may be on the verge of extinction.

Fernando: Similar to humans,

bananas are also facing a pandemic.

Narrator: Ninety-nine percent of bananas exported to developed countries

are just one group called the Cavendish.

And the Cavendish is vulnerable to Tropical Race 4,

or Panama disease,

a fungus that's now ravaging banana farms across the globe.

Fernando: So now you can compare,

this is Tropical Race 4 in a Cavendish banana.

Then this plant looks very healthy.

Narrator: One scientist recently developed a line

of Cavendish that is resistant to TR4,

but it was genetically modified.

Fernando: In Europe, the GMs are under regulation,

so we cannot use it.

Narrator: So scientists like Fernando

had to start from scratch to find a solution.

And they're working against the clock.

Because if TR4 is not stopped ...

James: It would wipe out Cavendish.

Narrator: And it's already happening.

Narrator: Globally, we're facing the collapse

of a $25 billion Cavendish industry.

So how did we get here?

And can we save one of the world's

most consumed fruits before it's too late?

You probably know the Cavendish banana.

You can find this type of banana

in every supermarket around the world.

Narrator: They're so popular because they're yummy,

they look nice, and they ripen as they transport.

James: It's high-yielding, so it's got quite a thick skin,

and so it travels well and tastes pretty good.

It comes in its own package.

Narrator: But there's a problem.

Fernando: They are sterile. They don't have seeds.

Narrator: No seeds means Cavendish bananas

are clones of each other.

So the only way to propagate them

is in vitro or by taking new growths,

called suckers, from the base of an older plant.

But since they're all genetic copies,

Cavendish are really vulnerable to disease.

Fernando: The domino effect.

If you have everything wrong with just one clone,

one disease can kill everything, plant by plant.

Narrator: That's exactly what's happening with TR4,

one of the deadliest plant diseases out there.

The fungus doesn't spread to humans,

but it does eventually kill the banana plant

so no more fruit grows.

Scientists guess the fungus probably started

somewhere in Southeast Asia in the '90s

and quickly spread across the globe.

Then in 2019, it hit Latin America.

Combined with the Caribbean,

that area grows 75% of the world's bananas.

Narrator: To make sure the fungus doesn't spread,

farms across Colombia have implemented biosecurity measures.

Eva Norte 2 was one of the first farms

in the country to detect TR4.

Workers wash down and disinfect the underside

of any car that comes in,

just in case there's infected soil hiding in the treads.

Narrator: Antonio's team built cement paths

throughout the farm.

So on their way to harvest,

workers aren't walking on open soil.

Narrator: Once they've reached the area

ready to be harvested, workers walk through

a sanitizing foot bath made of ammonium.

Narrator: Out in the field,

Workers measure the banana fingers

to make sure they're ready to harvest.

They're usually ready about 12 to 13 weeks

after the fruit stem shows up.

One worker cuts down a 65-pound bundle

while the other catches it and carries it to the cableway.

That cableway system brings all those banana bunches

to the packaging plant.

First, workers sanitize the bunches with chlorine.

Narrator: Then they check the bananas for quality

and any signs of Fusarium damage.

They cut off and throw bushels into a huge tank.

That bath not only preserves the bananas,

but washes off any of the latex

that naturally occurs on the peel.

The bananas get cut into smaller bunches of five to seven.

Narrator: Next come those famous stickers.

Narrator: Workers wrap the banana carefully

so they don't bruise. That wrapping has holes in it

so the bananas can ripen as they travel.

No more than four hours after the bananas are harvested,

those boxes end up on pallets loaded onto trucks.

Narrator: The bananas are trucked to the nearby port,

where they're moved onto ships.

This shipment's headed to the US.

With equipment, bananas, and people

moving along this global supply chain,

it's easy to see how the fungus could spread.

If TR4 does sneak into a farm,

the Colombian government has laid out

strict guidelines for containing the fungus.

Narrator: That means they found symptoms like ...

Fernando: The yellowing of the leaves.

The splitting of the stem.

Narrator: Once TR4 is identified in a plant,

you can't just kill that one plant.

The fungus goes about 10 feet deep into the soil.

Fernando: Once the pathogen is in the soil,

it's almost impossible to eradicate.

Narrator: So you have to kill off

all the plants in that area.

Narrator: To keep operating the rest of the farm,

Eva Norte 2 followed the government's three-zone plan.

Narrator: The injected herbicide

kills all the plants in Zone A.

Narrator: That tarp's so birds won't land

on the fungus and spread it around.

There are also canals around the zone

to keep any water away from the infected area.

In Zone B, called the buffer zone ...

Narrator: Finally, in Zone C, plants are allowed to grow,

but they're constantly monitored for signs of TR4.

Jose estimates biosecurity has cost this farm

as much as $5 million since 2019.

So they're pricey,

but the measures are working at keeping the fungus at bay.

Narrator: These biosecurity measures have contained

the fungus in Colombia and kept it from spreading to Ecuador,

the largest exporter of bananas in the world.

But fungus can wipe out an entire fruit variety

if not stopped.

We know because it's happened before.

In the early 1900s,

a banana called Gros Michel was the most popular.

But by the 1950s ...

Fernando: One strain of the Panama disease

wiped out the whole production of Gros Michel.

Narrator: Luckily, Cavendish was resistant

to that first strain.

So it took over as the banana of choice.

The problem was banana companies built their entire

supply chains around this one Cavendish variety.

In 2019, they exported 20 million bananas

and supported millions of jobs globally.

But now, the Cavendish is also vulnerable.

Fernando: History repeats itself now

with a Tropical Race 4 and the Cavendish.

Narrator: Cooking bananas like plantains

are also at risk for TR4.

Fernando: A risk for food security,

because the plantains are a staple food in Latin America,

in Africa, and many other countries.

They are part of our daily diet.

Narrator: So yeah, the newest race

of Fusarium is scary for both Cavendish and plantains.

But this time around, we have advanced science.

Researchers across the globe are working toward one goal.

Narrator: This guy actually invented a banana

that did just that.

Back in 2019, Dr. James Dale announced

that his team had successfully injected the DNA

from a resistant banana into a Cavendish.

And it worked.

James: We found the solution in the line of Cavendish

which appears to be completely resistant to TR4.

The thing we haven't done yet is a taste test.

And that's because they're GM.

They look, smell, feel exactly the same as every other,

but we've only changed one gene.

Narrator: But no one would buy

his miracle banana because it was genetically modified.

Narrator: In the EU, most member countries

have either partly or fully banned GMOs.

In the US, they're allowed but feared.

One argument against GMOs is that these modified plants

would quickly spread their genes

and kill out biodiversity.

But with bananas, that's not a problem.

James: The genes don't move because they are sterile.

You can grow a GM banana next

to a non GM banana for 50 years

and the gene will not move from under the other.

Incredibly frustrating.

There's a solution, but it's a scientific solution,

but not a political solution.

Narrator: So scientists

had to go back to the drawing board,

using what they learned from James to play the non-GMO game.

Fernando is a breeder for KeyGene, a genetics company

in the Netherlands.

And he thinks the best way to get around GMO regulations

is through traditional breeding,

meaning you take two different types of bananas --

the Cavendish and one that is resistant -- and you essentially

have them mate. And their kid is hopefully resistant

to Panama disease, but still tastes good

like Cavendish.

Fernando: Crossbreeding, or traditional breeding,

is something that happens every day in nature.

So the bees are pollinating the different flowers

with other flowers.

So that's what we are doing here.

We are acting as bees.

Narrator: Fernando has found a few resistant bananas

to cross with Cavendish, but ...

Fernando: Most of them are not even edible bananas,

they are bananas that are full of seeds, like this one.

Narrator: And to cross those with a Cavendish is hard.

Fernando: They are sterile, very difficult to breed.

It's not impossible.

So you can try to cross, but you need to do it

many, many, many times to get only a few seeds.

Narrator: For James to make that first GMO banana,

it took him ...

James: Nearly 10 years since our first field trial.

Narrator: For those future bananas

that are traditionally bred, it'll take just as long.

Fernando: It will take lots of years

because the life cycle of the banana is quite slow.

Narrator: But the longer it takes to traditionally

breed a resistant Cavendish, the more the disease spreads.

And the more strains of Fusarium could be released.

Fernando says there's a bigger-picture way

to attack this problem: diversity.

Take tomatoes for example. You go to the grocery store,

and there may be 10 or more different types

of tomatoes: cherry, vine, beef, Roma. That's diversity.

So if one tomato gets in trouble,

it won't be a huge loss.

Fernando and his colleagues have the same vision

for bananas.

Fernando: We have red bananas, pink bananas.

Why not try to incorporate that into the market

so that you can go to the supermarket

and have a complete bench of different options

of bananas that you can choose.

James: There are hundreds of different banana varieties

around the world.

A friend of mine collected one up in Papua New Guinea

that he said, if you didn't know it,

you'd think you're eating a strawberry.

Yeah. So amazingly different flavors.

Narrator: And diversity would also help farms.

Fernando: But if you have different types

of bananas grown together,

probably one banana will be more resistant

than the next one.

So that one can stop the spreading

of the disease to the next plant.

Narrator: So why haven't companies diversified?