Investigating transcriptome to design molecular marker system for the rapid selection of healthy living ash (Fraxinus excelsior) to breed dieback disease tolerant genotypes.
Background
European ash (Fraxinus excelsior) is a widespread native broadleaf tree in Ireland, majorly found in woodlands, hedgerows and farm landscapes. Ash supports a wide range of plant and animal species and provides important ecological, cultural, and economic benefits.
Ash populations across Ireland and Europe are under severe threat from ash dieback, a disease caused by the invasive fungal pathogen Hymenoscyphus fraxineus. First reported in continental Europe in the 1990s, the disease was detected in Ireland in 2012 and has since caused extensive mortality of ash populations. This has major implications for biodiversity, woodland structure, and future use of ash in forestry and the wider landscape.
Despite the scale of impact, a small proportion of ash trees (estimated at 1-3 %) show natural, heritable tolerance to ash dieback under field conditions. Understanding and harnessing this natural variation is key to securing the future of ash.
Aim and Objectives of the Project
The LivingAsh project aims to support the long-term survival of Fraxinus excelsior by identifying and characterising ash genotypes with enhanced tolerance to ash dieback and developing tools to support their rapid selection within breeding programmes. The project will:
- Investigate transcriptomic responses of ash genotypes that show contrasting levels of tolerance to ash dieback.
- Develop molecular and biochemical marker systems to enable rapid screening of ash populations for disease tolerance.
- Assess the potential of New Genomic Techniques (NGTs) as future tools for improving disease resilience in ash.
Approach
LivingAsh uses transcriptomic analysis to compare gene expression patterns between tolerant and susceptible ash genotypes following infection. This allows the identification of candidate genes and genetic variants associated with disease tolerance.
Based on these results, the project will develop molecular marker systems suitable for high-throughput screening of ash seedlings derived from tolerant parent trees. Biochemical markers, including antifungal coumarins such as fraxetin and esculetin, will also be evaluated to support tolerance validation.
Together, these approaches aim to deliver practical selection tools that can be applied at scale within breeding and conservation programmes.
Future perspectives
Outputs from the LivingAsh project will directly feed into the Teagasc ash breeding programme. Selected tolerant genotypes will be advanced to field trials and seed orchard development, supporting the long-term restoration of ash in Ireland.
By strengthening national capacity in ash improvement and disease resilience, the project will contribute to biodiversity conservation, climate-resilient forestry, and sustainable landscape management in Ireland and beyond.
Funding
LivingAsh project is funded by Teagasc under the Walsh Scholarship Programme for four years.
Further information
- Dr Dheeraj Rathore, Tree Improvement Researcher
- Bharatheeswaran Murugan, Walsh Scholar working on LivingAsh Project
- Report a healthy ash tree