Location: Floral and Nursery Plants Research2011 Annual Report
1a. Objectives (from AD-416)
1) Strategically expand and improve germplasm collections and associated information for priority woody landscape plant taxa. Priority taxa for collecting include Carpinus, Celastrus, Cercis, Celtis, Cladrastis, Clethra, Cornus, Cotinus, Hamamelis, Hydrangea, Magnolia, Ostrya, Stewartia and Viburnum. With the American Public Gardens Association, coordinate, extend, and strengthen the North American Plant Collections Consortium’s continent-wide ornamental plant germplasm conservation program. 2) Strategically conserve and regenerate National Plant Germplasm System (NPGS) woody landscape plant germplasm efficiently and effectively and distribute samples and associated information worldwide. Regenerate, store, and/or maintain in situ plantings of priority germplasm and associated information, emphasizing Cornus florida, native Magnolia, and selected Viburnum species. Continue to increase to more than 40 percent the proportion of germplasm backed up at second sites, emphasizing critical back-ups. Develop monitoring methods and periodically assay the viability, health and vigor of stored germplasm. Distribute on request accessions and information that meet the specific needs of researchers, breeders, and growers. 3) Strategically characterize and evaluate priority NPGS woody landscape plant germplasm for key traits, such as taxonomic identity, genetic variability, invasiveness, and ornamental merit, thereby enhancing their utility to users, and the effectiveness of germplasm management. Incorporate that information into GRIN. In cooperation with other ARS and university collaborators, develop and apply new genetic markers for taxonomic identity, genetic diversity analyses, and population genetic structure for native Fraxinus species, Cornus florida, and Corylopsis. Ensure that Acer accessions in repository, especially those collected during North America-China Plant Exploration Consortium expeditions, are correctly identified taxonomically and adequately documented. Update and apply phenotypic descriptors for Acer, Halesia, Ilex, Viburnum and other priority taxa via in-house and cooperative evaluation. Incorporate phenotypic evaluation data into GRIN and/or other databases. Introduce especially noteworthy or valuable material to the public via a formal germplasm release.
1b. Approach (from AD-416)
Collect, propagate, and establish sexual and vegetative propagules of priority germplasm. Use in-house, contracted, and collaborative collectors, focusing on threatened, disjunct, or unique provenances. Train field reviewers, develop regional recruiters and mentor network for public garden participation in national collections program. Coordinate collections of priority genera with national collections holders to fill gaps in germplasm availability and diversity and minimize duplication. Preserve orthodox seed in medium (for distribution) or long term (cryogenic) storage facilities. Maintain recalcitrant species in short term or active collections, or distribute to backup or remote-site locations. Regenerate seed of living collections for distribution, medium and long term storage, using artificial pollinations and pollination cages. Monitor and assay viability of older seed accessions; use Cornus florida accessions to test viability using seed moisture content, seed viability equations as a proxy for other similar stored genera. Maintain current availability lists of germplasm for distribution; coordinate with national arboretum main collections; upload GRIN data on a regular basis for new accessions and matriculating germplasm from active collections. Screen Fraxinus species collected by USDA-ARS North Central Regional Plant Introduction station for ploidy levels; compare morphology and test new species hypotheses. Test cross amplification of Chionanthus-derived SSR markers for utility in Fraxinus germplasm. Use SSR markers from Cornus florida to test diversity levels from edges of species range with previously identified genetic clusters; adjust collecting areas as needed to maximize diversity. Screen Corylopsis germplasm for ploidy level and use AFLP to determine level of hybridization and species identifications. Collect voucher specimens of all Asian Acer taxa for verifying identification; cross-reference with other collections to determine collection gaps and rare taxa. Update GRIN data for priority genera; include descriptors for invasiveness using appropriate models. Propagate and distribute elite material to nursery collaborators for evaluation and introduction.
3. Progress Report
The Woody Landscape Plant Germplasm Repository of the U.S. National Arboretum has expanded its collection efforts towards acquiring high quality, wild-collected germplasm of native North American species important to the nursery industry. We have either directly collected or facilitated the acquisition of nine new Cornus florida accessions from four states, two accessions of the newly described Hamamelis ovalis, five Hydrangea accessions, 11 new Magnolia accessions, and 27 new accessions of associated species from the southeastern United States. The repository has begun evaluating existing collections for seed viability, testing and documenting 52 accessions from storage to ensure storage conditions are optimal for seed longevity. Accessions with poor seed quality have been germinated to begin the regeneration process in order to maintain and conserve these accessions. New regeneration beds with pollination tents have been created in order to expand our capacity for seed regeneration. Germplasm distribution requests have increased in FY2011, with 185 accessions distributed to 33 organizations, including three international shipments to Russia, Canada and China. We continued collaboration with the American Public Gardens Association in its efforts through the North American Plant Collections Consortium (NAPCC) in genetic resource conservation. This program continues to be critical to USDA in accomplishing its goal of plant genetic resource conservation of woody landscape plants. Morphological, physiological, and genetic characterization of priority genera continues. Corylopsis is a taxonomically difficult genus, with an uncertain number of species confounded by different genome sizes. We evaluated the genome size using flow cytometry on a comprehensive collection of living material from the National Arboretum and cooperating botanical gardens. This data is being compared to molecular markers to determine the relationship between species and ploidy level in cultivated taxa. This data will facilitate germplasm regeneration, conservation, and breeding efforts in Corylopsis at the U.S. National Arboretum. In addition, germination studies in Corylopsis are determining the effects of cold treatment on germination by studying expression of the phytochrome C gene. In collaboration with ARS scientists, we have initiated a study to determine the relationship between morphology and ploidy level in the American ash species complex. The goal is to determine the nature and distribution of ploidy levels within this species so as to provide data on how best to conserve these species which face destruction from the invasive emerald ash borer. We continue to characterize and evaluate selections of Corylopsis, Halesia, Ilex, and Viburnum for ornamental traits.