at the regional and farm level.