Macrophomina phaseolina is a soil-borne fungal pathogen that causes a disease commonly known as charcoal rot. Currently, there is not an effective method for controlling the disease, because knowledge about the pathogen, the development of the disease and how it interacts with the plant host is limited. Therefore, a study is proposed to investigate the interactions between M. phaseolina and the plant species Medicago truncatula using a molecular genetics approach where the host genes involved in the disease development will be identified. We will first conduct a genetic screen in a mutant population of M. truncatula and look for strains that have altered susceptibility to M. phaseolina. We will then identify the genes that are involved in host-pathogen interactions.