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Unwrapping the genetic secrets of a chocolate bar

[ 2010-10-19 11:16]     字号 [] [] []  
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This is the VOA Special English Agriculture Report.

Cacao or cocoa trees grow in hot, rainy areas of Africa, Asia and Central and South America. Their beans are used to make cocoa powder, cocoa butter and of course chocolate.

There are five to six million growers, maybe more. Many are poor family farmers with only a few hectares.

West Africa produces more than half of all cocoa beans. Ivory Coast leads the world in production, followed by its neighbor Ghana.

The trees are usually in their fifth year when they start to grow the pods that contain the beans. The trees produce the most pods when they are ten, but they are still productive long after that.

Workers use large knives to cut the lower pods and long tools to remove pods from high on the tree. Later they break open the pods to remove the beans.

A half-gram of chocolate requires about 400 beans. The World Cocoa Foundation says an average pod contains 20 to 50 beans. And experts say growers can lose perhaps one-third of their harvest to diseases and insects.

But now scientists have genetic maps of two kinds of cocoa trees. These genomes are mostly complete and could lead scientists to new ways to increase production and prevent disease.

Mapping genes is the first step to understanding an organism. Next comes learning the job of each gene.

The American food company Mars took the lead in paying for mapping the genes of the Forastero cocoa tree. The Forastero provides 80 to 90 percent of the world's cocoa beans. Mars depends on those beans for its M&Ms and other chocolate candies.

The company's research partners included several universities and the United States Department of Agriculture.

The average West African cocoa farmer produces about 400 kilos of beans per hectare. But Howard-Yana Shapiro, head of plant science and external research at Mars, thinks that science could greatly increase the yield.

HOWARD-YANA SHAPIRO: "There's a yield potential of maybe 4,000 kilos, ten times what the average is in West Africa."

A competitor of Mars, Hershey's, supported the gene mapping of the Criollo, a far less common cacao tree. Cirad, a French government research center, led scientists from six countries in creating that genome.

We'll talk more about the cocoa industry next week, when we look at efforts to help child laborers in Ivory Coast and Ghana.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson and Steve Baragona. You can read and listen to our reports at voaspecialenglish.com. I'm Bob Doughty.

pod: a long thin case filled with seeds that develops from the flowers of some plants, especially peas and beans(荚;荚果)

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(来源:VOA 编辑:陈丹妮)