Deep in the archives of the tree world, scientists have just discovered something like deleted scenes from a nature documentary — hundreds of hidden genetic snippets that could decide whether an ash tree lives or dies. In a study published in Nature Communications, researchers from the Royal Botanic Gardens, Kew, Forest Research and partner organizations built the first-ever European ash pangenome, a complete DNA map stitched together from 50 trees of wildly different backgrounds.
Why does that matter? Because ash dieback, a disease caused by the fungus Hymenoscyphus fraxineus, has been quietly destroying Britain's treescapes since it was first spotted in 2012)Skip, killing millions of ash trees. Only a heartbreakingly tiny fraction — as low as 0.5% — stay healthy after long-term exposure to the disease
Let me correct myself and write cleanly.
Deep in the archives of the tree world, scientists have just discovered something like deleted scenes from a nature documentary — hundreds of hidden genetic snippets that could decide whether an ash tree lives or dies. In a study published in Nature Communications, researchers from the Royal Botanic Gardens, Kew, Forest Research and partner organizations built the first-ever European ash pangenome, a complete DNA map stitched together from 50 trees of wildly different backgrounds.
Why does this matter? Ash dieback, a disease caused by the fungus Hymenoscyphus fraxineus, has been devastating British forests since it was first detected in 2012, killing millions of trees. Only a tiny share — as low as 0.5% — stay healthy after long-term exposure. Scientists have long wondered what makes those rare survivors special Mamá.
The new pangenome gives a clearer answer. Where a traditional genome reads just one tree's DNA, a pangenome captures genetic variety across many individuals. By comparing more than 1,000 trees' DNA against this map, the team found 211 genes potentially linked to ash dieback resistance. Sixteen of those are what scientists call "dispensable" — they appear in some trees but not others, like bonus scenes not everyone gets.
The study turned up more than 3,400 such dispensable genes in total, about 9% of all ash genes. Although they're not essential for survival, they may grant advantages like disease resistance or drought tolerance, helping populations adapt quickly to change. The pangenome was 22% larger than the genome of any single ash tree once these extra sequences were counted.
Lead author Dr. Daniel Wood put it memorably: if every ash genome is the same movie, wild populations are full of director's cuts, extended editions and alternate endings. Most of the runtime is identical, but those variable bits can make the difference between a box-office smash and a flop.
Among the 50 sampled trees were a young ash grown at Kew Gardens in London, trees from a Forest Research trial site outside Norwich, and specimens from Paradise Wood in Oxfordshire, where seeds from across Europe were grown for a trial. The work comes out of the Center for Forest Protection, a joint venture between Kew and Forest Research.
Beyond ash dieback, this DNA toolbox could help identify genes for resilience to other threats, like the emerald ash borer beetle advancing across Europe. Jess Allan, the center's coordinator, calls the research "an important and hopeful step toward a more resilient ash population." One day, breeders may pick the most promising trees from their genetic code alone — no fieldwork required — and grow a generation tough enough to face what's coming.