|The Botanic Garden
of Smith College
rees and shrubs of the yew genus, Taxus (family Taxaceae), are the source of the anticancer drug taxol. Taxol and related compounds are present in tiny amounts in bark, roots, and foliage. For example, it takes 60 pounds of dried bark (equivalent to a dozen 10-inch-diameter, 12-foot-tall trees of Pacific yew, Taxus brevifolia) to produce enough taxol to treat one person with cancer, a disease which kills a million Americans yearly. Alternatives to wild-collected bark as a source of taxol are needed.
During the 1990s, the Smith College Botanic Garden, with support from the U.S. Department of Agriculture and Phyton Inc., a biotechnology firm, assembled a remarkable collection of Taxus. Phyton Inc. has perfected the technique of culturing plant cells to produce taxol and promises to become a major supplier of this precious compound. Collecting trips started in Northampton with research into books and herbarium specimens to determine the range of Taxus species, what the plants look like, and exactly where they have been found in the past. Trips into the field--to New England, Florida, Mexico, Scandinavia, Taiwan, the Philippines, China, and Vietnam--provided stem cuttings and seed that were brought to Smith and propagated in the greenhouses. One field trip to Oaxaca State in Mexico included student Xochitl Munn. Her relatives who lived in the mountain town of Huatla de Jimenez were instrumental in helping us find Taxus globosa, the rare Mexican yew. These efforts led to Smith's acquiring the most diverse collection of yews in the United States and perhaps worldwide.
Field-collected material was carefully labeled with species and exact plant of origin, and samples were sent to Ithaca so screening could identify the clone or genotype producing the highest concentration of taxol. Although all species of Taxus tested so far produce taxol or related compounds, species and individuals are quite variable in amounts of taxol produced. If genotypes producing the greatest concentrations of taxol can be identified and cultured successfully in the laboratory, it is hoped that humans can save remaining stands of wild yews from extinction.
The Smith College collection of Taxus is also enabling Taiwanese botanists to compile a revision of the taxonomy of the genus Taxus. This effort should shed light on the relationships among the six to ten recognized but difficult to distinguish species, which grow scattered throughout the northern temperate areas of Asia, Europe, North Africa, and North America.
For further reading, see Hal Hartzell, Jr., The Yew Tree: A Thousand Whispers, Biography of a Species, Hulogosi, Eugene, Oregon, 1991.
Keith D. Rushforth, Conifers, Facts on File, New York, 1987.
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