The effect of root exudates from mycorrhizal and non-mycorrhizal tomato plants on microconidia germination of the tomato pathogen Fusarium oxysporum f. sp. lycopersici was tested. Microconidia germination was enhanced in the presence of root exudates from mycorrhizal tomato plants. The more tomato plants were colonized by the arbuscular mycorrhizal fungus Glomus mosseae, the more microconidia germination was increased, indicating that alterations of the exudation pattern depended on the degree of root AM colonization. Moreover, alterations of the exudation pattern of mycorrhizal plants are not only local, but also systemic. Testing the exudates from plants with a high and a low P level revealed that the alterations of the root exudates from mycorrhizal plants, resulting in a changed effect on microconidia germination, are not due to an improved P status of mycorrhizal plants.

The effect of root exudates from plants colonized or noncolonized by the arbuscular mycorrhizal fungus Glomus mosseae on microconidia germination of Fusarium oxysporum f. sp. lycopersici (Fol) was studied. Root exudates from the Fol-host tomato and root exudates from Fol nonhost plants were tested. Root exudates from all tested plants stimulated microconidia germination. Mycorrhization increased the stimulatory effect exhibited by the root exudates from the Fol host tomato and from all Fol nonhost plants, showing that similar changes occur in the root exudates of all plants after mycorrhization.Résumé : Les auteurs ont étudié l'effet des exsudats racinaires de plants, colonisés ou non colonisés par le champignon mycorhiziens arbusculaire Glomus mosseae, sur la germination des microconidies du Fusarium oxysporum f. sp. lycopersici (Fol). Il ont testé des exsudats racinaires de tomates hôtes Fol et de plants non hôtes Fol. Les exsudats de toutes les plantes stimulent la germination des microconidies. La mycorhization augmente l'effet stimulateur des exsudats racinaires des tomates hôtes Fol et des plants non hôtes Fol, ce qui montre que des changement similaires surviennent dans les exsudats racinaires de toutes les plantes, après mycorhization.