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United States Department of Agriculture

Agricultural Research Service

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Research Project: COMPREHENSIVE COLLECTION OF FOTHERGILLA SPP. FOR CONSERVATION, IMPROVEMENT, AND PHYLOGENETIC STUDY

Location: Floral and Nursery Plants Research Unit

2013 Annual Report


1a.Objectives (from AD-416):
To establish a comprehensive germplasm collection for long-term ex situ conservation and utilization to be maintained at the Mt. Cuba Center, the Wood Landscape Plant Germplasm Repository (WLPGR) and USDA GRIN system, and shared with public gardens and commercial nurseries. To complete a taxonomic/systematic assessment of Fothergilla including molecular, cytogenetic, morphological, and ecological approaches. This germplasm collection will provide a valuable resource for plant breeders and commercial nurseries for further selection and improvement of Fothergilla. These efforts will also help elucidate the diversity and evolutionary relationships among species within Fothergilla, providing essential data to help guide future conservation efforts. On a broader scale, this study will provide further insights into the phytogeographic patterns and history of Southeastern flora.


1b.Approach (from AD-416):
Accessions from across the known range of Fothergilla in the Southeatern U.S., will be collected and propagated, vouched with herbarium specimens, and analyzed using flow cytometry and genomic genotyping (next-generation RAD-tag sequencing). Germplasm will be grown in experimental plots at the Mountain Horticultural Crops Research and Extension Center (MHCREC), NC State University, Mills River, NC for phenological and morphological evaluations. At the completion of the project, accessions and appropriate data will be transferred to the WLPGR for entry into GRIN.


3.Progress Report:

This is the final report for this project. The objectives of this research were to establish a comprehensive Fothergilla germplasm collection for long-term, ex situ conservation and utilization to be maintained at the Mt. Cuba Center and at ARS’s Woody Landscape Plant Germplasm Repository, and shared with public gardens and commercial nurseries. A taxonomic assessment of this collection, including molecular, cytogenetic, morphological, and ecological approaches has been initiated. Fothergilla (Hamamelidacea) is a small genus of uncommon, deciduous shrubs found exclusively in the Southeastern United States. Two species of Fothergilla are currently recognized: F. gardenii and F. major. However, variation in the genus is considerable and as many as four taxa have been recognized in the past. Fothergilla gardenii is found in the coastal plain and is tetraploid with 2n = 4x = 48. In contrast, F. major is found on upland sites in the piedmont and mountains and is hexaploid with 2n = 6x = 72. No diploid cytotypes of Fothergilla have previously been known. Samples from 35 populations were collected and tested for ploidy level and genome size. As expected, tetraploid and hexaploid plants were identified consistent with F. gardenii and F. major, respectively. However, populations of diploid plants were also discovered in Florida, Alabama, Georgia, and South Carolina. Considering that diploid plants differ morphologically and are isolated geographically and cytogenetically from other Fothergilla spp., this cytotype may represent a new and distinct taxon. Next generation DNA sequencing has been completed and analyses performed to reassess the systematics and phytogeography of Fothergilla. This work will further elucidate the diversity and evolutionary relationships among species, properly classify this new cytotype, and help guide future conservation efforts.


Last Modified: 9/20/2014
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