One of the most important tasks in grapevine breeding is to breed new grapevine varieties with high resistance to fungal pathogens.

This is a requirement for ecologically sustainable viticulture with greatly reduced pesticide use. It is therefore our focus to better understand the pathogen-plant interaction. The key questions are:

• How do fungi manage to infect the vine?
• And how does a resistant grapevine defend itself against them?

Microscopic methods are used, for example, to investigate the ability of downy mildew to which extent the spores can germinate, on different susceptible and resistant grapevines, and how the fungal mycelium penetrates the leaf through the stomata in order to multiply there. Various staining techniques allow to visualise if or how the grapevine reacts to the contact with the pathogen. The use of gene expression analyses and genome sequencing make it possible to understand which genes are responsible for a specific resistance and how the plant's defence reactions are genetically regulated. These results allow important conclusions regarding resistance mechanisms. This information is ultimately important for breeding as the combination of different, preferably complementary mechanisms, leads to more robust and resistant new grape varieties.