Ash f ightback

Coming soon, new trees resistant to deadly dieback (but they are more likely to be ravaged by beetles)

TREES resistant to the killer ash dieback fungus could soon be grown in Britain – but they will be more at risk from insect attacks.

In a fightback against the fungus, which it is feared may wipe out most of the UK’s 125million ash trees, scientists have isolated the genes which help them fight it off.

The breakthrough could mean a new generation of diseaseresistant trees, avoiding a repeat of the devastation caused by Dutch elm disease, which killed almost all of our 30million elms in the 1970s.

But, in a blow for the many experts involved, the trees with resistant genes also carry low levels of chemicals which defend them against insects. It means those which survive ash dieback could do so only to fall victim to the other major threat to ash trees – the emerald ash borer beetle.

The new threat is highlighted in a study published in the journal Nature. Joint lead author Dr Christine Sambles, of the University of Exeter, said: ‘Our research highlights the danger of selecting trees for resilience to ash dieback at the expense of resistance to insects that threaten this iconic UK tree species.’

Co-author Professor Murray Grant, of the University of Warwick, said: ‘Plants use a vast range of chemicals to defend against fungal attack and the primary objective was to identify differences which could be used to screen young ash trees and choose the best ones for replanting.

‘Our findings underline the need for further research to ensure that we select ash trees resilient to present and future threats.’

The ash is one of the most common trees in Britain. But ash dieback, which has spread like wildfire across Europe within less than a decade, has the potential to kill off In danger: The great British ash 90 per cent of them. In an effort to prevent this, Government organisations and universities joined forces to sequence the 38,852 separate genes found in an ash tree in Gloucestershire.

They found Britain may have a greater proportion of trees with chemical compounds which ward off ash dieback than in Denmark and Poland, where the fungus was first identified.

However the DNA which protects trees from fungus also appears to make them vulnerable to insects. This raises concerns over the emerald ash borer beetle, which has devastated vast swathes of ash in the US and whose population is making its way across Europe.

With tens of millions of ash trees across Europe already dying from ash dieback, the beetle is the next biggest threat, with trees needed which can resist both.

Nonetheless the breakthrough has been welcomed, with plans for ‘accelerated breeding’ of new trees.

Ash dieback, first discovered in the UK four years ago, is spreading at the rate of 12 miles a year. More than half of England’s trees are in affected areas, as are a third in Wales and almost one in six in Scotland.

The disease was first found in Scottish trees in 2012. Since then, a total of 180 cases have been found, mostly across the east of the country.

The fungus has no cure, although some trees have natural resistance. It spreads on the wind or through infected saplings.

Austin Brady, of the Woodland Trust, said: ‘Our cherished native trees are under growing attack from new pests and diseases.

‘Scientific selection and tree breeding could have a valuable part to play but is no silver bullet.’