Location: Floral and Nursery Plants Research2008 Annual Report
1a. Objectives (from AD-416)
Develop stress, disease, and pest-tolerant cultivars of common and underutilized landscape trees suitable for urban areas and height-restricted planting sites. Develop disease- and insect-screening assays for identifying resistant parent taxa and hybrid progeny. Identify interspecific and intergeneric barriers to introgression of desired traits into adapted germplasm. Develop non-invasive tree cultivars, via wide-hybridization and inter-ploid crosses, to limit naturalization and gene-introgression into natural populations. Quantify genome sizes and ploidy levels in related taxa and identify parental taxa for interploid crosses. Develop methods for ploidy-manipulation of vegetative meristems to facilitate interploid crosses and ploidy bridges. Use molecular techniques for hybrid verification and genetic-relatedness tests within cultivated germplasm of important tree species.
1b. Approach (from AD-416)
Develop in vitro and in situ disease and insect screening assays for identifying resistant parent taxa and hybrid progeny; determine inter- and intrageneric barriers to introgression of resistance and ornamental traits into adapted germplasm via controlled pollinations and fluorescence microscopy; quantify genome sizes and ploidy levels using flow cytometry and manipulate ploidy level via mitotic inhibitors; verify hybrid and cultivar parentage using molecular markers. Evaluate progenies and make clonal selections for pest resistance, stress tolerances, non-invasiveness, and ornamental traits. Test plants for geographic and climatic adaptability and horticultural traits through cooperative procedures.
3. Progress Report
A long-term breeding program for Catalpa was initiated to develop disease-tolerant, non-invasive cultivars with novel ornamental traits. Reciprocal hybridizations were conducted between Asian and North American Catalpa to elucidate self-compatibilities and intra- and interspecific compatibilities. Nyssa breeding has continued, with a series of controlled artificial hybridizations between select F1 parents to generate large F2 populations segregating for improved plant habit, fall color, and leaf spot tolerance. A leaf spot organism has been cultured from Nyssa for microscopic and molecular identification. Flow cytometric analysis has been performed on Celtis and Ulmus americana revealing significant intraspecific ploidy variation for both genera. Molecular markers have been developed and tested in Chionanthus for analyzing genetic diversity among cultivated and non-cultivated Chionanthus taxa. This research supports problem statements 3B (Capitalizing on Untapped Genetic Diversity) and 3C (Germplasm enhancement/release of improved genetic resources and varieties) under Component 3 (Genetic Improvement of Crops) of National Program 301 (Plant Genetic Resources, Genomics, and Genetics Improvement). Cooperative Agreements. Summaries to document research conducted under Specific Cooperative Agreements between the Floral and Nursery Plants Research Unit and others can be found in the following specific annual reports: “Utility-adapted tree research, production and out-planting project” (project #1230-21000-053-01R with Western Maryland Resource Conservation and Development Council); “Utility-adapted tree research and evaluation of out-planting” (project #1230-21000-043-02S with University of Maryland); and, “Developing a vegetatively-propagated hemlock evaluation network” (project #1230-21000-053-03R with the U.S. Forest Service).