Magnaporthe grisea, also known as rice blast fungus, rice rotten neck, rice seedling blight, blast of rice, oval leaf spot of graminea, pitting disease, ryegrass blast, Johnson spot, and neck blast is a plant-pathogenic fungus that causes a serious disease affecting rice. It is now known that "M. grisea" consists of a cryptic species complex containing at least two biological species that have clear genetic differences and do not interbreed. Complex members isolated from "Digitaria" have been more narrowly defined as "M. grisea". The remaining members of the complex isolated from rice and a variety of other hosts have been renamed Magnaporthe oryzae, within the same "M. grisea" complex. Confusion on which of these two names to use for the rice blast pathogen remains, as both are now used by different authors.