Taxonomy of Maize

Zea is a genus of the family Gramineae (Poaceae), commonly known as the grass family. The genus consists of some four species: Zea mays, cultivated maize and teosinte; Zea diploperennis Iltis et al., diploperennial teosinte; Zea luxurians Bird; and Zea perennis Reeves et Mangelsd., perennial teosinte. Various of the species have been assigned to the segregate genus Euchlaena, which is not currently recognized, or have been divided into numerous small species within the genus Zea.

The closest generic relative to Zea is Tripsacum, a genus of seven species. Tripsacum differs from maize in many respects, including chromosome number (n = 9), in contrast to Zea (n = 10). All species of Tripsacum can cross with Zea, but only with difficulty and only with extreme sterility.

Cultivated maize is presumed to have been transformed from teosinte, Zea mays subspecies mexicana (Schrader) Iltis, more than 8,000 years ago. During this transformation, cultivated maize gained several valuable agronomic traits, but lost the ability to survive in the wild. Teosinte, however, remains a successful wild grass in Mexico and Guatemala. Despite some confusion over proper taxonomic groupings of the noncultivated members of Zea, wild members maintain a successful array of annual or perennial plants with visible chromosomal peculiarities and ploidy levels, and many adaptive macroscopic phenotypes. Cultivated maize and the wild members of diploid and tetraploid Zea can be crossed to produce fertile F1 hybrids. Nonetheless, in the wild, introgressive hybridization does not occur because of differences in flowering time, geographic separation, block inheritance, developmental morphology, and timing of the reproductive structures, dissemination, and dormancy.

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