The world's favorite fruit, the banana, is in trouble as an untreatable fungal disease that has been threatening banana crops in Asia is now spreading to other parts of the world, scientists warn.

Fusarium fungus, a soil-borne fungus otherwise known as Panama disease, is threatening banana crops worldwide and may lead to the fruit's extinction—again. This is not the first time that a variety of banana was wiped off the planet by this lethal fungus.

Fifty years ago, people were eating bananas that tasted better, lasted longer and did not require artificial ripening. The Gros Michel banana variety was widely popular worldwide until a fungal disease caused it to become commercially extinct. In 1965, Panama disease affected most banana crops in Central America and it spread to the whole world. Hence, farmers had no choice but to burn all the bananas.

Growers opted to plant another breed of bananas, this time an inferior species, the Cavendish cultivar. In the last five decades, farmers and plantations quickly adapted this type of banana. However, a group of researchers from Wageningen University and Research Center found that a clone of Fusarium fungus dubbed as Tropical Race 4 has infected Cavendish bananas in many countries worldwide.

After analysing data of many fungal specimens from eight countries affected, they determined that the strains collected were genetically identical, or clones. Cavendish is a monoculture, which means the variety lacks genetic diversity.

"The Cavendish banana is very susceptible to TR4," Gert Kema, a banana expert at Wageningen, said in a press release.

It's the only variety of bananas various plantations grow each year and this is why a new strain of the Panama disease is spreading. Once one plant is infected, it infects all plants in the vicinity. The soil-borne fungus enters plants through their roots, kills them, and then plots infested with the fungus remain contaminated for years. So far, there's no way to fight the disease; the only way to keep it from spreading is by quarantine, but efforts to contain it are unsuccessful.

"That's why we have to intensify awareness campaigns to reach small- and large-scale growers in order to help them with developing and implementing quarantine measures preventing the fungus from continued spreading," Kema added. Bananas are among the top 10 food commodities for Southeast Asia, Africa, and Latin America, researchers note.

Kema's team is joining with global groups to develop a short-term solution for the growing predicament involving banana crops, in an effort to avoid another pandemic on the scale of the one which wiped out the Gros Michel variety. Researchers tracked this fungus strain's spread from Taiwan to China, Malaysia, Indonesia, Australia and the Philippines, and into Lebanon, Jordan, Pakistan, with reports of it in Mozambique and Oman.

"However, eventually we have to come up with long-term solutions, particularly host resistance, which can only be developed in strong, multidisciplinary alliances with various partners and industry," Kema added. 

The study was published in the journal PLOS Pathogens

Photo: Ian Ransley | Flickr 

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