Corn races emerge
Corn spread from its origin in central Mexico to much of North and South America over an 8000-9000 year period. Its annual life cycle, transportability and large endosperm favored its use as a food source. Cross pollination biology of corn favored genetic variability and thus adaptation to multiple environments as it coincided with movement of humans across these two continents. As people settled in different areas, they tended to select desired genetics favored by that location and their culture. Over time, distinct types, or races, of corn developed. These races varied in time to flowering, size of kernels, types of starch stored in the endosperm and pigments in endosperm. Obtaining these features also required genetics for resistance to local corn pathogens and insects, root structures to fit the soil types and moisture levels, leaf shapes to capture maximum sunlight, and hormone systems to stimulate timely flowering for both male and female flower parts.
This pattern spread to other parts of our earth after the European immigrants arrived, not only getting introduced to this new food source but also bringing livestock that would thrive on corn. This species was then spread to other continents where it became adapted to other environments.
The culture of identifying ‘varieties’ of corn that was perceived as best fit for their livestock and food needs was adapted by American farmers a few hundred years ago. These farmers saved the seed from the plants with the most favorable features, especially emphasizing the amount of clean grain from single plants growing in their fields. As result they continued the isolation of hundreds of individual, genetically-diverse populations. These populations experienced some inbred depression, as some recessive genes becoming homozygous would cause a negative effect on yield performance.
Occasional mixing of populations occurred however with unexpected results. The Reid family in Ohio had a poor field emergence with their soft starch variety (Southern Dent) that they had traditionally grown. They filled in the bare spots with an earlier variety of a hard-starched new England Flint variety. Saved seed from that field produced much larger yields than their original seed. This principle of hybrid vigor after crossing varieties with distinct genetics became evident in the late 1800’s, leading to university and USDA geneticists, and eventually others to develop methods to utilize the historical genetic development of this species to expand the use of its diverse history. That pattern continues as science and experience with corn advances.
The unique history of origin and humans’ interactions with corn are presented in many writings available in journals, books and the internet. This interaction is probably closer than that of any other between humans and a plant species. Humans have been dependent upon some plant species; the history of human migration and unique biology of this plant species has led to a distinct relationship.
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About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.