Heirlooms, Hybrids, and GMOs

Heirloom tomatoes | Photo: Art Siegel/Flickr/Creative Commons License

With the exception of wild-caught seafood, just about everything we eat has been genetically manipulated. Ever since the invention of agriculture we've been changing the genomes of plants, animals, and other organisms we like to eat in order to make them better tasting, easier to cook, and more productive.

Despite our history of tweaking the genomes of our food, there's still a big difference between the way we did so before 1985 or so, and the modern approaches usually called "Genetic Engineering." With the Proposition 37 vote coming up, passage of which would force the labeling of certain kinds of genetically modified food in California, it's important to know the difference.

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When our ancestors first started domesticating plants, they noted plants that had the traits they liked and saved their seeds. Crops were bred for flavor and sweetness and away from bitterness. Farmers and gardeners manipulated plants' physical structure, often with the intent of making the edible part of the plant larger. The wild plant from which modern carrots came -- commonly known as "Queen Anne's lace" -- has edible roots like domestic carrots, but only just barely. They're small, contorted and fibrous. Generations of farmers saved seed from those carrots that had bigger, sweeter, and less stringy roots. Grain growers selected for seed size, abundant yield, and "non-shattering" seedheads. Wild grasses tend to let their seed scatter all over to maximize the chances of that seed sprouting. It's better for farmers if the plant holds onto the seed tightly so that it can be more easily harvested.

All of that plant physiology and chemistry is controlled by -- among other things -- the plants' genomes. As they promoted some traits and weeded out others, the farmers were altering the plant varieties' genetic makeup. Our ancestors created the basics of the vast majority of our food through this kind of patient breeding, their knowledge of the science of heredity consisting mainly of the general awareness that offspring tend to resemble their parents.

Advancements in our understanding of plants changed things, starting in the 18th century. Botanists -- the famous Linnaeus among them -- started experimenting with things like deliberately creating hybrids between plant species, forcing plants that might not have "mated" without human help to have offspring. They noted that certain traits seemed to be "dominant" over other "recessive" traits, the way brown is dominant over blue in human eye color, but they didn't have an explanation for why. Gregor Mendel's famous experiments with peas in the 1860s showed that inheritance followed statistical rules that were quite straightforward. Not knowing of Mendel, Botanist Hugo DeVries rediscovered his results decades later, suggesting in 1889 that inheritance of specific traits came in "particles" which organisms inherited from their parents in some way. In a nod to Darwin's recently published theory of "pangenesis, DeVries referred to these hypothetical particles as "pangenes," which was later shortened to "genes."

Knowledge of what genes were, precisely, wouldn't come for another half century. But the concept worked, and plant breeders now had a basic theory to guide their experimentation. With the gene concept came the notion that you could move traits from one plant variety into another. Say your tomatoes were all succumbing to a disease, but a closely related weed with unpalatable fruit seemed to be immune. If you hybridized your tomatoes with that disease-resistant weed, perhaps you'd find some plants among their offspring that had the disease-resistance gene in them. If you then took those offspring and cross them with the tasty-fruited parents again, and again, you might be able to move the disease resistance gene into a new tomato variety that is otherwise very much like your old one.

And sometimes it doesn't take that long to get a mixture of traits you like. If you choose your parent stock carefully, the first generation of offspring may combine the best traits of both. Plants that are produced as a result of that kind of cross are called "F1 hybrids," and they're very common in agriculture and gardening.

F1 hybrids sold by seed companies have a few things going for them. They're predictable: that first generation of crossing two different strains tends, due to the rules of genetics, to be outwardly uniform. They tend to be robust and healthy, due to hybrid vigor. And they can be predictably mass-produced, which is good for the seed companies.

The process can be labor-intensive: the hybrids are made by taking pollen from the chosen male parent and using it to fertilize the flowers on the chosen female parent. (Pollen carries the male's contribution to the genetic makeup of the offspring; the other half comes from the egg cell in the female flower that the pollen pollinates.) Other pollen must be rigidly excluded. That's not always easy with plants that have both male and female flowers on the same plant, like corn, which has male flowers at the top of the plant that rain pollen down onto the female flowers below. If you want to make sure those female flowers are only pollinated by other male flowers, you have to send workers in to cut off the male flowers of all the plants before they start shedding pollen. Corn breeders resorted to measures like developing a male sterility trait, which in theory saves on costs in the long run. In practice, the male-sterile trait has introduced problems of its own.

Another thing that's good for seed companies: you have to buy F1 hybrids every year. Save seed from F1 hybrids, and the F2 generation may turn out to be wildly diverse as the genetic deck gets reshuffled. Some in the F2 generation may have all their grandparents' bad qualities. Some may be better in some respects than the F1s. If you're gardening for fun, growing saved seed from F1 hybrids can be really interesting. But farmers and most gardeners can't afford to gamble like that.

That's the basic difference between a "conventional" or hybrid tomato and an "heirloom" tomato. Heirloom tomato varieties were generally created through old-school, pre-1850 techniques. And because they aren't F1 hybrids, you can save their seeds, plant them, and get something very much like the previous generation of heirloom tomatoes. If you've heard the phrase "open-pollinated," that's what it means. F1 hybrids must be created in greenhouses with stringent measures in place to prevent unauthorized pollination: heirloom varieties can just let their flowers hang out and get pollinated by whoever.

Seed companies are fiercely protective of their lucrative F1 hybrids. They patent them, they protect their ancestry as trade secrets, they defend their "intellectual property" in court. A lot of people, myself included, criticize modern genetically engineered crops due to the intellectual property issues that come up -- say, when Monsanto sued farmer Percy Schmeiser after his canola fields were inadvertently pollinated by a nearby field of Monsanto's genetically modified canola. But when you get right down to it, a lot of the intellectual property unpleasantness involving food crops predates genetic engineering in the modern sense. It's the development of F1 hybrids that made it all possible. Breeders argued for the passage of the U.S. Plant Patent Act, which became law in 1930 after the death of F1-hybrid-creating master Luther Burbank, saying that new technology had "made inventors out of plant breeders."

Enter the modern era. We figured out that genes are located on chromosomes in 1910. We found that they consist of code for making proteins in 1941. In 1944 we found that genes consist of DNA and RNA. In the 1960s we started learning how to read the information coded into DNA and RNA. In the 1980s we figured out how to copy stretches of that code. In the 1990s we learned that some RNA acts to turn other genes off.

What people generally refer to as a "genetically modified organism" (GMO) is an organism in which a gene from another organism, perhaps only distantly related, has been spliced into the target organism's genome. A very common example is Bt corn, which has a gene from a soil bacterium spliced into it that codes for an insecticidal protein. Scientists are also looking at splicing the sections of RNA that turn genes off into new organisms, essentially subtracting a gene from the resulting GMO instead of adding one. There are a number of ways to move DNA or RNA into a new organism, including simply shooting it into a cell with a "gene gun," injecting it into the cell directly with a microscopic needle, or using a modified plant pathogen bacterium that's able to edit the plant's DNA.

And thus through genetic engineering techniques, we're able to manipulate an organism's genetic makeup much more efficiently than we did back when we had to rely on the organism's own reproductive system to do so. The trait we want to add doesn't need to belong to a closely related organism, and we need not worry as much about adding other traits along with the ones we want.

That's the big difference between GMOs and other crop plants, the distinction that offers so much commercial and technological promise -- and that makes people so nervous.

Still, it's odd that the divide between GMOs and everything else gets so much attention. The 20th century saw the advent of a lot of other technologies for creating new crop varieties, from laboratory tissue culture to creating mutations by exposing plants to chemical mutagens or radiation. Some of these techniques are potentially worrisome. None of them are particularly "natural."

If you compare all these different techniques -- industrial hybridization, irradiation, gene-splicing, tissue culture mixing -- there is one method that stands out as deeply and qualitatively different from all the others. But it isn't genetic engineering. It's the old-style selective breeding that created the open-pollinated, heirloom varieties we've had for centuries, sometimes millennia. Every technique developed since then has been a way of speeding things up somewhat unnaturally, if the word "natural" means anything anymore. Sometimes those advances worked to the benefit of the world's hungry people. They almost always worked to the benefit of someone's business plan.

Chris Clarke is an environmental writer of two decades standing. Director of Desert Biodiversity, he writes from Joshua Tree regularly at his acclaimed blog Coyote Crossing and comments on desert issues on KCET weekly. Read his recent posts here.

About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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