As the 20th century draws to a close, still little is known about the origins of a staple subsistence crop that feeds an estimated 600 million Third World people.
The plant is cassava (Manihot esculenta), a bushy plant producing tubers -- the starchy underground stem of the plant -- that have fed the indigenous people of the Americas for millennia and much of Africa since the 17th century.
But now biologists at Washington University in St. Louis have written the ultimate roots story for this plant in a paper published in the May 11, 1999, Proceedings of the National Academy of Sciences.
Barbara A. Schaal, Ph.D., Washington University professor of biology in Arts and Sciences, and her graduate student Kenneth M. Olsen, have pinpointed cassava's origins to the southern border of the Amazon River basin in Brazil. The Explorer's Club, National Science Foundation, the Rockefeller Foundation and the Guggenheim Foundation supported the research.
Using sophisticated DNA sequencing techniques that traced variation in a single gene found in cultivated and wild cassava, Schaal and Olsen have identified a cassava subspecies, still present in the diminishing wilds of the Amazon basin, as the plant's progenitor.
The find provides important insights into cassava's evolutionary origin. Their work also reveals a wealth of genetic diversity in wild and domesticated cassava strains, information that plant breeders can use to create hardier plants that are more resistant to disease. With the newly found genetic information, there are greater possibilities now to transform cassava from an "orphan" crop to a more commercially viable one that could be used as a fiber source.
Cassava ranks sixth among crops in global production. Denizens of the developed world have sampled cassava in tapioca and perhaps some flours at specialty food stores or specialty dishes in the Miami area. But the
Contact: Tony Fitzpatrick
Washington University in St. Louis