Teosinte is a wild grass, which is closely related to maize. In fact, it is generally considered the ancestor of modern maize and has been recovered from cave sites in Oaxaca, Mexico occupied by humans as long as 4000 years ago.
Teosinte grows in subtropical areas of Central America – regions of Mexico, Guatemala, and Nicaragua. Its distribution in Mexico and Guatemala parallels the ancient Mexican and Mayan civilizations, indicating that teosinte and maize have been in the same geographical area (sympatrically) for thousands of years. Teosinte growing in the Valley of Mexico was documented in Spanish writing four hundred years ago; they noted that teosinte is found in the same way that barley is found in wheat fields.
In terms of altitude, teosinte can be found up to about 2700 masl, though generally grows between 600 and 2000 masl, depending on the variety and the region.
The teosinte that can be found in farmer’s fields today is generally a hybridized form of teosinte. Teosinte found in Mexico is about 95% fertile with maize; Guatemalan teosinte is about 85% fertile with both maize and Mexican teosinte. This means that the Guatemalan teosinte has higher sterility and is likely an earlier form.
Hybrid clusters in fields can be attributed to a common parent that outcrossed in the previous year. An isolated teosinte plant surrounded by maize has a higher probability of outcrossing. If maize pollen and teosinte pollen reach the teosinte silks at the same time, often the teosinte will win.
In some areas teosinte is considered a weed and farmers would like to exterminate it. However, in the early stages of growth teosinte plants are difficult to distinguish from maize. Farmers are usually hesitant to weed young plants, as the characteristics identifying plants as teosinte do not become apparent until fairly late in the growth stages. A farmer will not want to accidentally remove maize plants, so will let
plants remain in the field a little longer to be sure.
It is not until the tassel emergence that differences are clear – teosinte has a distinctive branching pattern that becomes apparent during this stage (Figure 1). By this time the teosinte has shed its pollen and hybridization has taken place.
Another reason for teosinte to remain in the field is that farmers recognize its potential for other uses. It is being used as green forage for feeding to cattle. There are some farmers who have cows and are more interested in selling milk than they are in selling maize. Maize is sweet silage, but teosinte is also sweet silage, so to farmers more interested in dairy production the difference between the two is insignificant.
This means that there is a more relaxed approach to weeding the fields than there would be in areas more focused on maize production.
Modern teosinte is still part of the story of maize: the extinction of any teosinte population would weaken our genetic knowledge of how modern corn came to be. It would be difficult to argue that teosinte does not have any practical uses, as it has more genes than maize. Whenever you can expand a genome, implications arise from the gene interaction. For instance, teosinte may one day be able to increase the production efficiency of starch or make a new kind of starch, as it has a harder starch than maize. As we don’t know what the food processing needs will be in the future, it is not possible to say that teosinte will not have a significant role in the future.
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