Preparing for the introduction of exotic strains of the Ralstonia solanacearum species complex (i.e. of Ralstonia pseudosolanacearum and Ralstonia syzygii) – valorisation of culture collections and validation of diagnostics and methods for epidemiosurveillance (EXORAL)

General introduction

This project dives deep into the plant-pathogenic Ralstonia solanacearum species complex (RSSC). Over the past decade, 'exotic' strains of this bacterial complex have emerged in our region. The RSSC is classified as a quarantine pathogen subject to a strict zero-tolerance policy. As a result, plant protection services conduct intensive monitoring efforts, which would benefit from a better understanding of the epidemiology of this bacterial complex. Through this project, scientific experts can contribute up-to-date knowledge and techniques to support these efforts.

Bacteria belonging to the RSSC are known to cause wilt disease in crops such as potato and tomato, as well as in ornamental plants like Pelargonium and Anthurium. The RSSC consists of four phylotypes, classified into three different species: R. solanacearum (phylotype II), R. pseudosolanacearum (phylotypes I and III), and R. syzygii (phylotype IV). Best-known in the EU is R. solanacearum phylotype IIB sequevar 1 (IIB-1), due to its historical role as the causative agent of potato brown rot. However, since 2015, it is R. pseudosolanacearum phylotype I—traditionally considered a tropical pathogen—that has shown the ability to cause damage in European ornamental and herb plant production. This indicates an adaptation of this group to temperate climates.

Research approach

In collaboration with a dedicated international Euphresco network, the researchers are establishing a collaborative platform focused on the diagnostics, pathology, and epidemiology of the ‘tropical’ species R. pseudosolanacearum and R. syzygii. The aim is to deepen knowledge of the genetic diversity, population structure, and evolutionary dynamics of these Ralstonia species. Additionally, efforts are being made to harmonize detection and identification methods. The ILVO bacteriology team is responsible for compiling an inventory of bacterial strains, providing status updates on the occurrence of the two ‘exotic’ Ralstonia species in Belgium, validating diagnostic methods, evaluating typing methods based on whole genome sequences, and launching an interactive tool for epidemiological monitoring.

Relevance/Valorisation

Several plant species affected by Ralstonia bacteria are of economic importance to the EU. The results of this study will directly pay off in monitoring efforts under the current regulation as a quarantine pathogen. Competent authorities will be better equipped with tools to limit the potential impact of Ralstonia on local agriculture and horticulture.

Disciplines:Phytopathology, Bacteriology, Bio-informatics, Analysis of next-generation sequence data, Computational evolutionary biology, comparative genomics and population genomics, Agricultural plant protection

Project type:Collaboration project