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The genus Deutzia, in the Hydrangeaceae family, includes ≈60 species that range in ploidy from diploid (2 x ) to tetradecaploid (14 x ). There have been extensive breeding efforts for Deutzia, but this has been limited to a few parental species. Although there have been numerous studies of the cytogenetics of some species of Deutzia , the ploidy level of many species remains unknown, and there are few cytogenetic data available for Deutzia hybrids and cultivars. The purpose of this study was to validate the identification and determine the genome sizes and ploidy of a diverse collection of Deutzia species and hybrids using cytology and flow cytometry. Accessions were identified using the most current taxonomic key and voucher specimens were deposited for each at the North Carolina State University herbarium. Corrected and updated species names are provided for all cultivars and accessions studied. Traditional cytology was performed for roots of representative taxa to calibrate the genome size with the ploidy level. The genome size and estimated ploidy were determined for 43 accessions using flow cytometry. Ploidy levels were reported for the first time for three species of Deutzia including D. calycosa (2 n = 4 x = 52), D. paniculata (2 n = 4 x = 52), and D. glauca (2 n = 12 x = 156). The base and monoploid genome size (1C x ) were somewhat variable and ranged from 1.20 to 2.05 pg. No anisoploid hybrids were documented, suggesting the presence of an interploid block. The information produced from this study are beneficial to future curation, research, development, and improvement of this genus with corrected nomenclature and clone-specific data regarding cytogenetics.
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J. AMER.SOC.HORT.SCI.https://doi.org/10.21273/JASHS04779-19
Identification, Genome Sizes, and Ploidy of Deutzia
William G. Hembree, Thomas G. Ranney, and Nathan P. Lynch
Mountain Crop Improvement Laboratory, Department of Horticultural Science, Mountain
Horticultural Crops Research and Extension Center, North Carolina State University,
455 Research Drive, Mills River, NC 28759-3562
Brian E. Jackson
Department of Horticultural Science, North Carolina State University, Campus Box 7609,
Raleigh, NC 27695-7609
ADDITIONAL INDEX WORDS.cytogenetics, cytology, DNA content, flow cytometry, Hydrangeaceae, plant breeding, polyploidy,
taxonomy
ABSTRACT. The genus Deutzia, in the Hydrangeaceae family, includes
60 species that range in ploidy from diploid (2x)
to tetradecaploid (14x). There have been extensive breeding efforts for Deutzia, but this has been limited to a few
parental species. Although there have been numerous studies of the cytogenetics of some species of Deutzia, the ploidy
level of many species remains unknown, and there are few cytogenetic data available for Deutzia hybrids and
cultivars. The purpose of this study was to validate the identification and determine the genome sizes and ploidy of a
diverse collection of Deutzia species and hybrids using cytology and flow cytometry. Accessions were identified using
the most current taxonomic key and voucher specimens were deposited for each at the North Carolina State
University herbarium. Corrected and updated species names are provided for all cultivars and accessions studied.
Traditional cytology was performed for roots of representative taxa to calibrate the genome size with the ploidy level.
The genome size and estimated ploidy were determined for 43 accessions using flow cytometry. Ploidy levels were
reported for the first time for three species of Deutzia including D. calycosa (2n=4x= 52), D. paniculata (2n=4x= 52),
and D. glauca (2n=12x= 156). The base and monoploid genome size (1Cx) were somewhat variable and ranged from
1.20 to 2.05 pg. No anisoploid hybrids were documented, suggesting the presence of an interploid block. The
information produced from this study are beneficial to future curation, research, development, and improvement of
this genus with corrected nomenclature and clone-specific data regarding cytogenetics.
Deutzia species are a valuable group of temperate landscape
plants grown primarily for their profusions of showy white to
pink flowers produced in late spring. Several species have been
widely cultivated in Europe since the first Deutzia were
imported from Japan in the early 18th century. Deutzia gained
added global popularity in the early 19th century due to the
introduction of additional Asian species to cultivation (Styer
and Stern, 1979). With access to this diverse germplasm, many
additional Deutzia hybrids and cultivars were developed
through the breeding and selection efforts of Victor Lemoine,
his family, and the Lemoine Nursery staff in the 19th and early–
mid 20th centuries in Nancy, France (Wyman, 1971). The
development of new hybrids and cultivars has continued since
then.
The taxonomic history of Deutzia has seen it placed within
both the Saxifragaceae and the Philadelphaceae families,
although it is currently accepted as a member of Philadelpheae
within Hydrangeaceae (Soltis et al., 1995; Stevens, 2001).
Deutzia is most closely allied with Kirengoshoma, a small
genus of rhizomatous perennials that share several morpholog-
ical traits with Deutzia (Hufford et al., 2001). Deutzia repre-
sents a disjunct genus with species occurring in eastern Asia
and Central America. The genus has traditionally been divided
into three sections based on morphological differences, with the
Asian sections Deutzia and Mesodeutzia differing in the aesti-
vation of the petals (valvate/induplicate in Deutzia and imbri-
cate in Mesodeutzia). The central American Neodeutzia, rarely
treated as a separate genus, differs from its Asian relatives in the
number of stamens, with 12 to 15 in Neodeutzia compared with
10 in Deutzia and Mesodeutzia (Hwang, 1993; Styer and Stern,
1979; Zaikonnikova, 1975). Kim et al. (2015) constructed a
phylogeny of the genus and suggested that polyphyletic sec-
tions Deutzia and Mesodeutzia should be merged into a single
monophyletic section (Deutzia/Mesodeutzia), thus reducing the
number of sections to two.
Polyploidy has had an important role in the evolution and
divergence of angiosperms (Soltis et al., 2015; Wendel, 2015).
Repeated cycles of whole genome duplication (sometimes
coupled with hybridization) can lead to reproductive isolation,
genomic rearrangements, enzymatic multiplicity, epigenetic
changes, and novel phenotypes that contribute to biodiversity
and speciation (Adams and Wendel, 2005; Chen and Ni, 2006;
Received for publication 27 June 2019. Accepted for publication 18 Nov. 2019.
Published online 17 January 2020.
This research was funded, in part, by the North Carolina Agricultural Research
Service, Raleigh, NC; U.S. Department of Agriculture National Institute of
Food and Agriculture, Washington, DC; and Spring Meadow Nursery, Grand
Haven, MI.
We gratefully acknowledge the Arnold Arboretum, Jamaica Plains, MA;
Longwood Gardens, Kennett Square, PA; the JC Raulston Arboretum, Raleigh,
NC; Cornell Botanic Gardens, Ithaca, NY; Morris Arboretum, Philadelphia,
PA; United States National Arboretum, Washington, DC; Chicago Botanic
Garden, Glencoe, IL; Holden Arboretum, Kirtland, OH; Donglin Zhang,
University of Georgia, Athens, GA; Irene Palmer and Andra Nus, Mountain
Crop Improvement Lab, Mills River, NC; and the staff at the Mountain
Horticultural Crops Research and Extension Center for their cooperation,
technical assistance, and/or plant material.
W.G.H. is a Graduate Research Assistant.
T.G.R. is a JC Raulston Distinguished Professor.
N.P.L. is a Research Specialist.
B.E.J. is an Associate Professor.
T.G.R. is the corresponding author. E-mail: tom_ranney@ncsu.edu.
This is an open access article distributed under the CC BY-NC-ND license
(https://creativecommons.org/licenses/by-nc-nd/4.0/).
J. AMER.SOC.HORT.SCI.https://doi.org/10.21273/JASHS04779-19 1of7
Chen and Yu, 2013; Hegarty and Hiscock, 2008; Laport and
Ng, 2017; Madlung, 2013). For plant breeders, knowledge of
ploidy is particularly important because it influences reproduc-
tive compatibility, fertility of hybrids, and gene expression
(Ranney, 2006). There have been numerous cytological studies
of Deutzia, beginning with Sax (1931) at the Arnold Arboretum
(Boston, MA). Compared with other genera within Philadel-
pheae, Deutzia exhibits extreme variability in ploidy, with 2n=
2x=26to2n=14x= 182 (Table 1), possibly with ploidy
variations within species. The other speciose genus in this tribe,
Philadelphus, has a similar number of species (65) as Deutzia
(Dirr, 2009). However, unlike Deutzia, polyploidy is not found
in Philadelphus. The greater ploidy variation in Deutzia may
contribute to its higher degree of morphological variation when
compared with other genera in this tribe (Sax, 1931). Both
Deutzia and Philadelphus, as well as Fendlerella, also of
Philadelpheae, have a base chromosome number of x=13
(Sax, 1931; Ward, 1984).
Genome size (DNA content) can reflect biodiversity, ge-
nome evolution, and taxonomic relationships (Laport and Ng,
2017; Ranney et al., 2018; Rounsaville and Ranney, 2010;
Soltis et al., 2015). Genome size data can also be used to
estimate ploidy in closely related taxa when properly calibrated
with known cytological standards (Jones et al., 2007; Lattier
et al., 2014; Parris et al., 2010; Rounsaville and Ranney, 2010;
Shearer and Ranney, 2013). A previous report of the genome
size of Deutzia was the first report of genome size of
Hydrangeaceae. Using Feulgen densitometry, Hanson et al.
(2001) determined that the 1Cxgenome size of D. prunifolia is
1.9 pg. The more recent development of flow cytometry has
provided a more accurate and efficient method of determining
genome size (Dole
zel et al., 2007). We are not aware of other
reports of genome size of Deutzia using flow cytometry.
Despite the extensive use and wide cultivation of Deutzia,
correct identification of the species is challenging and prob-
lematic, and differentiation between species is often subtle
(Dirr, 2009). With more than 60 species of Deutzia,itis
possible that many species and cultivars have been traded
under incorrect names for years. However, an excellent key for
Deutzia that provides clear distinctions among taxa was devel-
oped by Zaikonnikova (1975).
The broad genetic diversity and array of desirable commer-
cial traits of Deutzia provide a valuable base for further
breeding and development of future cultivars. However, con-
fusion regarding the proper identity and lack of information
regarding cytogenetics of particular accessions and cultivars
Table 1. Previous cytological reports for Deutzia species.
Taxon Chromosome no. Reference
D. baroniana 2n=4x= 52 Fedorov, 1974; Hanson et al., 2001
D. bungoensis 2n=4x= 52 Niu and Ohba, 2000
2n=6x= 78 Niu and Ohba, 2003
D. compacta 2n=2x= 26 Fedorov, 1974
D. corymbosa 2n=2x= 26 Sandhu and Mann, 1989
2n=14x= 182 Chatterjee et al., 1989
D. crenata 2n=6x= 78 Funamoto and Nakamura, 1994; Niu and Ohba 2000
2n=10x= 130 Darlington and Wylie, 1955; Fedorov, 1974; Funamoto and Nakamura, 1994;
Niu and Ohba, 2000; Terasaka and Tanaka, 1974
D. discolor 2n=8x= 104 Darlington and Wylie, 1955; Fedorov, 1974
D. floribunda 2n=6x= 78 Niu and Ohba, 2000
D. gracilis 2n=2x= 26 Darlington and Wylie, 1955; Fedorov, 1974; Funamoto and Nakamura, 1992
D. gracilis var. gracilis 2n=2x= 26 Niu and Ohba, 2000
D. gracilis var. microcarpa 2n=2x= 26 Niu and Ohba, 2000
D. gracilis var. zentaroana 2n=4x= 52 Niu and Ohba, 2000
D. hypoglauca 2n=2x= 26 Darlington and Wylie, 1955
D. longifolia 2n=8x= 104 Cave, 1959
D. maximowicziana 2n=2x= 26 Funamoto and Nakamura, 1992; Niu and Ohba, 2000
D. mollis 2n=6x= 78 Darlington and Wylie, 1955; Fedorov, 1974
D. naseana 2n=4x= 52 Funamoto and Nakamura, 1992; Ohba and Akiyama, 1992
D. naseana var. amanoi 2n=4x= 52 Ohba and Akiyama, 1992
D. ogatai 2n=10x= 130 Niu and Ohba, 2003
D. parviflora 2n=2x= 26 Darlington and Wylie, 1955; Fedorov, 1974
D. pulchra 2n=8x= 104 Cave, 1964
D. purpurascens 2n=2x= 26 Darlington and Wylie, 1955
D. scabra 2n=2x= 26 Funamoto and Nakamura, 1992; Niu and Ohba, 2000
2n=10x= 130 Singhal et al., 1980
D. scabra var. sieboldiana 2n=2x= 26 Niu and Ohba, 2000
D. schneideriana 2n=10x= 130 Darlington and Wylie, 1955
D. staminea 2n=2x= 26 Cave, 1963; Sandhu and Mann, 1989
D. uniflora 2n=2x= 26 Funamoto and Nakamura, 1992; Niu and Ohba, 2000
2n=6x= 78 Cave, 1959; Fedorov, 1974
D. yaeyamensis 2n=2x= 26 Niu and Ohba, 2000; Ohba and Akiyama, 1992
D. ·candelabrum (gracilis ·scabra) 2n=2x= 26 Fedorov, 1974
2of7 J. AMER.SOC.HORT.SCI.https://doi.org/10.21273/JASHS04779-19
constrain the development of informed breeding strategies. The
objectives of this study were to validate the identification and
determine genome sizes and estimated ploidy of an extensive
collection of Deutzia species, hybrids, and cultivars.
Materials and Methods
PLANT MATERIAL.Plant material was collected from arboreta
and botanical gardens in the United States in June 2014. Plants
were propagated by stem cuttings by treating with 5000 mgL
–1
potassium salt of indolebutyric acid (KIBA) basal dip for 5 s
and maintained under intermittent mist until rooted. Plants were
then potted in 2.8-L containers with media consisting of 100%
ground pine bark supplemented with 1.04 kgm
–3
dolomitic
lime and 0.74 kgm
–3
granular micronutrients (Micromax; The
Scotts Co., Marysville, OH), and grown outdoors on a gravel
pad. Each container was topdressed with 12 g of 5- to 6-
month 15N–3.9P–10K slow-release fertilizer (Osmocote plus
15–9–12; The Scotts Co.). Accessions were field-planted in Fall
2014 at the Mountain Horticulture Crops Research and Exten-
sion Center in Mills River, NC. Flowering and vegetative
material of mature plants from each accession were collected
and pressed in May 2018. For root tip collections, selected taxa
were propagated and container-grown as described previously.
All accessions were identified according to Zaikonnikova
(1975) by Hembree. Herbarium specimens for each accession
were prepared and deposited in the North Carolina State
University Herbarium in Raleigh.
GENOME SIZE/PLOIDY DETERMINATION.Flow cytometry and
cytology were used together to determine genome size and
ploidy. For flow cytometry, samples were prepared from fully
expanded leaf tissue. Approximately 0.5 cm
2
of leaf tissue was
placed in a petri dish with 500 mL nuclei extraction buffer
(CyStain PI Absolute P Nulclei Extraction Buffer; Sysmex
Partec, G
orlitz, Germany) and finely chopped with a razor-
blade. The resulting solution was filtered through a 50-mm
nylon-mesh filter (CellTrics; SysmexPartec) into a 3.5-mL
polystyrene tube. Following filtration, 2 mL of nuclei staining
buffer (CyStain PI Absolute P; Sysmex Partec), 6 mL RNAse A
(Sysmex Partec), and 12 mL propidium iodide (Sysmex Partec)
were added to the mixture. Then, the solution was incubated at
4C in a refrigerator for at least 30 min. The incubated samples
were analyzed using a flow cytometer (PA II; Sysmex Partec).
A minimum of 3000 nuclei were recorded with a mean
coefficient of variation of 6.3%. Two subsamples were pre-
pared from two randomly selected leaves from each accession.
Mean fluorescence for each sample was compared with an
internal standard, either Pisum sativum ‘Ctirad’ (2C = 8.76 pg)
or Magnolia virginiana ‘Jim Wilson’ (2C = 3.92 pg) (Dole
zel
et al., 1998; Parris et al., 2010), depending on the genome size
of the sample. Genome size (2C) was calculated as follows:
[DNA content of the standard ·(mean fluorescence of the
sample / mean fluorescence of the standard)]. The 1Cxmono-
ploid genome size was calculated as (2C genome size / ploidy).
To calibrate the genome size with ploidy levels, chromo-
some counts were performed for root tips from selected acces-
sions. Root tips from actively growing roots were collected
from the root system after removing the container. Root tips
were excised and placed in a pre-fixative solution of 2 mM8-
hydroxyquinoline + 0.24 mMcycloheximide to arrest mitosis.
Roots were left for 3 h at room temperature (20 C) in the dark
before being moved to a refrigerator for incubation at 4 C for
an additional 3 h. After the cold incubation period, the roots
were triple-washed in cold, distilled water before being trans-
ferred to a 1:3 fixative solution of propionic acid and 95%
ethanol and stored at room temperature overnight. After a
minimum of 14 h, roots were transferred to a storage solution of
70% ethanol. Fixed roots were hydrolyzed in a 1:3 solution of
12 M hydrochloric acid and 95% ethanol for 90 s. The roots
were moved to a slide where the tips were excised before being
transferred to a new slide with a drop of modified carbol fuchsin
(Kao, 1975). After several minutes, a cover slip was placed over
the root tips. Then, they were squashed and viewed with a light
microscope at 1000·magnification. Highly resolved cells were
observed and photographed for each counted accession.
Results and Discussion
Forty-three accessions were included in this study represent-
ing 13 species and 7 interspecific hybrids including 24 named
cultivars (Tables 2 and 3). Of the taxa studied, species desig-
nations of 13 were inconsistent with the key created by
Zaikonnikova (1975) (Table 2). The names of the Zaikonnikova
key were compared with the current taxonomy of Deutzia and
updated when appropriate (The Plant List, 2019). Species
names were also corrected when appropriate (Table 2). There
were many possible factors that could have contributed to these
discrepancies. As Zaikonnikova (1975) stated, Deutzia com-
prise ‘‘a difficult group’’ that present many ‘‘problems of
identification.’’ It is difficult to know how many of our
germplasm sources have been revisited and re-examined since
the date of their initial accessions, and it is likely that the
concept and scope of the genus Deutzia and species designa-
tions have changed considerably since then. Often, particularly
in commerce, species names are accepted without question,
especially when there are no resident experts at the receiving
institution. Therefore, plants may be widely shared and distrib-
uted, and they may come to be known by a name that is
taxonomically incorrect.
Chromosome counts were completed for D. gracilis ‘Nikko
Dawn’ (2n=2x= 26), D. ·kalmiiflora (2n=2x= 26), D.
paniculata ‘Dippon’ (2n=4x= 52), D. ogatai (2n=4x= 52),
D. ·magnifica ‘Nancy’ (2n=6x=78),andD. discolor (2n=8x=
104) (Fig. 1). These taxa served as references for calibrating
estimated ploidy with genome sizes.
Estimated ploidy of Deutzia included in this study ranged
from 2xto 12x. The first known ploidy estimates of D. calycosa
(2n=4x= 52), D. paniculata (2n=4x= 52), and D. glauca (2x=
12x= 156) were also determined. Ploidy of D. ogatai,D.
parviflora,D. naseana, and D. longifolia were inconsistent with
previous literature (Table 2). It is likely that previous cytolog-
ical studies of Deutzia were challenged by the same taxonomic
issues and difficulty with correctly identifying species that were
encountered in this study. As such, it is difficult to know for
certain which taxa specifically were being used in these studies
and if the species designations were correct because herbarium
vouchers generally do not exist for these studies. The difficul-
ties surrounding the identification of members of this group are
omnipresent and influence the results of virtually all studies
thereof. Without the ability to confirm which species have been
studied previously, it is sometimes difficult to validate the
results of prior studies of Deutzia.
Several species of Deutzia have been reported as having a
ploidy series, including D. bungoensis,D. corymbosa,D.
J. AMER.SOC.HORT.SCI.https://doi.org/10.21273/JASHS04779-19 3of7
Table 2. Genome sizes and estimated ploidy levels of Deutzia species and cultivars.
Taxon Received as
Accession no./NCSC
voucher no.
z
Source/ID no.
z
2C Genome size
[mean ± SE (pg)]
1CxGenome
size (pg)
Estimated
ploidy (x)
D. gracilis
‘Nikko’ D. gracilis 2014-068/Hembree 2 MCIL 2.87 ± 0.01 1.43 2
‘Nikko Dawn’
y
D. gracilis 2014-057/Hembree 48 JCRA 100404 2.84 ± 0.01 1.42 2
‘Pink Minor’
x
D. scabra 2014-100/Hembree 4 Cornell BG 2.92 ± 0.03 1.46 2
D. hypoglauca
x
D. rubens 2014-134/Hembree 6 USNA 67798 2.85 ± 0.04 1.42 2
D. calycosa
x
D. monbeigii 2014-074/Hembree 13 USNA 59699 6.76 ± 0.12 1.68 4
D. calycosa
x
D. ningpoensis 2014-067/Hembree 11 USNA 59620 6.75 ± 0.01 1.68 4
D. ogatai
y,w
D. gracilis var. ogatai 2018-060/Hembree 49 JCRA 130638 5.45 ± 0.11 1.36 4
D. paniculata
‘Dippon’
y,x
D. gracilis 2014-098/Hembree 12 Chicago Botanic Gardens 8.20 ± 0.01 2.05 4
D. parviflora
x,w
Deutzia sp. 2014-065/Hembree 14 USNA 64514 7.48 ± 0.02 1.87 4
D. discolor
v
D. vilmoriniae 2014-107/Hembree 19 Arnold Arboretum 296-2000A 10.27 ± 0.03 1.28 8
D. discolor
y
D. discolor 2014-125/Hembree 17 USNA 67633 10.71 ± 0.01 1.34 8
D. discolor
v
D. globosa 2014-105/Hembree 38 Arnold Arboretum 957-86-A 11.80 ± 0.16 1.48 8
D. pulchra
x
D. taiwanensis 2014-133/Hembree 21 UGA 11.08 ± 0.15 1.39 8
D. crenata
x
D. coreana 2014-119/Hembree 24 Arnold Arboretum 460-73-A 11.97 ± 0.13 1.20 10
D. crenata 2014-066/Hembree 39 USNA 72020 12.85 ± 0.02 1.29 10
‘Candidissima’
x
D. scabra 2014-112/Hembree 29 Arnold Arboretum 923-81-A 12.69 ± 0.21 1.27 10
‘Codsall Pink’
x
D. scabra 2014-108/Hembree 26 MCIL 12.47 ± 0.02 1.25 10
‘Summer Snow’ D. crenata 2014-058/Hembree 27 JCRA xx0228 12.51 ± 0.21 1.25 10
‘Variegata’
x
D. gracilis 2014-056/Hembree 25 JCRA xx0591 12.56 ± 0.04 1.26 10
‘White Splashed’ D. crenata 2014-099/Hembree 32 Cornell BG 12.15 ± 0.10 1.22 10
D. longifolia
‘Elegans’
w
D. longifolia 2014-106/Hembree 33 Arnold Arboretum 850-80-A 12.68 ± 0.21 1.27 10
D. naseana
x,w
D. parviflora 2014-073/Hembree 40 JCRA 001389 12.88 ± 0.07 1.29 10
D. schneideriana
v
D. schneideriana var. laxiflora 2014-102/Hembree 41 Morris Arboretum 1943-020*A 12.71 ± 0.08 1.27 10
D. glauca
x
D. glabrata 2014-069/Hembree 42 MCIL 16.16 ± 0.20 1.35 12
D. schneideriana
w
D. schneideriana 2014-122/Hembree 23 Arnold Arboretum 196-96-A 17.07 ± 0.18 1.43 12
z
Arnold Arboretum, Boston, MA; Chicago Botanic Garden, Glencoe, IL; Cornell Botanic Gardens (Cornell BG), Ithaca, NY; William G. Hembree (Hembree); JC Raulston Arboretum
(JCRA), Raleigh, NC; Morris Arboretum, Philadelphia, PA; Mountain Crop Improvement Lab (MCIL), Mills River, NC; North Carolina State University Herbarium (NCSC), Raleigh;
University of Georgia (UGA), Athens; U.S. National Arboretum (USNA), Washington, DC.
y
Ploidy confirmed with chromosome counts.
x
Indicates keyed to new species.
w
Ploidy inconsistent with the literature.
v
Indicates keyed to same species as received, but taxon has been reclassified as noted here.
4of7 J. AMER.SOC.HORT.SCI.https://doi.org/10.21273/JASHS04779-19
Table 3. Genome size and estimated ploidy levels of Deutzia hybrids.
Taxon
Accession no./NCSC
voucher no.
z
Source/ID no.
z
2C genome size
[mean ± SE (pg)]
1Cxgenome
size (pg)
Estimated
ploidy (x)
D. ·elegantissima (D. purpurascens ·D. scabra
var. sieboldiana) ‘Rosalind’
2014-109/Hembree 9 MCIL 2.67 ± 0.04 1.33 2
D. ‘NCDX1’ (D. ·rosea ·D. gracilis) H2007-190-001/Hembree 50 MCIL 2.82 ± 0.01 1.41 2
D. ‘NCDX2’ (D. ·rosea ·D. gracilis)
y
H2010-310-034/Hembree 51 MCIL 2.76 ± 0.03 1.38 2
D. ·rosea (D. gracilis ·D. purpurascens) 2014-114/Hembree 5 Longwood Gardens 1985-0281 2.92 ± 0.03 1.46 2
‘Carminea’ 2014-096/Hembree 7 Cornell BG 2.87 ± 0.05 1.43 2
‘Nikko Blush’ 2014-063/Hembree 3 USNA 74356 2.89 ± 0.05 1.44 2
D. ·kalmiiflora (D. parviflora ·D. purpurascens)
y
2014-064/Hembree 10 USNA 59578 2.88 ± 0.04 1.44 2
D. ·magnifica (D. scabra ·D. discolor) 2014-121/Hembree 34 Arnold Arboretum 920-81-A 11.64 ± 0.04 1.46 8
‘Nancy’
y
2014-101/Hembree 15 Cornell BG 9.13 ± 0.14 1.52 6
‘Rubra’ 2014-075/Hembree 16 USNA 59622 10.96 ± 0.02 1.37 8
‘Superba’ 2014-110/Hembree 30 Arnold Arboretum 841-80-C 11.59 ± 0.06 1.44 8
‘Eburnea’ 2014-120/Hembree 31 Holden Arboretum 69-25-85 via
Morton Arboretum
11.59 ± 0.05 1.44 8
‘Formosa’ 2014-113/Hembree 35 Arnold Arboretum 922-81-A 11.75 ± 0.15 1.47 8
D. ·hybrida (D. longifolia ·D. discolor)
‘Strawberry Fields’ 2014-131/Hembree 20 JCRA 001170 10.89 ± 0.08 1.36 8
‘Tourbillon Rouge’ 2014-070/Hembree 18 JCRA 020130 11.22 ± 0.19 1.40 8
‘Magicien’ 2014-124/Hembree 22 Holden Arboretum 99-249 11.27 ± 0.03 1.41 8
‘Pink Pompom’ 2014-097/Hembree 36 Chicago Botanic Gardens 11.56 ± 0.04 1.44 8
D. ·myriantha [D. parviflora ·D. setchuenensis
(Hillier and Lancaster, 2014) or
D. gracilis ·D. purpurascens (Sargent, 1924)]
2014-116/Hembree 37 Arnold Arboretum 9-87-A 11.72 ± 0.13 1.47 8
z
Arnold Arboretum, Boston, MA; Chicago Botanic Garden, Glencoe, IL; Cornell Botanic Gardens (Cornell BG), Ithaca, NY; William G. Hembree (Hembree); Holden Arboretum, Kirtland,
OH; JC Raulston Arboretum (JCRA), Raleigh, NC; Longwood Gardens, Kennett Square, PA; Morton Arboretum, Lisle, IL; Mountain Crop Improvement Lab (MCIL), Mills River, NC; North
Carolina State University Herbarium (NCSC), Raleigh; U.S. National Arboretum (USNA), Washington, DC.
y
Ploidy confirmed with chromosome counts.
J. AMER.SOC.HORT.SCI.https://doi.org/10.21273/JASHS04779-19 5of7
scabra,D. uniflora, and D. crenata. In our study, a ploidy series
was not found for D. crenata, but it was found for Deutzia
schneideriana, which has not been previously reported as
having a ploidy series. If the accessions in this study were not
keyed and verified, then our results would have been quite
different. For example, D. gracilis ‘Pink Minor’ (2n=2x= 26),
D. crenata ‘Codsall Pink’ (2n=10x= 130), and D. crenata
‘Candidissima’ (2n=10x= 130) were received as D. scabra
before being keyed out. Deutzia scabra and D. crenata have
shared a close and confusing taxonomic and horticultural
history. The common name Pride of Rochester, which is
sometimes used as a cultivar name, is variously ascribed to
both species (Clapham, 1959; Clarke, 2007). Additionally, D.
crenata has, at times, been considered a synonym of D. scabra
(Hillier Nurseries, 1974), and the Flora of China (Huang et al.,
2001) recognizes Deutzia crenata as being synonymous with D.
scabra var. crenata. Kim et al. (2015) showed that the two are
very closely related as sister species in a phylogenetic study of
the genus, thus adding to the confusion surrounding the
circumscription of the putative taxa.
The accession received as D. parviflora 2014-073 and keyed
to D. scabra var. latifolia, which is a synonym of the currently
accepted D. naseana, has been reported as tetraploid
(Funamoto and Nakamura, 1992; Ohba and Akiyama, 1992).
This accession was found to be 2n=10x= 130, which has been
reported for D. scabra (Singhal et al., 1980), but not for D.
naseana.
Most of the accessions received as D. scabra were cultivars,
including ‘Candidissima’ and ‘Codsall Pink’, two decaploids,
and ‘Pink Minor’, a diploid. ‘Candidissima’ and ‘Codsall Pink’
were keyed to D. crenata. Both D. crenata and D. scabra have
been reported to include decaploids (Niu and Ohba, 2000;
Singhal et al., 1980). ‘Pink Minor’ was keyed to be D. gracilis,
consistent with all other diploid D. gracilis included in this
study.
Two of the three accessions that were identified as D.
discolor were received under the names D. vilmoriniae and
D. globosa. The ploidy of D. vilmoriniae and of D. globosa
have not been reported in previous literature. Flow cytometry
data indicated both to be octoploid, which is consistent with
prior reports of D. discolor (Darlington and Wylie, 1955;
Fedorov, 1974).
Deutzia parviflora has been reported as diploid by Darlington
and Wylie (1955) and Fedorov (1974), but our accession had a
genome size consistent with other tetraploids. The accession of
D. ogatai, which has been reported as decaploid (Niu and Ohba,
2003), was found to be tetraploid through flow cytometry and
chromosome counts.
The one accession of D. longifolia had a genome size
equivalent to other decaploids, even though it is reported as
an octoploid (Cave, 1959). For D. schneideriana, which has
been reported as a decaploid (Darlington and Wylie, 1955),
there was a considerable difference in the genome sizes
between our two accessions. D. schneideriana 2014-102,
received as D. schneideriana var. laxiflora, had a genome size
consistent with that of other decaploids. However, D. schnei-
deriana 2014-122 had a genome size in the range expected for a
dodecaploid, which has not been reported for Deutzia.Deutzia
glauca had a large genome size simila to that of D. schnei-
deriana 2014-122, but its ploidy has not been reported in the
literature. Despite considerable efforts, we were unable to
confirm the chromosome numbers of these putative dodeca-
ploids with cytology.
The ploidy of hybrids varied from diploid to octoploid and
were all isoploid (Table 3). Hybrids sometimes had inconsistent
ploidies when compared to their reported parents, although it is
difficult to confirm without knowing the ploidy of the exact
parents. The lack of any anisoploid hybrids points to the
probability of incompatibility of interploid crosses. Some
efforts have been made to create interploid hybrids [e.g., D.
·hybrida ·D. gracilis (T.G. Ranney, personal observation)],
but no success has further reinforced the likelihood of an
interploid block in Deutzia.
The proportions of plants used in this study that were
determined to be misidentified underscore the challenges of
Deutzia taxonomy. The correct identification and determination
of genome sizes and ploidy of a wide range of Deutzia species
and hybrids will provide a valuable resource for breeders and
curators. The most current comprehensive key (Zaikonnikova,
1975) was completed in 1966 and is now older than half a
century. There have been numerous taxonomic changes in the
genus; therefore, an updated and revised key with referenced
voucher specimens would be valuable for the continued under-
standing of Deutzia. In addition to the phylogeny of Deutzia
(Kim et al., 2015), these data will help inform decisions
regarding potential interspecific crosses with greater potential
for success.
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J. AMER.SOC.HORT.SCI.https://doi.org/10.21273/JASHS04779-19 7of7
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