A Brief History of Bananas

Pleasant taste and texture, great source of potassium, portable, fun to peel; what’s not to like about bananas? The banana is one of the earliest, if not the earliest, cultivated fruit. Evidence suggests that bananas were grown 8,000 years ago in southeast Asia. The name banana comes from banan in Arabic, meaning “finger.” It’s known by its older scientific name Musa sapientum, meaning “fruit of the wise men,” in some circles, but today’s cultivated fruit are seedless crosses of M. acuminata and M. balbisiana.

What about plantains? Yes, very banana-like. Compared to the so called “desert banana,” plantains are “cooking bananas” with greener, thicker skin, and starchy flesh. But there is no real difference between bananas and plantains with the plantain recognized as Musa x paradisiaca.

Bananas grow on things that look like trees in tropical regions around the globe. Yes, they only look like trees. The banana is a large herbaceous plant with an “apparent” trunk that is actually more of a stem. The finger-like fruit are green during development and turn yellow, red, or purple when ripe. They exist in bunches hanging from the top of the plant. A banana fruit is technically a berry since each one is derived from a single flower and ovary. In any case, the tiny seeds in the most mass-produced cultivar, the Cavendish, which supplies about 99 percent of the banana market, won’t germinate.

The Cavendish is not the greatest tasting banana, is susceptible to shipping damage, takes a lot of resources to produce, and cannot be grown from seeds (since there really aren’t any). Bananas are reproduced clonally from suckers that arise around the base of mature plants making every Cavendish plant pretty much identical to every other one. It replaced its predecessor the Gros Michel (Big Mike) in the 1940s and ’50s because it was resistant to Fusarium wilt tropical race 1 (TR1), a fungal disease that devastated the Michel. Being a clonal crop makes for great consistency, but it comes with a risk.

(Read also: Fusarium Wilt: Unwanted & Unwelcome)

Despite being resistant to TR1, the Cavendish is not so lucky when it comes to the latest fungal scourge, TR4, a strain of Fusarium that has worked its way from Taiwan in the 1990s to most of the banana producing regions of the world. Once a plant is infected there is no cure. The inexorable advance of TR4 along with a weak biological safety response from banana producing countries, has led to an increasingly bleak outlook for the future of the Cavendish. It is now thought that TR4 is established in most Cavendish plantations, most recently in Central and South America. To make things worse, a number of other diseases caused by fungi, nematodes, and viruses are a serious threat. What to do?

Breeding seedless bananas is hard (people generally don’t like large banana seeds) because of, well, a lack of viable seeds. There are other genetic barriers to breeding which makes traditional approaches time consuming, expensive, and of limited success. Enter the CRISPR age. CRISPR* is the Nobel Prize-winning technology allowing for precise (up to a point) modification of an organism’s DNA.

Mostly in the news because of debates surrounding the ethical use of the technology with respect to the human genome, CRISPR is rapidly being employed across biology to study, understand, and modify plant and animal genomes. The banana genome has been the focus of several improvement efforts by scientists in Australia, Africa, the Philippines, and the UK, using more established methods of genetic manipulation, along with CRISPR. One approach is to insert genes from resistant cultivars, into the Cavendish genome. Another approach is to try to “turn on” genes already in the Cavendish that confer resistance, but for some reason are inactive. Despite the commitment to the Cavendish, there are many other varieties of bananas out there that are not susceptible to TR4. If consumers are willing to accept new varieties of the world’s most popular fruit, to include perhaps a few seeds, there is hope. Otherwise, like it or not, genetic modification may be the only way to prevent the virtual extinction of bananas as we know them during the next several decades.

*To learn more about CRISPR see “What are genome editing and CRISPR-Cas9?”

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