Abstract : The induction of oxidative stress during infection plays a crucial role in host defense mechanisms. , The plant family Brassicaceae includes many important crop plants and the model species Arabidospsis thaliana. Within this plant family, the oxidative stress can be generated either by reactive oxygen species (ROS) released around the infected area during the oxidative burst, or by plant secondary metabolites, such as isothiocyanates (ITC). The necrotrophic fungus Alternaria brassicicola is the causative agent of black spot disease of Bassicaceae. Despite this host defense system, this fungus is still able to complete its infectious disease cycle, indicating the existence of strategies to cope with this oxidative. In this study, we showed that oxidative stress tolerance of A. brassicicola was partly dependent on the mannitol metabolism, which was involved in conidial resistance during the in planta oxidative burst, and in protection against intracellular damages caused by ITC during the early step of infection. Our results also supported the potential involvement of Glutathion-S-transférase enzymes in ITC detoxification mechanisms. Alteration of mannitol metabolism or inactivation of selected GST resulted in reduced virulence indicating that their targeting would be an attractive option for antifungal strategies.