In the January 8 Proceedings of the National Academy of Sciences, researchers from the Smithsonian Tropical Research Institute (STRI), The Cucurbit Network and the University of Puerto Rico establish mitochondrial DNA analysis as a powerful tool for understanding relationships among flowering plants. A comparison of mtDNA from cultivated squash, pumpkins, gourds and their wild ancestors strongly supports hypotheses based on archeological and ethnobotanical evidence for six, independent domestication events in the New World. Even Oris Sanjur, who conducted the genetic analysis was "surprised by the resolution" offered by the nad1 gene as a genetic marker.

As excellent sources of edible, protein-rich seeds, members of the genus Cucurbita were among the first plants to be domesticated in the New World. As one of the three sisters (corn, beans and squash) cropping system, squash is prominent in the creation stories of indigenous Americans. In the Iroquois version, corn sprouts from the chest of Sky Woman, squash springs from her belly and beans grow from her hand.

For the last two decades, scientists have pushed to fill in many gaps in the history of agriculture in the humid tropics where archaeological evidence is extremely hard to come by. Last year, Dolores Piperno, archaeologist and staff scientist at the Smithsonian Tropical Research Institute in Panama and colleagues reported the first use of Cucurbita in the Americas at the end of the last ice age (10,000 years ago) based on the presence of tiny plant remains called phytoliths at a site in Ecuador.

Whereas archaeological plant remains tell us that cultivated plants were present at a given time and place, mtDNA sequence data showing similarities among a domesticate and a specific wild population can unambiguously identify the geographic region where prehistoric gardeners first planted the wild ancestors in their gardens, a "promising breakthrough" according to Kenneth Olsen, plant po
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Contact: Oris Sanjur
sanjuro@naos.si.edu
202-786-2094 x8824
Smithsonian Tropical Research Institute
7-Jan-2002

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