African Journal of Biotechnology Vol. 9(39), pp. 6503-6508, 27 September, 2010
Available online at http://www.academicjournals.org/AJB
ISSN 1684–5315 ©2010 Academic Journals
Full Length Research Paper
Breaking seed dormancy in oil rose (Rosa damascena
Mill.) by microbial inoculation
Soner Kazaz1*, Sabri Erba2 and Hasan Baydar2
1Department of Horticulture, Faculty of Agriculture, Suleyman Demirel University, Isparta 32260, Turkey.
2Department of Field Crops, Faculty of Agriculture, Suleyman Demirel University, Isparta 32260, Turkey.
Accepted 11 August, 2010
This study was carried out to determine the effects of microbial inoculation in breaking seed dormancy
and on the germination of Rosa damascena Mill. Seeds of R. damascena Mill. are the most used
scented rose species in rose oil production. The most important production centers around the world
are Turkey and Bulgaria. The seeds were subjected to 4 weeks of warm stratification at 25°C, followed
by 150 days of cold stratification at 4 ± 1°C. Before stratification, 4 different microbial fertilizers, EM•1®,
B:speel™, BioplinTM and Phosfert™ were inoculated to the seeds. In the study, the microbial
inoculation treatments significantly (p < 0.01) promoted the premature germination percentage during
cold stratification. During the stratification, the highest premature germination percentage was
obtained from the EM•1® (69.3%). The highest germination percentage in terms of cumulative
germination percentage was determined in EM•1® (100.0%), followed by Phosfert™ (84.0%) and B:
seepel™ (84.0%), whereas the lowest germination percentage was found in the control treatment
(69.3%). The EM•1® shortened the mean germination time by 1.7 days in comparison to the control. In
conclusion, it was observed that with microbial inoculation (particularly EM•1®) to oil rose seeds and a
stratification time of 150 days, dormancy was broken and germination highly improved.
Key words: Rosa damascena Mill, dormancy, germination, microbial inoculation, stratification.
The genus Rosa has over 130 species (Cairns, 2001)
that are native to the Northern Hemisphere (Krüssmann,
1981), and of these species, 25 are distributed in Turkey
(Kutbay and Kilinc, 1996; Ercisli, 2004). The primary
species used in rose oil production among rose species
are Rosa damascena Mill, Rosa gallica Linn., Rosa
centifolia Linn. and Rosa moschata Herm. (Tucker and
Maciarello, 1988). Among these species, R. damascena
is commonly used in oil production (Douglas, 1993).
Although oil rose is cultivated in many countries such as
*Corresponding author. E-mail: skazaz@ziraat. sdu.edu.tr. Tel:
+90 246 211 4656. Fax: +90 246 237 1693.
Abbreviations: ABA, Abscisic acid; PSB, phosphate
solubilizing bacteria; PGPR, plant growth promoting
rhizobacteria; GP, germination percentage; MGT, mean
Turkey, Bulgaria, India, Iran, Egypt, Morocco and Syria
(Büttner, 2001), the most important production centers in
the world are Turkey and Bulgaria. R. damascena Mill., a
perennial shrub, produces pink flowers in May-June. Oil
rose is a temperate zone plant and has well adapted to
climate zones, which receive abundant light and
adequate rain, and do not experience negative climatic
factors such as drought, excessive rainfall and freezing
during the flowering period but in which dew occurs
during the early morning hours. The primary products that
are obtained from oil rose and that are greatly demanded
in cosmetics industries include rose oil, rose water, rose
concrete and rose absolute (Kaur et al., 2007; Kazaz et
al., 2009). Fruits, fruit flesh and seeds of R. damascena
contain ascorbic acid 332.0, 546.0 and 145.0 mg/100 g,
respectively. Also R. damascena fruits can be used as
food and food additive similarly as with dog rose fruits
(Rosa canina) (Kazaz et al., 2009).
Rose seeds show both endogenous (morphological
and/or physiological) and exogenous (physical and/or
6504 Afr. J. Biotechnol.
mechanical) dormancy (Gudin et al., 1990; Ueda, 2003).
Rose seeds are surrounded by a hard-coated pericarp,
and the pericarp prevents water absorption and air diffu-
sion of the seed and at the same time is a physical
barrier to embryo expansion (Ueda, 2003; Zlesak, 2007;
Meyer, 2008). In addition, it was stated that high
concentrations of abscisic acid (ABA) in the pericarp and
testa of rose seeds was a major germination inhibitor in
roses (Jackson, 1968; Cornforth et al., 1966; Bo et al.,
1995; Hartmann et al., 2002). It was reported that the
amount of ABA in a rose seed was 10- to 1000-fold
higher than those in other plants (Ueda, 2003). Due to
the above-mentioned reasons, the germination of rose
seeds is generally difficult. Prolonged dormancy delays
germination and reduces germination percentage. This is
a serious problem particularly in rose breeding and seed
propagation (Yambe and Takeno, 1992; Bo et al., 1995;
Hosafci et al., 2005; Zlesak, 2007).
The degree of dormancy varies by the time and
temperature required to overcome dormancy as well as
by germplasm, maturity at hip collection, time of seed
extraction, temperatures during seed development and
temperature and duration of stratification (Semeniuk and
Stewart, 1962; Gudin et al., 1990). One of the most com-
monly used methods to break dormancy and stimulate
germination in rose seeds is stratification (Zlesak, 2007).
Various methods, such as gibberellic acid (Hosafci et al.,
2005), hot water treatment (Younis et al., 2007), scarifi-
cation with sulphuric acid (Bhanuprakash et al., 2004)
and macerating enzymes (Yambe and Takeno, 1992),
have also been tried besides stratification. Even though
these methods are used alone or as a combination, it has
been reported that the germination percentages in some
rose species are still low. It was reported that the
germination percentages ranged from 0 to 10% in the 1st
year and from 24.7 to 73.7% in the 2nd year (Hosafci et
al., 2005). Belletti et al. (2003) reported that they ranged
from 0.5 to 50.3% and that this percentage was 18.8% in
R. canina L. according to Alp et al. (2009), while the ger-
mination percentages were 13.8 and 13.5% in Rosa
pulverulenta Bieb. and Rosa dumalis Bechst., respec-
tively (Alp et al., 2009). In Rosa bracteata Wendl, they
ranged from 1.8 to 41.5% according to Anderson and
One of the methods used to break dormancy in seeds
and promote germination percentage is microbial
inoculation to seeds or germination medium. It was
reported that microorganisms macerated the hard-coated
seed pericarp and facilitated germination (Morpeth and
Hall, 2000). The objective of this study is to determine the
effects of microbial inoculation in breaking seed dorman-
cy and on the germination of R. damascena Mill. seeds.
MATERIALS AND METHODS
Seed origin and seed collection
The mature hips of the species R. damascena Mill. were collected
from the oil rose plantations in Isparta Province (Isparta, Turkey,
45' N latitude, 30°
33' E longitude and 997 m altitude) in October
2008. Rose hips contain 2.35 seeds per hip on average. The
annual mean temperature, relative humidity, total annual precipi-
tation, wind speed and sunshine duration per day in the area are
12.4°C, 55%, 524.4 mm, 2.4 m s-1 and 7.6 h, respectively
(Anonymous, 2003). With these climate characteristics, Isparta
features a semi-arid climatic characteristic (Ucar et al., 2009).
The research was conducted in a plastic covered greenhouse
located at the Agricultural Research and Application Center of
Agricultural Faculty at Süleyman Demirel University (latitude 37°
N, longitude 30°
32' E, altitude 1019 m).
Seed preparation and determination of moisture content and
1000 seeds weight
After the seeds had been manually extracted from hips, they were
cleaned in water and the unwanted materials were removed. Later,
the seeds were soaked in water for 24 h and then the floating seeds
were discarded and the seeds that sunk in water were used in the
treatment as they were assumed to be mature and viable (Zhou et
al., 2009). After the seeds had been dried in the open air for 3 days,
they were kept in polyethylene bags at room temperature (20 -
24°C) until the beginning of the treatments. Seed moisture content
(four replicates of 100 seeds) was determined at 103°C for 17 h
and 1000 seeds weight was determined based on 8 replications of
100 seeds (8 x 100 seeds) (ISTA, 1993).
Microbial treatments and warm plus cold stratification
Some 4 different microbial fertilizers (EM•1® EM Agriton and Kina-
gro Agriculture Inc, Turkey), B: speel™ (Bioglobal Inc. Turkey),
Bioplin™ (Bioglobal Inc, Turkey) and Phosfert™ (Bioglobal Inc,
Turkey) were used in the study. EM•1® primarily contains 3 types of
microorganisms, namely phototrophic bacteria (Rhodopseudomonas
palustris), lactic acid bacteria (Lactobacillus plantarum, Lactobacillus
casei, Lactobacillus fermentum and Lactobacillus delbrueckii) and
yeasts (Saccharomyces cerevisiae). B:seepel™ is a bioorganic
seed dresser and contains a mixture of microorganisms (1x107
cfu/g) fixing nitrogen in dormant form, a mixture of phosphate
solubilizing bacteria (PSB) (1x107 cfu/g), plant growth promoting
rhizobacteria (PGPR) and metabolic extracts of different microbes.
Bioplin™ contains efficient rhizosphere inhabiting, nitrogen fixing
and plant growth promoter producing strains of Azotobacter
(Azotobacter chroococcum and Azotobacter vinelandii 1 x 107
cfu/g). Phosfert™ contains plurality of strains of Azotobacter (A.
chroococcum, A. vinelandii, Bacillus polymyxa 1 x 107 cfu/g).
Firstly, the seeds were left in water for 24 h and then they were
left in Bioplin™ (15 ml/l), Phosfert™ (15 ml /l) and Phos-
fert™+Bioplin™ (1:1, v/v) solution for 15 min and in EM•1® solution
(300 ml /l) for 20 min. In the B:seepel™ treatment, B:speel™ (20
g/kg seed) was sprinkled over the seeds, and the seeds were
covered completely with B:speel™. On the other hand, no microbial
fertilizer treatments were performed on the seeds in the control
Stratification was applied to the seeds treated with microbial
fertilizer and to the seeds of the control group. Sphagnum moss
was used as the stratification medium. Those seeds that were
mixed with moistened sphagnum moss (1 part of seed and 4 parts
of sphagnum moss, v/v) were subjected first to 4 weeks of warm
stratification at 25°C and then to 150 days of cold stratification in
Kazaz et al. 6505
Table 1. Effects of microbial inoculations on seed germination percentage (%) and mean germination time (day).
germination1 (%) Greenhouse
germination2 (%) Cumulative
germination3 (%) Mean germination
Phosfert™ 44.0 b 71.5 b 84.0 ab 7.8
B:seepel™ 52.0 b 66.7 b 84.0 ab 7.3
Bioplin™ 0.0 d 68.0 b 68.0 b 7.8
EM•1® 69.3 a 100.0 a 100.0 a 7.2
Phosfert™ + Bioplin™
14.7 c 63.9 b 69.3 b 9.3
Control 13.3 c 61.0 b 66.7 b 8.9
F value 129.40** 8.59** 14.34** 2.58 ns
1Germination during stratification; 2germination in greenhouse (seeds without premature germination); 3premature germination plus
**Mean values in the same column followed by the same letter are not significantly different at the 0.01 level according to the Duncan’s test.
ns: not significant at p < 0.05.
refrigerator at 4 ± 1°C in polyethylene bags. In order to keep spha-
gnum moss moist in the stratification medium and for aeration, the
polyethylene bags were opened once a week during the stratifi-
cation period, and water was added as needed.
At the end of stratification, premature germination took place in all
treatments, except for Bioplin™. The number of prematurely germi-
nated seeds in each treatment was recorded, and the germination
percentages of these seeds were further analyzed in order to
determine the difference between the treatments. The prematurely
germinated seeds were not sown in the germination medium in the
greenhouse, and only those seeds that did not germinate at the end
of duration of stratification were sown. The seeds treated with warm
plus cold stratification were sown in peat-containing vials in the
plastic covered greenhouse on May 28, 2009. The misting irrigation
system was used with adequate moisture both in the greenhouse
and in the germination medium after the sowing of seeds.
Germination tests were carried out in greenhouse at 25°C day/15°C
night temperature and a relative humidity of 70%. A seed was
considered to have germinated when the cotyledons had emerged
above the soil surface, and it was recorded for up to 30 days.
Germinated seeds were counted and removed every 24 h for 30
days. Final germination percentage was calculated when no further
germination took place for several days. The germination percen-
tage (GP) was calculated for each experimental unit. Mean
germination time (MGT) was calculated using Equation (1) (Chuanren
et al., 2004)
MGT = nd/N
Where, n is the number of seeds that germinated between scoring
intervals; d the incubation period in days at that point in time and N
the total number of seeds that germinated in the treatment.
Experimental design and data analysis
A completely randomized plot design of 3 repetitions was used, and
each replication consisted of 25 seeds. The percentage of prema-
turely germinated seeds during cold stratification in the experiment,
the germination percentage of those seeds that were not
germinated at the end of the duration of cold stratification and sown
in the greenhouse immediately afterwards, the cumulative germina-
tion percentage of both prematurely germinated seeds and the
greenhouse-germinated seeds, and the MGT were analyzed using
SAS (1998) statistical analysis program. The germination percen-
tages were transformed into arcsine before analysis. After
evaluation, data were back transformed and original data presen-
ted. The mean values were compared by Duncan’s multiple range
test at the 0.01 probability level.
In this study, moisture content of seeds was 11.15%, and
weight of 1000 seeds was 20.9 g. Microbial inoculation
treatments significantly (p < 0.01) stimulated premature
germination during cold stratification. At the end of this
period, premature germination was observed in all treat-
ments, except for the Bioplin™. The highest premature
germination percentage was determined in the EM•1®
(69.3%), followed by B:seepel™ (52.0%) and Phosfert™
(44.0%). However, premature germination was 13.3% in
the seeds treated only with warm plus cold stratification
(control) (Table 1).
The germination percentages of seeds sown in the
greenhouse after cold stratification are presented in
Table 1. Statistically significant differences were determi-
ned between the germination percentages of the
treatments (p < 0.01). Among the treatments, the highest
germination percentage was obtained in the EM•1®
(100.0%), whereas the other treatments were included in
the same statistical group.
When the germination percentages of prematurely
germinated seeds at the end of the duration of stratifi-
cation and of greenhouse-germinated seeds were
considered together (cumulative germination percentage),
microbial inoculation treatments statistically significantly
affected cumulative germination percentage. All seeds
germinated with the EM•1®. Furthermore, Phosfert™ and
B:seepel™, with their germination per-centage of 84%,
were included in the same group with EM•1®. 66.7%
germination occurred in the seeds (control) which were
6506 Afr. J. Biotechnol.
Phosfert™ B:seepel™ Bioplin™ EM•1® Phosfert™ +
Figure 1. Effects of microbial inoculations on seed germination (%).
only stratified without any microbial inoculation treatments.
Mean germination time
No statistical difference in mean germination time was
found between microbial inoculation treatments and the
control treatment. Nevertheless, although no statistical
difference was found between treatments, the mean
germination time of the EM•1® (7.2 days) was 1.7 days
shorter than that of the control (Table 1).
This study showed that the germination percentage of oil
rose seeds was significantly affected by microbial
inoculation. During 150 days of cold stratification follo-
wing 4 weeks of warm stratification, premature germi-
nation was observed in seeds in all treatments, except for
the Bioplin™. This indicates that the stratification duration
of 150 days might be adequate to break dormancy of the
seeds of the species R. damascena. The most common
treatment to break dormancy of rose seeds is cold
stratification (Zlesak, 2007; Zhou et al., 2009), and the
degree of dormancy varies by species and duration of
stratification (Stewart and Semeniuk, 1965). For instance,
the species Rosa multiflora and Rosa setigera need 30
days of cold stratification; the species Rosa wichuraiana
needs 45 days of cold stratification; and R. setigera
'Serena' and Rosa x reverse need 90 days of cold
stratification to obtain maximum germination percentages
(Steward and Semeniuk, 1965). Moreover, it was
reported that a stratification duration longer than 150
days was needed to remove embryo dormancy of oil rose
seeds and that the germination percentage was over
80% through soaking seeds in 70 and 80% sulphuric acid
for 10 min followed by 150 to 180 days of stratifi-cation
(Hajian and Khosh-Khui, 2000). Higher germi-nation
percentages were obtained in this study. The higher
premature germination percentage of oil rose seeds in all
microbial inoculation treatments except for Bioplin™
during stratification than the control treatment might be
due to an increase in the number of microorganisms in
the seed pericarp during stratification and might be
because these microorganisms macerated the hard and
thick seed pericarp, thereby facilitating germination. A
similar case was reported by Morpeth et al. (1997) and
Morpeth and Hall (2000).
In this study, microbial inoculation treatments signifi-
cantly increased germination percentage in comparison
to the control. The results of the present study are also
supported by the findings of Morpeth and Hall (2000) in
Rosa corymbifera (95%) and of Belletti et al. (2003) in R.
canina (50.25%) that microbial inoculation to the seeds
increased germination percentage.
Among the treatments, the highest germination percen-
tages were obtained from the EM•1®, followed by the
Phosfert™ and B: speel™ (Figure 1). In both the prema-
turely germinated seeds during stratification and those
seeds that did not germinate during stratification but
germinated in the greenhouse immediately afterwards,
Kazaz et al. 6507
Phosfert™ B:seepel™ Bioplin™ EM•1® Phosfert™ +
Mean germination time (days)
Figure 2. Effects of microbial inoculation on mean germination time (days).
the lowest cumulative germination percentage was
obtained from the control treatment (66.7%). Although
there was no statistically significant difference between
the Phosfert™, B: speel™ and the control (which might
be because the EM•1® showed a very high germination
percentage), both treatments showed a 20.6% higher
germination percentage than that of the control treatment
in terms of cumulative germination percentages. It might
be stated that this percentage is quite high in commercial
The effect of treatments on the mean germination time
of oil rose seeds was statistically insignificant. However,
despite the statistically insignificant difference among
them, the mean germination times in EM•1® (7.2 days)
and B: speel™ (7.3 days) were 1.7 and 1.6 days shorter
than that of the control, respectively (Figure 2). Belletti et
al. (2003) reported that different doses of compost
activator treatments in R. canina further shortened the
mean germination time by 8.48 to 9.64 days in com-
parison to the control.
This study suggested that microbial inoculations greatly
increased the germination time and percentage of R.
damascena seeds and that all seeds particularly germi-
nated with the EM•1®. The observation of a high rate of
premature germination (69.3%) of the R. damascena
seeds during stratification with the EM•1® indicates that
the time required for stratification in this species might be
further reduced with the EM•1®. The inoculation of micro-
organisms to the seeds during preliminary treatment and
the development of microorganisms immediately after-
wards facilitated the germination of seeds. The study also
showed that 150 days of cold stratification (4 ± 1°C)
following 4 weeks of warm stratification (25oC) might be
enough to break dormancy. How long it takes for dorma-
ncy of the species R. damascena to be broken will be
clarified with further studies that we will be later
conducted on EM•1® and other microbial fertilizers with
different durations of stratification.
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