Saw this really amazing video[0] the other day about American Chestnut Foundation's breeding program in Virginia to revive the American chestnut
Basically they hybridized it with Chinese/Japanese chestnuts (which are blight resistant). Then they take the offspring, test for blight resistance and rebreed those back with purebred American chestnuts. Then they repeat the process. Take those offspring, select for blight resistance, rebreed with American species, etc
After a few generations they created an American chestnut tree that looks almost exactly like the purebred versions but retains the blight resistance of the Japanese and Chinese species
Basically they hybridized it with Chinese/Japanese chestnuts (which are blight resistant). Then they take the offspring, test for blight resistance and rebreed those back with purebred American chestnuts. Then they repeat the process. Take those offspring, select for blight resistance, rebreed with American species, etc
After a few generations they created an American chestnut tree that looks almost exactly like the purebred versions but retains the blight resistance of the Japanese and Chinese species
Really amazing work
[0] https://www.youtube.com/watch?v=DbrY-J0bpto