"Sequencing the cocoa genome is a significant scientific step that will allow more directed breeding of cocoa plants and perhaps even enhance the quality of cocoa, the key ingredient in chocolate," privately held Mars said in a statement.

"The collaboration will enable farmers to plant better quality cocoa and, more importantly, help create healthier, stronger cocoa crops with higher yields, pest and disease resistance, and increased water and nutrient use efficiency."

While conventional plant breeding techniques can transform a crop, having the complete genome offer researchers the opportunity to take short-cuts to changing the plant's qualities.

"Sequencing the genomes of agriculture crops is a critical step if we want to better understand and improve a crop," said the USDA's Judy St. John.

The first crop to have its genome sequenced was rice -- an international effort that took years and which was finished in 2002. In April, a team at the University of Hawaii sequenced the genome of a genetically engineered papaya.

(Reporting by Maggie Fox; Editing by Julie Steenhuysen and Cynthia Osterman)