What did we achieve with VALITEST an EU project on validation in plant pest diagnostics?

peer reviewedEnsuring the reliability of diagnostic activities is an essential cornerstone of Plant Health strategies to reduce the risk of entry and spread of plant pests in a region and ultimately their impacts. Diagnostic tests should be validated to ensure that they are fit for purpose. Validation is usually done by diagnostic laboratories although companies commercializing diagnostic kits also produce validation data for their products. Due to the high number of pest , matrix and method combinations and given the significant resources required to validate tests, it is essential that validation data are shared with the entire diagnostic community and produced in a harmonized way to facilitate their use by different stakeholders. Indeed, the selection of tests to be used in specific contexts is not the sole responsibility of diagnostic laboratories and also involve National Plant Protection Organizations. The VALITEST EU project (2018-2021) was established to tackle all these issues. New validation data for tests targeting important pests for the EPPO region were produced. Guidelines to improve and harmonize the validation framework were developed. Sharing of validation data and experience was ensured through the development of new or existing databases, the organization of training courses and the dissemination of the project outputs in scientific publications and Standards. Finally, the involvement of researchers, diagnosticians, policy makers, inspectors, industries etc. and the establishment of the European Plant Diagnostic Industry Association were important actions to strengthen the interactions between Plant Health stakeholders

Polymorphismes biologiques et moléculaires chez le complexe d'espèces Nacobbus aberrans (Thorne, 1935) Thorne & Allen, 1944 (Nematoda: Pratylenchidae)

Diplôme : Dr. d'UniversiteOriginaire des Amériques où il occasionne des dégâts importants sur diverses cultures le nématode phytoparasite Nacobbus aberrans est un ravageur potentiellement dangereux pour les pays ou les zones encore indemnes comme l'Europe. Afin d'éviter son introduction et d'évaluer le risque représenté par ce ravageur inscrit sur les listes de quarantaine européennes, il est indispensable de mieux cerner les contours de ce complexe d'espèces et de déterminer certains facteurs clefs de sa biologie. Dans un premier temps nous avons évalué en conditions de laboratoire les capacités de différentes populations de N. aberrans à se développer sur différentes cultures. La nature du parasitisme varie selon le couple hôte-population de nématode étudié et corrobore la notion de race physiologique. En outre une catégorie de plantes qualifiées de réservoirs a été identifiée. Elle permet au nématode d'y réaliser son développement jusqu'au stade J4, stade qui se maintient en état de dormance sans assurer la multiplication de l'espèce. Un type original chez les Tylenchides de parasitisme du second stade juvénile a été caractérisé avec le recours à un puits métabolique et l'induction de la synthèse de plastes d'amidon par les cellules adjacentes au nématode. Dans un deuxième temps la variabilité génétique du nématode a été appréhendée d'une part l'étude du caryotype, qui se révèle varier entre 6 et 8 chromosomes à l'état haploïde, d'autre part par l'analyse de l'ensemble de la zone ITS de l'ADN ribosomique. Cette dernière nous a permis de mettre en évidence l'existence de deux groupes distincts au sein du complexe actuellement identifié comme N. aberrans. La reconstruction phylogénétique d'un des groupes a permis de proposer un scénario évolutif impliquant l'apparition d'évènements d'insertions-délétions au sein de la région ITS d'un groupe puis l'apparition d'évènements d'insertions-délétions au sein de la région ITS d'un groupe, puis d'hybridations entre plusieurs groupes divergents

Crossing experiments with South American populations of Nacobbus aberrans (Thorne, 1935) Thorne and Allen, 1944 (Nematoda : Pratylenchidae)

International audienceBecause differing opinions have been expressed concerning the taxonomic status of Nacobbus aberrans, experiments based on crossing combinations of different N. aberrans populations were undertaken. Five (N1 to N5) South American populations differing in their host preference (N1, N2, N3 able to infect potato and sugarbeet; N4, N5 able to infect sugarbeet, but not potato) were reciprocally crossed. Three populations assigned to different race groups, N1 (Bolivia, potato group), N2 (Peru, potato group) and N4 (Peru, sugar beet group) were readily able to cross between each other and to give fertile and viable progeny, regardless of their geographical origin, race group and for most of the crossing combination (female x male). When crossing a sugar beet population (unable to develop on potato) as female with a male from a potato population, the progeny was able to develop on potato. The N5 population, which belongs to the sugarbeet group from Argentina, was able to cross with other populations, but the progenies obtained were always infertile and nonviable. This population should be considered as a separate species. These findings provide evidence that the N. aberrans complex in South America comprises at least two specie

Variability of the ITS rDNA and identification of Nacobbus aberrans (Thorne, 1935) Thorne & Allen, 1944 (Nematoda : Pratylenchidae) by rDNA amplification

International audienc

Obligatory amphimixis and variation in chromosome number within and among South American populations of Nacobbus aberrans (Thorne, 1935) Thorne & Allen, 1944 (Nematoda : Pratylenchidae)

International audienc

Eléments de biologie chez Nacobbus aberrans (Thorne, 1935) Thorne & Allen, 1944 (Nematoda: Pratylenchidae) : 1 - Capacités de quiescence et de diapause

National audienc

A cyst nematode 'species factory' called the Andes

International audienceThe cyst nematode, Globodera pallida, is a major pest of potato, a plant native to South America. To investigate its phylogeography, an extensive sampling survey was conducted in 2002 in Peru and has laid the foundations of the ancient evolutionary history of this nematode species. We argue that the uplift of the Andes Mountains has triggered a variety of adaptive biotic radiations for Solanaceous plant-parasitic nematodes and has represented a key factor for the evolution and specialisation of Globodera species. We discuss the consequences of the wide genetic diversity observed in South American populations on the efficiency and durability of potato resistance and also the reliability of current molecular identification tools for quarantine purposes. Finally, we emphasise the need to get a more in-depth taxonomic characterisation of some of these nematode populations, and to conduct more extensive sampling in South America, especially south of Lake Titicaca, in order to understand fully potato cyst nematode evolution and their adaptation to their host plants

Eléments de biologie chez Nacobbus aberrans (Thorne, 1935) Thorne & Allen, 1944 (Nematoda: Pratylenchidae) : 2 - Capacité de développement sur hôtes en condition in vivo et in vitro

National audienc

Assessment of PCR-based tools for the specific identification of some temperate Meloidogyne species including M-chitwoodi, M-fallax and M. minor

International audienceSeveral conventional PCR tests have been developed for the identification of the European quarantine root-knot nematodes Meloidogyne chitwoodi and M. fallax but data are lacking for the evaluation of their performance in terms of sensitivity, repeatability, reproducibility and specificity against a large range of populations. This study evaluated the performance criteria of three conventional PCR tests recommended by the consensus diagnostic protocol for Meloidogyne chitwoodi and Meloidogyne fallax published by the European and Mediterranean Plant Protection Organization (EPPO): a species-specific PCR (IGS target), a SCAR PCR, and a rDNA ITS PCR-RFLP. Evaluation was carried out with DNA extracts from juveniles, males and females according to EPPO recommendations for test validation. A minimum of 34 populations of target and non target nematode species were tested to check the specificity of these three PCR assays. The three PCR tests were ranked according to their specificity (with regard to cross reaction with other nematodes species or genus) and their sensitivity (detection of a single juvenile or mixed with other species). The species-specific PCR proved to be more sensitive but less specific than the SCAR PCR. The PCR-RFLP enables the identification of several Meloidogyne species but profile analysis can be difficult when several species are present in the mixture. Specific PCR products and RFLP profiles were also observed for M. arenaria and M. enterolobii, and described for M. minor and M. artiellia

Nématodes à galles, les détecter et les identifier

National audienceLes nématodes à galles affectent le rendement et déprécient les cultures. Pour préserver la qualité des plants français, la FN3PT s'est engagée dès l'automne 2009, avec l'ANSES, dans des recherches sur la détection et l'identification des nématode du genre Meloidogyne