Non-native pathogens represent a major threat to natural ecosystems worldwide. The chestnut blight fungus Cryphonectria parasitica has been introduced from Asia into Europe in the 1930s. Current quarantine regulations aim to avoid new introductions from outside the continent. Because of the lack of co-evolution with the new host, non-European genotypes of C. parasitica may be more virulent than genotypes already present in Europe and their introduction could lead to a worsening of the disease. This project aims to test the hypothesis that C. parasitica genotypes, which have never encountered C. sativa, are more aggressive on this species than genotypes already occurring for a long time in Europe. For this, Chinese and North American C. parasitica genotypes will be inoculated on seedlings of the European chestnut in the biosafety greenhouse. The size of the bark lesions induced by those genotypes will be compared to that caused by genotypes from the European C. parasitica population.