American Rice: Out of Africa

16 November 2007 (All day)


African waves.
A successful variety of rice called Carolina Gold may have come from Ghana.

In colonial America, slaves from west Africa made many a plantation owner rich by growing a particular high-quality variety of rice. Now, genetic research suggests the slaves not only supplied the labor and the agricultural skills they'd gained in their home countries but also may have brought the valuable crop with them.

When slaves were brought to the American colonies from west Africa, they often grew various kinds of rice in small gardens to feed themselves. Rice became a cash crop for plantation owners, however, with the advent of a high-quality variety of rice in 1685. The variety came to be known as Carolina Gold, and for good reason. By 1720, rice was South Carolina's most valuable export. But from where did the key cash crop come?

The first reported import in the New World of what is thought to be Carolina Gold occurred in 1685, when a slave ship from Madagascar unloaded a cargo of rice in Charleston, South Carolina. That suggested that the rice came from that island nation off the east coast of Africa, or that, perhaps, it came from Asia and was picked up at a port on the way to America. Africa has an indigenous rice, Oryza glaberrima, which may have been domesticated about 1500 B.C.E. along the upper Niger River. It spread to west Africa, and when the first Portuguese explorers reached Guinea in 1446, they found extensive fields. Perhaps Carolina Gold descended from this plant.

To trace the origins of the crop, rice geneticist Anna McClung of the U.S. Department of Agriculture (USDA) in Stuttgart, Arkansas, and molecular geneticist Robert Fjellstrom of the USDA in Beaumont, Texas, searched the USDA Rice Germplasm Collection for varieties with a molecular marker, RM190, for a gene that controls the starch content in Carolina Gold. This marker turned up in fewer than 1% of the varieties.

To narrow the search, they next looked for 43 other molecular markers in Carolina Gold. McClung and Fjellstrom found one variety that shared 42 markers. Called Bankoram, it had been sent to the USDA collection in 1972 from a seed bank in Ghana. "It's nearly a perfect match," McClung says, who presented the results last week at the annual meeting of the American Society of Agronomy in New Orleans, Louisiana. When the researchers grew the Bankoram seed, the plant was very similar to that of Carolina Gold. The finding suggest that Carolina Gold came from west Africa, just like the slaves who cultivated it.

McClung stresses that the research is preliminary. She can't yet rule out, for example, the possibility that Carolina Gold may have been taken back to Africa and wound up in the seed bank in Ghana. "There are a lot of things we need to nail down," she says. But geographer Judith Carney of the University of California, Los Angeles, says a Ghanaian origin of Carolina Gold fits with the idea that Carolina Gold arrived in the colony as food on slave ships and was then planted by the slaves.

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