Lack of Sex Life Threatens Banana Crops

Steve Conner
The Independent (London)
July 27, 2001

The banana's sex life—or lack of it—is cause for growing concern to farmers and scientists.

The domestic banana that we know and love is an asexual clone, one that results from the sedate, artificial act of vegetative propagation. And no pollinated sex means no annoying seeds, which may be good news for hungry consumers but also means that there's little or no genetic variation—and hence little or no resistance to the banana's many natural enemies.

Devoid of sex, the poor cloned banana is a sitting target for any pest. Finding a way of introducing a little spice—and therefore genetic variety—into the reproductive life of the banana (and its cousin the plantain) is therefore a pressing problem.

That's why a project to do just that has now begun. Announced recently, it involves scientists from 11 countries forming a consortium to decode the banana's genome within the next five years.

As with the human genome project, the information will reveal much about the genes that make a banana what it is, and more importantly what it might be with a little extra help. This information—and any resulting advances in genetic modification—will be of profound importance, not just to banana boffins, but to a large proportion of humanity.

The banana is the world's fourth largest staple crop, one on which the livelihoods of half a billion people depend. But, recently, an evil-sounding beast called the Black Sigatoka fungus has been throwing those livelihoods into jeopardy.

Black Sigatoka, along with the weevils, worms and viruses that also routinely attack bananas, is a particularly disturbing menace in the tropics, where the cooking banana and starchy plantain provide up to a quarter of the daily intake of essential calories.

Disaster Looms for Subsistence Farmers

Only the banana plantations supplying the lucrative export markets can afford the expensive pesticides and fungicides to defend their crops. For many subsistence farmers, an attack of Black Sigatoka means disaster, and sometimes even starvation.

"Resistant strains are essential for small-holder farmers, who cannot afford the expensive chemicals to begin with," says Emile Frison, director of the International Network for the Improvement of Banana and Plantain (Inibap), the French-based organization that is helping to run the banana genome project. "When Black Sigatoka strikes, farmers can do little more than watch their plants die. Increased hunger can swiftly follow."

The sweet dessert bananas that all Westerners know are big business, but they only account for about 15 percent of the 95 million tons of bananas grown annually. The vast bulk of the banana family is made up of the starchy cooking bananas and plantains grown as a staple.

But all the minor varieties of cultivated banana are essentially sterile, genetically uniform clones. The banana varieties that do exist have come about not through the normal process of genetic shuffling that occurs during sexual reproduction, but by mutations within a clone that are vegetatively propagated by taking cuttings or "suckers" growing from the base of the plant.

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