Corn smut (español: huitlacoche) is an edible fungus known in Mexico as the delicacy huitlacoche. It is served in soups or as a filling in tacos and other tortilla-based foods. It has been called Mexican truffle and Aztec caviar. It is a plant disease caused by the pathogenic fungus Ustilago maydis that causes smut on maize and teosinte. The fungus forms galls on all above-ground parts of corn species. Huitlacoche is rich in potassium, which reduces blood pressure and protects against stroke, osteoporosis, and kidney stones.