Teosinte

Teosinte is a group of large, Central and South American grasses of the genus Zea. There are five recognized species of teosinte: Zea diploperennis, Zea luxurians, Zea mays, Zea nicaraguensis and Zea perennis. The species Zea mays is further divided into four subspecies: ssp. huehuetenangensis, ssp. mays, ssp. mexicana, and ssp. parviglumis. Zea mays ssp. mays, (maize or corn) is the only domesticated taxon in the genus Zea, derived directly from Zea mays ssp. parviglumis, with up to 12% of its genetic material obtained from Zea mays ssp. mexicana through introgression. It should also be noted that members of the genus Tripsacum are locally referred to as teosinte in some regions.

The genus Zea includes both annual and perennial species. Zea diploperennis and Zea perennis are perennial, while all other taxa are annual. All species are diploid (n=10) with the exception of Zea perennis, which is tetraploid (n=20). The different species of teosinte can be readily distinguished based on geographic origin and morphological differences.

As would be expected, teosinte strongly resembles maize in many ways. Some populations of Zea mays ssp. mexicana have been observed displaying mimicry within cultivated maize fields, having adapted to a maize-like form as a result of the farmers' selective weeding pressure. This provides opportunities for introgression from teosinte to maize, which encourages further mimicry.

The the most significant way in which teosinte differs from maize is in its distinctively small female inflorescence, which matures to form a two-ranked 'ear' of between five and ten hard, triangular or trapezoidal black seeds. Teosinte seeds have an indurate, cupulate fruitcase which protects them from the digestive processes of ruminants, which forage on teosinte and aid in seed distribution through their droppings. Members of Zea exhibit no seed dormancy behavior, and will germinate almost immediately when conditions are favorable.

In some areas of Mexico, teosinte is regarded by maize farmers as a noxious weed, while in other areas the farmers regard it as a beneficial companion plant, and encourage introgression. Virtually all populations of teosinte are either threatened or endangered; Zea diploperennis exists in an area of only a few square miles. The Mexican government has taken action in recent years to protect wild teosinte populations, using both in-situ and ex-situ conservation methods. There is currently a large amount of scientific interest in conferring beneficial teosinte traits, such as insect resistance and perennialism, to cultivated maize lines.