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M A I Z E - ZEA MAYS

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Author Topic: M A I Z E - ZEA MAYS  (Read 1073 times)
Bianca
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« on: November 07, 2008, 09:42:34 am »










                                                            O R I G I N





 
There are several theories about the specific origin of maize in Mesoamerica:



It is a direct domestication of a Mexican annual teosinte, Zea mays ssp. parviglumis, native to the Balsas River valley of southern Mexico, with up to 12% of its genetic material obtained from Zea mays ssp. mexicana through introgression.

It derives from hybridization between a small domesticated maize (a slightly changed form of a wild maize) and a teosinte of section Luxuriantes, either Z. luxurians or Z. diploperennis.

It underwent two or more domestications either of a wild maize or of a teosinte.

It evolved from a hybridization of Z. diploperennis by Tripsacum dactyloides. (The term "teosinte" describes all species and subspecies in the genus Zea, excluding Zea mays ssp. mays.) In the late 1930s, Paul Mangelsdorf suggested that domesticated maize was the result of a hybridization event between an unknown wild maize and a species of Tripsacum, a related genus. However, the proposed role of tripsacum (gama grass) in the origins of maize has been refuted by modern genetic testing, refuting Mangelsdorf’s model and the fourth listed above.



The first model was proposed by Nobel Prize winner George Beadle in 1939.

Though it has experimental support, it has not explained a number of problems, among them:



how the immense diversity of the species of sect. Zea originated,

how the tiny archaeological specimens of 3500–2700 BCE (uncorrected) could have been selected
from a teosinte, and

how domestication could have proceeded without leaving remains of teosinte or maize with teosintoid traits until ca. 1100 BCE.
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