Ash dieback, caused by Hymenoscyphus fraxineus, is a serious disease of common and

narrow-leaved ash in Europe. The resistance of individual trees seems to be important for

the maintenance of ash in European forests. In this in situ wound inoculation study, the

susceptibility and differences in resistance to H. fraxineus between Fraxinus excelsior and

F. angustifolia clones were assessed. Neither of the tested clones revealed total resistance

to ash dieback; variety between the tested clones was observed. Differences in necroses

lengths were significant between clones and between two ash species. Longer necroses were

formed in F. angustifolia than in F. excelsior. Some clones exhibiting some resistance to the

pathogen were identified.