How corn conquered the world - Chris A. Kniesly
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Where did corn come from?
Corn’s origin had long been a mystery. Unlike many other domesticated plants, corn does not have an obvious wild equivalent. The carrot looks remarkably similar to the wildflower Queen Anne’s Lace. Einkorn wheat and domestic wheat are almost indistinguishable, besides the size and behavior of the kernels. Corn has no such look-alike. For many years, botanists assumed the ancestor of corn must be a now extinct species, lost to time and memory. An American geneticist and Nobel laureate named George Beadle spent his life fascinated by corn. During his time as a graduate student, Beadle worked under Rollins Emerson, the acclaimed maize geneticist who had independently discovered Mendel’s laws of inheritance. Their research found that corn and teosinte each had ten chromosomes and that the two could cross naturally and produce fertile offspring. These characteristics were often used by biologists to determine whether two organisms are part of the same species, and thus Emerson and Beadle concluded that corn came from teosinte. Their findings were not widely accepted. Beadle went on to have a long career studying the genetics of fruit flies and bread mold.
After his retirement, Beadle dedicated his time and energy into proving that corn came from teosinte. He bred a hybrid, or a plant with one set of genes from corn and one set of genes from teosinte. He then took this hybrid and crossed it with itself. His goal was to determine how many genes were different between corn and teosinte. If the number of genes separating these two was low, then Beadle argued the two must be closely related. The number of genes separating two different purebreds can be determined using a hybrid cross and Punnett Squares. Beadle knew that 1/(4^n) offspring of a hybrid cross will look like one of the purebred parents, with “n” being the number of divergent genes. Beadle grew 50,000 plants and found that 1 out of every 500 offspring appeared purebred. He concluded that between 4 and 5 genes separated teosinte and corn Learn more about the history of corn.
Although modern genetic analysis has failed to confirm Beadle’s “4 or 5 genes” hypothesis, study after study has recognized corn’s link to teosinte and determined several key genetic differences which would turn a bushy grass into an essential staple grain. To learn more about the genetic evolution of corn, click here!
What types of corn are there?
Although “dent” corn is the most commonly cultivated today, there are actually six major types of corn, each one with a different appearance and purpose.
Dent Corn: This variety gets its name from a small dent which can be found on the top of each mature kernel. It is used for cornmeal, corn chips, corn tortillas, animal feed, corn syrup, bioplastic, and many other applications.
Flint Corn: This ancient variety of corn gets its name from its hard outer shell, or pericarp. Flint corn is one of the varieties bred by early Mesoamericans and is used to make hominy or cornmeal. It can also be popped or used as ornamental decorations.
Popcorn: An extremely hard outer hull and starchy inside, or endosperm, of 14-20% moisture are the signatures of this variety. When heated, the proteins, oils, and staches inside the corn expand. Unable to break through the hard pericarp, the insides gelatinize. When the pressure increases to the point where the pericarp ruptures, the insides rapidly expand and cool, forming a biological foam.
Flour Corn: Flour corn has a thin pericarp and soft, starchy endosperm, making it the perfect corn to be ground into a fine powder.
Sweet Corn: When most people think about eating corn, they are probably thinking about sweet corn. Sweet corn has a naturally higher sugar content when immature. Sweet corn is harvested before the kernels harden and is then cooked and eaten as a vegetable.
Pod Corn: This is a mutant variety of any of the other types. It gets its name from the leaves which form around each kernel. It is an exclusively ornamental type.
Learn more about the botany of crop plants!
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