Determining management strategies to control ash dieback disease through the study of molecular and environmental interactions

Ash dieback (ADB) disease, caused by the devastating fungus Hymenoscyphus fraxineus Baral, Queloz & Hosoya, currently poses a significant threat to forest health by decreasing the ash population across the UK and Europe. In our study, we evaluated how environmental conditions, silvicultural management, and genetic factors influence the spread and severity of ash dieback. We combined these factors in a statistical model for susceptibility. Leaves were collected from twenty-two stands across a large semi-natural woodland in Southern England, encompassing a range of disease symptoms. We conducted gene expression assays of tolerance genes previously identified by Associative Transcriptomics and evaluated how stand structure, tree vigour, and individual tree characteristics affected the disease progression. Our results demonstrated that the severity of symptoms is significantly impacted by tree vitality, genetics, and tree size. We identified a diameter at breast height (DBH) group with the highest explained variation (42%) in the disease susceptibility model, with the tree vitality and genetic markers emerging as key determinants. Our findings highlight that lower susceptibility to ash dieback results from a combination of moderate to high genetic tolerance, good individual tree vitality, and appropriate stand management.