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.

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.

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.

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

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.

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).

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

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

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

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

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

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