Craddock, J. Hill
Aborn, David; Boyd, Jennifer
University of Tennessee at Chattanooga
Place of Publication
The American chestnut, Castanea dentata, has been devastated by the exotic invasive pathogens Cryphonectria parasitica and Phytophthora cinnamomi to which it has no resistance. The American Chestnut Foundation (TACF) has developed an interspecific backcross breeding program to introgress disease resistance from Asian chestnut species, primarily Castanea mollissima, into C. dentata hybrid populations. The genetic base of this program can be expanded by utilizing vegetative propagation through grafting in order to collect and conserve American chestnut individuals not amenable to traditional breeding. As the majority of the surviving American chestnuts are confined to the understory, they are shaded out by the forest canopy and unable to reach sexual maturity. Additionally, southern populations of chestnut harbor greater genetic diversity and more frequent occurrence of rare alleles. Conservation of these diverse populations would widen the genetic base of TACF breeding program and strengthen restoration of the species. This study has located and collected scionwood from 33 American chestnuts, 19 (~58%) of which have not been collected prior, across 9 sites in Tennessee and Alabama which will be conserved through grafting. Four types of rootstocks (C. dentata, C. mollissima, and F1 and BC3F2 hybrids) were chosen to account for possible graft incompatibility, although compatibility was not measured in this study. The whip-and-tongue and bark-flap grafting techniques were used depending on scion-rootstock diameter. These container-grown grafted plants will be conserved ex situ in a nursery where, released from competition for light, they should produce flowers. Pollen collected from these grafts will be used by TACF breeders to capture cytoplasmic genes and potentially develop new line of resistance when crossed with novel Asian Castanea sources.
This project was funded by an external grant from The American Chestnut Foundation
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.
Deason, Trent, "Conservation and collection of Castanea dentata germplasm in the South" (2018). Honors Theses.