Maize is the domesticated variant of teosinte. In Mesoamerica, wild teosinte was domesticated to maize by 4000 BC. Maize was domesticated from the wild grass teosinte in West Mexico by 6700 BC. In Mesoamerica, wild teosinte was bred into maize by 6,000 years ago. The annual teosinte variety called "Zea mays mexicana" is the closest botanical relative to maize. Maize arose through domestication of "teosinte", which is considered to be the ancestor of maize. Individual knobs are polymorphic among strains of both maize and teosinte. "Zea mays" (maize) and "Zea diploperennis", which is a perennial type of teosinte. "Ustilago maydis" is a pathogenic plant fungus that causes smut disease in maize and teosinte. Zea luxurians is a true grass species in the genus "Zea" and a teosinte. In the Americas, crops domesticated in Mesoamerica (apart from teosinte) include squash, beans, and cocoa. He found over 10,000 teosinte cobs in the Coxcatlan Cave. The original corn plant known as teosinte is still grown in Mexico. Common names for the species include Florida teosinte and Guatemalan teosinte. In several laboratories he grew a series of Teosinte/Maize crosses.