World maize production in 1992–94 oscillated between 470 and 569 million t produced on about 127–132 million ha. The average yields were in the range of 3.7–4.3 t/ha, which are the highest among the most important world cereal food crops: wheat, rice and maize (FAO 1995). Its production, however, is not evenly distributed. More than 40% of world maize production comes from the United States. Maize is widely adapted between 55°N and S latitudes (Guidry 1964) and at altitudes from sea level to 3600 m in cool tropical highlands of the Andes. Adapted maize germplasm is cultivated in tropical lowlands, tropical and subtropical mid-altitudes, temperate and cool tropical highland climates.

Hybrid maize was first introduced in the United States before World War II and further development of single-cross hybrids from the 1960s in most temperate maize-growing countries has been a significant factor in increasing maize production (Hallauer et al. 1988). Hybrid maize technology is being employed for the other maize types grown in tropical, mid-altitude and highland maize production regions where, however, an important part of maize production is the use of landraces (traditional local maize varieties) and improved varieties for food preparations of preferred grain texture and colour.

BOTANY AND DISTRIBUTION

Cultivated maize is Zea mays L. (Species Plantarum 971. 1753) or Zea mays L. subsp. mays Iltis (Iltis and Doebley 1980), and two of its relatives, Tripsacum and Teosinte, are described later in this volume.