Numerous viruses, bacteria, fungi and nematodes threaten our cultivated plants. These phytopathogens are genetically highly flexible. How do new variants arise and spread? Which factors promote these processes? How can we detect new aggressive variants? Such research issues are addressed by the Institute for Epidemiology and Pathogen Diagnostics.

Phytopathogenic viruses, bacteria, fungi and nematodes are naturally evolving. Depending on selective pressure exerted by the host plant or the environment, emerging variants establish locally and may spread epidemically over large distances. Infected cultivated plants decline in yield and product quality. Emerging variants of pathogens often evade the defence system of cultivated plant varieties. Other variants may resist a pesticide. Or they improve adaption to a vector or an alternate host to spread more efficiently.

We investigate the biological and genetic flexibility and within-species diversity of phytopathogens to understand how and by which mechanisms they evolve in the frame of modern agriculture.

• Viruses have exceptionally flexible and small genomes, which nowadays can be completely sequenced within a short time. How do new biological traits relate to genetic changes?
• Bacteria exchange mobile genetic elements that carry virulence factors or genes for other new traits. How is gene transfer facilitated?
• Recently some fungal pathogens largely spread in Germany. Is this provoked by climate change, or are these more successful variants of these fungi?
• Plant-parasitic nematodes secrete effectors to attack and manipulate the host plant. How do effector genes vary when the nematode invades the plant more efficiently?

Our results on the variability and diversity of phytopathogens are the basis for the development of powerful and highly specific diagnostic tools. This is a major prerequisite for target-oriented plant protection. Our findings also contribute to the breeding of plants for sustainable resistance to pathogens. The research is indispensable for the development of crop protection strategies for integrative as well as organic farming. The early detection of emerging varieties of phytopathogens enables a foresighted political consulting.