By Kevin M. Folta, Ph.D., Contributing Editor
Todays genetic engineering processes, especially those used on food crops, are the subject of much contentious debate. Much of that debate centers on the assertion that the process is unnatural" and therefore the result of the technology is inherently dangerous. Opponents use frightening images of Frankenfoods" and assert natural" heirloom varieties are the only plants man was meant to eat. In this four-part series, Kevin Folta, Ph.D., examines the development and uses of high-performance plants through the lens of science.
Part 1: The Dawning of Crop Science
Some 20,000 years ago, early humans started to notice details about the plant products they ate and the plants that bore them. They observed how plants reproduced and learned that seeds came from flowers. They also noticed that plants appearing identical at first sight featured important variations upon exanimation. They almost certainly took note of the times of year plant products were produced, as well as the flavors and textures of those products, including which ones made them feel ill. As man became more aware of the role of plants played in their lives, there was an increased desire to improve them. This impetus created the first generations of plant breeders, really the worlds oldest profession.
Plant breeding is not a natural process. Todays improved varieties result from human-directed plant sex between partners never intended by nature; selection of the genetic combinations with the best traits, and careful intervention and husbandry to ensure preservation of desired features. It is a process of moving traits, or more precisely, moving the genes that control those traits. Humans intervene to transfer desirable genetics to inferior genetic lines, or sometimes provide a single genetic adjustment to an otherwise outstanding variety.
The archeological record suggests that some of the earliest plant breeders (prior to 6300 BC) were genetically tinkering with teosinte, an ancient relative of modern-day corn. Teosinte grew as a grassy shrub in areas of Mesoamerica. On a good day, one might stumble upon a teosinte plant loaded with its prized product, a handful of small pods, each bearing a stick covered with a dozen rock-hard kernels that could be ground with water to a paste and then cooked and eaten. That is the base of corns family tree.
The genetic construction from teosinte to todays improved corn required human intervention for thousands of years. Humans intentionally chose to keep plants with superior traits, such as more seeds, rather than eating them. This practice led to improved yields and more edible kernels. Early maize was also likely prized for its inherent sweetness, and was the main source of sweet flavors in the diet. Nature lent a hand by providing pressures of disease and abiotic stress (e.g., drought, flood, heat) that would only permit the most suitable cultivated genetic lines to survive.
Nature also shaped the humans that ate improved varieties. With better nutrition (and fewer plant-borne toxins), humans were able to continue planting and expanded the range of cultivation. As teosintes range spread north and south, it was crossed with interfertile wild variants, or possibly was deliberately crossed to other unusual lines raised by early farmers. Strangely, the more unusual and genetically distant the cross pollination was, the stronger the offspring werethe phenomenon of hybrid vigor. Together, man and nature conspired to produce the foundation of modern-day maize.
The genetic voyage from teosinte to todays corn is just one part of a much bigger story. Maize improvement is only a chapter in the rich history of crop domestication and plant breeding. Chances are that youd barely recognize any of the ancient wild versions of plant products you now enjoy every day. Tomatoes were barely edible little berries on poisonous vines confined to Central and South America. Important grains like wheat existed as small, unproductive ground plants. Potatoes were small bean-like subterranean nodules growing in Bolivia and Peru. The taming of wild weeds by plant breeders has provided the bounty of fruits and vegetables we have today, allowing them to be grown in places never before possible. Even though we dont think about it, we also benefit from superior post-harvest qualities that limit spoilage, keep food safe from toxic fungal and bacterial rots, and provide for greater, more-efficient distribution.
Check back tomorrow for Part 2: It's All in the Genes
Kevin M. Folta, Ph.D, is an Associate Professor in the Horticultural Sciences Department, and Graduate Coordinator for the Plant Molecular and Cellular Biology program at University of Florida. He was the contributing author of the sequence to the strawberry genome and studies how genes and the environment work together to improve plant traits. He also has been recognized for his commitment to community outreach and student training in laboratory science. Contact him at [email protected] .