Project Director

Craddock, J. Hill

Department Examiner

Chapman, Elise


Dept. of Biological and Environmental Sciences


University of Tennessee at Chattanooga

Place of Publication

Chattanooga (Tenn.)


Cryphonectria parasitica (Murr.) Barr is the causal agent for the chestnut blight disease, which was brought to North America in the late 19th century on nursery stock from Japan (Anagnostakis 1987). A pandemic of chestnut blight lasted for the next half century, nearly wiping out all American chestnut trees (Castanea dentata Borkh.). Restoration works to restoring the American chestnut to its native range in North America’s canopy has been going on for the past century. The American Chestnut Foundation has strived to breed a resistant American chestnut by backcross breeding with Chinese species (C. mollissima Blume) since the 1980s. The backcross breeding program has a strict screening method by using phenotyping and progeny testing to predict parental resistance in F1, B1, B2, B3, B4, and F2 generations. In 2022, UTC participated in an alternative small stem assay (ASSA) on less-than-year-old seedlings to measure variation of resistance within and among hybrid progeny of 15 different families at seven generation levels (B2F2, B3F2. B3F3, B4F2, F2, F1, and pseudoB1). All trees that survived to after inoculation were planted in the field. We inoculated around 650 individual seedlings with C. parasitica. Although there were significant differences between canker length in Chinese and American control groups, there were no significant differences between the F1 family and American control groups. The Alternative small stem assay did not prove to be a reliable method of differentiating between intermediate levels of resistance in backcross and hybrid families of Chinese and American crosses, as shown by Dunn’s post hoc test.


I would like to thank the Fortwood Greenhouse crew and all the volunteers from The American Chestnut Foundation. Thank you, Caleb Hendren for advising my data analysis. Thank you to Dr. Elise Chapman for agreeing to be on my committee and making suggestions to the manuscript. Thank you, Dr. Paola Zannini, for keeping us organized and on track to success. Finally, thank you Dr. Hill Craddock for your encouragement, knowledge, and inspiration. His enthusiasm gave me the confidence that I needed to complete this thesis project.


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--Disease and pest resistance; Chestnut blight; Chinese chestnut--Disease and pest resistance


American Chestnut; Cryphonectria parasitica; Small Stem Assay; Chinese Chestnut; Breeding


Botany | Plant Pathology

Document Type



24, [xvi] leaves