Corn’s unique biology encouraged diversity beginning with peoples’ selections of its desirable characteristics over its history. It continues to carry the essential C4 photosynthesis mechanisms attributed to its origin in a tropical environment and the separation of male and female flowers allowing the easy cross pollination with other corn plants.
The C4 photosynthesis system allowed large potential for converting light energy into carbohydrates. Separation of male and female flowers allowed the diversity and ultimately the broad genetic base and adaptation by humans to their use of corn. Being an annual plant also allowed quick adaptation to diverse environments as humans distributed the seed with their desired attributes. This happened long before humans were describing and understanding of genetics and biology.
As people started more intense farming methods, they increased their efforts to select corn seed with desirable characteristics adapted to their environments. The broad genetic base encouraged by its separation of sexes, allowed selection of plants with flowering and grain maturity appropriate for the frost-free season. They also selected seed from their crop with desired grain hardness and volume. Eventually multiple farmers selected their own seed from many areas of the earth. In North America, the soft starch form in the grain was desired whereas in the northeast states those with hard endosperm starch was selected. These two extremes in starch were also selected elsewhere corn was distributed.
Diversity of genetics within Zea mays also allowed selection of plants with root growth appropriate for the local soils and water supplies. Also selected were genetics that allowed close timing for emergence of female flowers and pollen resulting in successful grain development. Plants with desirable resistance to local pathogens and insects were selected by individual farmers.
This selection of genetics within regions resulted in some restriction of genetic diversity within that region and eventual limits in grain production to only to a small fraction of what is expected by today’s corn growers. That began to change in the late 1930’s and continues today. That phenomenon will be discussed in the next Corn Journal issue.
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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.