The last stand?

Ash canopy

29 June 2013

Few people will have missed the news that Britain's 80 million ash trees are under threat from an apparently unstoppable fungal disease, Chalara. But there is a glimmer of hope. Richard Hollingham talks to Richard Buggs from Queen Mary University of London, and Jo Clark, from the Earth Trust.

Jo Clark: We're in Paradise Wood, the research woodland of the Earth Trust. Set up about 20 years ago it's the largest collection of genetic broadleaf trials in the country, dedicated to improving the quality of some of our most important timber trees.

Richard Hollingham: Where we are right now the trees are really quite small and stubby.

Jo Clark: Yes, that's partly because we're in a bit of a frost pocket here so it's not ideal for planting trees. But also these are a special line of ash trees that have been cross-bred with themselves, which has an impact on their growth.

Richard Buggs: For me to sequence a genome it is really important that these are inbred trees. Normally trees have one genome copy from mum and one from dad and they can be quite different so it can be hard to untangle the two to sequence the genome. But a plant that is the product of self-pollination has the same mum and dad which makes assembling the genome much more efficient and gives us really good results.

Richard Hollingham: Jo, I mentioned that alarming statistic of 80 million trees likely to be affected by ash dieback, but how important are ash trees?

Jo Clark: Ash is one of our most important trees, it's the third most common tree and the second most widely planted broadleaf tree. A lot of British biodiversity depends on the structure of our broadleaf woodland and ash is a very important component of that. It's also very important for timber - it's quite elastic, quite good at absorbing impact so it's used in things like flooring and door frames. Morgan cars are still made from ash trees - it's widely used.

Richard Hollingham: So, Richard, what are you actually going to do?

Richard Buggs: Today I'll be collecting a sample from the ash and taking that back to my lab where PhD student Yasmin Zoren will extract the DNA from the bark. We send that DNA to Eurofins in Germany and they'll send back a whole load of short reads [of the chemical structure] covering the genome 155 times over. We then put that all together, using high-performance computers to assemble the actual genome sequence.
Sequencing a genome is a bit like building up a picture of an unexplored island. All we know is how big the island is; to find out what the interior's like we might take lots of small aerial photos which we then have to piece together like the reads of DNA. In this case we have to put all the DNA bases together like a big jigsaw puzzle in the computer to find the whole genome code of the ash tree.

Richard Hollingham: How does the DNA sequence help you understand which trees are going to be resistant to the disease?

Richard Buggs: The genes for resistance aren't just going to pop out of the genome as soon as we sequence it, we'll have to find them. We'll do that by looking at lots of trees to find ones that are resistant, then genotyping them - not the whole genome but enough of it to pick out the genes associated with resistance or susceptibility to ash dieback.

Jo Clark being interviewed by Richard Hollingham

Jo Clark being interviewed by Richard Hollingham.

Jo Clark: The underlying genetics is of paramount importance, whether you're trying to produce robust populations to combat climate change, or to resist a novel disease like this fungus, Chalara. The genetics is what underpins all our research work to produce productive timber trees for the future.

Richard Hollingham: Richard, how long is this going to take?

Richard Buggs: Sequencing the genome should take less than a year - we should be releasing a draft assembly of the ash genome very quickly. Technologies have moved on really fast in the last five years and this is now quite a routine thing to do.

Richard Hollingham: And, Jo, how soon do you expect to be able to use this information?

Jo Clark: Once we have individuals that are likely to be resistant we have very good techniques for grafting them onto a rootstock; then you can be producing seeds perhaps in five years' time. The public can help by identifying trees they think are resistant, and letting researchers know on the Future Trees Trust website. Those are the ones we would like Richard to be screening to see if they are resistant and we can breed from them.

Richard Buggs: This is obviously a huge natural disaster for Britain but one of the really encouraging things is this has shown us how much the public cares about woodlands. And within the scientific community I have seen a huge enthusiasm to get involved with trying to combat this problem. People with different research skills are coming together and saying, look, here is something that I can bring to the table, let me work on this. We're all looking to collaborate to combat this together as a scientific community within Britain.

This Q&A is adapted from the Planet Earth Podcast, 5 February 2013.