Did you know that the banana is the world’s most popular fruit crop? Well, it is and every year, over 100 million metric tons are produced in over 130 tropical and subtropical countries. But, edible bananas are actually a genetic accident in nature. And one that we hope to be able to continue to enjoy for many, many years.

Nearly every banana sold across the Western world belongs to the “Cavendish” subgroup of the species. These bananas are sterile and therefore depend on propagation by cloning (either by suckers and cuttings taken from the underground stem) or through modern tissue culture. However, this familiar, bright yellow fruit, is in serious danger because the worldwide monoculture of genetically identical plants leaves the Cavendish vulnerable to disease outbreaks.

From the article:
“One of the most prominent examples of genetic vulnerability comes from the banana itself. Up until the 1960s, Gros Michel, or “Big Mike,” was the prime variety grown in commercial plantations. Big Mike was so popular with consumers in the West that the banana industry established ever larger monocultures of this variety. Thousands of hectares of tropical forests in Latin America were converted into vast Gros Michel plantations.”
But the popularity of the variety led to its doom; in the 1950s and ’60’s a fungal disease- Fusarium wilt (which is very difficult to control and spreads easily in soil, water, and infected plant material, it can also persist in the soil for decades) or Panama disease- nearly wiped out the Gros Michel and brought the global banana export industry to the brink of collapse. “A soilborne pathogen was to blame: The fungus Fusarium oxysporum f.sp. cubense (Foc) infected the plants’ root and vascular system. Unable to transport water and nutrients, the plants wilted and died”, reports the article.
So, because Cavendish bananas are resistant to Fusarium wilt, they were able to replace the Gros Michel (even though it’s less rich in taste) and the entire banana industry was restructured. To date, Cavendish bananas account for 47 percent of the bananas grown worldwide and 99 percent of all bananas sold commercially for export to developed countries.
The Cavendish has a weakness called Black Sigatoka that, if left uncontrolled, could cause banana yields to decline by 35 to 50 percent. And to make matters worse, the species is now under attack from a strain of Fusarium oxysporum, known as Tropical Race 4 (TR4).
Cavendish varieties have shown little if any resistance against TR4.
So, if there is a lesson to learn from the history of the Gros Michel, it’s that reliance on monoculture is a risky strategy, there has to be more genetic diversity with our cultivated bananas.
More from the article:
“Over a thousand species of banana have been recorded in the wild. Although most do not have the desired agronomic characteristics — such as high yields of seedless, nonacidic fruits with long shelf life — that would make them a direct substitute for the Cavendish, they are an untapped genetic resource. Scientists could search within them for resistance genes and other desirable traits to use in engineering and breeding programs.”
Let’s hope that scientists are able to increase our pool of genetic diversity in cultivated bananas so we don’t have to depend on single clones like the Cavendish or the Gros Michel. We wouldn’t want history to repeat itself.

Source: CNN