A banana apocalypse: World's plantations are at risk of being wiped out

A new fungal threat could wipe out the world's banana plantations, which have lost the ability to mutate and produce disease-resistant varieties

“Banana republic” was coined by O'Henry in the early 20th century to describe Latin American nations controlled by corporations that ran banana plantations. The definition expanded to apply to any nation where crony capitalist corporations run undemocratic governments.
 

The banana itself is grown in 140-odd countries, and is a staple in global diets. India and China are the world’s largest banana-producing nations, but Ecuador, Colombia, and Guatemala, along with the Philippines, are the largest exporters. Beyond its economic importance, the banana is an important link in the global ecosystem, as millions of acres of plantations support insects, birds, and animals.
 

In the 1950s, John Christopher wrote a post-apocalyptic science fiction novel, The Death of Grass, which imagines a virus wiping out all grasses, including rice and wheat. As a result, billions starve, and nation states fall apart.
 

A banana apocalypse would lead to similar horrible outcomes and it is not a science fiction scenario. It has nearly happened in the past, and could well happen in the near future.
 

There are 1,000-odd varieties of bananas. But they are mostly genetically vulnerable. One variety, the Cavendish, is by far, the most economically important.
 

The trade value of the organised banana market is estimated to be $13.5-14 billion. The Cavendish variety holds around 47 per cent of the market share and accounts for over 95 per cent of exports. As one of the oldest cultivated fruits, the banana has been bred for millennia to be seedless (or very low seed producing) and thus, have maximum flesh. A lack of seeds leads to it being cultivated only by taking cuttings from plants.
 

When every plant is a clone of its parent, there’s no option for mutations. That makes it terribly vulnerable. If a banana is hit by disease, it cannot mutate to develop disease- resistant strains.
 

In the 1950s, bananas were hit by a fungus, known as Panama Disease (Fusarium wilt of banana, or FWB, as botanists refer to the fungus). At that time, the key “cash cultivar” banana was the Gros Michel. It was pushed into extinction.
 

Cavendish was resistant to that strain of FWB and plantations switched to it wholesale. The Cavendish grows unaffected in fungus infested soil and it stays green for weeks after being harvested. That makes it ideal for exports.
 

The dark cloud on the horizon: Unlike the Cavendish, FWB does mutate. A new strain, TR4, does infect Cavendish as well as other bananas. Infected plants cease to produce bananas and die. So far, it has proved impossible to eradicate the FWB fungus from the soil.
 

This has led to a crisis. Colombia declared a national emergency when the new strain was discovered. Finding bananas that are immune, hardy, high-yield and with long ripening periods is a possible solution.
 

But replanting half the world's crop would take years even if such a variety is discovered. That means economic devastation. Also, since the fungus (and other fungi) can mutate and most bananas cannot, the fruit remains a sitting duck.
 

In Nature, genomicist Li-jun MA describes how this fungus works and how the new strain overwhelms plants.
 

According to Dr Ma, who runs the Ma Lab at the University of Massachusetts, Amherst, the TR4 affects over 120 plant species and some variants can affect humans.
 

Dr Ma suggests a two-pronged defence. One method is to find ways to interfere with the fungus, or eradicate it. In particular, the new TR4 strain of FWB releases bursts of nitric oxide gas, which harm the Cavendish. Blocking this release, or scavenging the gas quickly, could protect plants. This would be a great scientific achievement.
 

But it would be a stopgap. Fungi will continue to mutate, leading to new strains and new problems. The other option is to induce greater genetic diversity in the banana, which will be a complex, market-driven process. Bioscientists may enable mutations, and find disease- resistant variants. But the market has to consume these variants to create demand that scales.
 

Rice and grains have also lost genetic diversity as they have been bred for high yields, and wild strains have gone functionally extinct. Preventing a banana apocalypse by learning how to reintroduce genetic diversity could also help us avert the death of grass.