Bacterial leaf spot disease is caused by Xanthomonas fragariae. This disease causes much damage in strawberry propagation and production. This slow-growing bacterium is difficult to trace.

Infested plants often take a quite a long time before showing symptoms. But as soon as symptoms are developing, the bacterium can multiply very rapidly, resulting in a high risk of the bacterium spreading itself.

To investigate when and under which conditions the latent infestation turns into symptom development, PRI has applied the newly developed  Fluorescent Protein Imaging (FPI) technique. This technique marks the bacterium with green fluorescent protein resulting in green fluorescence under blue light. Bacterial growth can then easily be followed by microscopic techniques as well as FPI. FPI entails scanning of large parts of a plant with a laser and processing of the fluorescence signal with a light-sensitive camera.