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Chestnut trees planting a comeback?

Last modified: 1/3/2016 12:27:29 AM
New Hampshire is home to hundreds of American chestnut seedlings growing as part of attempts to produce a blight-resistant chestnut tree through traditional cross-breeding, but in a few years it might also have some trees that were created through a different process: genetic modification.

“We hope to have 10,000 blight-resistant seedlings ready for distribution” in as little as three to five years, said Allen Nichols, president the American Chestnut Foundation’s chapter in New York state.

Seedlings will first go to members of the state chapter, which includes some New Hampshire residents who joined partly to get in line, Allen said.

“A lot of people from Vermont, New Hampshire, Maine are on the list to get the tree,” he said. “There has been a lot of excitement about it.”

The trees are being developed under a decadeslong program at the College of Environmental Science and Forestry in Syracuse, part of the State University of New York system.

Called the American Chestnut Research and Restoration Project (www.esf.edu/chestnut/genes.htm), the project is trying to return the majestic chestnut to American forests.

Through the late 1800s, chestnuts made up as much as one-third of hardwood trees in Eastern forests, and were valued for their wood and for the prodigiuos amount of high-fat, high-protein nuts that they produced. But a fungus carried here on imported Japanese chestnut trees caused a blight that virtually wiped out the species by 1920, killing as many as four billion trees.

Researchers with the College of Environmental Science and Forestry program are trying to create a version of the American chestnut that can shrug off the effects of the fungus, which kills trees by producing oxalyic acid that prevents the circulatory system from carrying water and nutrients up and down between the roots and the leaves

The project takes what is known as the OxO gene from wheat and implants it into chestnut trees. The OxO gene causes cells to produce an enzyme called oxalate oxidase, which detoxifies the acid and reduces the harm.

Early tests indicate that the gene makes American chestnut trees approximately as resistant to the blight as Chinese chestnut trees, which have a natural resistance, although it can take years of growth and study to be certain.

An alternative attempt to create blight-resistant trees, run by the American Chestnut Foundation, involves crossbreeding American and Chinese chestnut trees. The idea is to get a tree that has the resistance of the Asian species but the appearance, wood quality and nut production of the American species.

Hundreds of such crossbred trees are being grown on sites across New Hampshire, although it will be at least a decade more before potentially resistant trees are available for planting by the general public. It takes at least six generations of crossbreeding and each generation takes about five years to mature.

Genetic modification is much faster and can produce trees that are fully American chestnut, rather than trees with Asian characteristics, but it is controversial because of concerns about unintended consequences.

The College of Environmental Science and Forestry spends considerable time on its website addressing that concern. In particular, it notes that while OxO comes from wheat it has nothing to do with gluten, apparently to calm concern about its effect on the edibility of chestnuts.

“We like this gene because it is eaten daily by billions of people around the world. It is not associated with gluten found in wheat, but it is a natural defense gene that helps protect wheat from disease,” the website reads.

The transgenic trees will have to undergo regulatory review by several federal agencies, including the EPA and the U.S. Department of Agriculture, before they can be released into the wild.

Nichols noted another benefit of using the OxO gene. Because it does not directly affect the fungus, it does not produce evolutionary pressure that could lead the fungus to become resistant.

Naturally evolved resistance is an issue with grains which have been modified to produce a natural toxin called Bt. These plants kill off Bt-susceptible insects, removing competition from the occasional Bt-resistant mutant and allowing those mutants to flourish. This has created several Bt-resistant species of insects affecting corn and cotton.

(David Brooks can be reached at 369-3313, dbrooks@cmonitor.com, or on Twitter @GraniteGeek.)


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