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Exploring Complex Ornamental Genomes: The Rose as a Model Plant
Th. Debenera; M. Lindea
a
Leibniz University of Hannover, Faculty of Natural Sciences, Institute for Plant Genetics, Hannover,
Germany
To cite this Article Debener, Th. and Linde, M.(2009) 'Exploring Complex Ornamental Genomes: The Rose as a Model
Plant', Critical Reviews in Plant Sciences, 28: 4, 267 — 280
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Copyright © Taylor & Francis Group, LLC
ISSN: 0735-2689 print / 1549-7836 online
DOI: 10.1080/07352680903035481
Exploring Complex Ornamental Genomes: The Rose
as a Model Plant
Th. Debener and M. Linde
Leibniz University of Hannover, Faculty of Natural Sciences, Institute for Plant Genetics,
Hannover, Germany
As cultivated plants they are economically very important.
Despite its high economic importance, little is known about rose Roses belong to the top five ornamentals worldwide. In most
genetics, genome structure, and the function of rose genes. Reasons developed countries sales due to ornamental plant production
for this lack of information are polyploidy in most cultivars, simple exceed those for vegetables and fruits. Worldwide production
breeding strategies, high turnover rates for cultivars, and little pub-
values for flowers and pot plants were estimated to be about
lic funding. Molecular and biotechnological tools developed during
24 billion Euros per year, based on values from 1995 to 2007
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the genomics era now provide the means to fill this gap. This will
be facilitated by a number of model traits as e.g., a small genome, (Heinrichs, 2008). In 2007, roses accounted for about 20% (723
a large genetic diversity including diploid genotypes, a compara- million EUR) of all ornamentals exported from the EU into other
tively short generation time and protocols for genetic engineering. countries. Imports of roses into the EU in 2001 had a value of
A deeper understanding of genetic processes and the structure of
the rose genome will serve several purposes: Applications to the
447 million Euros. About 31% of all cut flowers traded at the
breeding process including marker-assisted selection and direct European auctions were cut-roses with a total value of about
manipulation of relevant traits via genetic engineering will lead to 858 million EUR (Heinrichs, 2008).
improved cultivars with new combinations of characters. In ba- This, however, is no reason to choose roses as an object
sic research, unique characters, e.g., the biosynthesis and emission of research or even to choose it as a model plant. One rea-
of particular secondary metabolites will provide new information
not available in model species. Furthermore comparative genomics
son to do so is that roses combine some model traits not
will link information about the rose genome to ongoing projects on found in any other woody species (Table 1). These are the
other rosaceous crops and will add to our knowledge about genome following:
evolution and speciation. This review is intended as a presentation
and is the compilation of the current knowledge on rose genetics
a small genome size
and genomics, including functional genomics and genetic engineer-
ing. Furthermore, it is intended to show ways how knowledge on an enormous biodiversity with a large number of morpholog-
rose genetics and genomics can be linked to other species in the ically and physiologically diverse species and cultivated
Rosaceae in order to utilize this information across genera. varieties
no juvenility period and in recurrent flowering genotypes a gen-
Keywords Rosa, rose, Rosaceae, structural genomics, genetic map- eration time of about one year
ping, functional genomics, polyploidy, molecular mark- easy vegetative propagation for most genotypes
ers, disease resistance, positional cloning, fragrance,
easy generation of segregating progeny on various ploidy levels
flower color, ornamental traits, transgenic plants, recur-
rent flowering even between different species
availability of several regeneration and transformation
protocols
a close phylogenetic relationship to other rosaceous crops for
I. INTRODUCTION
which more extensive genomic information is available
For more than five thousand years roses have delighted hu-
mans as ornamental plants, and have been used as medicinal
In addition, they display particular morphological, physio-
plants and even as food (Shepherd, 1954; Gudin, 2000). A sym-
logical, and genetic characteristics that can not be studied in
bol for beauty and elegance, they became an object of diverse
other model species. Among these are the biosynthesis and
forms of human art.
emission of a large number of different volatiles in petals, a
high morphological diversity with a variety of flower structures,
growth types, and prickle morphologies as well as a unique
Address correspondence to Th. Debener, Leibniz University of type of meiosis not found in other taxa. Furthermore, roses
Hannover, Faculty of Natural Sciences, Institute for Plant Genetics, are long-lived woody perennials (Krüssmann, 1981) and inter-
Hannover, Germany. E-mail: debener@genetik.uni-hannover.de esting questions on the generation and maintenance of genetic
267268 T. DEBENER AND M. LINDE
diversity in natural populations can be investigated in diploid North American Rosa palustris. Today the genus is distributed
and polyploid species. over the temperate regions of the northern hemisphere in Europe,
North America, East and West Asia also reaching into subtrop-
Taxonomy ical areas of Mexico (with R. montezumae as the only discov-
ered species in Mexico), the near East (Iran and Iraq), northwest
All true roses belong to the genus Rosa (L), which together
Africa (Morocco, Ethiopia) and Asia (Southern China), with the
with species from genera Fragaria, Rubus, Potentilla, and Geum
exception of some Arctic and tropical regions and some central
belong to the subfamily of the Rosideae within the family of
Asian areas. R. acicularis is regarded as the only naturally oc-
Rosaceae. They are therefore related to economically important
curring species in polar regions of Europe, Asia, and North
fruit crops as e.g., apple and pear (subfamily Maloidea) and
America (Zlesak, 2006; Henker, 2003; Krüssmann, 1981). An
cherry and peach (subfamily Prunoidea).
important center of diversity of the genus Rosa as it is known
The genus Rosa comprises about 180 species of woody
today is central and south western Asia including China and
perennials, mostly shrubby species with a basic chromosome
Turkey. In contrast to the natural distribution of rose species,
number of seven and ploidy levels ranging from 2x to 8x. All
cultivated roses are grown all around the world in almost all
species have conspicuous showy flowers with four to five petals
climates.
that are mostly scented. Roses are mostly outbreeders, but some
species from the Caninae section display a certain tendency for
apomixis (Wissemann and Hellwig, 1997).
Breeding and Cultivating Roses
The current classification is based on the system of Rehder
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Today’s cultivated roses are the product of many interspe-
(Rehder, 1940) with some modifications (Wissemann, 2003) and
cific hybridizations to which about 10 different rose species
is still under discussion. It divides the genus into four subgenera
contributed parts of their genomes (Wylie, 1954; Gudin, 2000).
(Hulthemia, Platyrhodon, Hesperodos and Rosa). In this clas-
In horticultural literature various systems for the classification
sification the largest subgenus Rosa is further subdivided into
of rose cultivars have been proposed mostly based on morpho-
ten sections with the section Rosa of the same name comprising
logical characters, origin, or horticultural use (Cairns, 2003).
almost all of the cultivated varieties.
As these schemes reflect only marginally genetic relationships,
Recent molecular evidence from an extensive study using
they are of little use for genetic or genomic research (Scariot et
AFLPs to reconstruct the phylogeny of the genus Rosa indi-
al., 2006). Phenetic analysis using molecular data distinguishes
cates that several modifications should be applied to the clas-
two major clusters of cultivars. One has a European genetic
sification of Rheder (1940) and Wissemann (2003). Based on
background with cultivars related to the section Rosa (with R.
UPGMA clustering, Wagner parsimony, and Baysian inference
×damascena and R. gallica) belonging to the Damask, Centifo-
Koopmann et al. (2008) suggested amongst others the follow-
lia, Gallica, Alba, Moss and Portland cultivar groups. The other
ing alterations: 1) the two small subgenera Hulthemia (with
has an Oriental genetic background related to the section Syn-
1 species) and Plathyrhodon (with 1 species) do not deserve
stylae (R. moschata, R. multiflora and R. wichurana) with cul-
this status, but should be integrated into the subgenus Rosa. 2)
tivars arranged in the Bourbon, Moschata, Multiflora, Noisette,
The section Carolinae (with 5 species) should be integrated into
Polyantha and Tea cultivar groups (Koopman et al., 2008). Most
the Cinnamomeae (with about 80 species). 3) The only sup-
modern cultivars are tetraploid and recurrent blooming. There
ported subsection in section Caninae is subsection Rubigineae
are three major horticultural groups for which breeding strate-
as a monophyletic group. All other 5 subsections are not sup-
gies differ significantly and which have divergent though over-
ported by the data from Koopman et al. (2008). These suggested
lapping gene pools: garden roses, pot roses, and cut-roses.
changes in the Rosa phylogeny demonstrate the complexity of
Breeding for all three groups is based on traditional strate-
the relationships caused by extensive hybridization events, the
gies starting with intercrosses between superior genotypes. Most
recent radiation, polyploidy and incomplete speciation. A sec-
breeders select marketable varieties among the first generation
ond major source of confusion is caused by the splitting into
hybrids with various numbers of selection cycles combined with
many species solely based on few morphological characters
vegetative propagation of the selected clones. In garden roses
which in addition are often under selection pressure (Olsson
this results in cycles of 8 to more than 10 years between the
et al., 2000; Koopmann et al., 2008).
crosses and registration of the variety for garden roses as each se-
lection cycle corresponds to one growing season (Noack, 2003).
Distribution For cut- and pot roses cycles are between three and six years as
The original geographical distribution of modern roses is the cultivation of these groups allows all year production and sev-
northern hemisphere, between 20 and 70 degrees latitude. Roses eral selection cycles per year. Selection for commercial pot rose
are not indigenous in the southern hemisphere. Fossil records for production takes place under highly controlled and automated
roses date back 37 million years. Leaf marks found in sedimen- production conditions in factory like greenhouse environments.
tary rocks in Florissant (Colorado) were allocated to the genus A large part of the cut-rose production is done at higher altitudes
Rosa (MacGinitie, 1953) and display a high similarity to the in the tropics combining high irradiation with mild temperaturesTHE ROSE AS A MODEL PLANT 269
which favors high productivity all year round (de Vries, 2003; gametes. In embryo sac mother cells the bivalents divide and
Chaanin, 2003). segregate at anaphase I while the univalents collect at one pole
A key factor for genetic analyses is the use of diploid segre- without division. At anaphase II all univalents collect at one pole
gating populations. Three genetic backgrounds have been used and a set of chromosomes from the bivalents divide and two cells
to date: genotypes resulting from introgression of genes from with 28 chromosomes each are formed. One of these develops
garden roses into diploid Rosa multiflora genetic backgrounds as the ovum. These processes originally observed by standard
(Debener, 1999), crosses of diploid varieties with diploid R. cytological techniques have recently been confirmed by analyses
wichurana genotypes (Shupert et al., 2007) and crosses between with polymorphic microsatellites in which the transmission of
dihaploid R. hybrida genotypes with R. wichurana genotypes only one genome through the pollen could be confirmed (Nybom
(Crespel et al., 2002). et al., 2004, 2006).
II. CONVENTIONAL GENETICS Self-incompatibility within the Genus
Considering the importance of roses as ornamental crops Based on observations that many diploid species do not set
conventional genetic analyses in roses are scarce. This is be- seed after self-pollination a gametophytic self incompatibility
cause genetic analyses in the predominantly tetraploid varieties system in diploid roses has been postulated (Ratsek et al., 1939;
are complicated as compared to diploids. Another reason is Cole and Melton, 1986; Ueda and Akimoto, 2001; Heslop-
that diploid populations of sufficient size segregating for agro- Harrision and Shivanna, 1977). Within the group of the mostly
nomically interesting characters have been rare compared to tetraploid modern cultivars and several polyploid species self-
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tetraploid populations as they have mostly no economic impor- fertilization is a common phenomenon (Morey, 1959; Rajapakse
tance (Debener, 1999). In addition, public research in breeding et al., 2001; Zlesak, 1998) indicating a breakdown of the SI sys-
and genetics of roses has been rare compared to that of major tem in tetraploids. Whether this breakdown is due to heteroga-
food crops or fruits. metic competition as found in Solanaceae or to the accumulation
The availability of linkage maps and the application of molec- of mutant alleles as found in Prunus (Hauck et al., 2006) is un-
ular markers to segregating populations greatly facilitated ge- known. Although generation of interspecific hybrids is possible,
netic analyses (Debener and Mattiesch, 1999; Malek et al., 2000; various symptoms of hybrid breakdown and incongruity often
Rajapakse et al., 2001). occur. Low fertility and reciprocal differences are found in in-
terspecific crosses between diploid hybrid rugosa and hybrid
china cultivars (Svejda, 1974, 1976).
Cytogenetics
As mentioned above roses comprise species with ploidy lev-
els of 2x to 8x with the majority of the wild species being Recurrent Flowering
diploid and most of the cultivars being tetraploid (Erlanson, Recurrent flowering is one of the key characters crucial for
1933; Krüssmann, 1981). Aneuploidy, incomplete sets of chro- the success of roses as ornamental crops as it leads to supe-
mosomes and the presence of supernumerary or B chromosomes rior genotypes flowering throughout the whole growing season.
are rarely reported for roses (Erlanson, 1933; Rowley, 1961; This trait was most probably introgressed from R. chinensis
Shahare and Shastry, 1963; Lata, 1982). In general diploids and R. odorata in the early nineteeth century. It affects the ver-
have regular meiosis with 7 bivalents whereas many tetraploids nalization requirement of rose shoots for flower induction and
have 14 bivalents and also show regular meiosis (Shahare and allows the plants to flower without vernalization therefore ex-
Shastry, 1963; Ma et al., 2000; Byrne and Ma, 2003; Ma et al., tending the flowering period. As segregation could be observed
2003). Genetic experiments with molecular markers indicate in many crosses between recurrent and nonrecurrent cultivars
tetrasomic inheritance due to four homologous genomes in some it was speculated since the 1940s that this trait is caused by a
hybrid tetraploid genotypes (Malek et al., 2000). However, pen- single recessive gene. However, statistically sound experiments
taploid species in the Caninae section display an aberrant type were first made with diploid R. wichurana populations support-
of meiosis that often is referred to as the canina or permanent ing theses hypotheses (Semeniuk 1971a, b). These were later
odd polyploid meiosis. Here, the male gametes transfer only confirmed by other authors also analyzing diploid populations
one of the genomes (n =7), whereas the ovules transmit four (deVries and Du Bois, 1984; Debene,r 1999; Crespel et al.,
genomes (n = 28; Lim et al., 2005). During pollen development, 2002; Dugo et al., 2005).
this is achieved through the formation of seven bivalents at the
first division of meiosis while all other chromosomes remain Flower Morphology
unpaired (Nybom et al., 2006). Flower morphology is another key character in rose breeding
In pollen mother cells, both bivalents and univalents divide as commercially important groups such as the cut roses are al-
and segregate but only the bivalents divide and segregate at most exclusively bred with “multi-petaled” (so-called “double”
anaphase II. The univalents do not segregate and instead form flowered) flowers. Flower morphology is affected by a range of
micronuclei that are excluded from further development of the parameters including the number, size and the shape of petals,270 T. DEBENER AND M. LINDE
number of stamens and the number and shape of styles and Black Spot Resistance
ovaries. Wild roses with the exception of R. sericea and R. Three major resistance genes have been characterized in
omeiensis have five sepals and petals, but a variable number of tetraploid and diploid populations, two of which are linked
stamens and carpels. In so-called “double flowers” with more within 10 cM on the same linkage group (Malek and Debener,
than five petals additional petals seem result from the homeotic 1998; Kaufmann et al., 2003; Zhang, 2003; Yan et al., 2005;
transformation of stamens into petals (Debener et al., 2003). Gebreyesus and Linde, personal communication). The Rdr1 lo-
The inheritance of double (>5 petals) versus single (5 petals) cus is the most intensively studied among these and approaches
flowers was shown to be caused by a single dominant gene in to positional cloning of Rdr1 led to the construction of two BAC
1999 (Debener 1999; Debener and Mattiesch, 1999) and later contigs spanning the locus (Kaufmann et al., 2003; Biber et al.,
confirmed by other authors (Crespel et al., 2002; Yan et al., submitted). A minimum of four BAC clones with a total length
2005a; Linde et al., 2006; Shupert et al., 2007). The locus of about 300 kb span the locus. Sequencing of these clones
has been mapped on several rose linkage maps (Debener and with a combination of 454 sequencing and Sanger sequencing
Mattiesch, 1999; Crespel et al., 2002; Zhang, 2003, Linde et al., revealed a group of nine highly similar TIR-NBS-LRR genes,
2006; Hibrand-Saint Oyant et al., 2008). First analyses with five of which are expressed in rose leaves within 200 kb of
anchor SSR markers analyzed in several of these populations the contig (Terefe et al., in preparation). In addition to these
indicate that the double flower locus is identical in all of the RGA candidate genes 29 other genes as predicted by BLAST
analyzed populations (Hibrand-Saint Oyant et al., 2008). Inter- searches are located on the contig resulting in an average gene
estingly in populations segregating for single and double flow- density of one gene every 8 kb. From this contig several markers
Downloaded By: [University of Michigan] At: 07:29 7 January 2011
ers, additional genetic factors influence the number of petals in tightly linked to Rdr1 were developed among which three SSR
the double-flowered genotypes. Some QTLs for additive genes markers cosegregating without recombination to Rdr1 and am-
could be located on several linkage maps (Debener et al., 2001; plifying DNA of several rose species (Biber et al., in press) are
Zhang, 2003; Hibrand-Saint Oyant et al., 2008). Flower size useful as anchor markers for the location of black spot resistance
appears to be quantitatively inherited and several QTLs could on rose maps.
be identified and placed on linkage maps (Lal et al., 1982; In addition to single qualitative genes, quantitative inheri-
Dugo et al., 2005; Shupert et al., 2007; Debener et al., in tance of black spot resistance has also been postulated based on
preparation). the observation that continuous variation can be observed be-
tween 11 cultivars infected with black spot (Xue and Davidson,
1998). A transgenic approach was tested by Marchant et al.
Moss Phenotype (1998a) transforming the floribunda ‘Glad Tidings’ with a chiti-
The moss phenotype gave rise to a group of rose cultivars nase transgene. Some of the resulting genotypes showed a 13–
called “moss roses.” It is characterized by glandular protuber- 43% reduction in black spot disease symptoms. As for the other
ances densely covering calyx tubes, stems, petioles, pedicels, fungal diseases, research has also been done in detail on the
and even petals leading to a mossy appearance of rose flowers disease development in the leaves (Blechert and Debener, 2005;
and flower buds (Hurst and Breeze, 1922; De Vries and Du Bois, Gachomo and Kotchoni, 2007) and the effects of the thickness
1984). It originated from sports of R. centifolia in the 17th cen- and composition of the leaf cuticle on the resistance to D. rosae
tury and was shown to be inherited as a single dominant gene in (Goodwin et al., 2007). In this study, Goodwin and coworkers
crosses between tetraploid moss roses and tetraploid non moss examined five cultivars for natural infections with black spot in
varieties (De Vries and Du Bois, 1984). the field. The cv. ‘Knockout’ showed, with 10% of the leaves
exhibiting symptoms, the highest quantitative resistance. Be-
cause only five cultivars were evaluated and phytopathological
Disease Resistances experiments were not conducted under controlled conditions
Disease resistances have long been neglected in rose breed- the results have to be considered as tentative and need more
ing since in the past, the application of agrochemicals in orna- thorough investigations.
mentals were less problematic compared to agricultural crops.
However, both increasing costs and environmental concerns lead
to an increasing pressure to significantly improve resistance of Powdery Mildew Resistance
rose cultivars to the major diseases. In contrast to morphological Only one description of a single dominant resistance gene
and physiological characters, genetic analyses of disease resis- (Rpp 1) to powdery mildew based on repeated inoculations with
tance require the isolation of defined pathogenic races of the single conidial isolates has been published so far (Linde et al.,
pathogen. This has been done by several groups for black spot 2004). In addition, major loci (Rpm, CRPM1) were described
(Wenfrida and Spencer, 1993; Debener et al., 1998; Carlson- by analyses of natural infections on field sites, in greenhouses or
Nilson, 2000; Whitaker et al., 2007), powdery mildew (Linde by artificial infections with polysporous isolates (Zhang, 2003;
and Debener et al., 2003; Leus et al., 2006) and downy mildew Xu et al., 2005). The Rpp1 and Rpm loci were mapped in a
(Schulz et al., 2007) and will not be discussed in detail here. diploid population of R. multiflora hybrids and a SCAR markerTHE ROSE AS A MODEL PLANT 271
was generated from a closely linked AFLP marker (Zhang, 2003; crosses to tetraploid modern rose classes, most miniature cul-
Linde et al., 2004), whereas the major gene CRPM1 was mapped tivars are also tetraploid. The frequent occurrence of dwarfs
in a population of R. roxburghii (Xu et al., 2005). In addition to in rose progenies already indicated a simple genetic control,
these major genes several QTLs were mapped in three diploid which was supported by observations in diploid and tetraploid
mapping populations (Zhang, 2003; Dugo et al., 2005; Xu et al., segregating populations where a single dominant gene could be
2005; Linde et al., 2006; Xu et al., 2007). Furthermore, Li et al. confirmed (Dubois and De Vries, 1987).
(2003) transformed the cultivar ‘Carefree Beauty’ with Ace-
AMP1, a gene coding for an antimicrobial protein resulting in
transgenic plants showing an enhanced resistance to powdery III. STRUCTURAL GENOMICS
mildew.
Genome Sizes
Nematode Resistance Genome sizes of roses are, similar to other Rosacea, rela-
Four different geographic isolates of Meloidogyne hapla tively small (Yokoya et al., 2000; Folta and Davis, 2006). The
were used in artificial inoculation experiments to study resis- astonishing finding that R. wichurana had an extremely small
tance in genotypes of R. multiflora and R. indica genotypes as genome of 0.1 pg/haploid genome (Bennett and Smith, 1991)
well as progeny from four crosses (Wang et al., 2004b). Re- could not be confirmed by more recent analyses with flow cy-
sults show clear differences between genotypes and indicate tometry with a value of 0.55 pg per haploid genome (Yokoya
polygenic control of resistance to nematodes in roses. et al., 2000). Several studies found genome sizes of 0.3–0.8 pg
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per haploid genome for a total of 33 rose species and several
cultivars. This is equivalent to approximately 294 Mb (Dolezel
Prickles
et al., 2003) for R. blanda with the smallest genome which is
In contrast to thorns, prickles are derived from the epidermal comparable to the genome of R. persica and about two times as
cell layer of the stem and occur in a large diversity of forms and large as the Arabidopsis genome (Dickson et al., 1992; Shulaev
densities in different rose species and varieties. While they have et al., 2008). The study of Yokoya et al. (2000) is the most
a certain ornamental value in garden roses they are usually neg- extensive investigation and includes 34 rose genotypes from
atively selected in cut- and pot roses (Chaanin, 2003). Several 29 different species and 5 cultivars. Differences were found in
studies have shown that prickles on stems are inherited as sin- DNA amounts between the sections and the subgenera within
gle dominant genes (Debener ,1999; Zhang, 2003; Linde et al., the genus.
2006; Shupert et al., 2007) and that they are independently in-
herited from prickles on petioles (Lal et al., 1982; Crespel et al.,
2002; Zhang, 2003). Both single genes and QTLs could be lo- Linkage Maps/Populations
cated on several rose linkage maps (Table 2, Rajapakse et al., Over the last ten years a number of linkage maps have been
2001; Linde et al., 2006). constructed most of which are based on diploid populations
(Table 2). In all mapping projects, the mapping strategy was
Dwarf Phenotype based on the so-called double pseudo test cross strategy, firstly
Dwarf phenotypes probably introgressed from the diploid R. constructing independent maps for each parent and later joining
chinensis minima (Sims) were used to breed miniature roses the linkage groups by markers segregating with alleles from
(Shepherd, 1954; De Vries, 2003). Through repeated back- both parents.
TABLE 1
Major Characteristics of Roses as Compared to other Rosaceae Model Species
Rosa (diploid genotypes) Malus x domestica Prunus persica Fragaria vesca
No. of species in the genus ∼180 Approx. 35 Approx. 53 Approx. 20
Genome size (Mb/C) Approx. 300Mb 750 280 206
Chromosome number 2n = 2x =14 2n = 2x = 34 2n = 2x = 16 2n = 2x = 14
Generation time272 T. DEBENER AND M. LINDE
TABLE 2
Linkage Maps and Populations Available for Roses
Name of Number of Number of Linkage
population individuals markers Phenotypic traits mapped groups Reference
94/1 (93/1-119 × 99 F1 605 Double flowers, Pink flower 7 and 7 Debener and Mattiesch,
93/1-117) color 1999; Debener et al.,
diploid 2002; Yan et al.,
5 Petal number QTLs 2005; Spiller et al., in
5 Petal length QTLs
preparation
3 Petal width QTLs
2 Petal color QTLs
10 QTLs for plant vigor
6 QTLs for 4 scent volatiles
97/7 (95/13-79 × 170 F1 233 Double flowers, Rdr1 7 and 7 Linde et al. 2006;
82/78-1) resistance, prickles, white Zhang 2003
diploid stripes, 28 QTLs for
powdery mildew resistance,
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Rpp1 powdery mildew
resistance
HW (H190 × R. 91 F1 241 Double flowers 7 and 7 Crespel et al., 2002;
wichurana) Hibrand-Saint Oyant
1 Petal number QTL
diploid et al., 2008
1 Blooming date QTL
90–69 (86–7 × 52 F2 685 Prickles 14 and 15 Rajapakse et al., 2001
82–1134)
tetraploid
(“Blush Noisette” 96 F1 133 Double flowers 7 and 7 Dugo et al., 2005
(D10) × R.
wichurana 4 Flower size QTLs
(E15)) diploid 2 Flowering time QTLs
5 Leaf size
2 Powdery mildew resistance
QTLs
Three maps are based on crosses between R. multiflora and 490 cM of the female (93/1-119) chromosomes and covers
hybrids into which various genes from garden roses have been approximately 90% of the rose genome with an average distance
introgressed during the early 1970s (Debener, 1999; Debener between markers from 1.2 (linkage group A4) to 3.6 cM (linkage
and Mattiesch, 1999; Yan et al., 2005a; Linde et al., 2006). The group A6). Meanwhile this map was again extended by addi-
first rose map published is based on 60 individuals of the pop- tional ESTs and SSRs, some of which segregate codominantly
ulation 94/1 a cross between two half sib R. multiflora hybrids (Spiller et al., in preparation). Ninety-nine individuals of
that are seedlings of the same maternal genotype. This map was this population were analyzed. The updated map of the male
constructed with 157 RAPD and 119 AFLP markers. In addition 93/1-117 now has a length of 427 cM containing 260 markers,
to the molecular markers single dominant loci for double flow- including 186 AFLPs, 59 SSRs, 13 ESTs and a locus for flower
ers and pink flower color could be mapped. The total map length color. The largest gap with 14 cM was located on the lower
was 326 and 270 cM for each parent respectively and 5 pairs of end of linkage group 4. The female 93/1-119 map includes
linkage groups could be linked by at least two markers segregat- 345 markers on 570 cM length, with 243 AFLPs, 75 SSRs, 17
ing from both parents. Subsequently this map was extended with ESTs and loci for the flower color, double flowers. A gap of 16
SSR markers (Debener et al., 2001) and with additional plants cM occurred on the lower end of linkage group 7. The parental
(88 individuals) and markers (Yan et al., 2005a) which led to the linkage groups could be linked to the map of Hibrand-Saint
most extensive map published so far. It comprises a total of 520 Oyant et al. (2008) by 6 and 7 SSRs and the morphological
markers including 58 SSR loci, CAPs and one RFLP marker markers in both populations. An extended analysis of volatile
for the Rdr1 locus and the genes for double flowers and flower scent components was performed for the individuals of the
color (Yan et al., 2005a). It spans 487 cM of the male (93/1-117) 94/1 population, leading to 6 significant (LOD>5.0) QTLs forTHE ROSE AS A MODEL PLANT 273
the nine evaluated components on nearly all linkage groups have been mapped. Among these, 91 annotated EST markers
except group 2 and group 6 of the male parent. Other flower will also be mapped onto different diploid populations allowing
traits were the petal number, petal length and width. All were the alignment of diploid and tetraploid maps (Zamir, personal
analyzed over various years and environments. communication).
Pink flower color was recorded as an additive trait both vi- All published maps contain some STS markers (SSRs and
sually and photometrically at 525 nm after extraction of antho- ESTs) potentially suitable to link the maps. A range of markers
cyanins resulting in one significant QTL for each of the male have already been exchanged between the labs to integrate both
and female maps. A further map based on R. multiflora hybrids diploid and tetraploid maps comprising genomic and EST SSRs
(population 97/7) using 170 F1 individuals has been published and ESTs. This map should allow a more efficient use of molec-
by Linde et al. (2006) and comprises 233 markers (172 AFLPs, ular markers across the maps, enabling the comparison of map
50 RGAs, 4 SSRs, 4 morphological and 3 others). The total positions of horticulturally important characters across genetic
map length for this map is 370 and 354 cM respectively and backgrounds and labs.
72 biparental markers could be used to link all complementary
linkage groups from the maternal and paternal map. The pheno-
Synteny to Other Rosacea
typic markers mapped comprise the genes for double flowers, a
A few studies have demonstrated syntenic relationships
single dominant gene for prickles, the Rdr1 gene for black spot
of various degrees between genomes across the rose family.
resistance, and the occurrence of white stripes on the petals.
Whereas synteny within the genus Prunus is very high with
However, the main reason in constructing this map was the
essentially collinear genomes (Arus et al., 2006; Dirlewanger
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analysis of QTL loci for powdery mildew resistance for which
et al., 2004), several rearrangements have been detected be-
a total of 28 QTLs could be located on the map some of which
tween Prunus and Fragaria representing the Prunoideae and
are stable across environments and experimental years.
the Rosoideae (Vilanova et al., 2008). Here, the analysis with
The second group of maps published made use of R. wichu-
71 markers detected a larger number of rearrangements due to
rana hybrids or R. wichurana selections crossed to diploid R.
27 inversions and 9 translocations. In roses, attempts to utilize
hybrida genotypes. Population Hw was obtained from an inter-
genomic SSR markers from the well established Prunus maps
cross between a R. wichurana hybrid and a dihaploid R. hybrida
failed, as only a few markers gave consistent PCR amplifica-
genotype generated by pollination of a tetraploid variety by X-
tion and detected polymorphisms in roses (Rajapakse et al.,
ray irradiated pollen and embryo rescue (Crespel et al., 2002;
2001; Dugo et al., 2005; Zhang et al., 2006; Hibrand-Saint
Meynet et al., 1994). The population comprised 91 individuals
Oyant et al., 2008). However, attempts to use ESTs or EST
and segregated for double flowers and recurrent flowering. The
derived SSR markers from Fragaria in Rosa were mostly suc-
map was constructed independently for the female and male
cessful and a macrosynteny study between the two genomes is
parent with 68 and 108 AFLP markers respectively. Both the
in progress (Hibrand-Saint Oyant and Denouyes, unpublished).
recurrent flowering and double flower loci were mapped to link-
First results indicate that although Fragaria and Rose share the
age groups A6 and B4 respectively. In addition to these genes
same basic chromosome number of 7, numerous rearrangements
two QTLs for the number of prickles were also located close
have occurred since the genera diverged (Hibrand-Saint Oyant
to the recurrent flowering locus. This map was extended by
and Denouyes, unpublished).
Hibrand-Saint Oyant et al. (2008) on the same population, map-
ping an additional 23 genomic and 18 EST-SSRs from roses,
2 SSRs from Prunus, one from Malus and one from Fragaria. BAC Libraries
Two other diploid maps involving R. wichurana hybrids were To date three BAC libraries have been constructed in roses
generated, mapping some important phenotypic traits in relation (Kaufmann et al., 2003; Hess et al., 2007; Biber et al., in press).
to various molecular markers (Table 2, Dugo et al., 2005). One of the libraries was constructed from DNA of a chromo-
In addition to the diploid maps, a map has been constructed some doubled R. rugosa genotype (Kaufmann et al., 2003).
in a small F2 population of tetraploid plants (Rajapakse et al., With an average insert size of 102 kb and a total of 27262
2001). The map of the female parent was comprised of 171 clones it covers 5.2 genome equivalents that results in a prob-
markers distributed over 15 linkage groups whereas the male ability of more than 99% to recover any given rose sequence
map consisted of 167 markers on 14 linkage groups. In addi- from the library. The second published library was made from
tion, a dominant gene for the presence of prickles on the petiole, the diploid R. chinensis cv. Old Blush, with the aim to isolate
segregating independently from prickles on stems, was located the recurrent flowering gene via positional cloning (Hess et al.,
on the female linkage map on the telomeric end of linkage 2007). It comprises 30,720 clones with an average insert size of
group seven (Rajapakse et al., 2001). Another more extensive 108 kb resulting in a 5.9 × genome coverage. The third library
tetraploid map is currently under construction at the Hebrew was constructed from DNA of the R. multiflora hybrid 88/124-
University of Jerusalem in Israel. This map is based on 160 46 carrying the monogenic dominant black spot resistance gene
progeny of a cross between the cultivars Golden Gate and Fra- Rdr1. In contrast to the first two libraries which were constructed
grant cloud, on which a larger number of molecular markers in pBeloBACII and pECBAC1 vectors respectively, the library274 T. DEBENER AND M. LINDE
from 88/124-46 was constructed in PCLD04541 (Jones et al., studies on scent related genes in roses were started and resulted
1992), originally designed as a binary cosmid vector suitable for in the characterization of a number of genes involved in volatile
Agrobacterium mediated transformation (Tao and Zhang, 1998). biosynthesis (see above).
This library comprises about 60,000 clones with an average in- In addition to these published projects a new set of ESTs has
sert size of 48 kb. The smaller insert size was chosen to facilitate been sequenced recently from vegetative apices of R. wichurana,
Agrobacterium transformation of individual clones. A particular a non recurrent wild species and floral buds of R. hybrida Black
problem faced during the construction of all three libraries was Baccara a recurrent modern cultivar (Foucher et al., submitted).
the high amount of polysaccharides and polyphenols present in After clustering, a total number of 2,336 unique sequences were
rose leaves which complicates the isolation of high molecular obtained that will be used to investigate the flowering control in
weight DNA. This problem was circumvented for the R. rugosa roses.
and the 88/124-46 library by the use of high concentrations Interestingly, in both EST projects a larger number of tran-
of PVP 40, DIECA and 2-mercaptoethanol, whereas modified scripts (around 30%) did not match to any annotated sequence
plant cultivation conditions and an increased number of washing in the common databases (Channeliere et al., 2002; Gutermann
steps were used for the R. chinensis library. The libraries from et al., 2002). One reason for this might be technical problems
both R. rugosa and the R. multiflora hybrid 88/124-46 were used generally encountered during homology searches with partial
to construct contigs around the Rdr1 black spot resistance gene. transcripts. However, the high number of these “non-matches”
The R. rugosa contig comprises six clones spanning an interval is a first indication that a larger number of rose petal genes are
of 0.36 cM. From this contig probes were used to construct a ho- either unique or too divergent from genes from other taxa to
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mologous contig from 88/124-46. With additional segregating be picked up via sequence homology therefore underlining the
progeny the new contig could be reduced to four clones span- necessity for further transcriptome analysis in this genus.
ning an interval of 0.2 cm and 300 kb of DNA (Biber et al., in Currently the EST collection is being enlarged by an extended
press). A problem that occurred during the contig construction EST project the aim of which is the sequencing of several rose
was the assembly of allelic BACs caused by the high level of tissues harvested under different physiological conditions by
heterozygosity in roses. means of the novel 454 sequencing strategy (M. Bendamahne,
personnel communication).
IV. FUNCTIONAL GENOMICS
Functional genomics in roses is still in its infancy and com- Floral Fragrance
pared to other rosaceae e.g. apple or model species little in-
Fragrance is one of the most important characters of orna-
formation about expressed genes is yet available. Most of the
mental roses and therefore an important trait selected in breeding
published reports on gene expression focus on floral character-
programmes for garden roses. However, in cut roses this char-
istics like flower color, flower morphology, flower senescence,
acter seems to be inversely correlated to vase life and resistance
and floral fragrance. Major progress was achieved through two
to stress during transportation (Chaanin, 2003). This leads to
flower petal projects that apart from generating data on volatile
a loss of strong fragrance in cut-rose varieties and therefore
biosynthesis genes led to the publication of useful EST se-
only a few very lightly scented cut-rose varieties are available
quences (Channeliere et al., 2002; Guterman et al., 2002).
to date (Chaanin, 2003). Phytochemical analyses of rose scent
composition date back to the 1970s and more than 400 differ-
EST Libraries ent volatiles have been identified in rose petals (Flament et al.,
Several small scale EST sequencing projects in roses have re- 1993). Therefore, fragrance is a complex character determined
sulted to date, in a total of about 9,300 ESTs available in public by mixtures of volatiles that can be grouped into the following
databases to date. These can be accessed via two web links. A five major series: hydrocarbons (mostly sesquiterpenes), alco-
smaller set of about 5,300 ESTs is stored at the GDR (Genome hols (mostly terpenes such as geraniol, nerol, and citronellol),
database for the Rosaceae, http://www.bioinfo.wsu.edu/gdr/ esters (mostly acetates such as hexyl acetate or geranyl acetate),
projects/rosa/unigeneV3/index.shtml) at Washington State Uni- aromatic ethers (3,5-dimethoxytoluene, benzyl methyl ether and
versity, whereas a larger set of about 10,000 ESTs is methyl-eugenol), and others such as aldehydes, aliphatic chains,
hosted by URGI (Genomic-info Research Unit, http://urgi. rose oxides, and norisoprenes such as ß-ionone (Antonelli et al.,
versailles.inra.fr/GnpSeq/) run by the INRA in France. Chan- 1997; Caissard et al., 2005).
neliere et al. (2002) analyzed 1794 ESTs from petals of the R. Several O-methyl transferases were isolated by differential
chinensis cultivar Old Blush. These clustered as 877 unigenes. expression (Guterman et al., 2002), EST analysis (Channeliere
In a similar study Guterman et al. (2002) sequenced and ana- et al., 2002; Scalliet et al., 2002) or by homology to published
lyzed 3,500 ESTs from petals of two cultivars, Fragrant cloud sequences (Wu et al., 2003). They are responsible for the last
and Golden Gate, which clustered into 2,139 unigenes. A large steps in the biosynthesis of phenolic methyl esters as e.g.,
number of sequences (about 15%) were unique sequences puta- DMT (3,5-dimethoxy toluene), TMB (1,3,5-trimethoxy ben-
tively related to scent metabolism. From both projects functional zene), or methyleugenol. Two of these genes (Rh OOMT1 andTHE ROSE AS A MODEL PLANT 275
RhOOMT2) were shown to be upregulated during petal devel- rose homologues for genes involved in ethylene biosynthesis
opment and localized predominantly in the adaxial epidermal include an ACC oxidase (RhACO1) and three ACC synthases
cells. The function of rose OOMTs was confirmed by feed- (Muller et al., 2000b; Wang et al., 2004a; Ma et al., 2006).
ing experiments with cell free petal extracts and heterologous In addition, homologues of genes involved in ethylene percep-
expression in E. coli. tion and signaling like e.g., CTR1 and 2 (Muller et al., 2002)
In addition to the OOMTs phloroglucinol O- EIN3 (Muller and Stummann, 2003a), ETR1-3 (Ma et al., 2005,
methyltransferases (POMTs) were isolated and characterized 2006) have been isolated by homology based approaches. Stud-
(Wu et al., 2004). These enzymes are crucial for the synthesis ies of flower development revealed differential regulation during
of TMB as in contrast to OOMTs they are able to methylate different developmental stages as well as differences between
phloglucinol. genotypes with differences towards artificial ethylene treatment
Transcriptomic experiments using a small rose petal microar- (Ma et al., 2005; Ma et al. 2006; Tan et al., 2006). However these
ray (Guterman et al., 2002) were also able to characterize a ger- results so far do not fit the known ethylene signaling networks
macrene D synthase involved in the biosynthesis of Germacrene as e.g., analyzed in Arabidopsis and need further investigation.
D, an important sesquiterpene volatile. Analysis of cell free ex- Flower senescence was studied in pot rose varieties with
tracts as well as expression experiments in E. coli confirmed differing vase life. R. hybrida cv. Vanilla has a long vase life and
that the enzyme is responsible for the conversion of farnesyl is less sensitive to ethylene, whereas R. hybrida cv. Bronze has
diphosphate into Germacrene D (Guterman et al., 2002). a short vase life and a high sensitivity to ethylene. Transcript
Key enzymes in the biosynthesis in volatile acetate esters levels of RhACS increased in ‘Vanilla’ but remained low in
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are alcohol acetyltransferases (AATs). Acetate esters are major ‘Bronze,’ whereas transcript levels of RhACO increased more in
constituents of the volatile profiles of some rose varieties (Shalit ‘Bronze’ as compared to ‘Vanilla’ (Muller et al. ,2000b). Similar
et al., 2003). The expression of an AAT gene isolated from a differences were found for transcript levels of RhETR1 and
rose petal EST library was shown to be regulated during petal RhETR2 which were higher in ‘Bronze’ than in ‘Vanilla’ or for
development. The function of the gene product was analyzed RhETR3 that was only expressed during senescence in ‘Bronze’
in feeding experiments after expression in E.coli extracts and (Muller et al., 2000a). However, as for flower development these
geraniol was shown to be the preferred substrate (Shalit et al., observations as well as observation on the regulation of Rh
2003). CTR1/2 (Muller et al., 2002) and RhEIN3 (Muller et al., 2003a)
are in contrast to common models of regulation of ethylene
signaling (Bishopp et al., 2006) thus indicating that additional
Flower Color
experiments are needed to elucidate the role of ethylene in rose
Genes coding for proteins involved in flavonoid metabolism
flower senescence.
are among the most extensively studied genes in ornamental
plants. Therefore, they were also among the first rose genes
isolated. A gene for dihydroflavonol 4-reductase (DFR) has Plant Morphology Architecture/Flower Morphology
been characterized as being developmentally regulated in petals
The functional characterization of genes involved in floral
and also expressed in sepals, prickles and styles (Tanaka et al.,
morphology so far has been restricted to MADS box genes
1995). Functional studies with this gene were done by heterolo-
with homology to homeotic Arabidopsis floral organ identity
gous expression in Petunia resulting in the accumulation of high
genes (Weigel and Meyerowitz, 1994). Homologues of the C-
amounts of pelargonidin and therefore confirming the function
type gene AGAMOUS were isolated from R. rugosa (Kitahara
of the cDNA.
and Matsumoto, 2000) and Rosa hybrida cv. Montrea (Chmel-
Many compounds of the flavonoid pathway are glycosylated
nitsky et al., 2003) with degenerate primers for the conserved
at various positions. One glycosyltransferase has recently been
MADS box domain. In R. rugosa two genes (Masako C1 and
isolated and characterized (Ogata et al., 2005). In addition to
D1) are expressed in stamens and carpels comparable to expres-
the few genes characterized in more detail several ESTs with
sion patterns of AGAMOUS (Kitahara and Matsumoto, 2000).
significant similarities to known genes in the biosynthesis of
Overexpression under the 35S promoter in Arabidopsis and Tor-
flavonoids are present in the EST libraries mentioned above
renia induced homeotic transformations of floral organs as ex-
(Guterman et al., 2002; Channeliere et al., 2002).
pected for C-function genes and indicating a redundant function
in rose flower development (Kitahara et al., 2004). With a sim-
Ethylene Metabolism ilar strategy the B function genes MASAKO BP and B3 ortho-
Ethylene signaling is involved in a number of physiological logues of PISTILLATA and APETALA 3 respectively were iso-
processes in roses among which are germination, growth, organ lated (Kitahara et al., 2001). Both genes are expressed in petals
abscission, flower development, and leaf and flower senescence and stamens as expected for B-type genes. In this study an-
(Müller and Stummann, 2003b). In roses mostly flower develop- other B-type gene, MASAKO euB3 with similarity to APETALA
ment and flower senescence have been studied (Ma et al., 2005; 3 that is expressed in all floral organs was isolated (Hibino
Tan et al., 2006; Müller, 2000a, b; Wang et al., 2004a). Cloned et al., 2006). Phylogenetic analyses indicate that MASAKO euB3276 T. DEBENER AND M. LINDE
belongs to the euAP3 lineage whereas MASAKO B3 belongs to target cells were based on Agrobacterium mediated transfor-
the TM6 lineage (Kitahara et al., 2001; Hibino et al., 2006). mation. A range of Agrobacterium strains for example C58C1
When all three genes were overexpressed in Arabidopsis and and AGL0 (Derks et al., 1995; Condliffe et al., 2003), GV3101
tobacco no homeotic phenotype could be observed. However, (Souq et al., 1996; van der Salm et al., 1997, 1998; Li et al.,
the combined overexpression of Masako BP and Masako B3 in- 2002b), EHA 105 and GV2260 (Dohm et al., 2001, 2002),
duced transitions from sepals to petals and modified carpels to LBA4404 (2004b) were successfully used in transformation ex-
staminoid carpels similar to phenotypes induced by ectopic ex- periments under various experimental conditions. All reported
pression of the Arabidopsis PI/AP3 genes (Hibino et al., 2006). rose transformation experiments made use of the neomycin
The combined overexpression of Masako BP and Masako euB3 phosphotransferase gene (npt II) as a selectable plant trans-
transformed sepals into petals. This indicates that in roses the formation marker with varying concentrations of kanamycin for
combined action of the gene products of Masako B3 and Masako the selection of transgenic tissues. Transformation rates reach a
BP is involved in petal and stamen development whereas the maximum of 3% but are strongly dependent on the genotype due
combined action of the products of Masako BP and Masako to genotype-dependent regeneration frequencies (Dohm, 2003;
euB3 is only involved in petal development. Burrell et al., 2006).
A major goal for genetic engineering in many ornamental
crops has always been the manipulation of flower colors (Tanaka
V. ROSE BIOTECHNOLOGY
et al., 2008). In roses blue flower colors do not occur natu-
Rose biotechnology dates back to the 1970s when the first in
rally and therefore speculations on biotechnological approaches
vitro cultures were reported (Elliot, 1970). Since then in vitro
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to obtain blue hues in rose petals go back to the early 1990s
techniques have been widely used to rapidly multiply cultivars,
(Lawson, 1991). Only recently this goal was reached by ma-
to produce healthy and disease-free plants and finally as a pre-
nipulating three genes simultaneously (Katsumoto et al., 2007).
requisite for genetic engineering of rose genotypes. The largest
Roses with light blue petals were obtained after silencing the
number of reports focus on the optimization and application
endogenous DFR gene and the introduction of a DFR gene
of micropropagation of rose shoots which have been reviewed
from Iris as well as a F3 5 H from violets (Takahatsu et al.,
several times (Skirvin et al., 1984; Rout et al., 1999; Borissova
2007). However, clearly blue petals were only obtained after a
et al., 2000; Jabbarzadeh and Khosh-Khui, 2005; Pati et al.,
large number of rose varieties had been screened for the right
2006) and which will not be discussed here. A key technique
pH of petal cells and proper copigmentation (Tanaka, personal
for rose biotechnology has been the induction and regeneration
communication) indicating that even engineering simple bio-
of somatic embryos as reviewed in Roberts et al. (1995) as all
chemical pathways may be very challenging.
published transformation protocols make use of regeneration
Another target for genetic engineering in roses has been in-
of transgenic plants from somatic embryos. Explant sources for
creased disease resistance. Overexpression of a rice chitinase
somatic embryogenesis include leaves (de Wit et al., 1990; Rout
gene increased resistance to black spot (Marchant et al., 1998b).
et al., 1991, Dohm et al., 2001; Kim et al., 2004; Estabrooks
Expression of the Ace-AMP1 antimicrobial gene from onion
et al., 2007), stem segments (Rout et al., 1991), immature seeds
seeds increased the resistance of transgenic roses to powdery
(Kunitake et al., 1993), petioles and roots (Marchant et al.,
mildew both in detached leaf as well as in vivo greenhouse as-
1996; Sarasan et al., 2001), filaments and petioles (Burrell et al.,
says (Li et al., 2003). A Chitinase, a glucanase, and a ribosome
2006), roots (van der Salm et al., 1996a) and protoplast derived
inhibiting gene from barley as well as a gene for T4 lysozyme
callus (Matthews et al., 1991; Schum et al., 2001). The latter
increased resistance to black spot, powdery mildew, and downy
reports focus on the isolation of protoplasts from roses, their fu-
mildew (Dohm et al., 2001; Schulz, personal communication).
sion and the regeneration to intact plants. However, to date only
In order to manipulate plant architecture ROL A, B, and C genes
Matthews et al. (1991) could regenerate protoplast fusion prod-
were transferred to rose cultivars and rootstocks and enhanced
ucts between two different species into intact plants. Several
adventitious root formation and stimulated axillary bud break
reports investigated the amount of somaclonal variation after
in non transgenic scions grafted on transgenic rootstocks (Souq
regeneration of somatic embryos and conclude that the amount
et al., 1996; van der Salm, 1997, 1998). In addition, a number
of variation is low (Arene et al., 1993; Souq et al., 1996; Dohm
of marker genes including GUS and GFP were transferred dur-
et al., 2001; Condliffe et al., 2003, Kim et al., 2004a).
ing establishment of transformation protocols (Matthews et al.,
1994; Firoozabady et al., 1994; Li et al., 2002b; Kim et al.,
Genetic Engineering 2004b).
Several rose transformation and regeneration protocols have
been published over the last 15 years (reviewed in Dohm, 2003)
and in several labs rose transformation although tedious due to VI. CONCLUSION
low transformation rates can be considered to be a routine tech- Based on a favorable combination of genetic parameters roses
nique. All but two reports (Marchant et al., 1998a, b) in which are a very interesting model for complex ornamental genomes
particle bombardment was used to deliver the transgenes to the and in particular for woody perennials. Linkage maps in diploidTHE ROSE AS A MODEL PLANT 277
populations with no juvenile period have already significantly Blechert, O. and Debener, T. 2005. Morphological characterization of the in-
contributed to the understanding of the genetics of major traits. teraction between Diplocarpon rosae and various rose species. Plant Pathol.
The small genome will facilitate whole genome sequencing in 54: 82–90.
Borissova, A., Tsolova, V., Angeliev, C., and Atanassov, A. 2000. Somatic
the near future especially when further progress in sequenc- embryogenesis of Rosa hybrida L. Biotechnol. and Biotechnol. Equip. 14:
ing technology and bioinformatics will reduce cost and time of 44–51.
whole genome approaches. An area that will immediately profit Burrell, A. M., Lineberger, R. D., Rathore, K. S., and Byrne, D. H. 2006. Genetic
from new technology is transcriptomics with some EST projects variation in somatic embryogenesis of rose. HortScience 41: 1165–1168.
Byrne, D. H., and Ma, Y. 2003. Meiosis. In: Encyclopedia of Rose Science.
utilizing new 454 sequencing strategies already in the pipeline
pp. 273–279. Roberts, A. V., Debener, T. and Gudin S., Eds. Elsevier Ltd.,
(Bendamahne, personal communication). Existing protocols for Oxford, UK.
rose tissue culture and transformation will allow complementa- Cairns, T. 2003. Classification / Horticultural classification schemes. In: Ency-
tion analyses for gene identification and proof of concept studies clopedia of Rose Science. pp. 117–124. Roberts, A. V., Debener, T. and Gudin
for engineering useful traits. S., Eds. Elsevier Ltd., Oxford, UK.
Caissard, J. C., Bergougnoux, V., Martin, M., Mauriat, M., and Baudino, S. 2005.
As a prerequisite for whole genome sequencing genomic
Chemical and histochemical analysis of Quatre Saisons Blanc Mousseux a
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Chaanin, A. 2003. Breeding/Selection strategies for cut roses. In: Encyclopedia
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of Rose Science. pp. 33–41. Roberts, A. V., Debener, T. and Gudin S., Eds.
and populations; Elsevier Ltd, Oxford, UK.
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to other rosaceae but also to species beyond the boundary of Motrea. Plant Growth Regul. 39: 63–66.
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