An international team of researchers, brought together by the EU-funded project BeXyl – Beyond Xylella,
has made progress toward improving early detection and surveillance tools to control the bacterium Xylella fastidiosa across various plant species.
The Context
The research, coordinated by Antonio Vicent (Instituto Valenciano de Investigaciones Agrarias) and Pablo Zarco-Tejada (University of Melbourne), brings together experts in plant pathology, molecular diagnostics, sensing technologies, remote sensing, and modelling, to provide new, integrated approaches on surveillance, early detection, and monitoring of Xylella fastidiosa and its vectors.
Molecular approaches for early and rapid detection
The researchers tested state-of-the-art nucleic acid-based diagnostic tools for the quantification, typing and in-situ detection of Xylella fastidiosa in plants and vectors. Loop-Mediated Isothermal Amplification (LAMP), Recombinase Polymerase Amplification (RPA), Droplet Digital Polymerase Reaction (ddPCR) and high-throughput DNA sequencing technologies were tested on crude extracts from almond, grapevine, olive, coffee, and avocado samples, often without prior DNA purification.
The analyses confirmed the complexity of Xylella fastidiosa across host plants. ddPCR showed the highest sensitivity, while LAMP and RPA assays proved highly suitable for rapid and field-deployable diagnostics, particularly in almond. Optimisation is ongoing for avocado.
In Addition, a sequence-capture enrichment procedure coupled with high-throughput DNA sequencing enabled strain typing of Xylella fastidiosa from plant and insect samples at the subspecies and sequence type level. This approach increased detection and typing sensitivity by two orders of magnitude compared with direct sequencing of total DNA.
Investigating asymptomatic infections
Using proximal sensing, hyperspectral imaging, and high-throughput plant phenotyping platforms, researchers detected physiological and structural traits associated with the infection before the onset of symptoms. Classification models successfully discriminated infected and healthy plants as early as two months post inoculation, in both olive and grapevine, demonstrating the potential of these tools for early detection and anticipating intervention.
Remote sensing for large-scale detection and monitoring
Monitoring large infected areas remains a challenge in Europe and elsewhere in the world. Scientists scaled up current airborne and remote sensing technologies in field campaigns conducted in Mallorca (Spain), California (USA), and La Rioja (Argentina), covering almond, grapevine, and olive.
The use of airborne and satellite imagery, including hyperspectral, thermal, and WorldView-3 data, demonstrated the potential to assess disease incidence and severity at plot and regional scales, supporting the development of a global model for Xylella fastidiosa detection and monitoring.
Canine olfactory detection as an innovative tool
Building on previous research on other plant pathogens, researchers tested sniffer dogs’ ability to detect Xylella fastidiosa. The tests showed high sensitivity and accuracy, indicating that the soil where an infected plant grows plays an important role in the volatiles that dogs perceive. This finding will simplify dog’s training procedures and support the potential operational use of canine detection for inspections at ports, nurseries, and field scale.
Optimised surveillance and outbreak management strategies
Surveillance is key to effective outbreak management. BeXyl scientists developed upgraded surveillance tools for Xylella fastidiosa and its vectors, using statistical models supported by spatial, individual-based models of disease spread. By adapting sampling strategies to previously collected data, researchers demonstrated that sequential and risk-based surveillance schemes are key to boosting both the effectiveness and the efficiency of surveillance.
Towards an integrated approach
Overall, the different tests and experiments carried within the BeXyl project demonstrated that an integrated, early and science-based approach for the management of Xylella fastidiosa outbreaks is achievable. BeXyl’s results provide concrete and complementary options to support authorities and stakeholders in mitigating the impact of one of the most serious plant health threats facing agriculture and natural ecosystems today.
Xylella fastidiosa
Xylella fastidiosa is one of the world’s most threatening plant pathogens, able to colonise over 700 plant species. It is responsible for diseases causing millions of dollars’ worth of agricultural and biodiversity losses in the US and Brazil. In October 2013, the bacterium was detected in the EU for the first time, on olive trees in the Apulia region of southern Italy. Since then, outbreaks have also been detected in regions of France, Spain and Portugal. Further information can be found at: https://www.efsa.europa.eu/en/topics/topic/xylella-fastidiosa
Fonte: BeXyl – Beyond Xylella
