EN
Health status analysis of 14 stands in the Rokita Forest District showed severe intensity of disease in ash trees (Fraxinus excelsior L.). The most common symptoms included the death of whole branches or their apices, tree-top dieback, crowns defoliation, local necroses on the trunks and twigs and epicormic shoots. After three years in newly established experimental plots only 36.2% (plot Moracz) and 57.2% (plot Samlino) of ash seedlings did not show any macroscopic disease symptoms. The fungi most often observed in the necrotic tissues of ash shoots in the stands, as well as in the experimental plots were: Hymenoscyphus pseudoalbidus (anam. Chalara fraxinea), Botryosphaeria stevensii (anam. Diplodia mutila), Fusarium avenaceum, F. lateritium and species from the genus Cytospora and Phomopsis. H. pseudoalbidus developed large quantities of apothecia on previous year ash rachises in the litter. The BSA (Bulked Segregant Analysis) method enabled identification of molecular markers linked to resistance of F. excelsior to the disease process, which has been observed for 20 years.