Bananas: The Long Goodbye
The demise of the domestic banana has been on the horizon for quite a while, and it is drawing nearer. Dan Koeppel reports in The Scientist:
Our standard supermarket banana, a variety called Cavendish, may be at the brink of disaster. Chosen for its resistance to a fungal pathogen that wiped out its predecessor, the Gros Michel banana, the popular fruit has long battled a related fungus, which has all but devastated the banana industry in certain parts of the world. Now, it appears the Cavendish variety is facing a new threat—the very same fungal disease that drove Gros Michels off the market.
Cavendish bananas account for about 45 percent of the fruit’s global crop, with an annual export value of US$8.5 billion, according to the United Nations Food and Agriculture Organization. It was chosen to replace the original Gros Michel banana after a deadly fungal infection, known as Panama disease (Fusarium oxysporum f. sp. Cubense), wiped out much of the world’s banana crop in the first half of the 20th century.
Farmers adopted the Cavendish variety because it appeared to resist the blight, as well as about a dozen other banana diseases that also threaten the worldwide crop. But it wasn’t long before it too started suffering from disease. In the late 1980s, a mysterious malady began to wipe out Asian Cavendish plantations. Soil samples were sent to plant pathologist Randy Ploetz of the University of Florida’s Tropical Research and Education Center, who made the shocking identification: Panama disease was back, in the form of a new strain, which he dubbed Tropical Race 4.
Race 4 is just as virulent to Cavendish as Race 1 was to Gros Michel. The fungus enters the plant via its roots through infected soil or water and spreads via the plant’s vascular system. Once exposed, the plant yellows, and begins to look obviously sick—dried-out, sunken, and sagging. As the disease progresses, brown and purple stripes appear on the trunk, and the plant eventually dies. The disease, however, lives on, spreading via infected soil from plant to plant, plantation to plantation.
Today the disease has spread across Asia, into the Pacific, and to Australia, where it has devastated the island country’s banana industry. Though Race 4 has yet to hit Latin America, where bananas imported to the United States are grown, there’s little doubt it will, said Ploetz.But it turns out that Race 4 is not the only threat to Cavendish bananas. As banana growers have fled from Race 4, replanting their Cavendish trees in areas only known to harbor Race 1, they quickly learned that Gros Michel’s old foe was now tormenting Cavendish bananas as well.
In 2010, scientists conducting a survey of plants infected in India, which grows and consumes more bananas than any other country in the world, were the first to conclusively identify the presence of Race 1 in the Cavendish banana. . .