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 Hanu Pappu
In spite of the flower’s popularity, only a few scientists in
the country work specifically with ornamental dahlias. Narrow that
down to the pathogens that affect the plant, and the list of
experts gets even smaller. One of those rare plant pathologists who
worked with dahlias was Sam Smith, who studied the subject at Penn
State years before coming to WSU to be president. In his honor, the
American Dahlia Society established a dahlia research endowment at
WSU in his name.
Hanu Pappu is the second plant virologist at WSU to hold the
Smith endowment, and as such is charged with studying diseases that
affect dahlias. His work is leading to new disease identification
aids, including the development of field tests so that growers can
perform their own diagnoses.
When asked if he grows dahlias at home, Pappu says he’s not into
healthy plants. “It’s the sick ones that fascinate me,” he says. A
virus like the dahlia mosaic virus (DMV) can impair the quality of
the flowers and affect the vigor of the plant. “But isn’t that
beautiful,” says Pappu as he shows a picture of an infected leaf
with a patchwork of dark and light greens.
Pappu has had an exciting few years since coming to WSU in 2002,
discovering, first, that diseased plants have not one, but three
separate viruses, and second, that one of the three DMV viruses is
actually inserting itself into the DNA of the plant and reproducing
itself as the plant reproduces.
Viruses won’t often kill the plant, but they will weaken and
discolor it. Because they can be transmitted through aphids, they
can easily spread to other dahlias nearby. Growers and hobbyists
who find virus in their dahlias tend to hang on to the plants
because of sentimental attachment, says Pappu. But professional
growers and garden centers are serious about detecting disease and
must act quickly to eliminate the infected dahlias, or lose
business and credibility.
Dahlias are only part of Pappu’s research. He also works with
vegetable crops like potatoes and onions. His is a tale of two
tubers, he says. On one end you have the affordable potato. On the
other, a desirable new dahlia can sell for hundreds of dollars.
Though the dahlias we grow now are from varieties imported from
Europe, the plant’s origin, like that of the potato, is in the
Americas. The Aztecs used dahlias as both medicine and garden
decoration. According to plant scientist Paul Sorensen’s “The
Dahlia: An Early History,” the first mention of the dahlia appears
in The Badianus Manuscript, a book on Indian medicinal herbs
written in 1552 by two Aztec Indians attending the college of Santa
Cruz in Mexico. The rare illustrated manuscript was brought to
Spain and then disappeared into the Vatican library for several
hundred years until it was rediscovered in 1929.
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