Ash dieback: Genomics research defends Europe's forests against disease
Ash dieback: Genomics research defends Europe's forests against disease
At a glance
- Ash dieback has killed hundreds of millions of trees across Europe since arriving on the continent in the early 1990s.
- Queen Mary University of London scientists sequenced the ash tree’s genome in 2013 in response to this threat.
- This led to their discovery of genetic variations that give some trees natural resistance to ash dieback.
- Their findings help policymakers and forest managers build a brighter future for ash trees through selective breeding and reduced felling of healthy trees.
- The UK government now recognises this innovative genomic approach as key to combatting disease in many other tree species, including elm and oak.
A genetic approach to tackling ash dieback
Ash dieback kills up to 85% of ash trees in Europe’s plantations and 69% in its woodlands, with grave environmental and economic consequences. Ash trees produce high-quality timber, remove carbon dioxide from the air, and provide food and shelter for over 900 wildlife species. The disease’s costs to the UK economy alone could come to £7.6 billion by 2029.
Research led by Professor Richard Buggs (School of Biological and Behavioural Sciences) has been building a detailed portrait of ash trees’ genes and evolution since 2013.
His evidence gives clear directions for policymakers and forest managers in their drive to protect and rebuild Europe’s ash woodlands and plantations. It shows that selective breeding and prudent felling can manage the disease efficiently.
Thanks to Buggs’ innovative approach, Defra now places genomics at the heart of UK forest protection for multiple species beyond ash.
Research
In 2013, Buggs produced the first draft ash genome with Elizabeth Sollars. This led to the sequencing of a mass screening of 1,250 UK trees, working with Jonathan Stocks, that identified genetic loci associated with ash dieback resistance. With Richard Nichols and Carey Metheringham, he later developed models to predict resistance.
His 2018 meta-analysis found mortality rates from the disease in Europe reached 85% in plantations and 69% in woodlands.
Buggs and Kew Gardens colleagues further revealed that the disease could be shaping ash trees' evolution, with young trees in natural woodland carrying more genetic resistance than older trees thanks to natural selection.
A new direction for forest policy in the UK
Buggs’ genomics research revealed ash trees’ natural resistance to ash dieback and how to identify resistant individuals. This was evidence for policymakers that selective breeding offers a long-term solution to the epidemic.
His findings underpin key sections of Defra’s Ash Tree Research Strategy (2019), which led to the collection of hundreds of more-resistant trees that could be used for breeding.
In 2022, then Defra minister, Lord Benyon, praised the fast-tracking powers of this new genome-based approach, explaining that we will not need to “wait for five decades [for the species to recover], as we have with elm”.
In recognition of this approach, Defra funded similar genomics research at its Centre for Forest Protection to help safeguard more species: birch, oak, elm and elder. Further, Defra appointed Buggs to their Trees and Woodlands Scientific Advisory Group in 2021, on which he provides genomics expertise in relation to numerous species.
Efficient and effective forest management
Buggs’ evidence indicates that forest managers do not need to pre-emptively fell all their ash trees to prevent the spread of ash dieback.
When the disease was discovered in the UK in 2012, 95% mortality rates were widely reported. However, Buggs’ calculations of mortality rates in Europe showed that, although highly concerning, the disease’s impacts were not as severe as first feared – with rates no higher than 85%. Some trees have genes that support natural resistance to infection and the species is evolving to overcome ash dieback, as his research also confirms.
This evidence led to new guidelines, issued by the Forestry Commission, the Tree Council and Natural England, among others. These advised forest managers to retain healthy trees and promote natural regeneration.
This targeted approach to disease management allows more trees to continue providing environmental and economic benefits and avoids costly replanting programmes.
A technology to accelerate tree-breeding programmes in Europe
Buggs’s team supplied their genetic markers of resistance to scientists on the EU B4EST project who were developing a genotyping array for ash in 2019/20. This technology allows the cost-effective study of genetic variations across thousands of ash trees. Trees that have a natural resistance to the disease can then be selected for breeding.
US company Thermo Fisher Scientific produces the Applied BiosystemsTM AxiomTM array which the following ash-preservation programmes now use:
- Eshe in Not (Austria)
- FraxGen within FraxForFuture (Germany)
- Optforests (France)
Key takeaways
- Ash dieback is devastating, but policymakers and forest managers can preserve ash trees’ future through selective breeding and cautious felling.
- Genomics provides policymakers and forest managers with precise data and tools to understand threats to a wide range of species beyond ash.
- Genomic predictions of how trees adapt to threats are becoming essential as global trade moves pests and pathogens around the world, and as our climate warms.