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Master Thesis

Étude de deux maladies chez la carotte porte-graine causées par les espèces fongiques Fusarium tricinctum et Diaporthe angelicae

Abstract : Recently, two fungal pathogens were identified in French’s carrot seed crops: as a new pathogen, Fusarium tricinctum, and a re-emerging pathogen, Diaporthe angelicae. In this work, 15 Fusarium strains and isolates from lesions on carrot crowns have been studied. Firstly, phenotypic and molecular typing based on ITS rDNA and β-tubulin sequences resulted in the identification of 10 F. tricinctum strains and 5 other strains belonging to three species: F. avenaceum, F. culmorum and F. redolens. Secondly, in vitro sensitivity tests of 2 F. tricinctum strains to 4 fungicides and 1 Alliaceae extract was performed demonstrating the nonsensitivity of these strains to the tested concentrations of the fungicides, whereas the Alliaceae extract (Veg`Lys®) was able to inhibit 99% of conidia germination. In addition, in vitro confrontations of three isolates of F. tricinctum against commercial and marine strains of Trichoderma sp., have been tested. Results showed that the two commercial strains were not suitable for biocontrol, while some parasitism properties were observed for the marine strain. In a second part, microscopic observations of artificially contaminated umbels showed that D. angelicae could penetrate the host through the stomata at the style basis. Finally, the localization of D. angelicae in xylem vessels and in parenchyma cells was observed highly suggesting that this fungus is a vascular pathogen.
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Master Thesis
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Corentin Chateau. Étude de deux maladies chez la carotte porte-graine causées par les espèces fongiques Fusarium tricinctum et Diaporthe angelicae. Sciences du Vivant [q-bio]. 2017. ⟨dumas-01627867⟩

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