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In North America Aronia has been promoted as a native replacement for invasive ornamental species because of its adaptability and multiseason interest provided by spring flowers, summer and fall fruit, and orange–red fall foliage ( Brand, 2010

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Kalmia L. is a small but diverse genus containing nine to 11 species ( Ebinger, 1974 ; Southall, 1973 ; Weakley, 2012 ) native to North America and Cuba ( Jaynes, 1997 ). Deciduous or evergreen woody shrubs, Kalmia spp. have a varied morphology

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Northern bayberry [ Morella (formerly Myrica ) pensylvanica ] is a semievergreen shrub native to North America, ranging from Ontario to Nova Scotia in Canada, south to North Carolina in the United States and west to Ohio (US Department of

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Abstract

Oregon boxwood or mountain box [Pax-istima myrsinites (Pursh) Raf.] in the Celas-traceae is an evergreen shrub native to western North America, from southern British Columbia and extreme southeastern Alberta south to California and New Mexico. It grows in well-drained soils in a wide variety of moderately moist to dry habitats in full sun or partial shade. It is often common as an un-derstory shrub in open coniferous forests. Plants remain as a single shrub or become an open colony speading slowly from underground sprouts or rooting lower branches.

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The native shrubs Spiraea alba (meadowsweet) and S. tomentosa (hardhack or steeplebush) grow to be 1 to 1.5 m tall with long-lasting terminal inflorescences (white and pink flowers, respectively) present throughout most of the summer. Both

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The issue of invasive plants has become a concern to a variety of groups, including environmentalists, policymakers, and nurserymen. Although many surveys of invasive plants have been made, little research on the biology of hybridization has been conducted. Bittersweet (Celastrus) species serve as a good model system to test the effects of interspecific hybridizations since native and introduced species are found in the U.S. The American bittersweet (Celastrus scandens L.) is a deciduous climbing or twining shrub native to eastern and central North America. Although the bark has been used for medicinal purposes, the plant is cultivated as a nursery crop primarily for its bright red berries. In its natural habitat, native bittersweet is also an important source of food and cover for wildlife. Over the past several decades, populations of native bittersweet have declined to such low levels that some states are considering listing it as a threatened species. One reason for the rarity of American bittersweet in the wild is thought to be competition and possibly hybridization with an aggressive introduced species, oriental bittersweet (Celastrus orbiculatus Thunb.), which was introduced from Asia into the U.S. in 1860 as an ornamental. This plant can form dense, tangled, impenetrable thickets or climb small trees to girdle and smother them. It has been seen in at least 21 states since it was first recorded as an escape plant in 1912. Our objective was to determine whether oriental bittersweet can hybridize with native bittersweet, thus contributing to the loss of native populations in the United States. We performed controlled pollinations using C. scandens as the female parent and C. scandens or C. orbiculatus as the male parent. Although the intraspecific pollinations resulted in significantly more germinating seedlings than the interspecific crosses, the seedlings from the interspecific crosses had less seed dormancy and were more vigorous and more quick to vine than the intraspecific seedlings. These results indicate that the decline of the American bittersweet may be due to interspecific hybridizations with the invasive introduced species.

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Long regarded as a genus of two species, Dirca L. was expanded to include a third North American shrub discovered in 1994 as one population in the Sierra Madre Oriental of Tamaulipas in northeastern Mexico. The designation of Dirca mexicana Nesom & Mayfield as a third species in the genus was based in part on geographical separation from Dirca palustris L. and Dirca occidentalis Gray, which occur farther north in eastern North America and in a small region of California, respectively. Morphologically, D. mexicana was regarded as more similar to D. occidentalis than to D. palustris. Our objectives were to obtain fruits of all species, germinate seeds, and compare the three species genetically through analyses of seedling DNA. Drupes of D. mexicana, D. palustris (from populations in Iowa), and D. occidentalis were collected as they abscised naturally from plants in native habitats in mid-May, late May to early June, and mid-June, respectively. Embryo extraction, gibberellin, and cold stratification were used to promote germination, and DNA was extracted from leaves of seedlings by using the fully automated Autogen Autogenprep 740 DNA extraction system. Genomic DNA templates were used to compare sequences of the internal transcribed spacers (ITS) and the 5.8S coding region of the nuclear ribosomal DNA repeat and to examine polymorphisms in inter-simple sequence repeats (ISSRs). These analyses reinforce the present morphologically based classification of the three Dirca species by confirming species-level divergence at the molecular level. ITS sequences and ISSR banding patterns also enabled us to reconstruct the phylogenetic relationship among the three extant species of Dirca.

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An Agrobacterium-mediated transformation system was developed for chokecherry (Prunus virginiana L.), one of the most popular native small tree or large shrub species for resource conservation and wildlife habitat in North America. Leaf tissues from in vitro plants previously maintained in MS medium with 2.5 μm BA were co-cultivated on woody plant medium (WPM) containing 10 μm BA and 200 μm acetosyringone with Agrobacterium tumefaciens strain EHA105 harboring the binary Ti plasmid pBI121 carrying the uid A gene encoding for β-glucuronidase (GUS) and the npt II gene encoding neomycin phosphotransferase II. Infected leaf explants were disinfected in sterile water and antibiotics and then transferred to WPM containing 10 μM BA and the antibiotics cefotaxime, carbenicillin, and kanamycin (CCK) for shoot regeneration at 25 °C with a 16-hour photoperiod. Agrobacterium concentration, pre-conditioning of explants, application of acetosyringone, infection time, and kanamycin tolerance of leaf tissues were evaluated for effects on transformation efficiency. Regeneration of chokecherry shoots on kanamycin-containing medium and screening by GUS histochemical assays showed that both the npt II and the uid A genes were successfully transferred into chokecherry. The transformation will be further confirmed by polymerase chain reaction (PCR) and Southern blot analyses.

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noticeably on warm, sunny days. These characteristics make ‘Blue Sea’ more desirable than the straight species for the nursery industry, which is seeking cultivars of North American native species for the ornamental landscape plant market. Fig. 1. Photographs

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