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VERTICILLIUM WILT IN TREES
Verticillium wilt in tree species - Developing essential elements for integrated and innovative management strategies

Verticillium wilt is of increasing significance in European agriculture, especially in tree hosts such as olive and stone fruits, and in shade tree nurseries. More efficient and environmentally sound strategies are needed to manage this disease. The research will concentrate on pathogen variability, host resistance, and detection and risk assessment. The specific achievements of the project include information on genetic variation within the pathogen and on the distribution and virulence of its sub-specific groups: resistant germplasm of olive, stone-fruits and maple; Verticillium resistance genes from Arabidopsis; molecular methods to detect the pathogen in soil and plants.

Objectives
The general objective is to provide essential tools and information needed for more efficient and environmentally sound strategies for managing Verticillium wilt in trees.
The scientific/technological objectives are:
1) to understand the genetic variability of V. dahliae in relation to its virulence and host range and to chart the distribution of that variability within Europe
2) to standardise and generalise methods to select and screen for resistance in woody species, and to identify resistant germplasm of important species
3) to improve risk assessment procedures by developing reliable methods of quantitative detection of V. dahliae in soil and plant materials, and of quantitative estimation of the importance of inoculum density level
Important additional aims are to harmonise methods in general, exchange experience between the participating groups and continue the successful European co-operation developed during a preceding concerted action.

Progress to Date
Research in all three areas is being carried out largely as planned.
At the first meeting methods and protocols were discussed extensively and agreements on co-operation and exchange of materials were made. At the second meeting, the first results and the plans for year 2 were the main topics of discussion. The third meeting was an extra meeting to discuss coordination of the work and to solve some practical problems in order to prevent serious delays.

Results
Area 1: Pathogen variability
1) Agreement prepared on protocols for collecting and storage of isolates.
2) A collection of 255 V. dahliae isolates (mainly from Europe) has been built.
3) Protocols for molecular testing were agreed, a reference collection has been distributed and molecular characterisation of isolates (AFLP) was started.
4) Probes for species and pathotypes (defoliating/non-defoliating) were developed.
Area 2: Host resistance
1) Detailed protocols on selection and screening methods have been prepared and exchanged.
2) Comparison of methods was continued and standardisation was started.
3) Selection for resistance in olive rootstocks and cultivars was continued, and vegetative propagation of promising new selections was started.
4) Recent maple selections have been propagated for field testing, and plants for a comparison of recent UK, NL and USA selections have been prepared.
Area 3: Detection and risk assessment
1) A prototype for a new device for quantification of soil inoculum levels has been manufactured.
2) The essential factors that influence the results of such a device were studied.
3) Experiments to investigate the effect of soil inoculum density on disease incidence in tree hosts are being continued.
4) Progress has been made in developing molecular probes for identifying V. dahliae and its pathotypes in pure culture as well as in soil samples.

Classified in FRUIT, CROP PESTS AND DISEASES, FORESTRY, SOIL, BIOLOGICAL DIVERSITY

Scientist responsible for the project

Dr J.A. HIEMSTRA
P.O. BOX 16
6700 AA Wageningen
Netherlands (The) - NL

Phone: +31 3174 77326
Fax: +31 3174 18094
E-mail: jelle.hiemstra@wur.nl

References

Project ID QLRT-1999-01523
Organisation Plant Research International B.V.
Area 5.1.1
Start date 01 March 2000
Duration (months) 48
Total cost 2 675 093 €
Total EC contribution   1 744 983 €
Status Completed
Web address of the project   http://www.eu-verticilliumintrees.org

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