“Several nonprofit organizations have begun backcrossing: breeding American trees with naturally blight-resistant Chinese varieties, then crossing those 50/50 hybrids with American trees until offspring are just 1/16th Chinese.
The hope is that these carefully mixed trees, known as B3s, will show Chinese resistance and American growth habits. Asian varieties exhibit a bushy horizontal branching pattern, a severe disadvantage when competing for sunlight in dense forest. They also leaf out too early and suffer from spring cold snaps. For backcrosses to survive in the wild, those traits must be bred out.”