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Development of practical tools to characterise the phytoparasitic nematodes Meloidogyne chitwoodi and possible related species recently discovered in Europe

Contract nr: FAIR-CT95-0896
Project nr: 896
Project type: SC
Starting date: 01/03/1996
Duration: 48 months
Total cost: 2,031,450 EUR
EC Contribution: 1,413,000 EUR
Scientific Officer: Richard HARDWICK
Research topic: Plant health

Meloidogyne chitwoodi is an major pest of potato crops in the USA, which has been recently discovered in Europe. In Washington, USA, M. chitwoodii has become widespread. Infected potatoes cannot be sold and 70% of growers now use nematicide fumigants. It is localised in Europe, but seems to be spreading. Current diagnostics are not 100% certain, however.

The objective is to develop modern diagnostic tests for M. chitwoodi. The project will survey the potato nematodes of Europe, looking for quarantine organisms M. chitwoodi and M. fallax and its close relatives (hapla, arenaria, javanica, incognita). It will improve diagnostic techniques(classic and biotech), and produce detailed reports on the situation. Occurrence of biological races means that characterisation to the species level is not always sufficient. Host range tests have to be performed to check which races have been imported into Europe, using the same hosts that are used in the USA but which are also found in Europe. Further identification of the variants and/or related species, found in the Netherlands, needs to be conducted and their host ranges carefully studied, if effective limitation and control is to be achieved.
The identification and characterisation of M. chitwoodi and related species is vital, not only for the future success of the European potato crop but also for the trade in ornamental and root-stock material.

The research activity comprises six tasks:
1) collecting European and American populations;
2) morphological and cytological studies;
3) assessment of virulence within Meloidogyne chitwoodi and related species;
4) identification of differentials, mainly in the genus Solanum;
5) isoenzyme typing, 2DE, RAPD-PCR, ITS, mtDNA, satDNA, specific antibodies and development of diagnostic assays;
6) preparation of reports and dissemination of results.

Current situation/results
1) A large collection of population is available to all participants. This includes i) numerous American populations of M. chitwoodi belonging to the different races and pathotypes described for their ability to develop on different plant and resistant genotypes of potato, ii) numerous European populations of M. chitwoodi and M. fallax found before and during the four years research contract, iii) numerous populations and clones of others species, such as M. incognita, M. javanica, M. arenaria, M. hapla, M. mayaguensis, M. naasi, M. artiella.
2) Morphological studies did not reveal useful differences between M. chitwoodi and M. fallax, looking at the juveniles. Perineal patterns of M. chitwoodi showed faint specific characters in the shape of the surrounding ridges, but M. fallax looks exactly like a smaller M. incognita type.
The reproduction was shown to be meiotical, with fertile hybridisation when male is present, which is generally the case. Thus, high variability is expected in these two species, compared to the mitotic species, such as M. incognita.
3) Differences in virulence and in aggressiveness were found, either against known genes of resistance, or in different plants belonging to the Cruciferous family. Some populations of M. chitwoodi are able to break the resistance, found in some Solanum genotypes as ex-S. fendleri and ex-S. bulbocastanum. In these cases, contrary to the case of M. incognita, all the progeny is virulent. With plants belonging to Cruciferous, interaction population x genotype is significant, with some of thee testes populations always appearing more aggressive than others.
4) Genes of resistance were detected in S. bulbocastanum, S. hougasii, S. fendleri, S. stoloniferum, S. chacoense; S. sparsipilum, S. schenkii. In the cases of S. bulbocastanum, S. hougasii and S. fendleri, the resistance is monogenic, with S. fendleri, resistance acting against M. chitwoodi, and M. fallax does not act against M. hapla. With S. stoloniferum and S. chacoense, resistance appears polygenic and some clones of S. chacoense are resistant only to M. fallax and not to M. chitwoodi.
5) Numerous tools were obtained, characterising M. chitwoodi and M. fallax, alone or together, from other species. Isoenzym patterns, mainly esterase and malatedehydrogenase separate both species from all others and from each other. Serological antibodies extracted from specific proteins found by two-dimensional electrophoresis distinguished both species from the others but not from each other. The same results were obtained using satDNA. Specific primers were designed and validated by a common test made by the different partners, which allows characterisation of both species between themselves and from others.
6) All annual reports, apart from the last one, were sent to the European Commission. Results were presented as full papers, during international congresses. The main conclusions were freely presented in February 2000 in Paris to European agents of European Plant Protection Service.


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  • Mireille FARGETTE
    Institut Francais de Recherche Scientifique pour le Développement en Coopération
    B.P. 5035
    F-34032 Montpellier
    Tel.: +33 4 67 61 71 15
    Fax: +33 4 67 61 55 81
  • Mark Stephen PHILLIPS
    The Scottish Crop Research Institute
    UK-DD2 5DA Dundee
    Tel.: +44 1382 56 27 31
    Fax: +44 1382 56 24 26
  • Richard JANSSEN
    CPRO - DLO - Centre for Plant Breedingand Reproduction Research
    Droevendaalsesteeg 1
    P.O. BOX 16
    NL-6700 AA Wageningen
    Tel.: +31 317 47 70 16
    Fax: +31 317 41 80 94
  • Carolien ZIJLSTRA
    IPO - DLO - Research Institute for Plant Protection
    Binnenhaven 5
    P.O. BOX 9060
    NL-6700 GW Wageningen
    Tel.: +31 317 47 61 55
    Fax: +31 317 41 01 13
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