Fusarium oxysporum Beyond good and evil

Strains belonging to the Fusarium oxysporum (Fo) species complex are largely known for causing wilt or root-rot disease on economically important crops. Despite their ability to reduce Fusarium wilt disease symptoms, little attention has been paid to Fo strains which colonize plants asymptomatically as endophytes. This thesis focuses on understanding how endophytic Fusarium strains can trigger endophyte-mediated resistance (EMR). We show that EMR in tomato consists of a diminished colonization of the pathogen Fo f.sp. lycopersici in roots and stems upon co-inoculation with a Fo endophyte. Moreover, EMR is independent of salicylic acid accumulation, jasmonic acid and ethylene biosynthesis and ethylene perception. Next, by performing comparative genomics of endophytic and pathogenic Fo strains, we could show that pathogenic strains have more putative effector genes and miniature impala transposons than endophytic strains. The level of endophytic colonization in tomato roots seems to be important for the level of resistance but may not be the only factor. Only pathogenic colonization alters the primary carbohydrate metabolism in tomato leaves. Endophytic colonization or co-inoculation of endophyte and pathogen does not alter the primary carbohydrate metabolism. Finally, we tested the viability of applying Fo endophytes in field conditions, and discuss the feasibility of employing endophytes as disease management strategy against Fusarium wilt disease.