Leaving devastation in its wake: the bacterium Erwinia amylovora attacks and kills fruit trees. | Image: Steffen Schmidt/Keystone

Brown leaves and dying apple trees – these are the tell-tale signs that the disease fire blight has been leaving in its wake for the past 60 years in Europe. A team from the Zurich University of Applied Sciences (ZHAW) has now found a special variable region in the otherwise stable genome of the bacterium that makes it possible to distinguish between different variants. Thanks to hundreds of historical samples, this means in turn that the spread of the disease can be traced. It began with two populations introduced separately from North America, then spread across Europe. In the last 20 years it has also reached Asia, where wild pome trees are now endangered.

M. Kurz et al.: Tracking the dissemination of Erwinia amylovora in the Eurasian continent using a PCR targeted on the duplication of a single CRISPR spacer. Phytopathology Research (2021)