Project Director

Craddock, J. Hill

Department Examiner

Bell, Rebecca; Stapleton, Ann; Townsend, Gavin


Dept. of Biological and Environmental Sciences


University of Tennessee at Chattanooga

Place of Publication

Chattanooga (Tenn.)


For almost a century, the fungus, Cryphonectria parasitica has existed in the United States as a wound parasite to American chestnut (Castanea dentata) trees. However, hypovirulence, evidence of spontaneous healing in Italy and Michigan, has given the American chestnut trees hope to one day be restored into its natural range. Viruses were the cause of such spontaneous healings. My hypothesis was that a viruscontaining hypovirulent strain of C. parasitica (in a brown background) would share alleles that control anastomoses with the local virulent strains, so a virus that causes hypovirulence could be transmitted into local virulent strains in vitro. Fifty bark samples removed from American chestnut trees at the Lula Lake Land Trust on Lookout Mountain, Georgia were explanted to an isolation medium. The C. parasitica isolates transferred to culture medium were paired twice with all three brown hypovirulent strains (containing either the "COLI","Euro7", or "GH2" virus) for possible conversion. Indication of conversion was the presence of a third sector or the virulent strains (recipient) exhibiting similar morphology to the H strains (donor). Putative converts were transferred again for comparison with recipient and donor strains to confirm conversion. Brown C. parasitica did indeed share alleles for anastomoses with V strains. Strains infected with the "GH2"virus had very similar morphologies to the brown virulent strain (5-9-lB), thus no data for conversion was collected. Twenty-six out of sixty virulent isolates were successfully converted by one of the two brown virus-containing hypovirulent strains with COLI or Euro 7 viruses. Local hypovirulent strains are now available for biological control experiments in the local area.


I am very grateful to Mark Double, William MacDonald, Sandra Anagnostakis, Dennis Fulbright, and lastly, J. H. Craddock for their assistance and guidance. I would also like to thank The University of West Virginia for allowing me to use their facilities on campus. Moreover, I want to thank my honors committee for the many suggestions and the use of their equipment.


B. S.; An honors thesis submitted to the faculty of the University of Tennessee at Chattanooga in partial fulfillment of the requirements of the degree of Bachelor of Science.




American chestnut; Chestnut blight; Cryphonectriaceae; Conservation biology


Natural Resources and Conservation

Document Type



vii, 37 leaves





Call Number

LB2369.5 .H826 2001