How are plants genetically modified? Basic approaches

You’ve probably heard terms like GMO, genetic engineering, genome editing, and selective breeding used to describe breeding crops. So it’s natural to ask questions about what these terms mean and what the science behind the modern food system is.

Here are some of the main ways plants were adapted and changed into the varieties, nutritional profile, taste and appearance we know today.

Traditional breeding

For nearly 10,000 years, we have been modifying our food to suit our needs and tastes. Most of the food we eat today comes from traditional breeding methods that include selective breeding, crossbreeding, and mutation breeding. Many modern corn varieties and seedless watermelons were produced by these methods.

  • Selective breeding yield, size, growth, resistance, etc. such as selecting plants or animals with specific characteristics (phenotypes) and selecting which organisms to mate to produce superior offspring for desired traits. These measurable phenotypes are the product of both environment and genetics (DNA) and the interaction of the two.
  • Crossbreeding involves the cross-pollination of two similar (yet different) plants to create a new plant with desired characteristics from the original plants.
  • Mutation breeding Since the 1930s, it has been used to speed up the natural process of mutation to create more genetic variation in plants. Mutations are not necessarily harmful. Many are neutral and some can be beneficial, so this method is useful in plant breeding.

Genetic variation is like your dictionary when writing a book. The more words you know, the more material you have to work through to choose the combination you want. The more genetic variation we have to work with, the more material we have when selecting desirable traits for our crops.

These processes can take many generations to make the desired changes and are not the most precise. Many genetic traits (genotypes) are linked and can be changed randomly, sometimes in desirable ways and other times in less desirable ways. Research has improved our knowledge of traditional animal husbandry. Specifically, genomic selection allows us to use an organism’s DNA markers, or SNPs (Single Nucleotide Polymorphisms, pronounced “snips”), to optimize matings based on markers associated with desirable traits and minimize unwanted traits.

Transgenics – GMO

As described by the US Food and Drug Administration, a Genetically Modified Organism (GMO) is an organism such as a plant, animal, or microbe whose DNA has been altered using recombinant DNA technology, or transgenics. It involves the transfer of a specific segment of DNA from one species to another. It can be from a different plant or a completely different species. This is possible because all organisms share the common language of DNA to define their characteristics.

Illustration courtesy of Alabama Cooperative Extension System

Transgenes are introduced into plant cells by two methods. One is to coat a microscopic metal pellet with the transgene and inject it into the plant cell at high speed, allowing the gene to be inserted into the plant cell’s genome in a small number of cases.

Another method is to infect the soil-dwelling bacterium Agrobacterium tumefaciens by inserting its DNA into plants in nature, thereby introducing the transgene into the plant cell. Genetic engineers make bacteria harmless so they don’t cause disease, but can transfer their DNA into plants. This method is more controlled than microscopic metal pellets, but does not work well on all plant species. Plant cells that accept the transgene are identified, then cultivated until they become a plant capable of producing seeds. Scientists make sure that the genes in these seeds are inherited in a normal way, that the desired characteristics are expressed and that there are no negative effects on the plant.

Extensive and controlled research is conducted to ensure product safety.

Transgenes allow scientists to take a useful gene from an organism, such as drought or insect resistance, and insert it into a crop that lacks that trait.

Most scientists consider “GMO” to be an imprecise term because almost all of our products have been “modified” for desired characteristics through the traditional methods outlined above. More often than not, you’ll hear scientific communities using “genetic engineering” when talking about non-conventional breeding.

Genome editing

The newest tool for plant genetics is genome editing. Genome editing refers to a new group of technologies that alter an organism’s DNA down to the single base pair level. Where transgenics is like taking a page from a book and pasting it into another, genome editing is changing a word or even a letter to change the meaning of a sentence.

In this way, a gene or part of a gene can be removed, added or changed very precisely. Genome editing tools make genetic improvement faster and more accurate than traditional methods.

Genome editing involves the CRISPR-Cas9 system, which can make genetic changes with great precision. In nature, this is a defense mechanism that some bacteria use to protect themselves by identifying and removing foreign DNA inserted by a virus. Scientists have adapted this tool from nature so that they can target genes for editing by cutting and pasting the desired sequence. “Molecular scissors” are directed by the guide RNA to the exact sequence that needs to be cut. This cut can either be repaired into any new sequence, or left in a broken state that silences the gene.

Image courtesy of

Why should plants be genetically engineered?

Genetic engineering refers to laboratory-based technologies that alter an organism’s genetics, including transgenics and genome editing. This is another tool in the toolbox for improving plant genetics. This gives plant breeders more specificity and takes significantly less time to make meaningful improvements.

Science uses these techniques to improve the shelf life, durability, sustainability and even nutrition of products.

Golden Rice Project
Image courtesy of The Golden Rice Project

Golden rice is an amazing example of a genetically modified food, where beta-carotene, which is converted to vitamin A when digested, is added to this staple food. It is extremely useful in developing countries that suffer from high incidences of vitamin A deficiency, which causes irreversible blindness in children.

Recently, some food packaging has been labeled “bio-engineered” to indicate that the food contains “detectable genetic material that has been modified by certain laboratory methods and cannot be created by conventional breeding or found in nature.”

Only 13 bioengineered foods are available in the United States, most of which are animal feed crops.

There are many myths and misconceptions about genetic engineering. Bioengineered products go through a long, rigorous and detailed approval and monitoring process to ensure they are as safe as their non-bioengineered counterparts.

More GMO myth busting lists can be found here and here.

There is a lot that goes into growing plants. Ultimately, the goal is to create affordable and sustainable products to feed people and animals. Each of these methods has its pros and cons, and all have their place in agriculture.

Michelle Miller, Farm Babe, is a farmer, speaker and writer who has worked with row crops, cattle and sheep for years. He believes that education is the key to bridging the gap between farmers and consumers.

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