Scientists' breakthrough research on disease killing off horse chestnut trees

Kim BriscoeNorwich scientists have made a breakthrough in research into a disease which is killing off the UK's horse chestnut trees.Kim Briscoe

Norwich scientists have made a breakthrough in research into a disease which is killing off the UK's horse chestnut trees.

Scientists at the Sainsbury Laboratory, at Norwich Research Park on the outskirts of the city, have decoded the genome of a bacterium that is threatening these trees.

The horse chestnut has become an iconic sight in Britain since its introduction in the 1500s, but in 2002 a new lethal disease appeared that now infects more 70pc of trees in some areas.

Bleeding canker, caused by the bacterium Pseudomonas syringae pathovar aesculi (Pae), causes lesions which bleed like open sores and in severe cases can kill large mature trees within one to two seasons.

'Comparing the genomes of British strains of the bacterium has shown us they are very similar and probably originated from a single introduction into the UK within the last few years,' said Dr David Studholme, who led the analysis of the DNA sequences at The Sainsbury Laboratory.

Dr Sarah Green, a tree pathologist with Forest Research which is part of the Forestry Commission, added: 'Detecting the origin of Pae is important from a biosecurity perspective.

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'There has been an unprecedented rise in invasive plant diseases, possibly linked to the rise in international travel and in the global plant trade.

'We now have the first clues to the evolutionary origin of the disease and to its ability to spread so fast.

'Pae might have been accidentally introduced to Europe through importation in the plant trade. We need to prevent it being introduced to new geographical areas such as North America.'

Before the European epidemic, the only reported case of Pae was in India. A similar strain infects the Indian horse chestnut but causes only minor lesions in the leaves. The strains that emerged in Europe appear to be more aggressive and attack the woody trunk and branches.

The genome sequence will allow scientists to determine which genes might be necessary for infection of a tree host so they can be targeted to control the disease.