Ustilago maydis

Ustilago maydis, also classified as Mycosarcoma maydis, is a basidiomycete fungus and the best-studied member of its class, Ustilaginomycetes, that causes corn smut in maize and teosinte wherever they are grown. The fungus invades the ovaries of its host, causing kernels to swell into gray-black, tumor-like galls up to four or five inches across, made up of hypertrophied plant cells mixed with fungal threads and spores. In Mexico the immature galls, harvested two to three weeks after infection, are eaten as the delicacy huitlacoche, prized for a mushroom-like, sweet, savory and earthy flavor and valued for a protein and lysine content equal to or better than most edible fungi; the species is also an important genetic model organism and a source of industrial chemicals such as ustilagic acid and itaconic acid.