The chestnut blight was brought in from Europe early in the 20th Century. By the 1970s, the Chestnut was wiped out except for a few large trees here and there and a few sprouts growing out of old, mostly dead trees.
Eventually, the remaining trees developed the blight.
The scientists have looked for resistant trees to propagate and crossed resistant European and Chinese chestnuts with a few American chestnuts. They irradiated chestnut seeds looking for mutations that would give resistance.
The loss of the chestnut helped destroy what remained of the Eastern Mountain people's economy.
There may have been some developments in the last few years, but I haven't followed the topic for a while.