Ustilago is a genus of approximately 200 smut fungi parasitic on grasses. There is a large research community that works on Ustilago maydis including researchers at the University of Georgia, Philipps-Universität Marburg, University of British Columbia and others. Research with this organism has led to better understanding of the genetics underlying self-non-self recognition through elucidation of the mating type system as well as fundamental aspects of signal transduction and cell-cycle regulation.