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See Inside October 2010

Death and Chocolate: Disease Threatens to Devastate Global Cocoa Supply

A blight is threatening the world's cocoa supply. Will genetic intervention save our desserts?



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In a rare tale of technology, bio­terrorism and chocolate, scientists are racing to sequence the cacao tree genome. They fear that without the genome in hand they will be unable to stop the spread of two virulent pathogens that threaten to devastate the world’s cocoa crop.

Cacao trees were first domesticated more then 1,500 years ago by Mayans living in what is now Central America, but fungal diseases such as witch’s broom and frosty pod have largely chased the bean out of its native habitat. The great worry is that one of these diseases will cross the Atlantic Ocean to West Africa, where 70 percent of the crop is now produced. Cacao trees in West Africa have no resistance to the pathogens, which form spores and spread via the wind, careless farmers and, in at least one case, bioterrorists. Scientists say that just a few infected pods would lead to the loss of one third of total global production.

One way to forestall such a crash is to breed plants that are resistant to infection. Scientists identify naturally resistant plants, artificially pollinate them, then test their offspring. This is a slow process, and having the cacao genome in hand would speed things up. Scientists would be able to identify the sections of DNA that confer increased resistance and select the best trees to breed. “It’s expensive work,” says Randy C. Ploetz, a plant pathologist at the University of Florida, “but once you have a genetic sequence, it makes that work a lot easier.”

Scientists expect to release a first draft of the cacao genome by the end of the year; identifying the genetic sites responsible for resistance will take a few years more. In the meantime, producers in Côte d’Ivoire and Ghana have instituted strict quarantines to help protect their crops.

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