Soils which are suppressive to soil-borne diseases are soils in which pathogens, although present, sometimes in large inoculum density, cannot carry their infectious activity. In most cases, biotic factors are responsible for this inhibition, although the abiotic environment regulates these factors. In this thesis, we propose to conduct an intermediate approach between the metagenomic analysis of soil suppressiveness to diseases and the search for fungi whose activities contribute to the inhibition of infectious pathogens. The aim is to define a set of fungal genes a priori associated with mechanisms reflecting the suppressiveness of given soils to a disease and to check whether these genes are common to all the suppressive soils to different types of disease regardless of the taxonomic biodiversity present in these soils. Bioassays were conducted in both suppressive and conducive soils, DNA was extracted from the rhizosphere of susceptible plants grown in these soils, 454 sequencing of prokaryotic and eukaryotic DNA is in progress and tools to manage the data are being setting up in the frame of the UE project Ecofinders FP7-ENV-2010-264465.