Exploring the Correlation between Castanea dentata Size (Diameter and Height) and the Presence of Cryphonectria parasitica

Furey, Katie

ABSTRACT: American chestnuts (Castanea dentata), a keystone forest tree species in the Appalachian Mountains during the turn of the century, have been functionally extinct for a century in their native range due to the invasive chestnut blight fungus (Cryphonectria parasitica). The roots, however, remain alive and the American chestnut continues to form sprouts in clumps (coppice) that are later killed by the chestnut blight fungus. Understanding where natural population levels of the chestnut blight pathogen inoculum is heavy may be important to restoring resistant hybrids of American chestnut to its native range. Knowledge of pathogen establishment on sprouts, especially in heavily concentrated areas, may provide valuable information for avoiding these areas when planting resistant American chestnut hybrids. To accomplish this objective, average numbers of sprouts per location, sprout height and diameter, and disease levels (cankers) were collected from up to 150 coppice clusters per site. I sampled 450 American chestnut coppice sprouts across three sites: two in Highlands, NC, and one at in the Great Smoky Mountains National Park. Results from the study, across locations and by locations, showed American chestnut sprouts of greater height and diameter had significantly greater disease levels than smaller American chestnut sprouts. This indicates that disease levels increase with larger coppice and potentially provide heavy inoculum concentrations if not managed. Furthermore, a bark sampling and pathogen isolation study in the laboratory confirmed that the visual disease ratings in the field were strongly supported by laboratory isolation data based on a Chi-square analysis. If American chestnut trees with resistance can grow large enough to fruit before succumbing to blight, the resistant trees can spread and eventually extend through their former range in eastern hardwood forests.