Craddock, J. Hill
Beasley, DeAnna; Bailey, Andrew
University of Tennessee at Chattanooga
Place of Publication
In 1904, Cryphonectria parasitica, the causal agent for chestnut blight, was imported into North America on chestnut nursery stock from China. Fifty-five years later, nearly all full-grown wild American chestnut trees (Castanea dentata) were dead. A century of work has been put into restoring the American chestnut to its rightful place among the forest canopy. Since the 1980s, The American Chestnut Foundation has pursued backcross breeding to introgress blight resistance into C. dentata from the resistant Chinese species (C. mollissima), and has used progeny testing to make predictions about parental resistance in B3F2 chestnuts. We performed a small stem assay on first year and one-year-old seedlings to measure variation of resistance within and among hybrid progeny of five cross types (F1, B1, BB1, F2, B3F2), and to eliminate blight-susceptible seedlings before they are planted in the field. We inoculated over 1,100 seedlings with C. parasitica. The small stem assay did not prove to be a reliable method of differentiating between generational resistance. Although there was significant difference in canker length in the American and Chinese control groups, hybrid crosses and the American control did not exhibit canker length averages inferred from their generation types, and all of the canker length means of the interspecific crosses didn’t significantly differ from the American control, as shown by Duncan’s multiple range test.
Thank you, Dr. Hill Craddock, for inspiring me inside and outside of the classroom; Thank you Taylor Perkins, for curing my aversion for data analysis; Thank you Paula Zannina, for keeping us on track and staying positive; Thank you Kirsten Hein and Trent Deason; Thank you members of the Fortwood greenhouse crew and all volunteers across TACF!
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.
Gentner, Kevin, "Evaluation of blight resistance in chestnut f2 half-sibling and full-sibling families via small stem assay" (2018). Honors Theses.