A new study says genetic testing can speed the return of the American chestnut tree that once dominated Eastern U.S. forests. The tree was functionally extinct by the 1950s because of a fungal blight and root rot. Researchers want the height and character of the American chestnut with the disease resistance of the shorter, Chinese chestnut. Their work found that resistance involves many genes, not one. Genetic screening helps pick the best seedlings, and faster. Some experts say gene editing would make the process even faster, while others worry that hybrids will never fully replace a true American chestnut.