Mystery melts as chocolate DNA decoded

Mystery melts as chocolate DNA decodedThe chocolate tree and woodland strawberry have become the latest life forms to have their genetic make-up decoded by scientists.

The work gives researchers an unprecedented view of the biological parts inside each crop and is expected to help produce hardier and more disease-resistant plants and lead to tastier treats.

An international team of scientists led by the French organisation CIRAD selected a variety of the Theobroma cacao chocolate tree called Criollo, which was first domesticated by the Maya around 3,000 years ago. The tree is one of the oldest tree crops still grown and is used to produce some of the finest dark chocolate.

Many cacao farmers grow trees that produce lower quality chocolate because they are more resilient to disease and so more likely to guarantee a good harvest.

The researchers identified 28,798 genes in the chocolate tree, including two kinds that help defend against disease and a group of genes the plant uses to make cocoa butter, a prized substance in making chocolate, drugs and cosmetics.

Other genes were involved in giving the chocolate aroma, flavour and colour, while some influence levels of natural antioxidants, hormones and organic chemicals called terpenoids. The study is reported in the journal Nature Genetics.

Fine cocoa accounts for only 5% of world cocoa production because the trees are susceptible to disease and produce lower yields than other strains of cocoa tree. Scientists hope to use the genetic code to breed more productive varieties and develop a sustainable cocoa economy.

The genetic analysis was led by CIRAD researcher Xavier Argout and his colleague Claire Lanaud, who set up the project. Argout said unravelling the genetic code of the chocolate tree could help spur scientific work on the crop. "This situation could encourage new investments in research on Theobroma cacao, the food of the Gods, that has spread throughout the world since the Maya and Aztec civilisations," Argout said.

The genetic make-up of the woodland strawberry is reported in a separate study in the same journal. The fruit, known as Fragaria vesca, is similar to the cultivated strawberry but biologically less complex, making it easier for scientists to study.

Analysis of the fruit's genome revealed genes involved with flavour, flowering and disease resistance.

"We've created the strawberry parts list," said Kevin Folta of the University of Florida's Institute of Food and Agricultural Sciences.

"For every organism on the planet, if you're going to try to do any advanced science or use molecular-assisted breeding, a parts list is really helpful. In the old days, we had to go out and figure out what the parts were. Now we know the components that make up the strawberry plant."

Co-author Mark Borodovsky, from the Georgia Institute of Technology in Atlanta, said: "The wealth of genetic information collected by this strawberry genome sequencing project will help spur the next wave of research into the improvement of strawberry and other fruit crops."

Powered by article was written by Ian Sample Science correspondent, for The Guardian on Sunday 26th December 2010 18.01 Europe/London © Guardian News and Media Limited 2010