Pioneer geneticists

By Anastasia on 26 May 2010

In the New York Times on 25 May 10, Sean Carroll shares his wonder at the domestication of teosinte into our favorite crop: Tracking the Ancestry of Corn Back 9,000 Years.

teosinte

Teosinte ear (left) and "reconstructed" small primitive maize ear (right). This small-eared form of maize was bred by George Beadle by crossing teosinte with Argentine popcorn and then selecting the smallest segregants. Beadle's intention was to reconstruct a primitive, small-eared corn that would resemble the earliest archeological corn recovered from the Tehuacán valley in Mexico. Doebley, 2001.

The most impressive aspect of the maize story is what it tells us about the capabilities of agriculturalists 9,000 years ago. These people were living in small groups and shifting their settlements seasonally. Yet they were able to transform a grass with many inconvenient, unwanted features into a high-yielding, easily harvested food crop. The domestication process must have occurred in many stages over a considerable length of time as many different, independent characteristics of the plant were modified.

Just as amazing as the domestication of maize is the untangling by geneticists of the relationship between teosinte and maize, started by George Beadle in the 1930s. A Brief History of Maize Domestication Studies can be found on Ed Buckler’s lab website.

Beadle proposed the “Teosinte Hypothesis” in which maize is simply a domesticated form of teosinte. He believed that, through artificial selection by ancient populations, several small mutations with relatively large effects could have transformed teosinte into maize. In contrast, Mangelsdorf suggested maize was the product of a hybridization between an undiscovered wild maize and Tripsacum, known as the “Tripartite Hypothesis.”

An extended history of the battle of these two hypotheses can be found in George Beadle’s Other Hypothesis: One-Gene, One-Trait (Doebley, 2001).

Maize researchers can all appreciate the work of early agriculturalists who domesticated maize and those early geneticists whose research built the foundations for our work today. Carroll appreciates them as well: “Every August, I thank these pioneer geneticists for their skill and patience.”

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