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INRA researchers are active in the fight against Xylella fastidiosa

Efforts to control X. fastidiosa are currently focused on plant eradication, given that more effective methods that directly target the bacterium are lacking. Researchers are actively studying this generalist pathogen in its endemic range—North and South America. Since 2013, INRA has drawn upon its expertise in plant health to gather the necessary scientific knowledge and tools to fight X. fastidiosa and to develop an active response plan.

The bacterium Xylella fastidiosa was found on the ornamental shrub Polygala myrtifolia in Corsica in 2015. © Wikimedia commons, BARRA A.
Updated on 03/31/2016
Published on 08/20/2015

It is thought that X. fastidiosa was introduced to Europe relatively recently, within the last decade, because the bacterium was only just discovered in 2013, on olive trees in southern Italy (the Apulia region). The trees had already been stricken by “quick decline” disease, the first symptoms appearing in 2008. Was the bacterium solely responsible for the illness? This question remains to be answered. Given that there are no effective authorized chemical tools that can be used against phytopathogens like X. fastidiosa in Italy or elsewhere, control efforts are focused on preventative measures, such as monitoring infections or placing infected plants in quarantine and destroying them. In France, the use of antibacterial agents, such as antibiotics, is prohibited because it could lead to bacterial resistance and the chemicals could ultimately end up contaminating the environment. Control efforts are also largely centered on the insects that vector X. fastidiosa, to prevent them from spreading the bacterium and, ultimately, any related diseases.

INRA plant health experts at the forefront of the fight

The first time a phyto-pathogenic bacterium has been sequenced

At INRA, research on X. fastidiosa commenced anew in 2013—preliminary studies were performed as part of the establishment of a control plan by the Ministry of Agriculture, Food, and Forestry. “In the 1990s, a fruitful collaboration between INRA Bordeaux and a consortium of Brazilian scientists associated with the Institute of Biology in São Paulo resulted in the sequencing of X. fastidiosa. It was the first time a phytopathogenic bacterium had been characterized,” comments Marie-Agnès Jacques of INRA Angers. More recently, thanks to a partnership with ANSES, INRA has helped characterize X. fastidiosa strains isolated from coffee bushes and has subsequently established a reference collection. Jacques continues, “We need to expand our knowledge regarding the bacterium. For instance, we need to explore its genetic diversity, identify the host ranges associated with the different strains found in Europe, and analyze these strains’ genomes to better understand how the bacterium interacts with its host plants, as well as its plant or insect vectors.”

        

Drawing on metaprogrammes, engaging in sequencing efforts, and promoting citizen science

Identifying potentially vulnerable agricultural sectors

It is crucial to identify the agricultural sectors that are potentially vulnerable to X. Fastidiosa outbreaks. Research being carried out by the INRA division of Plant Health and Environment is drawing on the expertise of scientists found across a range of disciplines, including epidemiology, phytopathology, bacteriology, virology, entomology, genomics, and population genetics. “Research in this area needs to move beyond developing tools of detection and methods of prevention, which are admittedly crucial in eradication efforts,” says Jean-Yves Rasplus, an entomologist at INRA Montpellier. He continues, “To be able to rapidly come up with effective control measures, we need to gather more information on the disease itself, identify all the different potential vectors, and more fully understand X. fastidiosa’s epidemiology in its introduced range. We need to develop an approach that addresses all the facets of the problem, while organizing them by priority. This work is broad in scope and will extend beyond our division. We will take advantage of the expertise afforded by INRA’s metaprogrammes, which will help us tackle multidisciplinary questions, such as those related to the bacterium’s virulence factors, the resistance shown by certain plants, and the ecological interactions taking place between semi-natural habitats and agroecosystems. To carry out this research, we need to rapidly find funding and put into place a high-quality, multidisciplinary research programme, inspired by the work that has already been done in the US. We will also take advantage of new sequencing and data acquisition technologies and ways of analyzing large datasets, including some citizen science projects. We will thus get a better handle on this disease, which is extremely difficult to control.”

European project - horizon 2020

POnTE, against microorganisms which are threatening Europe

The POnTE project, for Pest Organisms Threatening Europe, financed in the H2020 'SFS-03a-2014 programme: Native and alien pests in agriculture and forestry’, focuses on proposing integrated and sustainable control of four pathogens, including Xyllella fastidiosa, which are threatening a panel of crops and natural environments in Europe.

Concerning the bacterium Xylella fastidiosa, the partners of this project aim to:

  • determine the role of this bacterium and other pathogens (fungi and insects) in the etiology of Olive Quick Decline Syndrome – OQDS,
  • find out more about the strains present in Italy and France and the insect vectors in terms of diversity and find out more about the mechanisms of the bacterium, in particular its capacity for recombination,
  • develop new tools and procedures for disease surveillance
  • test different control solutions targeting the insects, the environment of the plots and survival of bacteria.

The Research Institute for Horticulture and Seeds (IRHS), part of the INRA Angers-Nantes Pays de la Loire Research Centre, studies the diversity of Xylella fastidiosa and sets up tools for crop surveillance and disease prevention.

Partners: the project is coordinated by Donato Boscia from the CNR (Consiglio Nazionale delle Ricerche) in Bari, Italy and has 25 partners in Europe, Costa Rica and Israel.