New Plantings Aim to Produce Blight-resistant Chestnut Trees

Jack Marshall of Free Union and Rod Walker of Sugar Hollow inspect a sprouted nut to be sure they are planting it with the proper orientation of root and trunk stems.

Some 160 sprouted American Chestnut nuts were planted in a deer-fenced field on the Fried Farm in Brown’s Cove April 7, part of a effort by the American Chestnut Foundation to breed an American Chestnut with the blight-resistance of a Chinese Chestnut.

The American Chestnut was once the dominant tree in America’s eastern forests, numbering probably four billion. They stood 120 to 140 feet tall. Its wood is easy to work and has rot resistance, making it useful for building framing, utility poles and fencing. Its nuts were  commonly used as hog feed (that’s the reason for those rock walls in the mountain forests) or roasted as a treat on holidays.

An oriental blight was introduced in New York in 1900 and within 50 years virtually all the native chestnuts had been killed by it. The virus is a fungus that is spread by air or water and enters trees through wounds in their bark. The blight affects the above-ground part of the tree. Stumps will sprout new growth but those shoots will not survive, and meanwhile they provide a home for the virus.

The ACF has been in a 40-year effort to transfer resistance from the Chinese variety to the American variety through a genetic strategy called backcrossing. Backcrossing involves pollinating Chinese Chestnuts through three successive generations with American Chestnuts that exhibit some blight resistance until in the fourth generation a tree results that is 15/16 American and possesses the blight resistance gene in the 1/16 that remains from the Chinese stock.

The seeds planted at Fried Farm are third-backcross stock grown on an ACF farm in Abingdon. That farm is not producing many nuts from resistant trees and that limits the speed with which the ACF can develop new plantings. The Fried Farm location will be planted again as more hybrid nuts become available.  The AFC wants to introduce resistant trees throughout the tree’s former natural range and is trying to develop stocks adapted to local conditions. Thus it is trying to get plantings in counties along the Blue Ridge. The planting in Albemarle used four families of trees drawn from Greene and Nelson Counties. Different families of trees must be developed so that sufficient breeding combinations are possible, one for each generation of the backcross. Other plantings exist in Warren, Clarke, Loudoun, Floyd, Fauquier, Culpeper,  and Madison Counties.

The new trees will produce nuts within seven years. Once their trunks are 2.5 inches thick, the ACF will infect each tree to test its blight resistance and those susceptible will be culled, according to John Scrivani, president of the Virginia chapter of the ACF. Only about one in eight of the trees planted will show moderate resistance, he said.

Scrivani and ACF science director Katy McCune showed the 32 volunteers who came out to help with the planting how to properly position a seed and protect it with a tube and stake. Volunteers used a hand-held auger to open holes for the seeds in plastic covered rows. Translucent vented tubes protect the seeds and encourage the tree to grow tall rather than spread out.

McCune said the Fried Farm is an ideal site. “Wild surviving trees are here and the chestnut was prevalent here at one point. We have good soil, good exposure and people willing to take care of the trees.” Farm owner Barbara Fried helped plant trees.