Maize (Zea mays L.) is a major staple food grain throughout the world, particularly in Africa, Latin America and Asia, and a major feedstuff in developed countries. The maize grain has many food (grain, flour, syrup, oil…) and non-food usages (cosmetics, adhesives, paints, varnishes). Maize starch and oil are also major products (Ecocrop, 2010). The maize grain is a major feed grain and a standard component of livestock diets where it is used as a source of energy. Other grains are typically compared to maize when their nutritional value is estimated. Many by-products of maize processing for flour (hominy feed, bran, germs, oil meal), starch (corn gluten feed, corn gluten meal) and alcohol/biofuel industries (distillers’ dried grains and solubles) can be fed to animals.
Maize breeders have created many cultivars that correspond to specific climatic or agronomic conditions and uses. “Dent corn” maize is the most widely grown type of maize and the one typically used for feed. Other types (flint corn, popcorn, sweet corn, flour corn) are more intended for food uses. Some varieties have been created to improve the industrial or nutritional value: high lysine, high tryptophan, high oil, high amylose, low phytate, etc. Brown midrib maize has a lower lignin content resulting in an increased digestibility in livestock. Genetically-modified (GM) maize varieties have been designed to improve grain performances (herbicide resistance, pest resistance, higher yields).
Maize is native to Central America (Oaxaca, Mexico) where it was domesticated, possibly as early as 5,500 to 10,000 BC. It later spread to Central America, the Caribbean, South America and North America. Through genetic selection and hybridation, it now grows worldwide between 58°N in Canada and Russia and 40°S in Chile and Argentina, from sea level up to an altitude of 3800 m in the Andean mountains (Ecoport, 2010). Optimal growth conditions are average day-temperature of 18-21°C, annual rainfall of more than 750 mm, and deep, well-drained rich soils.
Maize can withstand annual rainfall ranging from 230 to 4100 mm, with soil pH between 4.3 and 8.7, and a great variety of soils. Frost kills the plants. Drought is detrimental at flowering as it affects pollination and impairs yields. Maize has no tolerance to flooding (FAO, 2009; Duke, 1983).