Scientists say they have cracked the genetic code of a variety of cacao considered to produce the world's finest chocolate.

Cacao flowers on a tree — one of the oldest domesticated tree crops in the world. (Mark Guiltinan/Penn State)

A team of international researchers sequenced the DNA of Criollo, a variety of Theobroma cacao that the Maya domesticated about 3,000 years ago in Central America.

While it is one of the oldest domesticated tree crops, most modern growers prefer hybrid cacao trees that produce chocolate of lower quality but are more resistant to disease.

The research, published in the current issue of Nature Genetics, was led by Claire Lanaud of the French agricultural research institute, CIRAD, and plant molecular biologist Mark Guiltinan of Penn State in Pennsylvania.

"Fine cocoa production is estimated to be less than five per cent of the world cocoa production because of low productivity and disease susceptibility," Guiltinan, said in a release.

The research, financed in part by candy maker Hershey, follows an announcement in September of the sequencing of a different variety of cacao tree, financed in part by rival candy maker Mars.

Both groups say they hope their work identifying a variety of gene families in the trees' DNA that provide protection from diseases and insects will lead to more robust, higher-yielding trees.