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Mar 22, 2016 10:48 AMPublication: The East Hampton Press & The Southampton Press

Notes On The Long Island Natural History Conference: Restoring The American Chestnut

American chestnut survivors are most easily identified in the growing season by their distinctive leaves. MIKE BOTTINI
Mar 22, 2016 10:48 AM

While large crowds gathered at parades and pubs to celebrate St. Patrick’s Day last weekend, a group of nearly 300 naturalists gathered to attend the fourth annual Long Island Natural History Conference at Brookhaven National Lab.The two-day conference included 16 presentations by notable wildlife biologists, botanists, ecologists, and natural resource managers who are doing work on Long Island or, in the case of Dr. Bill Powell from SUNY Syracuse, doing research that has important implications for the island.

Dr. Powell’s work involves developing a genetically modified chestnut tree that has all the attributes of an American chestnut (Castanea dentata) but not the susceptibility to the Asian bark fungus (Cryphonectria parasitica) that causes chestnut blight. The fungus was inadvertently introduced to North America by way of imported Chinese chestnut nursery stock sometime in the 1890s. It was actually first noticed on trees in the Bronx Zoo in 1904. The non-native fungus spread rapidly through the Eastern Seaboard forests, decimating the North American population of chestnut trees by 1950.

The chestnut was once a major component of our hardwood forest: It’s been estimated that this one species comprised 25 percent of the trees over the area from southern Maine to Georgia along the Appalachian Mountains. It is a very fast-growing tree that reached average heights of 60 to 80 feet and a diameter of 3 to 4 feet, but on excellent sites could grow 100 feet in height and 10 feet in diameter. Its rapid growth and very durable wood made it a valuable species in the forest industry, and its large annual seed crop made it a very valuable source of food for wildlife.

The fungus attacks the living cambium layer (xylem and phloem) just beneath the outer bark, eventually girdling the tree and killing it. For some reason that I’m unsure of, the mature canopy trees initially infected by the fungus were not able to regenerate by root sprouts. However, their offspring (trees grown from nuts produced before the original canopy specimens succumbed to the blight) could stump-sprout after attack by the fungus. The vast majority of today’s multiple-trunked understory chestnuts arise from root systems established by nuts that germinated at the onset of the blight.

While this allows the American chestnut to survive as a member of the forest community here, the fungus kills the above-ground portion of the tree before it reaches an age where it can produce fertile nuts. This fact severely reduces the American chestnut’s ecological stature and role in today’s forest community.

The restoration effort has taken several tracks. The two most important involve, not surprisingly, genetic manipulation to develop a blight resistant version of our native chestnut. The American Chestnut Foundation cross-bred the American chestnut with its blight-resistant relative, the Chinese chestnut (C. mollissima) and has been back-breeding those hybrid trees with American chestnut to the point where they now have a hybrid with 96-percent American chestnut genes and the blight resistance. Seedlings from this campaign are ready to be planted in the field.

Dr. Powell’s work has focused on utilizing the tools of genetic engineering, a controversial field in the food industry, to enhance the blight resistance of American chestnuts. He found a gene in wheat that, when inserted into the 40,000 gene pairs in the chestnut genome, seems to provide a level of blight resistance that matches that of the Chinese chestnut.

Dr. Powell’s genetic-engineered seedlings will need to go through an extensive review—he estimates a minimum of three years—to be approved for use in restoration work.

If you would like to be involved in American chestnut restoration work here on Long Island, contact me at mike@peconic.org.

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