This isn’t the first and probably won’t be the last column on Genetically Modified Organisms (GMOs). There are many issues constantly brought up in the news, the courts, the Congress, and around the world regarding everything from labelling and safety to the escape of these traits to wild plant/animal populations. This week a brief review of how we breed plants and livestock might be helpful.
GMOs specifically involve the mutation, insertion, or deletion of genes in an organism. Most often it involves transferring the genetic material of one species to another in one of several ways. A more precise term for this would be genetic engineering because GMO really isn’t a good definition. Why? Simply, the purposeful genetic modification of organisms started over 10,000 years ago with the domestication of animals and plants. The ancestors of wheat, corn, and other crops bear little resemblance to what we plant today or even several hundred years ago. The same is true of modern livestock. This was accomplished through conventional breeding – the selection of a plant or an animal with desirable characteristics, discarding those with less or un-desirable characteristics, and increasing the population of what you want while continuously selecting desirable and discarding undesirable traits until a high level of uniformity is attained. This produces “varieties” that when reproduction occurs, the offspring are genetically identical to the parents. Modern wheat is varietal as was the corn planted into the 20th Century. Naturally, it’s much more complicated than this description and obtaining the desired traits, ranging from yield and standability to disease and insect resistance often takes many years of painstaking work. The next step in genetic modification was the development of hybrids.
A hybrid here is defined as crossing between populations, breeds or cultivars within a single species. In English, you have two varieties, each with a characteristic you want that is lacking in the other so you crossbreed them, mixing up their genetics, and hope you obtain a hybrid with the characteristics desired. Then the breeder must work to eliminate the undesirable trait(s) while keeping what you want. There is much more involved here and there are various types of crosses – single, double, three-way, and triple cross hybrids. Modern corn and grain sorghum are examples of hybrids. The advantages of hybrids include hybrid vigor, improved health for example, over a variety. A simple example of hybrid vigor would be the differences between a purebred dog and a mutt. Purebred dogs tend to be prone to certain health defects even with careful breeding while mutts due to genetic mixing are typically overall healthier and longer lived than many breeds. Downsides for hybrids include the time involved in crossing to produce the desired traits while eliminating the undesirable ones and most importantly for the farmer; you can’t keep and replant the seed of the hybrids since it is a mixture of genetics from the male and female parent. Therefore the hybrid must be produced each year from the desired parents as the seed of the hybrid plant will express a range of characteristics reflecting all the genetics of the parents.
The preceding explanation is a bit simplistic but will serve as we discuss genetic engineering. Next week covers how GMOs are “made” and where they are found in our world.