Phelipanche ramosa (L.) Pomel, branched broomrape, is a major root-holoparasitic damaging weed with a large host range besides a strong adaptation to rapeseed. Broomrape seed germination is necessarily triggered by host root exudates. This ensures that they germinate close to a host root where they attach and establish a vascular connection to take up water and nutrients. No efficient broomrape management technique has been validated yet. Biocontrol could be an alternative but there is currently no biological control agent on the market. Indeed tripartite interactions between the host plant, the parasitic plant and a pathogenic agent of the latter are complex and poorly understood. The objective here is to meet this challenge and identify biocontrol products of P. ramosa. These products may be fungal strains or fungal secondary metabolites phytotoxic for broomrape seeds and stems. A molecular approach will characterize the diversity of endophytic fungal communities of healthy and symptomatic broomrape stems. In addition, a microbiological approach will isolate fungi associated with broomrape lethal symptoms. They will be tested for their phytotoxic activity through pathogenicity tests, metabolomic analyses of plant-fungus interactions and cytological analyses. Fungal strains specifically pathogenic on broomrape will be provided to control the subterranean development of the parasitic plant and phytotoxic metabolites could constitute an innovative mycoherbicide to develop.