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Hongmei Ma and Margaret Pooler

Ornamental flowering cherry trees (Prunus species) are popular landscape plants that are used in residential and commercial landscapes throughout most temperate regions of the world. Most of the flowering cherry trees planted in the United States represent relatively few species. The U.S. National Arboretum has an ongoing breeding program aimed at broadening this base by developing new cultivars of ornamental cherry with disease and pest resistance, tolerance to environmental stresses, and superior ornamental characteristics. Knowledge of the genetic relationships among species would be useful in breeding and germplasm conservation efforts. However, the taxonomy of flowering cherry species and cultivars is complicated by differences in ploidy levels and intercrossing among species. We have used simple sequence repeat (SSR) markers developed for other Prunus species to screen a diverse collection of over 200 ornamental cherry genotypes representing 70 taxa in order to determine the genetic relationships among species, cultivars, and accessions. Data were generated from 9–12 primer pairs using an automated DNA genetic analyzer (ABI3770), and subjected to UPGMA cluster analysis. Extremely high levels of polymorphism were exhibited among the materials studied, thus indicating that ornamental flowering cherry germplasm has substantial inherent genetic diversity. This information, combined with traditional morphological characteristics, will be useful in determining genetic relationships among accessions in our collection and for predicting crossability of taxa.

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Margaret R. Pooler

Ornamental flowering cherry trees (Prunus L. species) are popular landscape plants, made famous in the United States by the historic Tidal Basin cherries planted in Washington, DC, in 1912. Planted primarily for their spring bloom, flowering cherries are used as street or shade trees in commercial and residential landscapes and are also valued for their fall foliage as well as ornamental bark. Approximately 1.2 million flowering cherry trees are sold each year in the United States with an estimated total sales of $32 million (USDA, National Agricultural Statistics Service, 2010).

The U.S. National Arboretum has an

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Margaret R. Pooler

Many popular crapemyrtle (Lagerstroemia L.) cultivars grown in the United States are interspecific hybrids between L. indica L. and L. fauriei Koehne. The 22 hybrid cultivars released from the U.S. National Arboretum contain primarily genetic material from L. fauriei PI 237884. Examining the genetic diversity ofL. fauriei specimens in the U.S. is valuable because of the historical and economic significance of the species, the increasing interest it is receiving as a source of new cultivars, and its threatened status in the wild. Our objectives were to examine molecular genetic diversity among L. fauriei accessions using Randomly Amplified Polymorphic DNA (RAPD) and Amplified Fragment Length Polymorphisms (AFLP) markers. Our results indicate: 1) RAPD and AFLP markers are generally consistent in the genetic relationships that they suggest; 2) the L. fauriei germplasm we examined falls into at least three distinct clusters; and 3) the genetic base of cultivated Lagerstroemia could be broadened significantly by incorporating some of this more diverse L. fauriei germplasm into breeding programs.

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Margaret R. Pooler

The genus Camellia L. (Family Theaceae Mirb., nom. cons.) contains 119 to 280 species (Chang, 1998; Ming, 2000, as referenced by Vijayan et al. 2009) that are native to China and southeastern and eastern Asia. Although the most economically important member of the genus worldwide is the tea plant (C. sinensis L.), several species (e.g., C. japonica L., C. reticulata Lindl., C. sasanqua Thunb.) are cultivated for their ornamental attributes of glossy evergreen foliage and showy winter or spring blooms. Ornamental camellias first arrived

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Margaret R. Pooler

The U.S. National Arboretum has released over 650 new plant cultivars since it was established in 1927. A key to the success of the plant breeding program has been the voluntary participation of universities and private nurseries in evaluating and propagating new plant material. The cooperative evaluation and stock increase programs play a critical role in the successful testing, introduction, and distribution of new cultivars of landscape trees and shrubs. These integrated cooperative programs depend on the involvement of nurserymen, researchers, botanic gardens, or individuals to evaluate potential new cultivars under diverse climatic conditions and hardiness zones, and wholesale propagation nurseries to increase stock of those cultivars destined for release.

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Margaret R. Pooler

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Margaret R. Pooler*

The crapemyrtle (Lagerstroemia) is one of the most widely planted and beloved woody ornamental landscape plant in the Southern United States. With hundreds of named cultivars that offer the grower and gardener diverse combinations of flower color, growth habit, and bark characteristics, crapemyrtles are planted primarily for their spectacular bloom in mid to late summer. The crapemyrtle breeding program at the U.S. National Arboretum was started in the early 1960s, and has resulted in the release of 31 improved cultivars of L. indica, L. indica × L. fauriei, and most recently, hybrids between L. indica, L. fauriei, and L. limii. The development of these cultivars, with a focus on the newly released red-flowering cultivars `Arapaho' and `Cheyenne', will be the focus of this poster. Information on Lagerstroemia germplasm, historical perspective, and breeding methodology and goals will be presented.

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Margaret R. Pooler

Viburnums (Genus Viburnum L.; Family Adoxaceae E.Mey., nom. cons.) comprise a diverse genus with ≈160 species and taxa found primarily in the northern temperate regions of the Americas, Europe, and Asia [U.S. Department of Agriculture (USDA), ARS, National Genetic Resources Program, 2010; Winkworth and Donoghue, 2005]. They are versatile shrubs that have become a mainstay of American landscapes for their showy and often fragrant spring blooms, richly colored sometimes evergreen foliage, and persistent winter fruit. Valued as a tough shrub that can tolerate various environmental stresses, over three million viburnums are sold annually in

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Margaret R. Pooler

Lilacs (Genus Syringa L.; Family Oleaceae Hoffmanns. & Link) are favorite garden plants in temperate regions throughout the world, prized for their showy fragrant early spring bloom and hardiness in the landscape. Native to East Asia and Southeast Europe (Krüssmann, 1978), lilacs were brought to North America with the first settlers and were sold by nurseries as early as 1800 (Fiala, 1988). Today, over two million lilacs are sold annually in the United States with a wholesale value of over $13 million (NASS, 1998). At least 2000 named cultivars exist,

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Margaret R. Pooler

Ornamental flowering cherry trees (Prunus L. species) are popular landscape plants, made famous in the U.S. by the historic Tidal Basin cherries planted in Washington, DC. Although planted primarily for their spring bloom, flowering cherries are also used as street or shade trees and are valued for their fall foliage as well as ornamental bark. Approximately 1.3 million flowering cherry trees are sold each year in the U.S. with an estimated total sales of $24.8 million (NASS, 1998).

The U.S. National Arboretum has an ongoing breeding program aimed at developing new cultivars of ornamental cherry with