Breeding plants resistant to the destructive Ash dieback fungus is essential if the iconic British trees are to survive, study finds
- Ash dieback came to the UK seven years ago from Europe and has no cure
- It leaves diamond-shaped scars on bark and can decimate tree populations
- With the current level of resistance about one in 100 ash trees survive the virus
- If one in 10 trees were tolerant the population would be cut to a third of its size
Conservationists should breed trees resistant to ash dieback in order to save Britain from the killer fungus.
Ash dieback is in danger of wiping out the UK’s 125 million ash trees, but around one in 100 can fight off the epidemic.
They may have a genetic advantage, possibly causing their leaves to die early in autumn, so that the fungus cannot burrow into leaves and infect a tree.
A British scientist has now worked out that resistant trees could prevent millions of deaths.
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Conservationists should breed trees resistant to ash dieback in order to save Britain from the killer fungus (pictured)
With the current level of resistance, which means about one in 100 ash trees survive the ash dieback virus, Professor Matthew Evans says 95 per cent of trees are likely to be wiped out by the end of the century.
But if one in 10 British trees were tolerant to ash dieback, the ash population could be cut to only a third of its current size.
Professor Evans, who created a computer model for tree deaths, concludes that enough resistant trees will not appear on their own.
Ash trees are pollinated by the wind, so pollen from a non-resistant tree can land on a resistant one, meaning its ‘helicopter’ seeds may not have the parent tree’s ability to ward off ash dieback.
This is why some experts support ‘selective breeding’ by taking cuttings or artificially pollinating resistant trees.
Professor Evans, from the University of Hong Kong, states: ‘As has been suggested by other authors, it seems reasonable that selective breeding could play a role in the conservation of ash forests.
‘The establishment of a source of resistant individuals that could be used to boost the numbers of naturally resistant trees in the population would help increase the chances of a population sustainability.’
Ash dieback came to the UK seven years ago from Europe, has no cure and leaves diamond-shaped scars on bark. Causing leaves to fall off trees, it can decimate 60 per cent of trees in woodlands.
Ash dieback is in danger of wiping out the UK’s 125 million ash trees, but around one in 100 can fight off the epidemic. This image shows and infected tree
A British scientist has now worked out that resistant trees could prevent millions of deaths. This image shows a closeup of the fungus
The new study suggests that the fungus could make ash, now one of Britain’s most common trees, more rare than oaks, sycamores, hazel and hawthorn trees.
The computer model, which was created based on Wytham Woods in Oxfordshire, shows a worrying vision of what would happen if ash dieback became established in the UK over the next decade.
Numbers will fall by a third in the next century if one in 10 trees are resistant, but 60 per cent more trees would die if only five per cent were resistant.
If just one per cent were resistant, as previous research has suggested may be the case in Britain, 90 per cent more trees would die. That is based on a high chance of offspring trees inheriting resistance.
Professor Evans concludes: ‘The rapid reduction in the numbers of an abundant species will have implications for the dynamics of the forest, and the remaining population will be additional assaults from future pests and diseases and/or the evolution of the current disease.’
Nick Atkinson, Senior Conservation Adviser at the Woodland Trust said: ‘We welcome any attempts to improve the chances of identifying tolerant or resistant trees on the understanding that this might come at the cost of resistance to other diseases, or other negative effects.
‘We are beginning to see apparently healthy ash trees in areas heavily stricken by ADB and the question is to what degree any tolerance is genetically based.’
The full findings of the study were published in the journal Royal Society Open Science.
WHAT IS ASH DIEBACK?
Ash dieback affects ash trees (Fraxinus excelsior) and is caused by the fungus Hymenoscyphus fraxineus, previously known by the names Chalara fraxinea and Hymenoschyphus pseudoalbidus).
It blocks the water transport systems in trees causing leaf loss, lesions in the wood and on the bark and ultimately the dieback of the crown of the tree.
This disease was first described in Poland in 1992 and has since swept westwards throughout Europe.
It was first identified in Britain in 2012 in nursery stock then in the wider environment in 2013 although it could have been in the country much longer.
The number of confirmed findings is continuing to increase and the distribution is reported by the Forestry Commission on a regular basis.
Young trees are particularly vulnerable and die quickly once they succumb. Older trees can be slowly killed by a yearly cycle of infection.
Spread of the disease in the UK is most likely to be as a result of the planting of infected nursery stock and wood but wind borne distribution of the fungal spores also occurs.
There are several key signs to look out for on ash trees. All of these symptoms can also be caused by other problems, so final diagnosis should be made by an expert.
Summer is a good time to look for symptoms as in autumn and winter, ash trees will naturally be shedding their leaves making it difficult to identify ash dieback.
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