Ash trees and the fungus that kills them

I’m intrigued by Graham Rowe’s idea about ash dieback disease. Dr Rowe noticed that ash trees (Fraxinus excelsior) in Eastern England resemble those in Denmark. And he noticed that F. excelsior in other parts of Britain resemble those in Spain and Portugal.

Could this be why ash dieback appeared first in Eastern England? Are those trees susceptible while other ash trees in Britain are resistant?

Before I go on, let me say that the ash dieback fungus has two names. It’s called Chalara fraxinea and Hymenoscyphus pseudoalbidus. Confused? You’re not the only one. Some kinds of fungi do have dual names like this, but the system is going to change at the start of 2013. Happy New Year, say I! No doubt some people will continue to use both names for ash dieback (and I can think of a few choice, unprintable names for it too) but most seem to be calling it C. fraxinea so I’ll do that.

Whatever we call this fungus, Dr Rowe suggests that ash trees with Danish cousins tend to die from it whereas ash trees with Spanish cousins tend to resist it. Could he be right? He’s a molecular ecologist who knows how species recolonised Europe after the last Ice Age. A lot of his work isn’t about trees, it’s about the adorable natterjack toad (Bufo Epidalea calamita), but the science of how species colonise land applies to any kind of organism.

The way C. fraxinea is spreading across Britain could be to do with tree genetics. It could be to do with imported trees carrying the fungus. It could be to do with wind blowing spores across the sea. Ash dieback was reported first in Poland in 1992 and it has spread across Europe. It’s now spreading fast across Britain, possibly too fast for any hope of stopping it.

So I hope the tree genetics idea turns out to be right. Or at least partly right. Even within the Danish ash population there’s evidence that trees vary in their susceptibility to dieback.

Neither the tree nor the fungus has yet been described by a complete genome sequence. But during 2012, reports came out about ash tree genetics and dieback fungus genetics. There are now ‘next generation’ methods for DNA sequencing, including the very fast 454 method. So perhaps we won’t have to wait long for complete genomes of the ash tree and the dieback fungus.

What could be done with those genome sequences? And with the data gathered by the AshTag project? I hope geneticists and arboriculturalists will find a good way forward, learning from the story of the elms.

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About argylesock

I wrote a PhD about veterinary parasitology so that's the starting point for this blog. But I'm now branching out into other areas of biology and into popular science writing. I'll write here about science that happens in landscapes, particularly farmland, and about science involving interspecific interactions. Datasets and statistics get my attention. Exactly where this blog will lead? That's a journey that I'm on and I hope you'll come with me.
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3 Responses to Ash trees and the fungus that kills them

  1. Pingback: Emerging disease threats to trees | Science on the Land

  2. Pingback: National Tree Week | Science on the Land

  3. Pingback: Biological control for pests and diseases | Science on the Land

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