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

Raykova, Aneliya

Abstract

Forest trees have been increasingly threatened by invasive pathogens,
endangering associated biodiversity, and reducing ecosystems. Such an alien pathogen,
Hymenoscyphus fraxineus, has had considerable impacts on the common ash tree
(Fraxinus excelsior) survival, causing up to 85 % mortality.
The first study, Chapter 2, investigated how environmental, silvicultural
management, and genetic factors contributed to the spread and severity of ash dieback.
Subsequently, these factors were combined in a statistical model for susceptibility. The
harvested ash leaves displayed various signs of disease infection from twenty-two seminatural stands at Rushmore Estate in the UK, showing a range of ash dieback symptoms.
The Associative Transcriptomics method was used to identify tolerant genes and
evaluated how stand structure, tree vigour, and individual tree characteristics affected the
disease progression. Ash individuals were inspected for genes associated with tolerance
to ADB by using PCR, qPCR techniques, and Sanger sequencing methods. The results
from the study showed that H. fraxineus severity is significantly impacted by tree vitality,
genetics, soil pH, size of a tree and elevation, outlining a tree age group that explained
42 % of the variation in the disease susceptibility model. The study findings might
suggest that moderate tolerance could be enhanced by a good individual tree and
appropriate stand management.
In our second study, Chapter 3, the aim was to detect and compare the spore
concentration and observed crown damage along the slope gradient, statistically proving
that the spore load was higher at the bottom of the valley than at the top of the valley,
thereby increasing the infection pressure in those areas.
This PhD aimed to address these multiple factors that were found to impact ash
dieback disease (Chapters 2 and 3) to develop a greater picture of the epidemiological
interactions and generate a holistic approach to reducing ash dieback across the UK.

Citation

Raykova, A. (2023). Determining management strategies to control ash dieback disease through molecular and environmental interactions. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 6, 2023
• Publicly Available Date: Sep 30, 2025
• Award Date: Sep 29, 2023