Scientists decodes the genetics of chocolate


Published: Monday, February 1, 2010 at 6:01 a.m.
Last Modified: Monday, February 1, 2010 at 1:43 a.m.

MIAMI — No one who loves chocolate needs to be told that it is experiencing a golden age. The very fact that the names of illustrious cacao types like Venezuelan Porcelana have made their way onto chocolate-bar labels shows a deepening hunger for vivid cacao character and careful artisanship.

On the scientific front, biochemists are unraveling chocolate's heart-healthfulness and archaeologists are gaining insight into its ancient ritual uses, but plant geneticists are engaged in the most exciting research. Their project to decode the cacao genome holds promise for farmers, manufacturers and chocolate lovers alike.

South Florida scientists are playing a vital role, and the geneticist who leads their efforts, Dr. Raymond Schnell, will speak Saturday at Fairchild Tropical Botanic Garden's International Chocolate Festival.

At Chapman Field, the Subtropical Horticultural Research Station of the USDA Agricultural Research Service, Schnell coordinates two programs aimed at constructing an overall genetic picture of Theobroma cacao: the International Marker System Selection Program and the Genome Sequencing Program. Funded by Mars, the project also involves scientists at five other sites.

South Florida's role in chocolate research dates to the 1950s, when the USDA established a quarantine station here to stop the movement of cacao diseases among the Americas, Asia and Africa.

After disease decimated the cacao crop in Bahia, Brazil, in 1998, threatening Mars' supply, the company offered to fund USDA efforts to develop disease-resistant plants to broaden the dangerously narrow genetic foundation of cacao plantations in Africa, the world's largest producer.

This program gave rise to far-reaching efforts to collect and — just as crucially — accurately identify cacao specimens. As Schnell told me when I visited his research station last year, this is no mere academic exercise.

DNA testing has revealed that some of the world's great germplasm banks are full of mislabeled specimens — a hindrance to any breeding program meant to exploit a particular cultivar's qualities, from subtle flavor nuances to disease or pest resistance. For the past decade, Schnell's team has been systematically examining germplasm from many collections, trying to set the record straight.

The Coral Gables research station sits on property that once belonged to horticulturalist and tropical plant explorer David Fairchild. Looking at the weathered gray stone walls that enclose the cacao collection, I felt transported to a Maya temple ruin. My tour guide, agricultural research technician Mike Winterstein, told me that had been just what Fairchild wanted.

In 1933 he had the garden enlarged as part of a Civilian Conservation Corps project, cannibalizing paving stones from a military airstrip to construct the thick walls. Fairchild knew that unimpeded Gulf Stream breezes made the spot several degrees warmer than surrounding areas. This slight boost plus the absorbed heat the walls radiate back at night raises the temperature in the sheltered garden by 5 to 7 degrees — enough for cacao and other tender tropical plants to survive this far north.

Among the scientists working on the mapping project is Venezuelan-born geneticist Juan Carlos Motamayor, who has shed light on the complexity of genotypes within the species Theobroma cacao. There are 10 known genetic clusters, all native to South America, and the number may grow as Motamayor examine cacao samples gathered in Bolivia and Peru.

When the project is complete in two or three years, it will help clarify the genetic origins of cacao and the relationships among its types. It will also allow scientists to select cultivars for farmers that are smaller, faster-growing, easier to prune and more resistant to pests and disease.

In the end, more accurate knowledge of genetics will turn cacao into a modern crop. The payoff for chocolate lovers will be a secure source for their favorite food and, perhaps, an even richer flavor palette.

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