Evaluation of Cryphonectria parasitica Isolates Collected from the Great Smoky Mountains National Park

To evaluate the frequency of naturally-occurring hypovirus-containing isolates in the southern Appalachian Mountains, one hundred fifty-nine cankers on one hundred thirty-nine American chestnut trees were sampled over a two-year period (2010-2011) in the Great Smoky Mountains National Park (GRSM). Trees were growing along GRSM hiking trails in Tennessee and North Carolina (USA). Cryphonectria parasitica was recovered from all cankers and from >95% of the samples. Vegetative compatibility (vc) testing identified fifty-two vc groups among the GRSM isolates using the sixty-four European Union (EU) vc testers. Isolates from one canker were putatively identified as hypovirulent, based on colony morphology, dsRNA extraction, single sporing and pathogenicity tests. These data indicate that a high level of vc diversity exists among the C. parasitica population in the GRSM and naturally-occurring hypoviruses are rare. Diversity in vc may represent significant restriction to hypovirus spread.