More info about this myth

Let’s start with a wild fact – oranges do not occur naturally. Really. Oranges are the result of extensive selective breeding over thousands of years. They are a hybrid produced from breeding pomelo (Citrus maxima) with the mandarin (Citrus reticulata). So many other easily recognized citrus fruits are also hybrids, including grapefruits, lemons, limes, tangelos, key limes, bergamot and yuzu.

While some of these hybrids appeared when different fruits planted nearby cross-pollinated one another (this is how grapefruits first came to be) others were bred by design. These designed fruits were crossbred very very slowly and took an enormous amount of guesswork. Breeders took plants with desirable characteristics (such as cold tolerance, seedlessness, sweetness or fruit size) and cross-bred generation after generation of plants with the hope of producing pleasing fruits. No doubt many of these experiments failed, which would be incredibly frustrating after the amount of time spent trying to create something new.

Guesswork isn’t the only way though! Now that researchers can sequence the whole genome of plants, they can identify the genes associated with the desirable phenotypic (aka observable) traits they want, in this case let’s say sweetness, and make sure that that genetic information is passed from the parent plants into the offspring. If both parent plants have genes that make their fruit sweet, and these genes are passed on to the baby plant, it too is very likely to have sweet fruit.

Let’s imagine a fictional gene for sweetness called ‘SUGr’, which in citrus fruit is recessive (remember if a gene is recessive the offspring must have a copy from one parent and one from the other parent in order to express that gene). You want to create a new fruit from the key lime and an orange, and you want it to be really sweet. Either you could just cross breed key limes and oranges, wait for the seeds to mature, plant them, and then wait for around 7 years for the tree to produce fruit and hope they are what you wanted or you could look at the DNA of the parent trees. You could search for a healthy key lime tree with two copies of the SUGr gene and take pollen from this plant, and use it to fertilize the flower of an orange tree that also has two copies of the SUGr gene. This will ensure any offspring will have two copies of the SUGr gene and produce sweet fruit. Not only can you select for desirable traits, but you could look for phenotypic traits that are not desirable, such as lots of seeds or disease susceptibility, and make sure your parent plants do not contain these genes and pass them on to their offspring!

Because no changes are being made to the genes (instead you are just looking for desirable genes that already exist) this is not genetic modification. Instead, this process is called advanced breeding, and it is a really cool way to use genomics to speed up the selective breeding process that humans have been using for thousands of years, without all that guesswork.

While there are many arguments for and against the use of genetically modified organisms (such as herbicide resistant sugar beets, disease resistant papaya, non-browning apples and bio-fortified ‘golden rice’) this is not the only use for genomics in agriculture. Advanced breeding has a great deal of potential to produce crops for fabric and food, trees for carbon capture and lumber, and animals that are healthier that will allow us to make the most of all the resources we rely on for food and shelter in our changing climate.

To learn more about genomics and agriculture you may like to visit this page on our website that discusses secure and sustainable food production.

You may also be interested in this short video we produced about selective breeding in cattle, or this short video about making dairy using microorganisms.



Educators: For an additional free resource to use with your students you may like to investigate the GMO suitcase activity which we can mail to you free of charge, or this great video activity about genomics, society and agriculture.