Ongoing breeding programs selected for crop varieties with high yield under favorable conditions: sufficient water supply (irrigation) and high levels of chemical fertilizers (N, P). However, increased abiotic stresses (drought, salinity, high temperatures) as well as ecological concerns demand for new traits to transition to more sustainable production systems. One approach may consist in better control and exploitation of root microbiota, which have the potential to protect their host plants from abiotic and biotic stresses, and to improve nutrition and productivity. It is assumed that plant innate immunity and root exudates scale and structure root microbiota, but exact mechanisms remain unknown. In this project, I propose to analyze “root-adhering soil” (RAS), the soil aggregated around roots, as a global proxy for shoot-to-root carbon allocation, root exudation and recruitment of exopolysaccharide-producing microbiota in Solanum lycopersicum (tomato). A respective PhD student shall analyze the RAS trait in a tomato natural variation panel towards the identification of underlying genes. Further, he/she shall directly inactivate candidate genes assumedly involved in root exudation (multiplex CRISPR/Cas). Lines with contrasting RAS phenotypes, from natural and/or induced variation, will be analyzed for microbiota recruitment and exudate composition. This will provide fundamental knowledge on the genetic control of root exudation and microbiome assembly and scaling cues. RAS may represent a valuable trait for the adaptation and performance of plants under lower input conditions, and may also facilitate enhanced storage of carbon in agricultural soils.