Gone bananas

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Forget pyjamas, the fate of this fruit lies in its genes

We Australians love a banana – we eat more than five million of them every day. Globally, more than 100 billion bananas are consumed every year, and they are a staple food in many countries making them one of the most important food crops worldwide.

But this much-loved snack is under attack from a sinister plant pathogen that could wipe it out for good. Thankfully, researchers at the Queensland University of Technology (QUT) have come up with a clever solution.

Banana extinction is nothing new

Nearly half of the bananas grown around the world are varieties of Cavendish bananas, and almost all of the 414,000 tonnes of bananas grown in Australia every year are Cavendish. But it wasn’t always the king of the fruit bowl.

Before Cavendish, the world’s favourite banana was the Gros Michel, or ‘Big Mike’. Big Mike was a popular guy, but his downfall came in the 1950s–’60s when a fungal disease called Fusarium wilt (or Panama disease) swept through plantations, nearly wiping the variety out completely.

The disease is caused by a soil-borne pathogen that infects the roots before spreading through the rest of the plant via its vascular system, causing the plant to wilt and die. It is resistant to fungicide, can’t be controlled with chemicals, and spores from the fungus can contaminate soil for decades, rendering land unusable for non-resistant varieties.

Cavendish was found to be resistant at the time, and replaced Big Mike everywhere. But while Cavendish was able to fight off this first wave of Panama disease, it is now under attack from a different strain, known as Tropical Race 4 (TR4). If TR4 was to spread to major plantations around the world, the banana as we know it could become extinct.

New hope for the Cavendish

Fortunately, researchers from QUT may have found a way to battle this strain of Panama disease. They took a gene from a TR4-resistant wild banana and used it to genetically engineer the Cavendish. They then planted the transgenic banana in a plantation in the Northern Territory that was heavily infested with the disease.

At the end of the trial, one genetically modified plant line was completely disease-free, while three others showed strong resistance. QUT’s lead researcher on the project, Professor James Dale, says this is a highly promising result.

“These results are very exciting because it means we have a solution that can be used for controlling this disease,” he says. “TR4 can remain in the soil for more than 40 years and there is no effective chemical control for it. It is a significant threat to commercial banana production worldwide.”

The gene is also present in Cavendish naturally, but it’s not very active. James and his QUT team now hope to find ways to increase the gene’s activity by using gene editing.

“It’s a complex process that is a way off, with four or five years of lab work,” he says. “We’re also looking at and screening wild bananas to identify other resistance genes, not only for resistance to TR4, but to other diseases.”

Optimising our staple snack

James and his team recently further advanced another decade-long research project developing a banana rich in pro-vitamin A. Between 650,000-700,000 children die from vitamin A deficiency each year. James hopes his bio-fortified banana will save lives.

“We tested hundreds of different genetic variations in our QUT lab and in field trials in Queensland until we got the best results,” he says. “These elite genes have been sent to Africa in test tubes where they have been inserted into Ugandan bananas for trials there.”

– Chloe Walker

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“These results are very exciting because it means we have a solution that can be used for controlling this disease.”

– Professor James Dale, QUT
Eliza Brockwell

Author: Eliza Brockwell

Eliza is the Digital Producer for Careers with STEM. Eliza is passionate about creating content that encourages diversity of representation in STEM.

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