Australian scientists race to save bananas

A fungus has wiped out Cavendish plantations in Australia and South-east Asia over the past decade and recently gained a foothold in Africa and the Middle East. Scientists say Latin America (above) is next.
A fungus has wiped out Cavendish plantations in Australia and South-east Asia over the past decade and recently gained a foothold in Africa and the Middle East. Scientists say Latin America (above) is next.PHOTO: REUTERS

DARWIN (Australia) • A slippery skin awaits the banana if the hazard is not removed. So in a field near Humpty Doo in Australia's Northern Territory, scientists are racing to begin an experiment that could determine the future of the world's most popular fruit.

Researchers will soon place into the soil plants that they hope will produce standard Cavendish bananas - the curved, yellow variety representing 99 per cent of all bananas sold in the United States.

The plants have been modified with genes from a different banana variety.

A fungus known as fusarium wilt has wiped out tens of thousands of hectares of Cavendish plantations in Australia and South-east Asia over the past decade.

It recently gained a foothold in Africa and the Middle East.

Scientists said Latin America, the source of virtually all the bananas eaten in the US, is next.

 

"These recent outbreaks confirmed that this thing does move," said plant pathologist Randy Ploetz of the University of Florida, who identified the fungus in 1989 in samples from Taiwan.

 

Ever since, farmers have been trying to escape the effects of fusarium wilt, also known as Panama disease Tropical Race 4, or TR4. Once it hits a farm, the only recourse is to eradicate the plants and start over.

For decades, researchers were foiled in efforts to bring disease resistance to the Cavendish or hybridise a replacement for the thick-skinned, slow-ripening variety that dominates exports, a US$12.4-billion (S$16.8-billion) global business.

Soon after TR4 was identified, farmers reported that a sub-species of the Musa acuminata variety of sweet bananas, which thrives in the wild in Malaysia and Indonesia, was "growing happily in plantations devastated by TR4", said biotechnology professor James Dale of the Queensland University of Technology in Australia.

It took years to isolate the gene responsible for the resistance. In 2004, his lab identified candidate genes worth testing.

Over three more years of painstaking work, he inserted genes from the sub-species into cells from a Cavendish. It takes about a year to grow a plant with roots that can be placed in the soil.

It was another three or four years before Prof Dale could get funding. He was able to start a small field trial in 2012, which lasted three years.

On the basis of that initial trial, he will be expanding the test over three years.

Botanists from the Royal Botanic Gardens in Kew, England, and research organisations from France to Honduras to Malaysia, are collecting samples of wild bananas to see whether, like the Musa acuminata variety, they possess resistance to TR4.

Professor Ploetz is optimistic about Prof Dale's trial, but thinks the latter needs "to test this new (fruit) in different environments".

The industry has seen all this before.

In the early 20th century, the banana most commonly sold worldwide was the Gros Michel, a short, uncurved and stubby fruit.

But a fungus - Tropical Race 1 (TR1) - drove it nearly to extinction in the 1950s. The Cavendish, a variety from China found growing in a hothouse belonging to England's Duke of Devonshire, was discovered to be resistant to TR1.

The ordinary bananas you find in stores today are all clones of the duke's plant.

Ironically, a major obstacle to replacing today's Cavendish with a TR4-resistant strain is the industry, which, for the most part, has dropped out of doing research, said Prof Ploetz. The result is that very few scientists have been focusing on the problem directly.

This means that even if Prof Dale's transgenic experiment in Humpty Doo is successful, the TR4 fungus' march to Latin America may be inevitable.

Breakfast may never be the same.

WASHINGTON POST

A version of this article appeared in the print edition of The Straits Times on October 13, 2017, with the headline 'Australian scientists race to save bananas'. Print Edition | Subscribe