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Zea Introduction

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Maize rootsMaize earsMaize tasselsMaize plant

Photos by Molly Fogleman

Maize, commonly referred to as corn in the United States, has been considered a unique plant since the time that the indigenous peoples of the Americas developed it to be their staple food. It is central to many sacred mythologies and creation stories which are still honored today (1, 2). Maize was introduced from the New World to the Old World in the 1400's, and it was planted between the harvesting of spring and winter crops, filling an important niche as a summer crop (1). Today, the United States, China, the European Union, Brazil and Mexico are the world's largest producers of maize (3). Together, the US and China produce approximately 60% of the world maize crop (4). Maize accounts for 15-20% of the total daily calories in the diets of more than 20 developing countries, located mainly in Latin America and Africa (5, 6). 68% of the land devoted to maize is located in the developing world, however only 46% of maize production occurs there, indicating the need for improving yields in developing countries where it is a major source of direct human consumption for many of the poor (7).

The United States is the world's largest producer and exporter of maize (3). Maize is the most important feed grain in the US because of its efficient conversion of dry substance to meat, milk and eggs, compared to other grains (8). In fact, the US devotes ~60% of its maize crop to animal feed. Approximately 20% is exported and the remaining crop is used for food and industry (9). There are 5 main endosperm types grown in the US: pop (<1% of commercial production), flint (14%), flour (12%), dent (73%), and sweet (<1%). Clearly, dent is the most important type, supplying livestock feed, starch, syrup, oil and alcohol (10). The Corn Belt Dents of the US are only ~100-150 years old but they are the most productive races of maize in the world, providing the basic genetic foundation for virtually all of the corn produced in the US as well in most other temperate regions of the world. However, breeding of new Corn Belt Dents varieties currently utilizes <5% of available worldwide maize genetic diversity (8, 11, 12).

Corn refineries use 14% of the $19 billion US maize crop, producing such products as corn oil, gluten for animal feed, corn starch, syrup, dextrose (used mainly by the pharmaceutical industry as the starting material for manufacturing Vitamin C and penicillin), alcohol for beverages, ethanol (which accounts for 12% of all automobile fuels sold in the US), high fructose corn syrup (used mainly by the soft drink industry which helped to surpass the use of sucrose in the US (8)), biodegradable chemicals and plastics (13), paper, textiles (14), ready-to-eat snack foods and breakfast cereals (4), cornmeal, grits, flour, and additives in paint and explosives (8). It is estimated that maize yields 4000 industrial products (9) and that there are more than 1000 items in US supermarkets that contain maize (5).

The maize plant is truly unique among the cereals. Maize is thought to be derived from teosinte, an ancient wild grass from Mexico and Guatemala (8). Unlike the other major cereal crops, there is physical separation of maize's male and female flowers. This allows for cross pollination and the large scale production of hybrid corn which is based on the exploitation of heterosis or hybrid vigor (8), broad morphological variation (10), and genetic plasticity and diversity (12, 15). Maize is able to take advantage of sunlight better than most other major cereal crops and grows more rapidly because of the size and distribution of its foliage (16). It has high productivity due to its large leaf area (10) and has one of the highest photosynthetic rates of all food crops (5). The high yield of maize compared to other cereal crops is possible because of the low position of the ear, where it is able to capture a greater proportion of the nutrients. This is unlike the other cereals whose seeds are found high up on the plant stalk. The ear is covered with a husk leaf, shielding the kernels from pests and accidental dispersal, unlike other cereals where individual grains are covered with bractea (16). Because of the husk leaves preventing the maize plant from dispersing its seed, some consider maize a human invention because it can not reproduce without the aid of humans (1). This exact trait prompted Arturo Warman to refer to maize as "a human offspring, our plant kin" (16).

With that brief introduction to maize, we encourage you to explore Gramene's Doorway to Zea to learn many more specific details about this unique grass species. If you are a breeder or researcher and are familiar with the general information of this page, please refer to Gramene Zea Statistics and Queries. These have been developed to make your time with Gramene more efficient.


1. Barreiro, J. editor, 1989. "Indian Corn of the Americas: Gift to the World." Northeast Indian Quarterly, Spring/Summer 1989. (Gramene Reference ID 9387)
2. Fussell, B., 1992. The Story of Corn. Alfred Knopf, Inc, NY, USA. (Gramene Reference ID 9388)
3. Meng, E. and J. Ekboir, 2000. "Current and Future Trend in Maize Production and Trade." CIMMYT World Maize Facts and Trends. (Gramene Reference ID 9389)
4. Smith, C., et al., 2004. Corn: Origin, History, Technology, and Production. Wiley Series in Crop Sciences. (Gramene Reference ID 9390)
5. Dowswell, C., et al., 1996. Maize in the Third World. Westview Press, USA. (Gramene Reference ID 9391)
6. CIMMYT Maize Program
7. Pingali, P. and S. Pandey, 2000. "Meeting World Maize Needs: Technological Opportunities and Priorities for the Public Sector." CIMMYT 1999-2000 World Maize Facts and Trends. (Gramene Reference ID 9392)
8. Sprague, G., et al., eds., 1988. Corn and Corn Improvement: 3rd Edition. American Society of Agronomy, Inc. (Gramene Reference ID 9393)
9. Missouri Ag Statistics Service
10. Salvador, J., 1997. Maize. The Maize Page. (Gramene Reference ID 9395)
11. Germplasm Enhancement of Maize
12. Chopra, V.L. and S. Prakash, eds., 2002. Evolution and Adaptation of Cereal Crops. Science Publishers Inc, NH, USA. (Gramene Reference ID 8381)
13. Corn Refiners Association
14. National Corn Growers Association
15. Morris, M., 2001. "Assessing the Benefits of International Maize Breeding Research: An overview of the global maize impacts study". p 25-34. In P.L. Pingali (ed.). CIMMYT 1999-2000 World Maize Facts and Trends. (Gramene Reference ID 9396)
16. Warman, A., 2003. Corn and Capitalism: How a Botanical Bastard Grew to Global Dominance. The University of North Carolina Press. (Gramene Reference ID 9397)