Avocados not only are one of the world’s healthiest fruits, they’re also among the most economically important, representing a $13 billion market in 2017.1 Avocados have been enjoyed since ancient times, but their DNA has been largely foreign — until now. A group of U.S. and Mexican scientists have sequenced the genomes of Mexican and well-known Hass avocados.
Their study, published in PNAS,2 reveals “ancient evolutionary relationships” that give clues to the fruit’s origins but also opens the floodgates to future genetic modification of this already perfect food. Indeed, as The New York Times put it, the research is “likely to become the foundation for breeding techniques and genetic modifications designed to produce avocados that can resist disease or survive in drier conditions.”3
Changing Climate Cited as Push for GMO Avocados
In 2018, scientists released a report detailing changing temperatures in California, along with changes in precipitation patterns, that could change agriculture significantly in the state. Avocados were one of the crops cited as being particularly vulnerable to temperature changes, such that the researchers estimated avocado production in California could decrease by 40% as a result.4,5
Luis Herrera-Estrella of Texas Tech University, who led the study, likewise stated that their research to sequence the avocado genome was necessary in order to make the plants “accessible to modern genomic-assisted breeding efforts.”6 He told The New York Times:7
“Because of climate change, temperature might not be the same, humidity might not be the same, the soil might be different, new insects will come and diseases will come … We need to be prepared to contend with all these inevitable challenges.”
Genetic engineering (GE) could be used to “fight threatening avocado diseases, and to optimize growth and desirable phenotypic traits,” the researchers concluded,8 but it will likely be years before a GE avocado is created, as the plant takes years to mature. Still, this is where the research is headed in creating “avocados for the future.” Herrera-Estrella continued:9
“There are avocados that grow in very hot places with little water, and there are avocados that grow more in rainy places … If we can identify genes that confer heat tolerance and drought tolerance, then we can engineer the avocados for the future.”
Other GE Fruits Already on the Market
Other fruits, including apples and tomatoes, have also had their genomes sequenced, which led to the creation of GE varieties. Apples genetically engineered to resist browning when sliced or bruised appeared in select grocery stores in the U.S. Midwest in 2017. Developed by Okanagan Specialty Fruits, the apples are engineered to suppress the production of the enzyme — polyphenol oxidase (PPO) — that causes browning.
The first two varieties of the so-named Arctic Apple — Arctic Golden and Arctic Granny — were deregulated by the U.S. Department of Agriculture in 2015. A third variety, Arctic Fuji, joined the mix in 2016,10 while in 2019 the company announced Arctic Golden and Arctic Granny fresh slices, which they’re suggesting is the perfect option to get kids to eat more apples.11
Packaging presliced apples raises a couple of immediate concerns, like increased packaging waste for a product that’s already perfect portable, as well as contamination risks, since the more you process a food — prepeeling and slicing it, for instance — the more the risk of contamination increases.
Will nonbrowning GE avocados also become a thing? Only time will tell, but it’s likely biotech companies will pounce on this opportunity to create a new, entirely unnecessary, GE product. Browning in avocados occurs through the same process that causes browning in apples, and both are completely harmless.
Cutting an apple or avocado exposes the cells to oxygen, which allows the PPO enzymes to rapidly oxidize the phenolic compounds in the fruit’s tissues into ortho-quinones (o-quinones). O-quinones form a natural antiseptic that helps protect the fruit from bacteria and fungi. While o-quinones have no color, they react with oxygen and amino acids to produce melanin, which turns the fruit brown.
GE Avocados May Not Be Labeled
By 2022, the USDA will require GMOs to carry labels, but it will only be in the form of a green circle with the words “derived from bioengineering.” However, the label only applies to a food that has had another organism’s genes spliced into it by a process called transgenesis. Other types of genetic engineering, such as CRISPR gene editing, do not need to be labeled at all.12
As noted by The Non-GMO Project executive director Megan Westgate, the USDA’s GMO labeling law “jeopardizes GMO transparency for Americans”:13
“In its current form, categorical exemptions prevent this law from delivering the meaningful protections Americans deserve. Highly processed ingredients, many products of new genetic engineering techniques such as CRISPR and TALEN, and many meat and dairy products will not require disclosure.”
This means that if avocados are genetically edited using CRISPR or similar technologies, it won’t be noted on the label and you’ll have no way of knowing whether the avocado you’re eating is a traditionally grown variety or one that has had its genes tweaked.
One possibility the featured study researchers are considering to make the idea of GE avocados more “tolerable” is making the rootstock, which is a tree stump used to graft branches onto, GE, rather than modifying the fruit itself.
Victor Albert, one of the study’s authors, told The New York Times, “That’s one big possibility to make G.M. tolerable to people that really care about it … You don’t have to make G.M. avocados, and even if you do G.M., you don’t have to make the avocados themselves G.M.”14 He continued in a University at Buffalo news release:15
“If you have an interesting tree that looks like it’s good at resisting fungus, you can go in and look for genes that are particularly active in this avocado. If you can identify the genes that control resistance, and if you know where they are in the genome, you can try to change their regulation. There’s major interest in developing disease-resistant rootstock on which elite cultivars are grafted.”
Already, however, the team has faced challenges as opposition to GMOs surfaces, including in Mexico. The Mexican agriculture ministry initially contributed a $2.5 million grant for the project, but didn’t renew the funding after three years, forcing the team to find money elsewhere.16
There Are Hundreds of Varieties of Avocados
Most avocado lovers are familiar with the Hass variety, which makes up 90% of cultivated avocados.17 One way to protect crops from pests and disease naturally would be to diversify and expand crops of the many different varieties of avocados available.
There are hundreds of varieties of avocados but, for comparison, only seven are grown commercially in California, and 95% of the total crop is the Hass variety.18 Some of the more unusual varieties listed by the California Avocados website include:19
Bacon — A green-skinned, oval-shaped avocado.
Fuerte — A pear-shaped fruit with smooth skin.
Gwen — This avocado has pebbly skin and is slightly larger than the Hass variety.
Pinkerton — Known for their long pear shape and small seed, which yields more fruit per tree.
Reed — A large round fruit with slight pebbling on the skin.
Zutano — A pear-shaped avocado with shiny yellow-green skin.
It’s believed that avocados originated in Africa before traveling to North America and Central America, and may have been enjoyed in Mexico as far back as 10,000 years ago.20 The genome study revealed that Hass avocado DNA is 61% Mexican and 39% Guatemalan,21 which suggests it has a more recent origin. Herrera-Estrella told the University at Buffalo:22
“Immediately after hybridization, you get these giant blocks of DNA from the parent plants. These blocks break up over many generations as you have more reproductive events that scramble the chromosomes.
But we don’t see this scrambling in the Hass avocado. On chromosome 4, one whole arm appears to be Guatemalan, while the other is Mexican. We see big chunks of DNA in the Hass avocado that reflect its heritage.”
Hass avocados are prized for their flavorful flesh and skin that turns from green to dark purple as it ripens. However, avocados differ not only in their size and skin color but also in their taste, texture and nutritional makeup. According to Food Republic:23
“Florida’s small [avocado] industry is focused on varieties like Choquette, Hall and Lulu — large, smooth-skinned fruits with juicy, sweet flesh popular among populations of Caribbean immigrants …
Many Florida avocado lovers, in fact, dislike the California-grown varieties, sometimes describing them as ‘oily.’ Californians, though, may backpedal from the taste and texture of the low-fat Florida avocados — and call them ‘watery.’”
One avocado variety, Choquette, can weigh up to 2 pounds and releases green juice when you cut it, as it’s high in water content. The Daily 11 is even larger, coming in at 5 pounds or more, while the Tonnage variety is smaller with a lower oil content of 8% to 10% (the Hass variety can have 20% oil content or more).24
There’s even the Mexicola Grande variety, which is a small, black plum-like fruit with black, papery skin. The skin is so thin you can bite right through it — it’s edible — and the flesh has a unique anise-like flavor.25
Why Eat Avocados
Avocados are worthy of their superfood status. With nearly 20 vitamins and minerals and healthy monounsaturated fat, they’re a nutrient-dense food that can also help your body absorb fat-soluble nutrients from other foods in your diet.26
Further, eating one-half of a fresh medium Hass avocado with a significantly inhibited the production of the inflammatory compound Interleukin-6 (IL-6), compared to eating a burger without fresh avocado, suggesting they have anti-inflammatory effects.27
Avocados are also a good source of antioxidants, including carotenoids, tocopherols and polyphenols, and may have cancer-fighting properties.28 Research also suggests that eating avocados is beneficial for cardiovascular health and may support weight management and healthy aging.29
When choosing avocados, these are among the cleanest fruits in terms of pesticide residues,30 so they’re one type of produce you can opt to buy conventionally grown if need be. However, if GE avocados are introduced, choosing organic will be important to ensure that your avocado is not one of them.