BIOTECHNOLOGYBy the end of World War I, the American chestnut, which once dominated many eastern forests, had nearly been wiped out by the Asian fungus Cryphonectria parasitica . Now, forest-biotech researchers believe genetic engineering might help restore this majestic species--and possibly other heritage trees menaced by disease, including elms, white pine, butternut, and several species of California oak.