Interspecific Hybrid of Xeric Shepherdia Rotundifolia And
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HORTSCIENCE 51(7):822–828. 2016. in LWL, establishment under environmental conditions characteristic of urban landscapes can be difficult (Mee et al., 2003). Urban soil Interspecific Hybrid of Xeric is often disturbed and poorly drained, traits typically at odds with native habitat soils of Shepherdia rotundifolia and Riparian IMW drought-adapted species (Edmondson et al., 2011). In the arid IMW, several Shepherdia argentea: Description, drought-adapted native species have been iden- tified for potential use in LWL, but are sensitive to wet soils and irrigation (Meyer et al., 2009). and Traits Suitable for Low-water Genetic improvement may enable domestica- tion and use of these native species in LWL. Urban Landscapes The genus Shepherdia (Elaeagnaceae) 1 contains S. rotundifolia Parry, common name Chalita Sriladda roundleaf buffaloberry, a shrub endemic to Department of Plants, Soils, and Climate, Utah State University, 4820 Old the IMW Colorado Plateau in southeast Utah Main Hill, Logan, UT 84322 and northern Arizona (USDA, 2012). Shepher- dia rotundifolia is dioecious (Nelson, 1935), Heidi A. Kratsch naturallyoccurringonverywelldrained,arid University of Nevada Cooperative Extension, 4955 Energy Way, Reno, NV hillside slopes and canyons (Sriladda et al., 89502 2014). This species has desirable aesthetic and practical traits, including extreme drought tol- Steven R. Larson and Thomas A. Monaco erance and evergreen, revolute, silver-blue USDA-ARS, Forage and Range Research Laboratory, Utah State University, (glaucous) foliage forming multiple clusters Logan, UT 84322 of attractive rosettes in a nearly perfect hemispherical crown form (Sriladda et al., FenAnn Shen 2014). However, anecdotally S. rotundifolia Vice President Research Office, Utah State University, Logan, UT 84322 is very slow growing and sensitive to over- watering and disturbed soils. Therefore, the Roger K. Kjelgren species is difficult to grow in either nursery Department of Plants, Soils, and Climate, Utah State University, 4820 Old or urban landscape settings. By contrast, S. argentea (Pursh) Nutt. (silver buffaloberry) Main Hill, Logan, UT 84322 is a closely related dioecious, deciduous, and Additional index words. AFLP, SEM, ecophysiology, roundleaf buffaloberry, silver buffaloberry fast-growing shrub found throughout much of western North America. Shepherdia argen- Abstract. Shepherdia rotundifolia Parry (roundleaf buffaloberry), a shrub endemic to the tea tolerates a wide range of conditions from U.S. Colorado Plateau high desert, has aesthetic and drought tolerance qualities dry to wet soils (Chen et al., 2009; Mee et al., desirable for low-water urban landscapes. However, slow growth and too often fatal 2003), but is limited to riparian areas in the sensitivity to wet or disturbed soil stymies nursery production and urban landscape use. IMW (Richer et al., 2003). However, S. argen- The goal of this study was to create an interspecific hybrid between the evergreen-xeric tea is thorny with an indistinct, rangy growth S. rotundifolia and its widely adapted, fast-growing, deciduous relative Shepherdia argentea habit less aesthetically desirable when com- (silver buffaloberry) distributed in western North America riparian habitats. Genetics pared with S. rotundifolia (Mee et al., 2003). and leaf morphology of the resulting S. argentea 3 S. rotundifolia hybrid are described Interspecific hybridization plays an im- and compared with the parents, as well as hybrid gas exchange as a reasonable proxy for portant role in plant adaptive evolution, and growth rate and potential tolerance of poor soil. Hybrid genotypes were heterogenous, the process often results in phenotypic nov- but contained an intermediate and equal contribution of alleles from genetically elty in the hybrid, both morphologically and heterogenous parent populations. Leaf morphology traits were also intermediate physiologically (Scascitelli et al., 2010; Soltis between both parents. Aesthetic leaf qualities (silver-blue color and revolute margins) and Soltis, 2009; Stelkens et al., 2009). sought from S. rotundifolia were conserved in all offspring. However, gas exchange There is no documented evidence of a natural responses varied widely between the two surviving hybrids. Both hybrids showed greater hybrid between S. rotundifolia and S. argentea, tolerance of wet, fertile substrate—and promise for use in low-water landscapes—than possibly because contrasting habitats creating S. rotundifolia. However, one hybrid conserved faster growth, and by inference possibly geographical barriers to pollination. A hybrid greater tolerance of wet or disturbed soil, from S. argentea, while the opposite was between S. rotundifolia and S. argentea may observed in the second hybrid. Following botanical nomenclature, we named this hybrid offer the potential of a new taxon suitable for Shepherdia 3utahensis. LWL in the IMW: aesthetic and extreme drought tolerance qualities of S. rotundifolia but greater tolerance of wet, disturbed soils and Across the arid to semiarid U.S. Inter- urban areas challenge managers to conserve faster growth of S. argentea. This study de- mountain West (IMW) human populations water in irrigated urban landscapes. Irrigated scribes an interspecific hybrid between the two increase but water supplies do not. Combined cool-season turfgrass landscapes in particular species in terms of genetics and leaf morphol- with cyclic drought, water shortages in IMW require large amounts of water (Kjelgren ogy comparison with its parents. We also et al., 2000). Low water-use landscaping compare with its parents hybrid leaf traits (LWL) is a key tool in reducing water use desirable for urban landscapes, and gas ex- in urban landscapes (Kjelgren et al., 2009; St. change responses as a reasonable proxy for Received for publication 20 Feb. 2014. Accepted Hilaire et al., 2008) in the arid to semiarid growth potential and soil tolerances. for publication 20 May 2016. IMW. Native IMW drought-adapted species We thank Linnea Johnson for help in genetic lab works and Graham Hunter for help in field data are needed for LWL to reduce water consump- Materials and Methods collection. We thank the Utah Agricultural Experi- tion, provide a native aesthetic, and enhance ment Station for financial support (Utah Agricultural urban biodiversity (Meyer et al., 2009). Hybridization. Male and female popula- Experiment Station paper 8707). Even though native drought-adapted species tions of both species were located near the 1Corresponding author. E-mail: [email protected]. can reduce water use and enhance biodiversity central Utah town of Torrey. We identified 822 HORTSCIENCE VOL. 51(7) JULY 2016 female populations of S. rotundifolia and S. field populations of S. rotundifolia (n = 5) were compared through scanning electron mi- argentea in native habitats where they were and S. argentea (n = 6), and from the five croscopic (SEM) images. Three leaf punches in close proximity. We hand cross-pollinated germinated hybrid plants. Leaf samples per plant were collected from three plants of five female S. argenetea plants in a population were dried in 28-200 mesh silica gel each species and the hybrid, and directly fixed adjacent to the Fremont River (38.3 N, 111.4 W). (Fisher Scientific, Pittsburgh, PA). DNA in formalin-aceto-alcohol solution in the field. Each female parent was bagged with five was extracted with the Dneasy 96 Plant Kit The fixed leaf tissue was subjected to critical pollination bags per plant including a control (QAIGEN, Valencia, CA). Amplified frag- point drying using Samdri-PVT-3D (Tousimis, bag with no pollination. We bagged (11 Apr. ment length polymorphisms (AFLPs) were Rockville, MD). Microscopic images of leaf 2008) before flowers opened to prevent un- assayed to fingerprint the genomes of the structure were collected from the SEM at the expected pollination from male plants. Five three taxa, as described by Vos et al. (1995) Nanoelectronics laboratory (Utah State Univer- female S. rotundifolia plants from a popula- with described modifications. The DNA sity, Logan, UT). Characteristics measured in- tion located on a rocky hillside of Boulder samples were pre-amplified with EcoRI cluded average leaf thickness and leaf trichome Mountain (38.2 N, 111.4 W) were similarly +1/MseI +1 using A/C selective nucleo- structures. In addition, hybrid plants were bagged on the same day with female S. argentea. tides. Selective amplification primers con- qualitatively observed for deciduous vs. ever- On 30 Apr. 2008, when flowers of both sisted of five EcoRI +3/MseI +3 primer green leaf habit over two winters, 2010–11 and female S. argentea and S. rotundifolia were combinations using AAC/CAA, AAG/CAG, 2011–12. open, fresh pollen was collected from male ACC/CAT, ACG/CTA, AGG/CTA, AGA/ Physiology. We collected physiological plants of both species from a population CCC selective nucleotides. The EcoRI selec- snapshots of gas exchange differences among located closest to the bagged female plants tive amplification primers included a fluo- the three taxa. Shepherdia rotundifolia is for reciprocal crosses. Pollen from S. argentea rescent 6-carboxy fluorescein label on 5# extremely slow growing compared with S. used to pollinate the female S. rotundifolia nucleotides. argentea and, initially, the interspecific hy- was collected from male plants at the same Selective amplification products were brid plants. Therefore, for the purpose of location with bagged female S. argentea. combined with GS600 LIZ internal lane size morphological and physiological studies,