The Linnaeoideae subfamily was created in Caprifoliaceae to represent the close relationship among the monophyletic genera Abelia, Diabelia, Dipelta, Kolkwitzia, Linnaea, and Vesalea. These closely related genera could possibly be a new source of ornamental traits for Abelia, an economically important genus of woody ornamental shrubs. Breeding among these genera could be challenging as only a few genera and species have a reported total DNA content, ploidy level, and chromosome number. The objective of this research was to fill that gap in the literature. We determined the total DNA content and DNA ploidy levels and estimated chromosome numbers of the species Abelia chinensis (two genotypes), Abelia macrotera var. engleriana, Abelia ×grandiflora, Abelia schumanii, Diabelia serrata, Vesalea floribunda, Zabelia tyaihyonii var. mosanensis, and the Abelia cultivars Edward Goucher, Francis Mason, Lavender Mist, Raspberry Profusion, and Rosy Charm® by flow cytometry. Raphanus sativus ‘Saxa’ was used as an internal standard for holoploid 2C total genome size estimation. For DNA ploidy and chromosome number, A. ×grandiflora (2n = 2x = 32) and Z. tyaihyonii var. mosanensis (2n = 36) were used as internal standards. We also measured the pollen size and stomata length of the species A. chinensis (two genotypes), A. macrotera var. engleriana, V. floribunda, A. ×grandiflora, A. schumanii, and D. serrata, and the Abelia cultivars Francis Mason and Raspberry Profusion. All genotypes have a 2C holoploid total DNA content between 0.87 and 0.95 pg DNA (∼850–930 Mb), except for V. floribunda and Z. tyaihyonii var. mosanensis, which have 1.94 and 1.91 pg DNA, respectively (∼1880 Mb). All genotypes are diploid with 2n = 2x = 32, except for V. floribunda and Z. tyaihyonii var. mosanensis, which have 36 chromosomes (2n = ?x = 36). We observed significant variability in stomata sizes and pollen diameter independent of and not correlated with genome size or chromosome number. A. ×grandiflora has a high percentage of dead pollen (∼30%), as does V. floribunda (43%). This high percentage of dead pollen in the natural species V. floribunda could be the result of aneuploidy. This is the first report of total DNA content in A. chinensis, D. serrata, and Z. tyaihyonii var. mosanensis; total DNA content and estimated chromosome number in V. floribunda; total DNA content and DNA ploidy levels in A. ×grandiflora, A. macrotera var. engleriana, and A. schumanii; and total DNA content, estimated chromosome number, and DNA ploidy levels in the Abelia cultivars Edward Goucher, Francis Mason, Lavender Mist, Raspberry Profusion, and Rosy Charm®.

Despite being in cultivation for more than 135 years, relatively few cultivars of Abelia have been developed and are commercially available. Cultivar development has been limited by self-incompatibility and crossing barriers with other species. To help overcome these barriers, self-incompatibility systems were investigated in Abelia chinensis R. Brown, Abelia macrotera var. engleriana (Graebner & Buchwald) Rehder, Abelia xgrandiflora (Rovelli ex Andre ') Rehder, and Vesalea floribunda M.Martens & Galeotti. A full diallel cross with self-pollinations was performed in greenhouse-grown plants on recently opened flowers. Styles were removed one and two days after pollination, fixed in a solution of ethanol and glacial acetic acid (3:1) for at least 24 hr, transferred to a solution of 4 N NaOH for 24 hrs to soften the tissues, and then stained with 0.1% decolorized aniline blue with 0.1 M K3PO4. Stained styles were analyzed for pollen tube growth under an inverted epifluorescent microscope. Pollen tubes were inhibited in the upper half of the style on self-pollinations and reached the base of the style on cross-pollinations suggesting the presence of gametophytic self-incompatibility in Abelia and Vesalea. In vitro pollen germination was evaluated in A. chinensis, A. macrotera var. engleriana and Diabelia serrata (Siebold & Zuccarini) Landrein. The most effective germination medium consisted of 10% sucrose, 0.01% H3BO3, 0.02% CaCl3 and 0.5% agar with a pH of 7. Pollen did not germinate in liquid medium and sucrose concentrations of 15, 20 or 25% were not effective. Three samples of pollen from different dehiscent anthers of recently opened flowers from greenhouse-grown plants were placed on top of a slide containing germination medium. Slides were placed on a petri dish with a wet paper towel to ensure 100% humidity and cultured in light at 28.5 +/- 0.5 degrees C. Germination of 100 pollen grains was evaluated at 2 hrs and 24 hrs after culture. Overall, Abelia macrotera var. engleriana had the highest germination, with 80% of the grains germinating after 24 hrs of culture. Diabelia serrata had 49.8% germination, while A. chinensis exhibited very low germination in the three different pH levels tested. In vitro germinated pollen grains of A. chinensis, A. macrotera var. engleriana, and Diabelia serrata were examined for number of nuclei. Pollen was stained for one hour with 0.25 mg center dot L-1 or 0.5mg center dot L-1 of a 4 ', 6-diamidino-2-phenyl-indole (DAPI) solution and evaluated under a fluorescent microscope. Observations indicate the presence of three nuclei in pollen in Abelia and Diabelia. This is the first report of a self-incompatibility system in Abelia and Vesalea, and pollen nuclei in Abelia and Diabelia.

Abelia R. Brown is an important genus of flowering landscape shrubs. Native to China, the genus is characterized by evergreen or semievergreen shrubs with a flowering period from spring to frost; white or pink flowers; and yellow-green, gold, red, or dark-green foliage, depending on the season (Dirr, 2011). Abelia is disease, pest, and deer resistant; heat and drought tolerant (Scheiber and Robacker, 2003); nontoxic to humans; attractive to a variety of pollinators (Mach, 2018); and a noninvasive species that rarely sets seeds naturally, make Abelia an important genus for the landscape and nursery industry (Dirr, 2011). In 2015, Abelia was reclassified into the Linnaeoideae subfamily (Caprifoliaceae s.l.) by Wang et al. (2015). Among the other members of the Linnaeoideae subfamily (Diabelia, Dipelta, Kolkwitzia, Linnaea, and Vesalea), only the monotypic genus Kolkwitzia Graebner has been used in the landscape with moderate success (Dirr, 2011). Kolkwitzia flowers on old wood. Flowers are pink with a yellow throat. The majority of Abelia cultivars are sports of Abelia xgrandiflora (Rovelli ex Andre) Rehder or have Abelia chinensis as a parent, with only a few cultivars derived from seedlings (Landrein et al., 2017). In an attempt to increase the diversity of abelia hybrids, we used Kolkwitzia amabilis as a parent.

Spring freezes in southeast US can cause damage to peach flowers after plant de-acclimation. Winter, on the other hand, is usually not cold enough to produce major damage. However, understanding the magnitude of internal damage produced by freeze events in peach floral buds is of importance. The objective of this project was to analyze the susceptibility of floral bud internal structures to freeze events using a vital staining technique. Floral buds were collected in winter of 2016-2017, and treated with low temperatures ranging from 4 to -24 degrees C in a temperature-controlled programmable freezing chamber. Fluorescein diacetate (FDA) staining was used to identify the vital structure of floral buds that were damaged after being subjected to low temperature treatments. Viable tissues stained with FDA presented a green fluorescence under 450-490 nm blue light. Cold damage was observed as a dark non-fluorescent region. Critical bud freezing temperatures that caused damage in 50% of samples (LT50) based on the fluorescence were calculated for each internal floral structure. For floral buds collected during the dormant bud stage (tight bud) on November 21, 2016, the flower pistils were short, ovaries were not swollen, and stamens were immature. We found that during this time, young pistils tended to show cold damage first, with a LT50 = -15.4 degrees C, followed by anthers (LT50 = -16.8 degrees C), and then petals and sepals (LT50 = -17.2 degrees C). As the floral buds further developed in the field in spring of 2017, internal structures in the floral buds developed with cold susceptibility of these structures being variable. Stamens tended to be most cold resistant (LT50 = -15.2 degrees C), and pistils and corollas were more cold susceptible (LT50 = -12.0 and -11.0 degrees C, respectively). This study offers important information on cold damage associated with specific floral bud internal structures.

Native and non-native bees are important pollinators of both food and ornamental crops. However, bee populations across the world have declined, mainly through loss of habitat. Careful selection of landscape plants in urban areas can help mitigate habitat loss and create new habitat for pollinators. Ten mature genotypes of Vitex, comprising V. agnus-castus L., V. negundo L., and a hybrid between V. agnus-castus x V. rotundifolia L. f., were evaluated during June and July 2016 to assess their attractiveness to pollinators. Pollinator counts were taken two times daily, at 9:00 a.m. and 11:00 a.m., twice weekly for three weeks. Pollinators were also captured from the Vitex plants for identification. Insects captured from Vitex plants were identified to genus and bumblebees [Bombus spp. (Latreille, 1802)] were further identified to species. Bumblebees and honeybees [Apis mellifera (Linnaeus, 1758)] were more numerous on Vitex plants than carpenter bees. V. agnus-castus plants attracted more bumblebees than honeybees. V. negundo and the V. agnus-castus x V. rotundifolia hybrid attracted more pollinators over the course of the study than V. agnus-castus. Our study shows that Vitex plants can be a good resource to support pollinators in an urban landscape. Index words: urban landscape, bumblebees, honeybees; Vitex agnus-castus, Vitex negundo, Vitex rotundifolia. Species used in study: Vitex agnus-castus L.; Vitex negundo L.; Vitex rotundifolia L.

Native grasses are increasingly used in the landscape. Little bluestem (Schizachyrium scoparium L.), a perennial bunchgrass native to most of the United States, has ornamental traits, such as variation in leaf color, differences in growth morphology, and attractive seed heads. Traditionally, cultivars of little bluestem are propagated by division, which limits the production of new plants. Our objective in this study was to develop an improved micropropagation protocol for little bluestem that would produce true-to-type plants. In 2016, we cultured immature inflorescences of eight genotypes of little bluestem on Murashige and Skoog (MS) medium with four combinations of kinetin (1.0 or 2.0 mg·L−1) and 2,4-D (0.5 or 1.0 mg·L−1) under three levels of light (dark, semilight, full light) to initiate callus. Cultures were evaluated 30 days after initiation and those that had initiated callus were subcultured. Media for subculturing and rooting contained either 0.1 mg·L−1 or no 1-Naphthaleneacetic acid (NAA). Light level had no effect on callus initiation. Initiation media with 1.0 mg·L−1 kinetin and either level of 2,4-D induced callus at almost twice the rate of media with 2.0 mg·L−1 kinetin, and cultures initiated on those media also produced almost twice the number of rooted plants over all genotypes. Genotype affected the number of rooted plants produced. The addition of NAA to medium for subculturing and rooting did not increase the number of rooted plants. In 2017, we cultured immature inflorescences of four genotypes of little bluestem on MS medium with 0.5 mg·L−1 2,4-D and either 1.0 mg·L−1 kinetin or 6-benzylaminopurine (BAP) under full light. Cultures were evaluated 30 days after initiation. Cultures that had initiated callus were subcultured onto MS medium with the same growth regulators as the initiation medium but without 2,4-D. Cultures were cycled between subculture medium with growth regulator and subculture medium with no additional growth regulator until rooted. Cultures initiated and subcultured on medium with BAP initiated two to three times more callus than those on kinetin and produced twice as many rooted plants. Our recommendation for rapid micropropagation of little bluestem is to initiate cultures on MS medium with 1.0 mg·L−1 BAP and 0.5 mg·L−1 2,4-D. After callus initiation, cultures should be subcultured to medium with BAP but no 2,4-D, alternating with medium with no additional growth regulators, until rooted.