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Monday 16 December 2019

Biosecurity

Bananageddon

One banana variety is sold all over the world – and it’s in trouble

By Fred Harter

“It all started here, this small patch of jungle in Derbyshire,” says gardener Faye Tuffney, gesturing to a dropping pod bearing several bunches of adolescent bananas. We are standing in a humid greenhouse teeming with ferns and fig trees on the grounds of Chatsworth House, a stately home perched on the edge of the Peak District. In front of us, tucked away in a stuffy corner, sits a banana plant. It looks unremarkable, and it is really – apart from the fact that it is directly descended from another plant brought here sometime in the 1830s.

That seminal specimen is widely thought to be the progenitor of the global banana industry. More than one thousand varieties of the world’s favourite fruit exist worldwide, from the short and stubby Sukali Ndizi banana – a staple of the Ugandan highlands – to the giant Rhino Horn, which grows longer than a person’s forearm. But walk into your nearest shop and only one type will be on offer: the gently curved Cavendish, named after the sixth Duke of Devonshire, who first grew them at Chatsworth nearly two centuries ago.

Chatsworth House, the stately home of the Duke and Duchess of Devonshire, near Bakewell in Derbyshire

Today the Cavendish makes up 99 per cent of global exports and is the only type of banana most Westerners have ever known. Their presence on supermarket shelves is taken for granted by millions of shoppers as a mundane fact of life. But that could change.

The Cavendish is threatened by a deadly blight called Tropical Race Four, a strain of a fungus known as Panama disease or Fusarium wilt. It was first identified in Taiwan in the late 1980s, where it wiped out around 70 per cent of the island’s banana production. From there it spread to China, destroying around 100,000 hectares of the country’s Cavendish plantations and prompting wild rumours that the fruit caused AIDs. Sales of the fruit plunged as banana hysteria set it. The fungus has since taken hold in the Philippines, Indonesia and other parts of south east-Asia, as well as Australia, Jordan and Mozambique. In 2018 its presence was confirmed in India, the world’s largest banana producer.

A worker checks bananas at a warehouse in China

Tropical Race Four attacks the roots of banana plants, sparking a host reaction that wards off the fungus but also clogs the plant’s vascular system, preventing it from absorbing water and nutrients. Starved of sustenance, first the plant’s leaves turn yellow and start to wilt; then its roots rot away and die. “The effect is sheer devastation,” says James Dale, a biotechnologist at the Queensland University of Technology in Brisbane.

The pest is spread by humans, carried in mud caked onto the bottom of a pair of dirty boots or as spores lingering on the blade of an infected knife. Another common route is the unwitting export of contaminated plants that bear no visible signs of infection. Once in the ground, the pathogen can sit there for decades. And whereas air-borne banana blights such as black sigatoka can be countered by pumping plantations with pesticides, there is no such cure for Tropical Race Four.

“You can compare it to a landmine,” says Gert Kema, a plant pathologist at Wageningen University in the Netherlands. “It sits in the soil unnoticed and suddenly – boom – it hits. It’s a very difficult problem.”

Washing bananas at the Santa Cruz plantation in Ciudad Hidalgo, Chiapas, Mexico

For decades Latin America, which grows around 90 per cent of the bananas eaten by Americans and Europeans, avoided the epidemic. But in August Tropical Race Four was reported in Colombia, whose government promptly declared a national emergency. Some 175 hectares of banana plantations are known to be affected, but the true figure could be higher.

“We expected this to happen sooner or later,” says Kema, who helped confirm the outbreak. “The chances that it will show up in other parts of Colombia and Latin America are extremely high. I can’t predict when that’s going to happen, but it will happen for sure. History shows you can’t stop the spread of this disease.”

If that were to happen, the economic effects could be ruinous. In neighbouring Ecuador, for instance, banana plantations employ more than 2.5 million people, around one third of the country’s total workforce. “People here are very worried,” says Freddy Magdama, a banana researcher at Ecuador’s Polytechnic School of the Coast. “The government is monitoring the borders and trying to guess where the pathogen might enter; thousands of farmers have to been trained to recognise the symptoms. But the disease is very hard to contain…It’s a huge threat.”

Harvesting bunches of green bananas in Mexico, which are shipped to clients including Chiquita, the leading American distributor

The Cavendish is not the tastiest type of banana. But exporters like them because their skins are relatively thick, meaning they can survive being tossed into boxes and dispatched along bumpy dirt tracks en route to supermarket shelves thousands of miles away. The plants also produce high yields and are short enough to withstand the hurricane winds that regularly batter the tropics.

Like all edible varieties, Cavendish bananas are sterile. Bite into a wild banana and you’ll find dozens of teeth-shattering seeds, whereas the ones in your fruit bowl have none. Because they cannot breed, Cavendish banana plants are grown through a form of cloning similar to taking a rose cutting, a process that produces genetically identical plants. Dan Koeppel, in his book Banana: The Fate of the Fruit That Changes the World, describes the Cavendish as the fruit equivalent of the Big Mac: utterly uniform in taste and appearance, whether bought in a corner shop in Lincolnshire or a Wal Mart in Los Angeles.

A lab technician stacks test tubes containing tissue cultured banana plantlets raised in a Filipino biotechnology research centre

This characteristic is the Cavendish’s great strength. It means farmers can plant them on a large-scale knowing how many fruits each stem will yield, and exporters can ship them across oceans confident that each bunch will ripen more or less at the same rate. It is the cornerstone on which big banana companies such as Dole and Chiquita have built their high-volume, low margin business models, and it helps explain why a banana from Guatemala only costs a shopper in London around 20 pence, roughly half as much as an apple from an orchard down the road in Kent.

“The international banana trade is completely addicted to the Cavendish,” says Randy Ploetz at the University of Florida. “It’s a very productive banana that producers can ship quickly and cheaply. They’ve got it down to a fine science.”

Fyffes bananas displayed for sale on a fruit and veg stall at a London market

This genetic uniformity, however, carries vulnerabilities. The plantations that grow Cavendish bananas for export to Europe and America are monocultures, containing only one crop. “They might look nice and green, but there’s nothing there, no biodiversity,” says Ploetz. Since there is no genetic variation between the plants, that means they are all equally susceptible to a given malady. So when one of them gets infected with a pathogen like Tropical Race Four, it can easily hop to neighbouring plants and then rip through the rest of the plantation. “It’s a very risky form of agriculture,” says Kema.

Britons eat about five billion Cavendish bananas every year. If you are in your mid-forties, calculates Koeppel, then the one you had this morning was around your ten thousandth. But Western consumers have not always been hooked on the Cavendish. Our grandparents grew up eating a different variety altogether – the Gros Michel, or Big Mike, a bigger and by many accounts much tastier banana than our Cavendish. It is also more robust. Whereas Cavendish bananas must be exported in boxes to prevent their flesh from bruising, bunches of Gros Michel bananas can be thrown directly into a hull of a ship, making them even more ideally suited for export.

They first appeared in American shops in the late nineteenth century and went on to dominate the export market until the 1950s. But the Gros Michel fell prey to an earlier strain of Panama disease known as Race One, which began tearing through monocultures of Gros Michel in Latin America almost as soon as they were planted.

Bananas loaded in Ecuador, c. 1955

The environmental effects were devasting. When one plantation of Gros Michel was hit by Race One and became unproductive, normal practice was to simply abandon it and clear a nearby patch of virgin forest to make room for a new one. When that plantation got infected and failed, the process was repeated. “The lowland tropical rainforests of Latin America were completely wiped out,” says Ploetz. “They no longer exist.” The practice continues today in areas such as Mindanao hit by Tropical Race Four.

By the 1920s, the damage wrought by Race One was so severe that some banana-addicted Central American economies teetered on the brink of collapse. A shortage of the fruit in American shops inspired the 1923 hit “Yes! We have no bananas”. By the 1950s the disease was spreading too fast for the banana companies to keep up. Luckily, they discovered that the Cavendish was immune to the ravages of Race One and switched production over to the new variety.

Today’s banana barons are confident they can save the Cavendish from the fate of the Gros Michel. “We’re vigilant but I wouldn’t say we’re very worried,” says Caoimhe Buckley, director of corporate affairs at Fyffes, the biggest shipper of bananas to Britain. Like other exporters, Fyffes has introduced tight controls on its Latin American plantations, including vehicle washes and restrictions on footwear. “If we strictly adhere to the biosecurity guidelines and we share that knowledge, there’s no reason that the Cavendish banana can’t continue to be very productive for a number of decades,” says Buckley.

Ecuador, banana plant in Guyaquil

Banana experts are less sanguine. “That’s bullshit,” says Ploetz. “This thing is moving whether you like it or not.” He points to the fact that Australia, an isolated island with the world’s most stringent biosecurity measures, was unable to prevent the arrival and subsequent spread of the disease. Moreover, many of Latin America’s banana growers are smallholders, with little access to the resources needed to implement expensive quarantine regimes. “If the Australians couldn’t do it, I don’t think anyone is going to be able to do it,” says Ploetz.

The best biosecurity measures can do is buy the banana industry enough time to either improve the Cavendish or find a new banana that’s resistant to Tropical Race Four, says Magdama in Ecuador. Yet despite the severity of the threat, few scientists are working on the issue. “The Cavendish’s resistance to the Race One strain of Panama disease made the banana sector fall asleep,” says Kema. “When Tropical Race Four appeared in Asia, it was just not on their radar. It was too far away”

“It spread barely unnoticed until 2014, when we reported it in Jordan,” he continues. “This was the first wakeup call. We were trying to tell them that things were going truly wrong here, to alert people. But we weren’t noticed.”

Some of the researchers combatting the blight are trying to increase biodiversity on banana plantations through the introduction of grasses and shrubs, hoping that the presence of other plants might stem the march of the fungus. Others are trying to selectively breed the Cavendish with wild varieties of banana in order to produce resistance, although this conventional method is made extraordinarily difficult by the fact the Cavendish is sterile – even with forced fertilisation, as many as ten thousand bananas might only produce a single seed that could be used to produce a new hybrid.

Kerry Allcock, a banana farmer from Innisfail, Australia, holding a new banana suckling, which was being planted to replace crops destroyed by Cyclone Larry in 2006

The work of James Dale, the Australian biotechnologist, to genetically modify the Cavendish perhaps holds the most promise. In 2004, he studied the DNA of a wild banana variety from south-east Asia and identified a gene that lends the plant a natural resistance to Tropical Race Four. Its fruits are inedible owing to their rock-hard seeds. But Dale managed to extract the gene and inserted it into several Cavendish plants, which he then planted in a field infected by Tropical Race Four in northern Australia. “We really didn’t know what they were going to do,” he says.

The three-year trial was a huge success. Practically all of the unmodified plants at the site died, whereas the modified ones survived with very low rates of infection; one line of the modified plants finished the trial with no signs infection at all. “We’re now doing a second trial on a much bigger scale and are getting much the same results,” says Dale.

For now, though, there is little prospect of Dale’s bananas resolving the blight: they are genetically modified organisms and are not yet cleared for human consumption under Australia’s strict biosafety laws. Tough European Union regulations also prevent their introduction to European markets. “Proving biosafety is a long, expensive and arduous process,” says Dale. “We haven’t overcome that hurdle yet.”

A vendor sells bananas at his booth in a market in Wenzhou of Zhejiang Province, China

Like other scientists, Dale worries about the impact of Tropical Race Four on the varieties of banana that represent the staple food of more than 400 million people in parts of Africa, Asia and Latin America. “It would be unfortunate, but the West would survive without bananas,” he says. “There are other places where the impact would be far, far greater.” Nonetheless he’s confident that scenario can be avoided. “With good quarantine measures, you’ve probably got a decade until you start seeing a big impact in Latin America. If we haven’t come up with a good replacement by then, we’re not trying hard enough. I don’t think that will happen.”

In fact, Dale sees the arrival of Tropical Race Four in Latin America as a long overdue opportunity to break free from the iron grip of the Cavendish. “For the consumer it will bring huge benefits, there’ll be more types of banana for us to eat. The possibilities are wonderful.”

All photographs Getty Images

 

Further reading

Dan Koeppel’s book, Banana: The Fate of the Fruit That Changed the World, is a fascinating—and highly readable—study of the environmental, economic and political history of the banana, particularly of the fruit’s association with Latin America. It’s ugly to say the least.

This New Yorker long read from 2011 contains some great reporting on Australian scientist James Dale’s work to save the Cavendish, as well as efforts to breed new varieties of banana in Honduras.

If you’re pressed for time, check out this quick primer on Tropical Race Four and the banana business from the BBC.

And if you are even more pressed for time, contemplate one of the great quick crossword clues of all-time (from a British tabloid newspaper). Curved yellow fruit (6 letters).