Researchers Crack the Cocoa Code

A team of international researchers has successfully sequenced the DNA of the Criollo variety of Theobroma cacao. The team's work identified a variety of gene families that may help improve cacao trees and fruit by enhancing their attributes or providing protection from fungal diseases and insects that affect cacao trees. As such, the sequencing and assembly of the chocolate tree genome will benefit the farmers who grow it, as well as the producers of high-quality chocolate.

"Our analysis of the Criollo genome has uncovered the genetic basis of pathways leading to the most important quality traits of chocolate—oil, flavonoid and terpene biosynthesis," said Siela Maximova, associate professor of horticulture, Penn State, and a member of the research team. "It has also led to the discovery of hundreds of genes potentially involved in pathogen resistance, all of which can be used to accelerate the development of elite varieties of cacao in the future."

The researchers identified two types of disease resistance genes in the Criollo genome. They compared these to previously identified regions on the chromosomes that correlate with disease resistance—QTLs—and found that there was a correlation between many the resistance genes' QTL locations. The team suggests that a functional genomics approach, one that looks at what the genes do, is needed to confirm potential disease resistant genes in the Criollo genome.

Hidden in the genome the researchers also found genes that code for the production of cocoa butter. Most cocoa beans are already about 50 percent fat, but these 84 genes control not only the amount but also quality of the cocoa butter.

Other genes were found that influence the production of flavonoids, natural antioxidants and terpenoids, hormones, pigments and aromas. Altering the genes for these chemicals might produce chocolate that is healthier, and has better flavors and aromas.