Selective Breeding Versus Genetic Engineering

It is thought that agriculture involving domestication of plants and animals was developed around 12,000 years ago. Human ventures of altering the communities of plants and animals are even older than that.

Over the centuries, man has carried out selective breeding between different but related plants. The best example of this selective plant breeding is origin of Maize. It has been estimated that around 7500 years ago, the farmers in Mexico had domesticated a wild plant called Teosinte, and kept doing selecting breeding improving the characteristics until their offsprings was turned into today’s Maize. The two plants viz. Maize and Teosinte are so different that the scientists kept them in different genera, until they were finally found to be of same genus with varying species. Thus, selecting breeding in plants (and animals) is as old as our history.

The selective breeding remains fundamentally same even today. The breeders take two different varieties of a plant, each of which has individual traits that make it useful over others and then breed them. For example, one variety may be of high yield while another may be pest resistant. The two varieties are interbred and from among the offsprings, random plants that show both high yield and pest resistance are selected. The resulting plants are called Hybrids. A Hybrid represents combination of two sets of genes, one set originating from each parent.

Traditional selective breeding versus Genetic Engineering

There are two main drawbacks of the traditional selective breeding. First, it is a slow process. Second, selective breeding is a random process. In this random process, it is possible that the selected plants may have also acquired some undesirable traits, which were not observed in parent. For example, parent was not susceptible to a particular virus but offspring was found to be.  Similarly, it is also possible that what was observed as a desirable trait in parent, was not seen in offspring. Thus, to avoid the undesirable traits, and to recover the desired traits, the scientist / breeders need to do something which is called back-crossing to one of the parent lines. The back crossing is done for usually three generations to arrive at what is desired. All this makes the process too long and tardy. Further, this process is limited by natural barriers which stop different species of organisms from breeding with each other. This is where genetic engineering comes into play. Genetic engineering can make things faster and allow mixing of genes of distantly related or even unrelated plants / animals.