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UGA researcher trying to revive the chesnut tree | The Red and Black

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UGA researcher trying to revive the chesnut tree

University researchers at Warnell School of Forestry are looking to save the American Chesnut tree. Courtesy University of Georgia Public Affairs

Until the invasive fungus chestnut blight was introduced in 1900, one in every four trees in the mountainous areas of the Eastern United States was an American chestnut.

Now, thanks to a group of University researchers in the Warnell School of Forestry and Natural Resources, the American chestnut may be making a comeback.

Scott Merkle

As part of a team of universities funded by the Forest Health Initiative and led by Professor Scott Merkle, the University’s research group is collaborating to investigate multiple options to save the chestnut.

Merkle, who has been working at the University for 28 years, focuses on inserting resistance genes directly into the DNA of the plant.

Markle takes the traits from the American Chestnut’s sister plant the Chinese chestnut, which is resistant to the blight, as well as anti fungal genes from orchids and immune system genes from wheat.

“Whatever will work,” Merkle said. “We’ll put it together and get a blight resistant tree.”

Chestnut blight – Cryphonectria parasitica – was introduced when the Chinese chestnut was introduced to America in 1904, beginning in New York. It spread quickly because the American chestnut had no resistance.

“It spread down through the Appalachians at a rate of 20 miles a year,” Merkle said. “It was like when Europeans brought smallpox to North America.”

The Chinese chestnut is immune to this fungus, which develops as bright orange cankers on the tree, eventually forming sunken sores that destroy the plant’s vascular system, essentially depriving the plant of nutrients and water, according to Merkle. The only part of the plant the fungus doesn’t destroy is the root system.

When the fungus first started killing trees, fungicides were proven ineffective and cutting the affected trees down didn’t work either, he said.

The American Chestnut Society, one of the other organizations that invested in Professor Merkle’s research, began trying hybrid backcrosses by breeding the offspring of an American and Chinese chestnut with the American parent in the 1980s, to get a chestnut that looks like an American tree but has the Chinese immunity to the disease.

“There are tons of things you can do with chestnuts,” Merkle said. “The wood is lighter than oak and rot resistant; it makes a perfect constructing material. It was used in railroad ties and telephone poles.”

The chestnut also provides a highly reliable food source because it flowers later than other trees and is less likely to suffer frost damage, he said.

“There are hardly any trees in the United states that make a big nut crop,” Merkle said. “The nuts store energy as starch rather than fat. They were eaten by deer, bears and turkeys. During the Great Depression, it was a source of food for the rural poor.”

There are concerns associated with creating genetically modified organisms like the trees.

“There’s always concern that we’ve engineered something that will weed because it’s a super tree,” Merkle said. “But the trees won’t have any advantage that they didn’t have before.”

The USDA Forest Service has to approve the new trees before they are released from the greenhouse. The soil is checked after the trees are removed to ensure no roots are left behind.

Because the resistance genes need to be inserted directly into the nucleus of a cell to make changes, the new trees are grown from single cells rather than seeds. Merkle and his team have been having more and more success with growing the plants from this basic stage, but still less success than they would like transferring the saplings from their nutrient suspensions to soil.

Merkle said the new plants his lab is growing are going to make a difference, despite concerns about GMOs and a less than perfect success rate.

“There’s a big effort now to get [the plants] out, get them tested so they can be reintroduced to the environment,” he said.


Written by vaphc

April 18, 2012 at 6:49 pm

Posted in Uncategorized

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