American maize cultivars

Timeline

1. 1521Valley of Mexico · Valley of MexicoIn 1521, chinampa floating fields in the Valley of Mexico grew maize cultivars adapted to high-humidity conditions, yielding multiple harvests a year intercropped with beans and squash; the Aztec tribute system used maize as its core unit of account (tribute in maize), sustaining the last food supplies during the siege of Tenochtitlan.
2. 1521–1530Andean highland terraces · AndesThe Inca Empire grew cold-tolerant, short-season highland maize cultivars (such as choclo types) on terraces at 2,500–4,000 meters elevation, forming a highland dietary triangle with potatoes and quinoa; 1520s tribute records still listed maize as an important item, and mit'a labor service ensured varietal selection and storage (qolqa warehouses).
3. 1530Four quarters of Tawantinsuyu · BoliviaIn 1530 the Inca civil war disrupted tribute and storage systems, but local maize cultivars retained genetic diversity through long-term regional selection; after the Spanish conquest these varieties would spread to Eurasia and Africa through the Columbian Exchange, becoming a genetic source for one of the world's most important food crops.