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DNA plays role in park's revival

| Thursday, March 2, 2006, 12:00 p.m.

No one knew about DNA when the city of Pittsburgh first landscaped Schenley Plaza.

This time -- as work continues to transform the plaza from a parking lot back into a park -- scientists are deploying high-tech genetics tools to help ensure that newly planted trees last as long as those that have welcomed visitors to the heart of Oakland for almost a century.

"Our goal is to make sure that 100 years from now, we'll still have nice, vibrant populations of trees on the site," said Philip Gruszka, director of parks management and maintenance policies for Pittsburgh Parks Conservancy, a public-private partnership to restore the city's four largest public parks.

Schenley Plaza, a six-acre expanse between the Hillman and Carnegie libraries off Forbes Avenue, has been undergoing restoration for a year. A community playground opened this week, although an opening ceremony won't happen until June.

About 80 years ago, city parks officials planted scores of London Planetrees on the plaza.

The hardy species, a hybrid between the Oriental Planetree and American Sycamore, with broad leaves and flaking bark, is a popular choice for urban parks because it can tolerate air pollution and poor-quality soil.

Of the 212 original trees planted at the plaza, 107 remain after withstanding disease outbreaks that killed the others, said Cynthia Morton, botanist at the Carnegie Museum of Natural History.

With a $19,000 grant from the Garden Club of Allegheny County, Morton used DNA fingerprinting techniques to study the genetic diversity of the surviving trees in the Fisher Scientific Biotechnology Lab at the museum.

Genetic diversity means there are many slightly different versions of the DNA in otherwise similar organisms.

Having a lot of genetic strains is key to species survival because it makes it harder for a single environmental threat to wipe out all of the individuals in a population.

Through her experiments, Morton found that the trees in Schenley Plaza were highly diverse, which makes them less susceptible to damage from insects, fungi and other pathogens.

By contrast, she discovered dangerously low genetic diversity among the more than 100 London Planetree samples she took from nurseries across the U.S.

That's because most nurseries today propagate trees by using cuttings rather than relying on seeds, which means the trees no longer diversify by swapping DNA during reproduction, Morton said.

"If these trees were planted and got attacked by something, they would all be wiped out," she said.

So far, the Parks Conservancy has planted 93 new London Planetrees that came from local nurseries at Schenley Plaza.

The organization plans during the next decade to replace all of the original trees on the plaza, most of which are now decaying. Based on Morton's genetic findings, Gruszka and his colleagues will select the trees from cuttings they've taken from the diverse population of London Planetree already there.

The project points to the power of genetic information to address everyday problems.

"There are a lot of interesting questions that people forget they can use molecular biology to answer," Morton said. "It's not just CSI programs or paternity cases."

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