Photo by Waldemar Brandt on Unsplash
One Banana to Rule Them All
Of the many varieties of bananas produced and consumed around the world annually, the Cavendish Banana stands out as the most common variety, accounting for around 47 percent of global production, according to the Food and Agriculture Organization of the United Nations. Globally, around 50 billion tons of the variety are produced, and it dominates US and European markets vis-à-vis other banana varieties.
Aside from consumer preference, the Cavendish variety is also favored by producers for its relatively higher yields and its ability to mitigate the negative effects of environmental factors. More resilient to the effects of global travel, it has become the ideal banana for international trade.
Creeping Doom
Commercially available bananas are produced asexually; stem-like structures called corms, along with fast-growing stems they produce called suckers, are cultivated in the soil, from which a new banana tree grows. Done this way, it makes genetic diversity impossible, as new banana trees would always be identical to their parent trees. The new trees inherit the same favorable characteristics that has made the Cavendish so tasty and popular—and also the same susceptibility to disease.
Without the introduction of new genes to help develop resistance against disease, Fusarium Wilt threatens the survival of the world’s most popular banana. Otherwise known as Panama Disease, its earlier variation or race has been responsible for the near decimation of the Gros Michel, the top variety of the 20th century, of which the Cavendish would later displace as the top favorite given its resistance to the earlier race.
The fungus responsible for the disease attacks the vascular tissue and the roots, causing the plant to wilt and die. The disease can be transported through asymptomatic suckers, and spores can be transmitted through water. In soil, spores could last up to 30 years, making the disease hard to stop and contain.
CRISPR: the way out?
CRISPR-Cas9 is currently one of the most precise and versatile gene-altering technology. It can be used to alter the DNA sequence to mute or activate genes or to introduce new ones to obtain the desired genetic trait. Research is currently ongoing exploring how CRISPR can help the Cavendish survive its pandemic.
For one, biotechnologist James Dale from the Queensland University of Technology is trying to turn on a dormant gene in Cavendish that offers resistance to Tropical Race 4 (TR4), a gene he found responsible for the resistance in a separate species, M. acuminate. Molecular biologist Leena Tripathi from the International Institute of Tropical Agriculture in Kenya and researchers in the Philippines are exploring to suppress genes that render Cavendish susceptible to TR4. Tropic Biosciences, a UK start-up, is focused on improving the immune system of the Cavendish by silencing genes in would-be pathogens through RNA strands.
CRISPR technology offers a promising solution to ensure that the Cavendish survives, as many people depend on it for nutrition and as well as their livelihood. The same technology can be applied to other varieties naturally resistant to the Panama disease to alter their genetic make-up and introduce traits much more appealing to consumers and traits that would make them economically viable to substitute the Cavendish. All approaches should be considered, as there is no silver bullet to swiftly deal with this problem.
References:
https://www.bbc.com/news/business-49331286
http://www.fao.org/economic/est/est-commodities/bananas/bananafacts/en/#.YVAXCbgzbIU
https://www.nature.com/articles/d41586-019-02770-7
https://www.promusa.org/Fusarium+wilt
https://www.yourgenome.org/facts/what-is-crispr-cas9
*Biotechnology Coalition of the Philippines*
