Abstract: In recent years alterations of chemical signals from plants and/or microbes havereceived increasing attention, as they are considered to play a central role in determining thepositive or negative outcome of interactions in the rhizosphere. However, there is still a lack inthe understanding how root exudates affect the development of fungal propagules in therhizosphere. In this work a complex system consisting of tomato (Solanum lycopersicum L.), theintercropping partner leek (Allium porrum L.), the soilborne tomato pathogen Fusariumoxysporum f.sp. lycopersici (FOL) and the arbuscular mycorrhizal fungus Glomus mosseae(AMF) was designed to assess metabolic changes in root exudation and the effects of theseexudates on FOL. Tomato and leek plants were grown together in pots and inoculated with FOL,AMF, FOL and AMF in combination. Uninoculated tomato and leek plants and two tomatoplants grown together were added as control treatments. After a period of 10 weeks undergreenhouse conditions root exudates were collected. The exudates were used for in vitro testswith FOL (e.g. spore germination, activity) and for analysing the components (e.g. sugars,secondary metabolites) of the exudates with HPLC-DAD and GC-MS, respectively. Furthermore,data about root weights, AMF colonization rates and FOL infection rates will be discussed.