Beyond the Peel

By Chuck Dinerstein, MD, MBA — May 10, 2024
The banana has shaped civilizations and sparked scientific inquiry. From its origins in the lush forests of New Guinea to its global domination as a staple of modern diets, the banana's journey is now in peril. Beneath its familiar yellow exterior lies a narrative encompassing genetic manipulation, disease, and global commerce.
Image by Steve Buissinne from Pixabay

Bananas have gone from being the first cultivated fruit to the most consumed and exported fruit in the world.”

The symbiotic relationship between the banana and man goes back thousands of years. Agroarcheologists used phytoliths, tiny complexly shaped particles of silica, found in fossilized bananas to uncover the travels of what is technically a berry. The earliest bananas were found in New Guinea, dating domestication back 6800 years. Fellow travelers of man, domesticated bananas, as marked by those phytolith passports, were found in Sri Lanka 1000 years later, in Uganda 5200 years ago, and in Pakistan 4200 years ago.

Our modern-day banana hails from Mauritius, the one and only home of the dodo. The initially uninhabited island passed through the hands of the Dutch, French, and British, populated by the French with the enslaved from Africa and the indentured of India by the British. The banana escaped in a botanical collection, finding its way to England and into the hands of a 33-year-old gardener for one of the “finest landscaped gardens of the time,” Joseph Paxton. Paxton was particularly interested in cultivating another tropical refugee, the pineapple, which required a new technology: greenhouses. It was in the greenhouse of William Cavendish, the Sixth Duke of Devonshire, that today’s banana first saw light. Paxton spent several years cultivating his plant until it produced fruit, which he named Musa Cavendishii after his employer. Paxton went on designing and building greenhouses, his masterwork being the Crystal Palace. [1]

Early globalization, when amateur and professional botanists shared their plant findings, allowed the Cavendish to continue to circumnavigate the globe, to the Canary Islands, and then to the Caribbean. The Duke shared the Cavendish with John Williams, a missionary who brought Christianity and the banana to Somoa and many other Pacific Islands, including its ancestral home in New Guinea.

“Williams did not see this himself as he was eaten in the New Hebrides in 1839 by islanders who were presumably unenthusiastic about his message.”

Stuart Thompson, Plant Biochemist

The banana arrived on our shores as part of the Centennial Exhibition of 1876, a more Victorian America where “the idea of eating a suggestively shaped banana was considered pretty uncouth… [with] recipes that show bananas must be cut and served in foil, anything to disguise their shape.”

The Banana is an original Frankenfood

In some sense, the domesticated form of the wild banana is what some might consider a Frankenfood [2], although with more natural origins. Human cells have two copies of our chromosomes; genetically, we are diploids – our sperm and eggs, haploids, each contributes a copy to create the fertilized egg. Some plants that develop through sexual reproduction produce multiple genetic copies, termed polyploids, with the most common form being tetraploids (four copies). Einkorn wheat, one of the earliest domesticated, is a tetraploid. These polyploids seem to reflect an evolutionary advantage with their creation correlating “with periods of extinction or global change, while polyploids often thrive in harsh or disturbed environments.”

Scientists believe that plants with three chromosomes, triploids, are a transitional form arising from an error in which sperm have two copies rather than one. Triploids are often hardier than their diploid parents but are sterile. The domesticated banana is a triploid, unable to grow seeds. That is not an insurmountable problem for plants; new plants can grow from cuttings, or bananas can grow from dividing and replanting the rootstock of an existing plant, its rhizome. The banana’s triploid character is both its strength and greatest weakness.

“So every Cavendish banana that we eat, every banana you eat, that I eat, that people eat in China and Europe, wherever, is exactly the same genetically as every other one. And just like human identical twins, what afflicts one afflicts the others."

- Dan Koeppel, author of Banana: The Fate of the Fruit That Changed the World

Its triploid nature has produced a much-loved and nutritious fruit. Because it arises from cuttings, all bananas are genetically identical, clones of one another. This has allowed banana cultivation to scale to production levels, making it one of our global food sources. In 2020, we produced 120 million tons of bananas in an area the size of Costa Rica, or six Yellowstones

The genetic diversity of plants produced by sexual reproduction as seeds may create a more variable product, but diversity allows for a greater possibility of disease resilience. [3] The farming of clones, monocultures facilitates the spread of plant disease. Plant pandemics are not new. Phylloxera, an insect, destroyed most French vineyards in the late nineteenth century, with wine grapes saved by grafting cuttings onto phylloxera-resistant rootstock.

The Returning Banana Apocalypse

For the banana, the villain is a wilt fungus, Fusarium oxysporum cubense (Foc), known as “Panama disease,” although it was first noted in Australia 150 years ago. Plants infected by the soil-borne fungus wilt and die because of blockages in the root channels bringing water and nutrients to the plant. These blockages seem to be an ill-fated effort by the plant to defend itself. There is no known cure.

Foc shares some characteristics with a more human pathogen, COVID-19. Both avoid detection, allowing for more successful infection, with symptoms appearing late in the disease.

“A plant can hide signs of infection for up to a year, continuing to appear healthy until its leaves suddenly turn yellow and wilt. … All that's left is to enforce the banana equivalent of COVID-19 prevention measures – disinfecting boots and preventing the movement of plants between farms, which is more or less the same as hand washing and social distancing – and hope for the best.”

- Treehugger

Diseased banana plants, which appear normal, are replanted, facilitating the spread of Foc, just as our asymptomatic spread of COVID. Finally, as with COVID, Foc evolves and generates new variants.

The original cultivar devasted by Foc was the Gros Michel (Fat Michael); the Cavendish, a runner-up in flavor and size, was immune. Gros Michel succumbed to the Foc variant, “Race 1;” the Cavendish is susceptible to the Foc variant, “Tropical Race 4” (TR4). It emerged in the 80s in Southeast Asia and has spread throughout Asia, West Africa, and Colombia, where a state of emergency was declared.

Foc’s persistent soil contamination means banana trees cannot be replanted in those areas. Moreover,

“it can spread with contaminated irrigation water and soil attached to implements, shoes and vehicles. Heavy rainfall can lead to increased spread of the pathogen from plant to plant and from the surface down to the roots. The run-off water may contaminate the irrigation reservoirs and increase the spread of the fungus through the plantation.”

The initial response has been chemical warfare. Banana cultivation is among the heaviest users of pesticides of all our global crops [4]

The Banana Food Chain

Bananas only grow in the tropics and sub-tropics, where there is never frost. This limits planting. While there is still diversity among bananas, few are suitable for global transport. The Glos Michel, the first worldwide banana and victim to Foc, had a tough peel, ideal for shipping. The Cavendish is more fragile, and the banana supply chain has been transformed to accommodate it.

The Cavendish has one of the highest yields per acre, roughly 40,000 pounds (apples clock in at 16,000). Moreover, it can be transported at a temperature range of 55-58 degrees Fahrenheit, requiring little refrigeration– making it economical to ship large distances. They are picked at their “green” stage, transported, and then treated with ethylene gas in ripening rooms closer to their destination. This food chain provides the consistent, inexpensive banana we find everywhere throughout the year. But with the banana increasingly threatened by TR4, what can be done to save this important food?

Climate change enhances the prevalence of TR4, just as low temperatures and both dry and humid conditions increase the prevalence of COVID.  According to the International Institute for Sustainable Development,

In the short term, the top challenge that climate change poses to the banana industry is its role in spreading diseases such as Tropical Race 4, which threaten to destroy the sector. Research conducted in Colombia found that changing climatic conditions raise the risk of spreading Black Sigatoka disease. Changing climatic conditions in the Philippines are expected to expand areas that are favourable to the Fusarium fungus to 67% of its banana-growing regions” [5]

One solution is quarantine, but the long asymptomatic phase of TR4 makes that more an aspirational than a practical goal. Soil management is also possible, but again, the tenacity of the fungus makes sterilizing the soil impractical – the mud on shoes and tires is sufficient to contaminate new areas. A European Journal of Plant Pathology study reported that rotation-planting banana fields with Chinese Leeks reduced the incidence of TR4 by 88% and the severity of the illness by 91%.

Organic farming is not a panacea. Bioorganic fertilizers, the pro-biotics of agriculture, have been shown to dampen the impacts of TR4. Organic banana cultivation in Costa Rica, primarily for the baby food market, yields sixfold smaller than conventional farming. As Dan Koeppel has said,

"There's not enough land to grow enough organic bananas to make them a practical replacement for all of our supermarket bananas. … there are just not enough high-altitude, cool-temperature places that are also hospitable to growing tropical bananas in order to make organic bananas a viable…replacement for those standard 69-cent-a-pound bananas you find in your local market."

We must also consider the elephant in the room, GMOs. The bananas we eat are genetically modified organisms by their very triploid nature. Those genetic changes have natural origins, but given that bananas are sterile, the only way they can be meaningfully diversified is through our hands, using conventional or sophisticated technologies.

TR4-resistant genes, found in a wild banana variety, have been inserted into the Cavendish. This transgenic Cavendish, with increased resistance to TR4, the QCAV-4 or Cavendish Grand Nain, was reported nearly seven years ago in Nature Communications. Just this past February, seven years after those initial reports, Australia, where the GMO was developed, became the first country to approve the QCAV-4 for commercial production. But who will buy them?

The regulations of the EU, which imports nearly a third of all bananas produced, are decidedly anti-GMO, putting a large portion of the market at risk. Anti-GMO advocates are not shy about blackmail. Potato growers provided with the Innate potato, a GMO resistant to Colorado potato beetles, were more than happy to adopt them until activists threatened the largest potato consumers with “brand risk.”

McDonald’s and Frito-Lay have enormous economic leverage as the biggest customers for frozen fries and chipping potatoes. They threatened those company’s brands with the prospect of unwanted press attention through targeted protests.  At McDonald’s, the decision was taken at the CEO level to avoid the brand risk, and so, in three phone calls to frozen fry producers, biotech potatoes were finished.” 

Even now, Australia has not designated the Cavendish Grand Nain for sale and consumption in Australia. Instead,

“QCAV-4 is a safety net for Australia’s $1.3 billion industry, which includes protected employment for 18,000 Queenslanders involved in banana production.”

– Professor James Dale, member of the development team

 

The protection of workers is a crucial point. Considering those individuals who consume bananas and plantains, along with those deriving income working the banana food chain, nearly 400 million rely on bananas for food security.

 

 

 

In the journey from New Guinea to the global marketplace, the banana’s story reveals our agricultural systems' ingenuity and vulnerability. Whether through genetic modification, sustainable farming practices, or international cooperation, the fate of the banana serves as a poignant reminder of our interconnectedness with the natural world and the urgent need for resilience in the face of adversity. The plight of the banana reflects our collective vulnerability and capacity for adaptation, offering a glimpse of the equilibrium with the niche we have created and the rest of the natural world. 

 

[1] Built of cast iron and plate glass, it was a 990,000-square-foot building, three times the size of St. Paul’s Cathedral, utilizing 60,000 panes of glass.

[2] The more woke amongst us might now refer to Frankenfoods as trans, as in transgenetic.

[3] Bananas are not the only fruit grown from cuttings and creating monocultures. Naval oranges have no natural seeds and are grafted, and Granny Smith apples and Hass avocados are deliberately grown from cuttings to reduce the variability of their offspring.

[4] Not to worry, as the EWG, that lawyerly bastion of pesticide awareness, writes, “Peeled bananas are generally tainted with very few pesticide residues, according to USDA analyses, probably because those tested are peeled first. In 2012, USDA scientists found just four fungicides on bananas they analyzed, compared to 10 on plums …Few of these applications reach the edible tissue of the fruit.”

[5] Black Sigatoka is a leaf spot disease caused by a different airborne fungus, Mycosphaerella fijiensis. Black Sigatoka, spread by wind and rain, can reduce yields by 35–50%.

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