Recherche et développement sur la noix - Des projets pour un nouvel élan

International audienc

Colletotrichum : New pathogen in walnut orchards. Caracterization of the fungus and research on control methods

International audienc

Colletotrichum en verger de noyers - Avancées des travaux sur ce pathogène complexe

National audienceDepuis 2011, les vergers de noyers du Sud-Est de la France, principalement, sont touchés par un nouveau pathogène : le Colletotrichum. Ce champignon, qui provoque une nécrose du brou, peut entraîner une chute précoce du fruit. Les pertes de rendement peuvent atteindre 70 % certaines années. Des travaux ont donc été mis en place avec différents partenaires afin de mieux comprendre son épidémiologie. Une analyse de la flore fongique des bourgeons dormants a permis d’identifier les principales espèces de Colletotrichum impliquées. L’amélioration des connaissances sur le pathogène fait partie des travaux en cours ainsi que la recherche de méthodes de lutte efficaces. De nombreux fongicides sont testés in vitro et sur fruits détachés. Des essais terrain sont aussi réalisés pour évaluer leur efficacité et tester des méthodes prophylactiques

Combined Metabarcoding and Multi-locus approach for Genetic characterization of Colletotrichum species associated with common walnut (Juglans regia) anthracnose in France

International audienceJuglans regia (walnut) is a species belonging to the family Juglandaceae. Broadly spread in diverse temperate and subtropical regions, walnut is primarily cultivated for its nuts. In France, Colletotrichum sp. on walnut was detected for the first time in 2007; in 2011 the disease led to 50–70% losses in nut production. A combined approach of metabarcoding analysis and multi-locus genetic characterization of isolated strains has been used for taxonomic designation and to study the genetic variability of this pathogen in France. Evidence indicates that four Colletotrichum species are associated with walnut in France: 3 belong to the C. acutatum species complex and 1 to the C. gloeosporioides species complex. Results also show that C. godetiae is the most abundant species followed by C. fioriniae; while C. nymphaeae and another Colletotrichum sp. belonging to the C. gloeosporioides complex are found rarely. Representative isolates of detected species were also used to confirm pathogenicity on walnut fruits. The results show a high variability of lesion’s dimensions among isolates tested. This study highlights the genetic and pathogenic heterogeneity of Colletotrichum species associated with walnut anthracnose in France providing useful information for targeted treatments or selection of resistant cultivars, in order to better control the disease

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