Theses and Dissertations

Issuing Body

Mississippi State University


Baird, Richard E.

Committee Member

Balbalian, Clarissa

Committee Member

Sabanadzovic, Sead

Committee Member

Nebeker, T. Evan

Date of Degree


Document Type

Graduate Thesis - Open Access


Plant Pathology

Degree Name

Master of Science (M.S.)


College of Agriculture and Life Sciences


Department of Entomology and Plant Pathology


A two-year study was conducted to collect and identify hypovirulent isolates of the chestnut blight fungus (Cryphonectria parasitica) from American chestnut trees located in the Great Smoky Mountains National Park (GRSM). During the survey, 339 isolates were obtained, 54 of which had abnormal morphological characteristics in culture and 3 of these contained dsRNA. Analysis of vegetative compatibility divided all 339 isolates into 34 distinct groups, 16 of which only contained a single isolate. A total of 19 isolates (compared to 3 controls) containing abnormal cultural morphologies or dsRNA were randomly selected for use in a field trial containing 44 natural occurring healthy American chestnut trees in the Nantahala National Forest, North Carolina. Following artificial inoculation during spring of 2007, data on canker radial growth and stromata production were obtained monthly for six months. Results from the field trial indicated that 5 of the isolates, 3 of which contained dsRNA, were potentially hypovirulent based on appearance and canker growth rates compared to the controls. Data from the field trial and VC pairings indicated that one isolate, 236-1C, has potential for use as a biological control agent for the chestnut blight fungus in the GRSM, but is limited to select VC groups. Since numerous VC groups occur in the park, additional hypovirulent isolates must be identified which form anastomosis with the majority of the important groups before large scale control can succeed.