RETURN OF THE DEAD: AMERICAN CHESTNUT

Feb. 16, 2017: No, that's not the title of a horror film, but it could be the title of an inspirational "Rockyesque" documentary of a once major tree that has vanished, for all practical purposes, but may have hope of beating the odds and returning. That tree is the American chestnut (Castanea dentata), not to be confused with the Chinese Chestnut or the Spanish chestnut.

Chestnut grove - pre-blightChestnut grove - pre-blightThe American chestnut (hereafter just referred to as "chestnut" to save me extra typing) was never part of the Pacific Northwest forests but was one of the dominant hardwood trees of the Appalachian mountains. There were billions (some estimate 4 billion) of them growing, some up to 120 foot heights and 8 feet or more in diameter. The mast crop of chestnuts produced were a major food source for animals and humans. Its wood was rot resistant and light weight. It was often used for furniture and you can tell a true vintage piece of furniture if you can identify chestnut as its material.

The chestnut is now classifed "functionally extinct" by the USDA. That means you cannot find a live chestnut tree anywhere (except a small handful I'll tell you about later), but you can find chestnut shrubs. So how did it go from being the dominant tree of the Appalachians to a rare to find shrub? Answer: the chestnut blight.

Somewhere around 1904, give or take a couple of years, a load of chestnut logs from Asia came into the States carrying a fungus, the chestnut blight. The Chinese chestnut is resistant to chestnut blight, developed through eons of evolutionary battle between the fungus and the tree back in Asia. Our chestnut though did not have that resistance and in the space of 40-50 years the American chestnut as a tree disappeared.

I used to be a forestry contractor in the 80's based in western North Carolina. Most of my contracts were in the southern Appalachians. What was amazing to me is I could still see in the woods these huge stumps of the chestnut that were still alive. The roots, which are not killed by the fungus, still sent up shoots. They would grow to about as about as big around as my arm and then the blight would kill them and then more shoots would arise. The chestnut would not die, even 40-50 years after the trunk was gone!

The fungus attacks the cambium, the small ring of growth tissue inside the bark, which in turn kills the Blight cankersBlight cankersbark and eventually girdles the tree which kills it. There is no preventative nor post-infection treatment to stop it. It was a killer and it couldn't be stopped. Less than a handful of isolated pockets of chestnut tree have been discovered. One pocket , found in 2006, on the Franklin Roosevelt's Little White House estate at Warm Springs caused a flurry of excitement as to whether these trees might have genes resistant to the blight or were they just isolated.

The major effort to bring the chestnut back from the dead has been focused on hybridizing it by crossing the American chestnut with the Chinese chestnut, which is resistant. This crossbreeding has been taking place since the 1930's with marginal success by the USDA. In 1983, several botanists and geneticists set up the American Chestnut Foundation (ACF)to try a different type of crossbreeding called backcrossing, where a Chinese and American chestnut are crossed and then their offspring are crossed back to the American chestnut for several generations in a row. It's slow work but has finally produced a resistant chestnut that is 15/16th's American chestnut and 1/16 Chinese chestnut. If there was AKC registration for trees it wouldn't make it but it's close.

The latest greatest news is that a genetically engineered chestnut has been developed. I can see you're thinking now, "OMG a Frankenchestnut!" But hear this out. The chestnut contains 40,000 genes. Geneticists have discovered one gene from the wheat plant that produces an enzyme which detoxifies the blight fungus. Gene spliced trees are 99.999% original American chestnut. and if you're still leery, remember that genetic engineering is happening all the time in nature. It's called evolution and it results in gene mutation (different genes) often much more profound than 1 gene out of 40,000. Hybridization leads to more gene manipulation with less control than genetic engineering

Not only are GMO chestnuts so close to being the original in genetic makeup but before these trees are even made available to the public they must stand the scrutiny of the USDA, EPA and FDA approval processes. This will be the first tree approved for genetic manipulation. When you consider all the other huge threats we have to our rural and urban forest such as Dutch Elm disease, Asian longhorned beetle, oak wilt disease, pine beetle and on and on, maybe this is a ray of hope. In a new world where biological threats can't be contained by distances it's time for a new approach to saving the old.

Several thousand hybrid trees have been replanted in the wild, but that's a long way from 4 billion. I hope to live to see Frankenchestnut emerge from the lab to the marketplace . I'll be the first to toddle out and plant one.

F & P