1. Margaret Pooler USDA/ARS U.S. National Arboretum Washington, D.C.
Genetics, Genetic Resource Evaluation, and Genetic Improvement of Landscape Trees and Shrubs
Margaret Pooler
USDA/ARS U.S. National Arboretum
Washington, D.C.

2. Overall Objective
Evaluate, breed, and release improved landscape trees and shrubs that are disease and pest resistant, tolerant of environmental stresses, and are of superior ornamental value.

4. Specific Initiative Objective
Use biotechnology to improve woody ornamental landscape plants by:
Establishing regeneration and transformation systems in redbud and flowering cherry.
Investigating and adapting molecular marker technologies for use in woody ornamental plant breeding.

5. Funding from Initiative used to hire postdocs or support scientists to conduct transgenic/molecular work:
Karen Hokanson
EunJu Cheong
John Cordts
Hongmei Ma

6. Research Approach – Tissue Culture
Establish in-vitro cultures of several species of Cercis (redbud) and Prunus (flowering cherry)
Test for ability to regenerate (organogenesis or embryogenesis).
Focus transformation efforts on those taxa that regenerate well.

7. Research Approach – Molecular Markers
Use markers for which genomic information is not necessary (e.g. AFLPs).
Use markers which have been developed for other species in the genus (e.g. SSRs in Prunus).

8. Results – Tissue Culture
Regeneration of Prunus taxa from cotyledons of mature stored seed.
Somatic embryogenesis and GFP transformation of Prunus incisa from root explants.

9. Results – Tissue Culture
Regeneration of Cercis yunnanensis from leaf pieces.

10. Results – Molecular Markers
Preservation and DNA fingerprinting of the historic Tidal Basin cherries
SSR markers from sweet and sour cherry are being used to characterize ornamental cherry germplasm

11. Results – Molecular Markers
Characterization of genetic diversity of Lagerstroemia fauriei
Identification of interspecific hemlock progeny
Genetic identity of the “African Firebush”

12. Future Prospects
Identify and obtain genes and gene constructs for transformation of Cercis and Prunus germplasm:
Viral resistance
Fungal resistance
Sterility

13. Future Prospects: Continue to develop molecular markers to determine:
Genetic identity of hybrids or accessions, including introgressive hybridization in populations.
Genetic distances among individuals in a breeding population or among species in a genus.
Conservation strategies
Taxonomic and evolutionary relationships