 Infection is local in range, so some isolated American chestnuts survive where there is no other tree within .The root collar and root system of the chestnut tree have some resistance to blight infection due to soil organisms adversely reacting to the fungus; consequently, a large number of small American chestnut trees still exist as shoots growing from existing root bases.However, these regrown shoots seldom reach the sexually reproductive stage before being killed by the fungus.