Scientists have decoded the genome of a bacterium that is threatening the UK's historic landscape.
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 over 70 per cent 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 in Norwich.
"Detecting the origin of Pae is important from a biosecurity perspective," said Dr Sarah Green, a tree pathologist with Forest Research. "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," said Dr Green.
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.
"This pathogen spread quickly through Western Europe and Britain and the information from the sequencing will help us discover how it is dispersed," said Dr Rob Jackson from the University of Reading. "It may be that it can cause precipitation so
|Contact: Zoe Dunford|
Norwich BioScience Institutes