Reviving the Chestnut Tree

In the meantime, scientists had discovered that Asian chestnut trees were somehow able to resist the fungus. Asian chestnuts, like their European cousins, are smaller trees and they can’t compete in American forests with taller trees, particularly oaks. Unless the chestnut towers over the forest canopy, it doesn’t get enough sun to flower and reproduce.

But Anagnostakis and others, saw an opening. Researchers found that at least two genes in the Asian chestnut allowed it to resist the fungus. The hope of survival for the American chestnut rested in transferring those genes.

So researchers began an aggressive cross breeding program, combining the Asian chestnut with its bigger American cousin in a surprisingly low-tech procedure.

Paper Bag Breeding

Working with experimental trees on the research station’s Connecticut farm, Anagnostakis waited for the flowers on the trees to begin to bloom, then she covered them with a paper bag to isolate them from pollen. After the flowers became fertile, the bag was removed, and the desired pollen was simply dumped on the flowers. Then the bag was replaced.

“We wait until fall and go around and cut all those paper bags off and take the nuts out and store them away for the winter,” she says. “In the spring, when the nuts have germinated, we plant them and we have another generation ready to go.”

By continually cross breeding, she has produced trees that are 15/16th American chestnut trees, and only 1/16th Asian. She plans to continue that process until the only Asian component is the desired genes that protect the tree from the fungus.

So the researchers are using biological warfare to protect the new trees from the fungus and genetic engineering to produce American chestnut trees that are genetically equipped to fight their mortal enemy.

In time, she says, she expects to see the chestnut restored to its past glory.

A Tree With History

Prized for its timber as well as its nutritious nuts, the trees were critical, especially to the people of Appalachia in the heart of the chestnut forest. The nuts were an important cash crop for many impoverished families who would cram their attics full of burlap bags packed with chestnuts. When the holidays approached, the bags were loaded onto railroad cars bound for the cities of New England.

The trunk of the chestnut tree was so straight that loggers could fill an entire railroad car with boards from a single tree. The straight grained wood was lighter than oak, and more rot resistant than redwood, lending itself to everything from telephone poles to fine furniture.

It didn’t take long for the fungus to wipe out the trees. Today, the survivors look more like bushes growing out of the stumps of fallen ancestors.

But there’s a bit of holiday cheer in the forest. Perhaps, just perhaps, the chestnut may finally be on the road to recovery.

Then we can really sing that old tune again, and roast a few chestnuts over an open fire.

Lee Dye’s column appears weekly on A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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