Plant species diversity is often associated with reduced disease risk. Yet, the scientific literature on diversity-disease relationships is unclear, showing conflicting relationships. This conflict highlights a major knowledge gap in our understanding of the mechanisms underpinning the diversity-disease relationships. Overcoming this gap is essential for transforming agricultural systems from monocultures that are sensitive to disease outbreaks to diverse cropping systems that are intrinsically resilient to pathogens. I aim to significantly advance our understanding of diversity-disease relationships in plants. I will transform our knowledge on belowground plant-pathogen interactions by integrating three advances from animal epidemiology. 1 Host quality Diversity in epidemiological traits has proven key to understanding disease dynamics in animals. I will systematically quantify such variation in plants and their consequences for disease risk. 2 Pathogen protection Microbes can protect animals from pathogen infection. I will investigate the role of symbiotic mycorrhizal fungi (AMF) in belowground pathogen protection in diverse plant communities. 3 Contact networks Pathogen transmission ultimately depends on contacts within the community. Plants are obviously sessile, but their root systems are not. By navigating the soil, they may interact with different neighbouring plants. I will examine how the nature of these root contact networks affects disease risk. I propose that plant traits are a bridging link between these epidemiological advances. I will use experimental and modelling approaches with a range of grassland species and three soil-borne fungal pathogens. I aim to transform our understanding of belowground plant-pathogen interactions in biodiverse systems with multiple pathogens, stimulate crossovers with phytopathology and animal epidemiology, and provide a knowledge base to design agricultural systems that are intrinsically resilient to pathogens.