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MAIZE Project - Ancestors of Maize

Ancestors of Maize

A seedling of the wild plant teosinte looks very similar to a corn plant.
Even as the plant grows to maturity, it looks similar to corn. But the fruit and seeds of the wild teosinte, look so different than modern corn, it took a long time for scientists to agree that teosinte is the ancestor of maize.

Evidence for Teosinte as the Ancestor of Maize

There are two major reasons why scientists believe that teosinte is the ancestor of maize. First, teosinte can pollinate cultivated corn and produce viable seeds. Second, DNA analysis confirms a very close relationship between corn and teosinte. In fact, teosinte is classified as a subspecies (Zea mays ssp. parviglumis) within the same species as corn (Zea mays ssp. mays).

What is teosinte?

Teosinte is the common name of a wild grass that grows in several areas of Mexico and Central America. There are several species of wild plants that have the common name of teosinte.

Here's a list:

  • Zea mays ssp. parviglumis (annual teosinte, grows in Oaxaca state, Mexico, closest wild relative to modern corn)
  • Zea mays ssp. huehuetenangensis (annual teosinte, occurs in border area of Chiapas, Mexico and Huehuetenango, Guatemala)
  • Zea mays ssp. mexicana (annual teosinte, grows in central and northern Mexico)
  • Zea luxurians (diploid annual teosinte, grows in Guatemala, Honduras and Nicaragua)
  • Zea diploperennis (diploid perennial teosinte, Jalisco, Mexico)
  • Zea perennis (tetraploid perennial, Jalisco, Mexico)

Note: A diploid teosinte species has the same number of chromosomes as corn. A tetraploid teosinte species has twice the number of chromosomes as corn.

Teosinte: Surviving in the Wild

The wild teosinte has several characteristics that help it survive in the wild. There is no real cob and the seeds break away from the stalk when mature, making dispersal more effective. The seed coat is hard, and seeds can remain in the ground waiting for the right environmental conditions to germinate and grow. Seeds are dark with a mottled pattern- making it more difficult for seed eaters (such as birds) to find and consume the seeds.
Escape from Bird Predation

Some early work on teosinte showed that birds will eat and digest teosinte seeds. In 1939, Raymond Standerlin observed several species of birds such as the blue grosbeak, indigo bunting, and russet tailed sparrow feeding in teosinte patches. When he examined their stomach contents, he found teosinte seeds without their hard outer seed coat. Local farmers said you could hear the birds cracking off the seed coats while they were feeding!

But teosinte seeds that fall to the ground may escape their bird predators because they have cryptic colors. In fact, teosinte seeds look like little rocks.

Can you find the teosinte and corn seeds?

Click on the photo to find the answer (image will open in a new window).

Genetic Differences Between Teosinte and Corn

The physical differences between corn and teosinte are produced by a few major differences in genes.

Branching: Teosinte plants are branched and produce many ears, while corn plants produce a single upright stem with ears.

Ear structure: Corn ears have 8-12 rows of seeds, while teosinte only has two rows.

Fruitcase: Each segment of the teosinte fruit can produce only one seed because one of the paired potential seeds (spikelet primordia) is aborted. Both of these spikelets are fertile in corn.

Seed structure: What looks like a seed of teosinte, is actually the seed surrounded by a hard "fruitcase". In modern corn, the fruitcase is reduced and develops into part of the corn cob.


To learn more about corn's wild relatives:
Websites
Books and scientific articles
  • Doebley, John. 2004. The genetics of maize evolution. Annu. Rev. Genet. 38: 37-59.
  • Smith, Bruce D. 1995. The Emergence of Agriculture. Scientific American Library. New York. 230 pp.
  • Wilkes, H. Garrison. 1967. Teosinte: The Closest Relative of Maize. Bussey Inst., Harvard Univ.: Cambridge. 159 pp.