Marc Orbach, PhD, uses Magnaporthe grisea, the fungal pathogen responsible for the rice blast disease, as a model system to study host-pathogen interactions at the molecular and biochemical level. This pathogen, like many other plant pathogens, interacts with its host in a gene-for-gene manner, where host resistance is induced when the plant contains a resistance gene and the pathogen, a corresponding avirulence gene. The main focus of his research program is to understand what the signals between the pathogen and its host are, that dictate whether the host is able to mount a resistance response. Genetic analysis of M. grisea have identified several avirulence genes that determine what their products are and how these products interact with host plants to induce host defenses. He is also interested in questions of genome stability and the generation of genetic variability in fungi. These questions are of significance in M. grisea because of the apparent ability of this pathogen to rapidly overcome host resistance in the field. Dr. Orbach spends time addressing these questions by studying genome variation in M. grisea at the whole genome level using electrophoretic karyotyping methods. He wishes to specifically analyze the role that a transposable element may play in genome variation and the high rate of mutation observed at some loci.