White Bracts Research Articles

‘Rebecca’s Appalachian Angel’: A Cultivar of Flowering Dogwood (Cornus florida) with Large Leaves and Floppy White Bracts

‘Rebecca’s Appalachian Angel’: A Cultivar of Flowering Dogwood (Cornus florida) with Large Leaves and Floppy White Bracts

CURCUMA IGNEA (ZINGIBERACEAE), A SPECTACULAR NEW SPECIES FROM THAILAND

Curcuma ignea Ruchis. & Jenjitt., a new species in Curcuma subg. Ecomatae from Thailand, is described here. This species is distinct from others by the combination of open flowers and L-shaped anthers. It is most similar to Curcuma glans but differs by having anther spurs pointing outwards (vs divergent), remotely pilose corolla lobes (vs glabrous), and vivid red, green, to white bracts (vs pale green to green, with red veins). It is assessed as Endangered using IUCN categories and criteria.

Astragalusbashanensis (Leguminosae), a new species from Central China.

A new species Astragalusbashanensis, from western Hubei Province, Central China is described and illustrated. The new species is morphologically similar to Astragalussinicus and A.wulingensis, but differs from both by its spreading pubescent indumentum on stems and petioles, longer petioles, white bracts, whitish or yellow corolla, longer claw of the keel-petal, hairy pods and smaller seeds.

First Report Davidia involucrate Baill Leaf Blight Caused by Nigrospora oryzae in Sichuan, China.

Davidia involucrata Baill. (D. involucrate), also known as dove tree, is listed as the first class national protected plant in China and the only extant member of the Davidiaceae family (Fu & Jin 1992). Referred to by the terms 'living fossil' and 'giant panda' owing to its evolutionary status as a Tertiary relic and its native distribution, D. involucrate exhibits substantial ornamental and academic value (Fang & Song 1975; Wu et al. 2004). A small rounded head inflorescence beneath its big white bracts have a unique charm to catch people's attention, thus they were cultivated in many areas of the world as an ornamental plant (Claßen-Bockhoff & Arndt 2018). In September 2021, dove trees in Meigu country (N 28°33', E 103°14'), Sichuan Province, China were found to appear symptoms of leaf blight of unknown origin. This blight disease incidence was 90% in a survey of 30 D. involucrata trees. Early symptoms appeared as circular, necrotic tissue that developed into circular or irregular spots (FigS1. A). Five leaves exhibiting typical symptoms of this form of leaf blight were excised from the margin between diseased and healthy tissue. These pieces were then treated for 40 s with 75% ethanol for surface sterilization, followed by treatment with 5% NaClO for 2 min, rinsed then plated on potato dextrose agar (PDA) medium supplemented with carbenicillin and ampicillin (each 50 μg/mL), and incubated in the dark for 4 days at 28°C. Pure cultures were then prepared by transferring hyphal tips from the edges of these colonies onto fresh PDA plates, with isolate LW11 being selected as a representative isolate for causal pathogen characterization. These cultured colonies were initially white before turning grayish-black over time (FigS1. B). Conidia were single-celled, black, spherical or oblate and ranged from 10 - 16.0 μm in diameter (mean = 12.5 ± 0.43 μm, n = 40) (FigS1. C), with conidia being present at the tip of conidiophores on hyaline vesicles. These morphological traits were found to align well with those of Nigrospora oryzae (Wang et al. 2017). To confirm this tentative identification, gDNA was extracted from isolate LW11, followed by the amplification of the internal transcribed spacer (ITS) region, beta-tubulin (TUB2), and translation elongation factor 1-alpha (TEF1) sequences with the respective ITS1/ITS4 (White et al., 1990), Bt-2a/Bt-2b (Glass & Donaldson 1995), and TEF1-728F/EF1-986R primer pairs (Carbone et al. 1999). Fragments of 577 bp, 442 bp, and 309 bp were obtained. A maximum likelihood bootstrapping approach (1000 bootstrap replicates) was used to construct a phylogenetic tree based on a combination of the ITS, TUB, and TEF1-α sequences, indicating that isolate LW11 clustered with other N. oryzae isolates (FigS2). The ITS, TUB, and TEF1-α sequences from isolate LW11 were deposited in GenBank with the accession numbers OL659284, OL685345, and OL685347, respectively. The pathogenicity test was performed by detached D. involucrate leaves with mycelial plugs, with the other half instead being inoculated using pure agar plugs as a negative control. Following incubation for 5 days, black lesions were evident on leaves inoculated with mycelial plugs (FigS1. F; FigS1, DE) but not on control leaves (FigS1. F). This report is the first to our knowledge of D. involucrata leaf blight by N.oryzae in China or anywhere else in the world. Further research is thus needed to better manage the spread of this disease with the goal of protecting this living fossil species.

Development of the petaloid bracts of a paleoherb species, Saururus chinensis.

Saururus chinensis is a core member of Saururaceae, an ancient, perianthless (lacking petals or sepals) family of the magnoliids in the Mesangiospermae, which is important for understanding the origin and evolution of early flowers due to its unusual floral composition and petaloid bracts. To compare their transcriptomes, RNA-seq abundance analysis identified 43,463 genes that were found to be differentially expressed in S. chinensis bracts. Of these, 5,797 showed significant differential expression, of which 1,770 were up-regulated and 4,027 down-regulated in green compared to white bracts. The expression profiles were also compared using cDNA microarrays, which identified 166 additional differentially expressed genes. Subsequently, qRT-PCR was used to verify and extend the cDNA microarray results, showing that the A and B class MADS-box genes were up-regulated in the white bracts. Phylogenetic analysis was performed on putative S. chinensis A and B-class of MADS-box genes to infer evolutionary relationships within the A and B-class of MADS-box gene family. In addition, nature selection and protein interactions of B class MADS-box proteins were inferred that B-class genes free from evolutionary pressures. The results indicate that petaloid bracts display anatomical and gene expression features normally associated with petals, as found in petaloid bracts of other species, and support an evolutionarily conserved developmental program for petaloid bracts.

Comparison between maceration and ultrasound-assisted extraction of white bracts with flowers of Bougainvillea spectabilis Willd.

Obtaining bioactive compounds depends on the extraction method, with maceration being the most well-known. This method is commonly used with ethanol as an extractor solvent and requires a long period to complete the process. Alternative methods, such as ultrasound-assisted extraction, have been applied to optimize these processes. In this context, to evaluate the effect of extraction time, the ultrasound-assisted and the maceration extraction methods were performed on white bracts and flowers from Bougainvillea spectabilis Willd. (Nyctaginaceae). The antioxidant activities and fatty acid content of the different extracts were determined. The amount of phenolic compounds obtained for the maceration technique was greater, however, in the evaluation of the potential antioxidant activity by the DPPH and ABTS+ free radicals scavenging, no significant difference was verified when compared to the extraction by ultrasound for 30 minutes. In the determination of fatty acids by gas chromatography coupled with mass spectrometer it was found that the highest contents were of palmitic, linoleic, and stearic acids for both extraction methods. The 30 minutes of extraction by ultrasound proved to be the time necessary to quickly and efficiently extract the bioactive compounds from B. spectabilis. Thus, the use of ultrasound-assisted extraction, when compared to the maceration method, is an alternative for obtaining plant extracts in a short time, reducing the instability that some compounds.

Genomic analyses of a "living fossil": The endangered dove-tree.

Davidia involucrata Baill, also known as the dove-tree, is a living fossil and an endangered species currently restricted to the mountains of southwestern and central China. It has a beautiful and innovative trait of high horticultural value: two white bracts covering the flower caputila. Here, we report on the chromosome-scale genome of this species using single-molecule real-time long reads and chromosome conformation capture (Hi-C) techniques. This species has a larger genome size of 1,169Mb and contains relatively more genes (42,554) than the closely related species Camptotheca acuminata (397Mb and 31,825 genes). Both species shared one recent whole genome duplication before their divergence. The expansion of the repetitive elements after their divergence contributed greatly to the increase in the genome size of the dove-tree. Photosynthesis-related genes were almost absent or showed reduced expression in the bracts of the dove-tree, while defence- and chemical-related genes increased greatly, highlighting the important roles of the bracts in protecting flowers and attracting pollinators. The effective population size of the dove-tree continuously decreased during the climate changes of the Quaternary. Such climate sensitivity should be fully considered in conservation efforts for this relict endangered species in the context of continuous climate warming in the future.

Three new species of Calathea (Marantaceae) endemic to Colombia

Calathea neurophylla H. Kenn., C. barryi H. Kenn., and C. velutinifolia H. Kenn., endemic to Colombia, are described as new. Calathea neurophylla is characterized by the single cauline leaf subtending one or more inflorescences of spirally arranged bracts and the markedly ridged, narrowly elliptic leaf blades (length 6.25–8.46 times width). Calathea barryi is characterized by the single cauline leaf subtending several inflorescences with 25–43 spirally arranged bracts and the very closely spaced lateral veins (ca. 67 per 3 cm). Calathea velutinifolia is distinguished by the 4–15 basal leaves, the densely appressed velvety tomentose adaxial the leaf surface and the 8–10 distichous, white bracts.

The complete chloroplast genome of the dove tree Davidia involucrata (Nyssaceae), a relict species endemic to China

The dove tree, Davidia involucrate, with its distinguishing pair of white bracts, is endemic to China. Here, we reported the complete chloroplast (cp) genome sequence and the cp genomic features of D. involucrata. The D. involucrata cp genome was 169,196 bp long, with 129 genes comprising 83 protein-coding genes (PCG), 40 tRNA genes, and six rRNA genes. The majority of the gene species occurred as a single-copy, while 18 gene species occurred in double copies, including six PCG species (ndhB, rpl2, rpl23, rps7, rps15, and ycf2), eight tRNA species (trnH-GTG, trnL-CAA, trnI-CAT, trnV-GAC, trnL-GAV, trnA-UGC, trnN-GTT, and trnR-ACG) and all four rRNA species (rrn4.5, rrn5, rrn16, and rrn23). A neighbor-joining (NJ) phylogenetic tree was reconstructed with sequences of complete cp, revealing that D. involucrata belongs to the asterids. The complete cp genome of D. involucrata will be useful for further investigations and the conservation of this endemic relict woody plant.

Blossom colour change after pollination provides carbon for developing seeds

Summary We tested the hypothesis that greening of the floral (involucral) bracts of Dalechampia scandens blossoms after pollination (when bracts are white) increases carbon assimilation and provides photosynthate to developing seeds. We investigated the importance of the involucral bracts for the process of seed development in two ways. First, we removed or shaded bracts of hand‐pollinated blossoms to prevent their photosynthesis and tested the effects of these manipulations on seed development. Secondly, we measured the photosynthetic rate of blossoms with white vs. green bracts and compared these rates with those of leaves. After four weeks of development, seeds from blossoms with bracts removed or shaded were lighter than those produced by unmanipulated blossoms. Furthermore, although the area‐based photosynthetic rate of green bracts was much lower than that of leaves, it was much greater than that of white bracts. Estimates of the daily carbon budget based on these measurements indicate that photosynthesis in green bracts is sufficient to meet the respiratory demand of the whole blossom, but not so in white bracts. Our results support the hypothesis that colour change in D. scandens bracts allows carbon assimilation that contributes to the carbon demand of nearby developing seeds.

Three New Cultivars of Cornus kousa: Empire, Pam’s Mountain Bouquet, and Red Steeple

The genus Cornus contains 58 species of trees, shrubs, and herbs that are mostly distributed throughout the northern hemisphere (Xiang et al., 2006). Flowering dogwood (C. florida), kousa dogwood (C. kousa), and their interspecific hybrids are considered the most popular and economically significant members of the genus in the nursery and landscape industries. These deciduous trees are valued for their spring display of pink, red, or white bracts, brilliant-red fall foliage, and exfoliating bark. Retail and wholesale sales of dogwood in the United States account for over $30 million dollars annually with 73.1% of these sales coming from eight states [Maryland, Minnesota, New Jersey, North Carolina, Ohio, Oregon, Pennsylvania, and Tennessee (U.S. Dept. of Agriculture–National Agricultural Statistics Service, 2010)]. Sales in Tenneessee account for 21.9% of total sales of deciduous flowering trees, making it an important crop for the state’s economy. Additionally, six counties in Tennessee produce substantial amounts of 1-year-old liners that are sold to out-of-state nurseries for finishing and resale. In nursery production, a liner refers to a small tree that is transplanted and allowed to become a larger tree for sale by wholesale or retail outlets. These liners ultimately supply 80% of the country’s dogwoods (Simmons, 2002). Large-bracted dogwoods are widely grown throughout midtemperate regions of eastern North America, both in the wild and as coveted ornamental trees in urban and suburban landscapes. Across this range, flowering dogwoods have been severely affected by dogwood anthracnose [Discula destructiva (Redlin, 1991)] and powdery mildew [Erysiphe pulchra (Li et al., 2009)]. Because of the importance of dogwoods to the U.S. agricultural economy, an improvement program was initiated over 20 years ago at the University of Tennessee to develop disease-resistant cultivars of dogwoods. These efforts have resulted in the release of the first flowering dogwood cultivar (Appalachian Spring) with resistance to dogwood anthracnose (Windham et al., 1998) and three powdery mildew resistant cultivars: Jean’s Appalachian Snow, Karen’s Appalachian Blush, and Kay’s Appalachian Mist (Windham et al., 2003). Cornus kousa is more tolerant to anthracnose and powdery mildew than C. florida (Holmes and Hibben, 1989; Ranney et al., 1995). Hybrids between these two species are generally more vigorous than typical plants of either parent species and have field resistance or tolerance to dogwood anthracnose and powdery mildew (Ranney et al., 1995). There are over 100 named cultivars of C. kousa and many cultivars are the result of either selection of open-pollinated seedlings or spontaneous sports rather than systematic breeding (Cappiello and Shadow, 2005). The objective of this project was to evaluate 400 seedlings of C. kousa for disease resistance and horticultural traits such as color, degree of overlap, size of bracts, tree form, and bark and leaf characteristics. From these, three genotypes were selected for development and release.

Three New Distichous-bracted Species ofCalathea(Marantaceae) from Panama

Three species of Calathea G. Mey. with distichous bracts, assigned to Calathea sect. Calathea (Marantaceae), are described as new from Panama: C. carlae H. Kenn., C. chiriquensis H. Kenn., and C. fredgandersii H. Kenn. All three are found in montane wet or cloud forest habitats at middle to higher elevations, 800–1400 m. Calathea carlae also occurs in Costa Rica, while the other two are endemic to Panama. Calathea carlae differs from related species by the leaf length:width ratios of 1.7–2.13:1, cream-colored bracts, claviculate bracteoles, yellow corollas, and yellow or pink-purple staminodes. Calathea chiriquensis is distinguished by the light green bracts, leaf length:width ratios of 1.3–1.56:1, absence of bracteoles, flowers borne singly rather than in pairs, and yellow flowers. Calathea fredgandersii is distinguished by the subround leaf, leaf length:width ratios of 1.15–1.55:1, a purple band along the leaf margin, a deep purple leaf sheath, verruculose petioles, white bracts, membranous bracteoles, white corollas, and white or pale pink to lilac staminodes.

White Bracts of the Dove Tree (Davidia involucrata): Umbrella and Pollinator Lure?

White Bracts of the Dove Tree (Davidia involucrata): Umbrella and Pollinator Lure?

Growth and Mortality of Dogwood Cultivars in Alabama

Abstract An open-field evaluation of 38 dogwood (Cornus) cultivars was conducted in central Alabama from May 1996 to March 1998. Mortality increased dramatically in giant dogwood (C. controversa Hemsl.), kousa dogwood cultivars (C. kousa Hance), and kousa x flowering dogwood hybrids (C. kousa x florida) from August 1996 to August 1997. Little mortality was observed for the flowering dogwood selections (C. florida L.) during this same period. Further characterization, based on height and stem diameter increases, was conducted on 23 flowering dogwood cultivars. Greatest average annual height and stem diameter increases for cultivars with white bracts and green foliage were observed in ‘Cloud 9’, ‘Fragrant Cloud’, ‘Ozark Spring’, ‘Springtime’, ‘Weaver’, ‘Welch Bay Beauty’, and ‘World's Fair’. Lowest average annual height and stem diameter increases occurred with ‘Autumn Gold’ and Wonderberry®. Among the selections with red or pink bracts and green foliage, ‘Stoke's Pink’ and ‘Welch's Junior Miss’ had greater annual average increases in height and stem diameter than ‘Purple Glory’. Annual average increases in height and final heights were similar among all cultivars with variegated foliage, with ‘First lady’ showing the greatest annual average increase in stem diameter and final stem diameter.

549 Three New Cultivars of Flowering Dogwood Resistant to Powdery Mildew

Powdery mildew (Microsphaera pulchra) of flowering dogwood (Cornus florida L.) has become a significant problem of trees in nursery production as well as in the landscapes and forests of the eastern United States. The disease significantly reduces growth and berry production by older established trees and may contribute to the inability of younger trees (liners) in production to survive winter dormancy. Disease resistance in named cultivars is limited to partial resistance found in `Cherokee Brave'—all other cultivars are extremely susceptible. Until now, the only disease control measure was to establish an expensive, labor-intensive, preventive fungicide program. We examined >22,000 seedlings and identified 20 that were extremely resistant to powdery mildew. Three trees with white bracts were selected from the 20 and released as patent-pending cultivars. `Karen's Appalachian Blush' has long, non-overlapping, pink fringed bracts with a delicate appearance. `Kay's Appalachian Mist' has creamy white, slightly overlapping bracts with deeply pigmented clefts. `Jean's Appalachian Snow' has large, strongly overlapping bracts with non-pigmented clefts. The three powdery mildew-resistant cultivars will be entered into an existing breeding program with `Appalachian Spring', a cultivar released by the Tennessee Agriculture Experiment Station and resistant to dogwood anthracnose, in an attempt to produce trees that are resistant to both diseases.

157 Susceptibility of Poinsettia Cultivars to Whiteflies

Twenty-four poinsettia cultivars (Euphorbia pulcherrima) were exposed to a population of greenhouse whitefly (Trialeurodes vaporariorum) and silverleaf whitefly (Bemisia argentifolii) for 6 weeks. Evaluation was based on the number of immature whitefly present on each of the marked leaves. The poinsettias that produce white bracts were more heavily infested with immature stages of whitefly than those cultivars that produce red bracts, while those that produce pink bracts were intermediate. There was a wide range in degree of whitefly infestation among poinsettia cultivars. Leaf trichome density also explained a portion of the variance in whitefly oviposition rates among several of the cultivars. Cultivars with high trichome densities sustained less whitefly oviposition than did cultivars with low trichome densities. Certain cultivars tested showed an appreciable natural resistance to whitefly (`Freedom Red', `Freedom Bright Red', `Red Velvet', `Cranberry Punch', `Pepride').

Evaluation of Poinsettia Cultivars for Susceptibility to Powdery Mildew

Powdery mildew (Oidium spp. Link) on poinsettias (Euphorbia pulcherrima Willd. ex Klotzsch) growing in commercial greenhouses was first observed in the United States in 1990. Susceptibility of poinsettia cultivars (`Freedom Red', `Hot Pink', `Jingle Bells 3', `Pink Peppermint', `Red Sails', `Supjibi Red', `Topwhite', `V-14 Glory', `V-14 Pink', `V-14 White', `V-17 Angelika White') to powdery mildew was investigated using 8- to 10-week-old poinsettias with mature bracts. Area under the incidence of disease progress curve was used to express the incidence of bracts infected over 31 d after inoculation. Three cultivars with red bracts (`Freedom Red', `Supjibi Red', `Red Sails') had significantly more infection than the other cultivars in both experiments, while one cultivar with white bracts (`V-17 Angelika White') had significantly less infection.

Ethylene Evolution from Bracts and Leaves of Poinsettia,Euphorbia pulcherrimaWilld

Woodrow, L. and Grodzinski, B. 1987. Ethylene evolution from bracts and leaves of Poinsettia, leaves contained mainly sucrose for translocation. The total free alpha-amino nitrogen content of the bract tissue was twice that of the leaf tissue. The leaves contained more ACC (1-aminocyclopropane 1-carboxylic acid) and produced proportionally more endogenous C2H4 than either the red or white bracts. ACC-stimulated C2H4 release was also greatest from the green tissue indicating that the EFE (ethylene forming enzyme) was most active in the leaves. The specific activity of the 14C2H4/12C2H4 released from (2,3-14C)ACC confirmed ACC as the primary precursor of C2H4 in this tissue. Ethylene release from the non-photosynthetic, bract tissue was not markedly affected by alterations in C02 or light conditions. In green leaf tissue endogeneous ethylene release increased from 1-5 to 6 0 pmol C2H4 cm 2 h 1 while ACC-stimulated ethylene release increased from 10 to 35 pmol C2H4 cm2 h1 as the C02 partial pressure increased from 100 to 1 200 /tbar.

Host Preference of Greenhouse Whitefly: Effect of Poinsettia Cultivars1

Abstract Sixty-eight poinsettia cultivars (Euphorbia pulcherrima Willd.) were exposed to a population of greenhouse whitefly (Trialeurodes vaporariorum Westw.) for 9 weeks. Evaluation was based on 6 degrees of infestation by immature stages of whitefly on the bracts and upper and lower foliage. The upper foliage showed the heaviest infestation and was considered to be the best indicator of relative susceptibility. White bracts were more heavily infested than red bracts, while pink bracts were intermediate. A wide range in degree of whitefly infestation was found among poinsettia cultivars. Certain cultivars tested for 2 years showed appreciable resistance to infestation (‘U.S.D.A. 68-82-1’, ‘U.S.D.A. 68-160-2’, ‘Annette Hegg Maxi’, ‘Red Baron’, ‘Rudolph’).