I have followed the development of the blight resistant American chestnut for a long time, the cross breeding has been going on for over 50 years. There are still a few pockets of original nut producing living American chestnut trees in the east and a bunch of them in the northeast because the blight didn't cross the Rockies.
So far, they have a 90% American chestnut that is blight resistant. From the American Chestnut foundation, the nuts cost $100 each, this money is used to support the foundation and their program. There were three of these seedling's planted near the walking trail I exercise on; one has died but the two remaining are about 10ft tall.
That said, with the advances in GMO, a group had introduced a blight resistant wheat gene into the American Chestnut genome that made the trees blight resistant in one generation instead of over 50 years. I haven't kept up this advancement so I don't know if this will be accepted by the forestry community.