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The fate, activity and threat of Ralstonia solanacearum; causal agent of potato brownrot in European soils, rhizospheres and water systems

Contract nr: FAIR-CT97-3632
Project nr: 3632
Project type: SC
Starting date: 01/01/1998
Duration: 52 months
Total cost: 1,165,700 EUR
EC Contribution: 920,000 EUR
Scientific Officer: Richard HARDWICK
Research topic: Plant health
Acronym: FATE

Potato brownrot, the disease caused by Ralstonia solanacearum, is a serious emerging problem in European agriculture, with severe losses recorded in recent years in potato cropping. Several recent reports have indicated that the causal agent, R. solanacearum race 3, may have established in European soil, plant and water systems in various EU countries.

This proposal by five European expert laboratories aims to assess the severity of infestation by the pathogen, as well as the effects of simple non-chemical practical methods taken against it. The project will first fine-tune available methods for the detection, identification and ecological monitoring of the brownrot bacterium. Partners will subsequently perform a European transect study aimed at investigating the prevalence as well as load of R. solanacearum in several European ecosystems. This study will provide information as to pathogen incidence, as well as generate strains which will serve as target organisms for subsequent ecological assessments of fate and persistence. Such strains will also be characterised for their aggressiveness versus a broad selection of potential host plants. In a third phase, the experiments will focus on the fate of R. solanacearum strains selected in the transect study, following a release from diseased potato tubers in soil, its fate should it enter waterways, and the potential for a diversity of plants to serve as reservoirs of the bacterium. The capability of the bacterium to enter a viable-nonculturable state, which would escape current certified detection methods, will be assessed. Furthermore, the response of R. solanacearum to stressful conditions encountered in soil and water systems, potentially leading to a multiple-stress resistant physiological state, will be determined.

The data on ecological fate obtained in the soil will be linked to feasible practical measures, i.e. effects of solarisation, inundation, covering of fields with farmer's plastic and addition of organic materials, will be assessed. Data obtained in water systems will serve to predict R. solanacearum persistence and spread, its potential for growth at low substrate concentrations, and its extinction as a result of the prevailing ecological conditions. A fourth project task will address the potential for development of an antagonistic microflora in selected soil systems, resulting in suppressive soils. An advanced molecular finger-printing method will be used hand-in-hand with a cultivation-based approach, in order to unravel the structure of the microbial communities in suppressive versus conducive situations, and a link will be sought between both data sets. Dominant members of the culturable fraction will be screened for their capacity to inhibit R. solanacearum. The aggressiveness of selected novel isolates will be determined and used in an assessment of the threat they pose to European potato cropping. In addition, an R. solanacearum resistant gene with potential for use in potato will be tested for its capacity to ward off infection pressure by a range of pathogen isolates. The data obtained from the transect study, the ecological fate studies and from the suppressiveness studies set in the perspective of farmers' measures, will serve to define a set of recommendations (guidelines) useful in the definition of feasible non-chemical disease management practices.

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  • Mark BAILEY
    Institute of Virology and Environmental Microbiology
    Polaris House
    UK-SN2 IEU Swindon
    Tel.: +44 1018 65 51 23 61
    Fax: +44 1018 65 55 99 62

  • Kornelia SMALLA
    Federal Biological Research Centre for Agriculture and Forestry competent authority
    Messeweg 11/12
    D-38104 Braunschweig
    Tel.: +49 531 299 38 14
    Fax: +49 531 299 30 13

  • André TRIGALET
    Institut National de la Recherche Agronomique
    147 rue de l'Université
    F-75338 Paris
    Tel.: +33 5 61 28 50 47
    Fax: +33 5 61 28 50 61

  • Maria Milagros LOPEZ
    Instituto Valenciano de Investigaciones Agrarias
    Carretera Moncada A Naquera Km. 4.5
    E-46113 Moncada
    Tel.: +34 961 39 10 00
    Fax: +34 961 39 02 40
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