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DISCOVAR
Development of diagnostic tools and host plant resistance to control the rapid spread of lettuce big-vein and ring necrosis disease in leafy vegetables

Lettuce big-vein and leaf necrosis disease are the most serious of soil-born, fungus-transmitted, viral diseases in leafy vegetables in Europe. They are extremely difficult to control because of the lack of major resistance genes in the current varieties and the persistence of resting spores of the fungal vectors, Olpidium brassicae. Direct economic losses in lettuce production alone run to more than 50 million euro per year in Europe. To control the rapid spread, growers depend heavily on soil sterilants (some are to be banned) against the fungal vector. The deliverables of the project proposed would allow a dramatic reduction in pesticide inputs, and the development of a sustainable system for the production of lettuce and other leafy vegetables through the integration of several control measures. These would include identification and exploitation of natural host plant resistance and the development of a management system based on disease avoidance.

Objectives
To combat the soil-borne, fungus transmitted varicosa viruses of lettuce and other leafy vegetables in Europe, the project objectives are:
1) the full characterisation and classification of the viruses causing big-vein (BVD) and ring necrosis disease (RND), and providing insight in the variability of these viruses
2) the development of diagnostics for the sensitive and specific detection, and quantification of the viruses and their fungal vector, Olpidium brassicae, in soil, irrigation water and breeding lines
3) the identification, characterisation and exploitation of natural host plant resistance of lactuca and cichorium to BVD and RND
4) the development of a sustainable system for the production of lettuce and endive through the integration of objectives 1, 2 and 3.

Results
Purification procedures have been established for the viruses associated with big-vein and ring necrosis disease.
The pruified virusus were used to raise antisera against LBV ophio- and varicosavirus and LRN.
The full genomic sequence of the viruses associated with lettuce big-vein and ring necrosis diseases have been determined and the molecular variability of isolates from different production areas in Europe are assessed.
Molecular detection tools have been developed for the three viruses associated with leyyuce big-vein and ring necrosis diseases.
DNA-based detection techniques for different Olpidium species have been developed.
A large collection of isolates of different Olpidium species from around the world was assembled. These are used to chracaterise the specificities DNA-based of detection techniques.
Resistance screening based on symptom expression has revealed resistant/tolerant Lactuca and Cichorium accessions.
Methods to avoid and limit the disease incidence in the field have been tested and gained promising results.

Classified in HORTICULTURE, CROP PESTS AND DISEASES, SOIL

Scientist responsible for the project

Dr. NICOLAAS HOGENBOOM
Binnenhaven 5 Box 9060
6700 GW Wageningen
Netherlands (The) - NL

Phone: +31 317476141
Fax: +31 317410113
E-mail: n.g.hogenboom@plant.wag-ur.nl

References

Project ID QLRT-1999-01471
Organisation Plant Research International B.V. Inst. of Agric. Environm. Engineering
Area 5.1.1
Start date 01 February 2000
Duration (months) 48
Total cost 2 437 542 €
Total EC contribution   1 333 255 €
Status Completed
Web address of the project   http://www.plant.wur.nl/projects/discovar/

The partners

  • Biologische Bundesanstalt für Land- und Forstwirtschaft Berlin und Braunschweig, Germany - DE
    h.j.vetten@bba.de
  • Consejo Superior de Investigaciones Cientificas - Dept. Mejora y Patologia Vegetal, Spain - ES
    vpallas@ibmcp.upv.es
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