Location: Southern Horticultural Research2012 Annual Report
1a. Objectives (from AD-416):
The objective of this cooperative research project is to develop strategies for breeding new and improved woody ornamental germplasm adapted to the southeastern United States that exhibit host-plant resistance to disease, insects, and other pests.
1b. Approach (from AD-416):
1) Elucidate the genetic/genomic bases of host-plant resistance to microbes, insects and/or nematodes in woody ornamentals, especially those characteristic of the southeastern United States; and 2) Apply the knowledge gained through the preceding research to developing effective genetic enhancement and/or improvement strategies for host-plant resistant woody ornamentals adapted to the southeastern United States utilizing molecular and conventional breeding techniques.
3. Progress Report:
Flowering dogwood (Cornus (C.) florida) populations were studied in the Great Smoky Mountain National Park. Two genetic clusters exist within the park separated by the main dividing ridges of the Great Smoky Mountains. Results confirmed that despite losses due to disease, the genetic diversity is still adequate to ensure the health of this important tree species. A segregating pseudo F2 population of 94 individuals of flowering dogwood, together with 255 simple sequence repeat (SSR) markers, was used to identify putative quantitative trait loci (QTLs) for foliage color. The QTLs will allow selection/assessment of seedlings for color characteristics prior to a 5-7 year maturation period. Dispersal of flowering dogwood pollen in an orchard was evaluated by performing parentage analyses on open pollinated seedlings collected from a single maternal tree. Insect pollinators for C. florida and C. kousa were assessed in East Tennessee. Visitation rate data were compiled throughout the flowering period of both tree species across a range of environmental conditions. Identification of specific natural pollinators for both C. florida and C. kousa will aid in breeding since protocols have been developed using insect pollinators within closed (caged) environments. The genetic diversity of 16 cultivars of Viburnam (V.) dilatatum and 2 hybrids with V. japonicaum was investigated using 11 microsatellite loci identified. The molecular markers are expected to help refine the phylogenetic relationship of V. dilatatum to other species and genera within the Adoxaceae. They will also aid in breeding for new cultivar development, and assisting with early detection and screening of plants that have escaped cultivation. Twelve microsatellite loci were developed for the endangered species Pityopsis ruthii and had between three to seven alleles per locus. Tissue culture protocols were developed for regeneration of Pityopsis ruthii plants from flower receptacles and leaf explants to produce thousands of plants in a relatively short time span. This perennial plant also has great ornamental potential since it flowers in the fall until frost, and is apparently drought and flood resistant.