The world’s favorite fruit is facing extinction forever, but researchers believe they have found the solution.

A closer look at the fungi that attack bananas has led to potential ways to control this pathogen.

When you walk into the supermarket, you see them immediately: bananas. At first glance, there doesn’t seem to be anything wrong with them. But appearances can be deceiving. Bananas haven’t been doing so well for some time now. Due to climate change and disastrous pests and diseases, the world’s favorite fruit is at risk of disappearing forever. Scientists are even talking about a real “banana apocalypse.” But now researchers may have found the key to their survival, they report in the journal Nature Microbiology.

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It’s clear: bananas are in a sorry state. This is mainly due to the bad banana disease caused by the fungus Fusarium TR4. This fungus prevents the plant from absorbing water and nutrients, eventually killing it. Isolating and protecting healthy plantations is the only solution. What’s more, no other banana variety is immune to the pathogen and could replace the Cavendish banana – which is now mainly available in supermarkets – on a large scale.

Gros Michel Banana
This isn’t the first time bananas have been hit by disease. Related fungi previously wiped out the Gros Michel, which was the main export banana until well into the 20th century. “The bananas we eat now are not the ones your ancestors ate,” says researcher Li Jun Ma. “The old Gros Michel was functionally extinct because of the first Fusarium outbreak in the 1950s.”

Cavendish banana
Today, the Cavendish banana is the most popular variety on the market. It was developed as a disease-resistant alternative to the Gros Michel. About 40 years ago, the Cavendish banana flourished all over the world. But by the 1990s, the good times for the Cavendish banana were coming to an end. “There was another outbreak,” said lead author Yong Zhang. “It spread like wildfire from Southeast Asia to Africa and Central America.”

Outbreak
Over the past decade, researchers have carefully studied this new outbreak. And that has led to some important insights. So we now know that the fungus Fusarium oxysporum It’s not a single species, but a “species complex” of hundreds of varieties, each of which attacks different plant species. These varieties arise by acquiring additional strain-specific genes in addition to a common core genome. “We now know that TR4, which attacks Cavendish bananas, does not originate from the strain that devastated Gros Michel bananas,” explains Ma. “The TR4 genome contains additional genes involved in nitric oxide production, which apparently determines TR4’s virulence.” In other words, the fungus uses additional genes to make nitric oxide, which helps it enter the plant.

two genes
The research provides opportunities for treatments and strategies to control the uncontrolled spread of TR4. Although the team does not understand exactly how the processes discovered contribute to the disease in Cavendish bananas, they found that TR4 virulence was significantly reduced when two genes that control nitric oxide production were deleted. “Finding these additional gene sequences offers great potential to reduce or even control the spread of TR4,” Young said. Discovering the molecular mechanisms that contribute to the fungus’ virulence offers hope for the future of banana farming, because these new insights may help save bananas from devastation.

However, the challenge remains, particularly because of the monoculture practice, which makes commercial banana production vulnerable to disease outbreaks. Almost all bananas in the supermarket are Cavendish bananas, which all descend from a single parent plant. And because they are clones, they all have the same genetic pattern. This, of course, poses problems. “If there is no diversity in a large commercial crop, it becomes easy prey for pathogens,” warns Ma. “The next time you buy bananas, try different varieties that you might find in your local store.”