The move from a wild weed Teosinte to a productive grain crop that we know as corn was the result of humans observing and selecting plants in the field that best fit the desires of the grower. The breadth of genetics available was largely due to the separation of male and female flowers on the corn plant, encouraging cross pollination, and humans’ movement of the species to many environments modern corn has nearly 40000 genes located on its 10 pairs of chromosomes.
Corn has attracted the interest of plant scientists with many specialties such as plant pathology, entomology and cellular biology. Some biologists were interested in trying to isolate corn cells from the plant into cultures of the cells that could be replicated, experimented with and then finally manipulated to produce normal plants. Techniques were discovered with some plant species in the 1950’s but some species including corn were difficult to go from cultured cells to mature plant. In the early 1970’s, the combination the right mix of plant hormones and corn varieties, allowed the stimulation of cultured corn cells to produce mature plants. This opened the way for manipulating corn cells in culture to produce unique plant characteristics.
Entomologists, and growers, were finding the more intense cropping of corn was allowing insects to damage the crop. Among those was the corn borer, a moth that produced larvae caterpillars capable of entering the corn stalk and ultimately causing the stalk to break, making the machine harvest difficult. A similar insect causes damage to other plants such as tomatoes. People had discovered that spraying a culture of a bacterium called Bacillus thuringiensis on tomato plants killed the caterpillars on tomatoes. This bacterium from the soil had genes that produced a protein that disrupted the gut of the insect larvae.
Geneticists were able to isolate the gene in this bacterium, giving the label of BT, and set off on the task of getting the gene into corn cells. Eventually a modified gun was used to fire a pure culture of the BT gene into a corn cell culture, inserted the gene into the corn chromosome. After screening in labs for the insertion in right position in a chromosome, the cell produced the protein toxic to the corn borer insect. Stimulation of that cell to grow into mature plants allowed it to be crossed to more agronomically productive corn varieties.
Combinations of scientists with varied specialties, commercial and public, and corn growers has allowed the current use of genes transferred from other species into corn. Probably genes were exchanged between species in the evolution of all living forms over time, but humans have found ways to accelerate and manipulate this for their use.
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.