From Teosinte to Maize

A Genetic Journey

Scientific name:

Zea mays spp. parviglumis

How did we get from this…

www.historyforkids.org/learn/food/corn

To this….?

http://soilcrop.tamu.edu/photogallery/cornsorghum+/images/corn%20ears.jpg

A significant difference

http://www.nsf.gov/news/mmg/media/images/corn-and-teosinte_h1.jpg

Morphological Differences Between Maize and Teosinte

Maize:• rigid, 3-12 ranked rachis with solidly attached

grains grains require human intervention for dispersal and propagation.

• Rachis segments bear pairs of grain bearing spikelets oriented perpendicular to rachis axis.

• Open fruit case

Cont. Morphological Differences

• Teosinte:• Two-ranked rachis that naturally disarticulates.• Single grain-bearing spikelet per rachis,

oriented parallel to rachis axis.• Grains are protected inside closed fruit case.

Comparison

http://teosinte.wisc.edu/morphology.html

Which traits were chosen?

• Early “farmers” did not want seeds to fall off easily. So they chose those individuals that had very attached seeds.

• They wanted many seeds per ear. chose those with mutations having several rows and ranks.

• They wanted big seeds chose individuals with the largest seeds.

When and where did it begin?

• Earliest evidence of cultivation 6,250 years B.P.• Earliest evidence found in Guila ‘ Naquitz,

Oaxaca Mexico• Earliest cultivators: Pre-ceramic hunter-

gatherers using cave shelters.

Photograph of three Guilá Naquitz archaeological cobs.

Benz B F PNAS 2001;98:2104-2106

©2001 by The National Academy of Sciences

Cultural Significance of MaizeProject

http://tvnoticias.files.wordpress.com/2008/04/maiz.jpg

-Pair up for this project-Use the internet to complete your research-You will have three class periods to work on this-Compile your findings into a power point presentation-Be prepared to present your project!-Follow your rubric closely!

References• Benz, Bruce, F. (2001). Archaeological evidence of teosinte domestication

from Guila’ Naquitz, Oaxaca. The National Academy of Sciences. Retrieved from http://www.pnas.org/content/98/4/2104.full on 9/3/2010.

• http://www.koshland-science-museum.org/exhibitdna/crops02.jsp• http://teosinte.wisc.edu/morphology.html