¥First, American and Chinese chestnut trees are crossed with each
other.
¥The progeny from this first cross are then backcrossed to American
chestnut.
¥Each cycle of backcrossing reduces the fraction of Chinese genes by a
factor of one half.
¥Finally, backcrosses are intercrossed to yield progeny that will breed
true.
¥Blight resistance is retained by inoculating progeny and selecting
resistant ones.