Ash dieback: A scientific update

As of the 7th October, the Forestry Commission reported that Chalara fraxinea– the deadly fungus ravaging European ash trees- is now present at 585 sites throughout the UK, including 15 English counties. But while Chalara is unfortunately continuing to spread further throughout Europe, the work from governments, science and the public has been increasing, providing new avenues for future action and research opportunities.

The science behind Ash dieback has progressed a lot, as can be seen in an overview by the EU commission. Genetic studies have proved extremely instrumental in understanding tree resistance and how the fungus itself works and attacks trees. Following the successful unraveling of the genetic codes of both the Chalara fungus and ‘Tree 35’, a Chalara resistant Danish tree, British scientists at the Bugg’s lab at Queen Mary University of London recently made a break through by mapping the UK native ash genome.

The tree, which was from the progeny of a self-pollination of ash trees, undertaken by David Boshier 10 years ago, was mapped as part of the British Ash Genome project. This marked an important step for furthering understanding in the resistance of ash trees to Chalara and could help underpin eventual plans to implement a breeding programme of resistant trees. Mapping a genome from a self-pollination is crucial as it has lower heterozygosity compared to its wild counterparts, which often have huge genetic diversity due to the complex sexual nature of Ash trees. This sequenced genome can therefore act as a reference when comparing genomes that show resistance to the Chalara disease, eventually enabling particular resistance genes to be uncovered.

Despite the negative impacts Chalara has had on Ash trees, a positive outcome has been the opportunity for collaboration between scientific research communities. Scientists from all over Europe have been working together on numerous country specific and EU funded research projects in order to answer some of the fundamental questions limiting current knowledge. Perhaps the best thing to result from such collaborations however is that most of their data is being made available online such as on the OpenAshDieBack hub,  meaning that scientists working on similar projects can access such data faster. This will hopefully help research in this field advance more quickly, enabling solutions to be identified more rapidly.

The public have also got involved in advancing the work of researchers. A variety of citizen science initiatives have been generated which have both increased public understanding as well as helped scientists directly. At a basic level, guides and apps have been created to enable the public to spot and report diseased trees. More recently however, there have been more novel projects launched. The University of East Anglia have launched a new project whereby people can physically tag both healthy and diseased trees and monitor their long term progress. Meanwhile, those members of the public who prefer to help from inside their homes can do so by playing a Facebook game, Fraxinus, which aims to use people’s pattern recognition to match genetic sequences using real data.

However, scientists now fear that the Chalara disease is not the only threat that Ash trees face. The Emerald Ash Borer has been decimating Ash trees in the USA and there are now reports of it being near Moscow and spreading further west. Whilst it is not an imminent threat, some scientists such as Professor Steve Woodward from the University of Aberdeen, are now recommending that research into this beetle should be increased as European Ash trees are likely to be highly vulnerable. Studying the Manchurian Ash, and therefore collaborating with scientists in the US, may be a future research direction as this species displays resistance to both Chalara and Emerald Ash borer.

There has been much effort from funding, research and legislation perspectives to tackle Chalara across both the UK and the EU. This has meant that there has been a lot of progress, particularly in science, which for the most part has been well joined up throughout Europe. The positive outcomes from this disease have been the development of new scientific collaborations and increased communication, as well as the increased opportunities for citizen science projects. Additionally, such attention to other future threats Ash face may not have been recognised as early had Ash dieback not posed such a serious problem. Whilst the threat of this disease, and future pests, is increasing, for the science at least we are well on the road to increasing our knowledge and developing solutions to tackle Ash dieback.