Transgenic Trees: A Plot To Save the American Chestnut

The American Chestnut once dominated the North American forests.
Photo Credit: Erin and Lance Willett

I remember walking through the hiking trails near my house when I was a kid and my dad showing me the American Chestnut saplings in the forest. I remember him telling me about the disease that wrought the destruction of this iconic plant. And I remember feeling a bit sorry for the sapling doomed to repeat it’s cycle of untimely death and rebirth.

The American Chestnut Trees (Castanea dentata) once reigned proudly amongst the tallest old growth trees … until the Asian Bark Fungus – or the Chestnut Blight (Cryphonectria parasitica) took its toll. Since then, the Chestnut Blight unjustly relegated the American Chestnut to the understory.

Trees with the blight never get much bigger than saplings and the American chestnuts that used to litter the forest floor can no longer be found.

However, with some tricky engineering, the American Chestnut might see the light of the forest canopy once more.

The History:
The Chestnut Blight was introduced in the late 1800’s and people started to notice its devastating effects by the early 1900’s. The blight infects the phloem and the xylem – the water and nutrient highways in the plant – of the chestnut trees, which ultimately kills the plant. New sprouts can grow back from the remains of the previous tree, but the chestnut tree will eventually succumb to the infection again.Although the American Chestnut Tree hasn’t been completley eradicated, trees don’t grow more than a couple meters tall.

An chestnut tree affected by the blight.

The American Chestnut was very important to the forest ecology as it provided food and shelter for many of the forest inhabitants. The chestnuts were a vital food source for many of the North American animals and some believe that the disappearance of the chestnuts expedited the extinction of the Passenger Pigeon. In addition, the American Chestnut wood is very sturdy and fallen logs create long lasting shelters for various species.  In fact, it was so sturdy that many people used the wood to construct homes and furniture.

The Future:
Arron Stoler and his colleagues have been working on a genetically engineered American Chestnut tree. The chestnut tree in question is 99% identical to the American Chestnut of the past, but has the gene for blight resistance inserted in it that was extracted from Chinese Chestnut trees. Aaron has already started growing some trial GMO American Chestnut trees but his latest batch of transgenic trees have been the most successful. Perhaps in the future this historical giant will return to the limelight.

Questions:
I think this is very promising research – but I wonder – if the American Chestnut is returned to the North American Forests, how the forest ecology will change. Considering we’ve managed without it the past 100+ years, I wonder how the forest communities will react in response to the introduction of this lost relic.

Reference:
Jabr F. March 2014. “New Generation of American Chestnut Trees May Redefine America’s Forests“. Scientific American 310(3): Web Exclusives.

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