Teka et al. BMC Complementary and Alternative Medicine (2015) 15:286
DOI 10.1186/s12906-015-0822-1
RESEARCH ARTICLE
Open Access
In vitro antimicrobial activity of plants used
in traditional medicine in Gurage and Silti
Zones, south central Ethiopia
Alemtshay Teka1,2*, Johana Rondevaldova3, Zemede Asfaw2, Sebsebe Demissew2, Patrick Van Damme1,3,
Ladislav Kokoska3 and Wouter Vanhove1
Abstract
Background: To overcome the escalating problems associated with infectious diseases and drug resistance,
discovery of new antimicrobials is crucial. The present study aimed to carry out in vitro antimicrobial analysis of
15 medicinal plant species selected according to their traditional medicinal uses in Gurage and Silti Zones, south
central Ethiopia.
Methods: Ethanol extracts of various plant parts were investigated for their antimicrobial activity against 20
bacterial and one yeast strains. The minimum inhibitory concentration (MIC) was determined by broth microdilution
method.
Results: Asparagus africanus, Guizotia schimperi, Lippia adoensis var. adoensis and Premna schimperi were active
against Candida albicans, Enterococcus faecalis and Staphylococcus aureus at a concentration of 512 μg/ml or lower.
Strong antibacterial activity (MIC ≥ 128 μg/ml) was observed for G. schimperi extract against 17 resistant and
sensitive Staphylococcus strains, at a concentration comparable to standard antibiotics. Moreover, this extract
showed higher antibacterial activity for the test against S. aureus ATCC 33591, ATCC 33592, SA3 and SA5 strains
(128–256 μg/ml) than oxacillin (512 μg/ml).
Conclusions: The study revealed in vitro antibacterial activity of plants used in folk medicine in south central
Ethiopia. The usefulness of these plants, in particular of G. schimperi, should be confirmed through further
phytochemical and toxicity analyses.
Keywords: Antibiotic-resistance, Anti-staphylococcal, Ethnomedicine, Ethnopharmacology, Guizotia schimperi
Background
Infectious diseases are an important cause of mortality and
morbidity, in all regions of the world. The increasing
emergence of antimicrobial resistance worsens the impact
[1, 2]. It has been shown that risk of negative clinical
consequences, mortality, and high treatment costs with
drug-resistant bacteria is generally higher compared to
patients infected with the same non-resistant bacteria [3].
* Correspondence: AlemtshayTeka.Sahile@UGent.be
1
Laboratory for Tropical and Subtropical Agriculture and Ethnobotany,
Department of Plant Production, Faculty of Bio-Science Engineering, Ghent
University, Coupure links, 653-9000 Ghent, Belgium
2
Department of Plant Biology and Biodiversity Management, College of
Natural Sciences, Addis Ababa University, P.O. Box 3434, Addis Ababa,
Ethiopia
Full list of author information is available at the end of the article
Increased prevalence of resistant bacteria, together with
lack and high cost of new generation drugs has escalated
infection-related morbidity and mortality particularly in
developing countries like Ethiopia [1, 4].
Numerous biochemical compounds obtained from medicinal plants possess important antimicrobial properties
[5]. Application of these compounds is preferred over
synthetic drugs as they have long been used in traditional
medicine and are considered safe to humans [6]. New and
effective antimicrobials identified from plants can consequently be considered in development of new drugs to
combat problems associated with drug resistance [7].
Using effective plant extracts to control human diseases
has the additional advantage of low production cost,
minimal environmental damage and higher accessibility to
© 2015 Teka et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
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Teka et al. BMC Complementary and Alternative Medicine (2015) 15:286
Page 2 of 7
rural communities [4, 8, 9]. Hence, medicinal plants are
expected to be the future alternative source of new
antimicrobial products [5, 10].
Treatment of infections with plant-derived compounds is
an age-old practice that is globally employed, especially in
developing countries [11, 12]. This point applies particularly
to Ethiopia, where dramatic geographic, climatic and cultural diversity contribute to a wide range of traditional
herbal knowledge and practices by the people [13, 14].
Numerous in vitro studies have been undertaken, and have
revealed the antimicrobial potential of herbal medicines
traditionally used in various regions of Ethiopia [11, 15–19].
However, many Ethiopian medicinal plants still await
scientific validation of their anti-infective properties.
The aim of this study was to assess in vitro antimicrobial activity of medicinal plant species selected based
on their traditional medicinal uses for infectious diseases treatment in local community of Gurage and Silti
Zones, south central Ethiopia. This analysis may also offer
a source of information to identify effective medicinal
plants against staphylococcal infections and facilitate selection of plants for further phytochemical investigation.
51.2 mg/ml, which was kept at −80 °C until use. Dried
residue yield figures (%) are shown in Table 1.
Methods
Selection of plants
Medicinal plants were collected from Gurage and Silti
Zones, south central Ethiopia. Specimens were collected,
pressed and identified by the first author and Melaku
Wondafrash, an expert from the National Herbarium
(ETH), through visual comparisons with authenticated
plant specimens and using taxonomic keys in the
volumes of Flora of Ethiopia and Eritrea [20–25]. Identifications were then authenticated by Prof. Sebsebe
Demissew of Addis Ababa University, Ethiopia. Voucher
specimens were deposited at the National Herbarium
(ETH), Addis Ababa University. Selection of plant species
was based on use reports of local informants and
traditional herbalists from the study area for treatment of
ailments caused by microbial agents. Ethnomedicinal use
reports of the 15 medicinal plant species selected, parts
used, and route of administration are summarized in
Table 1.
Preparation of plant extracts
Plant materials were air-dried and ground into powder
using an electric mill (GM100 Retsch, Germany). Each
powdered sample species (15 g) was macerated with
450 ml of 80 % ethanol and placed on a shaker
(200 rpm) (GFL3005, Germany) for 24 h. All procedures,
stated above, were carried out at room temperature.
Extracts were then filtered and concentrated using a
rotary vacuum evaporator (R-200 Buchi, Switzerland) at
40 °C. Dried residues were dissolved in 100 % dimethyl
sulfoxide (DMSO) to obtain a stock concentration of
Chemicals
Antibiotics ciprofloxacin (purity 99.5 %), oxacillin (purity ≥
81.5 %), tetracycline (purity ≥ 88 %) and tioconazole (purity
97 %), were purchased from Sigma-Aldrich (Prague, Czech
Republic). Potency of the powder was incorporated in the
formula for preparation of stock solutions according to
EUCAST [26]. DMSO (Penta, Czech Republic), ethanol
(Sigma-Aldrich, Czech Republic), and distilled water were
used as solvents. Cation-adjusted Mueller-Hinton broth
(MHB) (Oxoid, United Kingdom) equilibrated for testing
with Tris-buffered saline (Sigma-Aldrich, Czech Republic)
was used as a bacterial culture media.
Microorganisms
In this study, 20 bacterial strains and one yeast were
tested. The following American Type Culture Collection
(ATCC) standard strains were purchased from Oxoid
(United Kingdom) for analysis: Candida albicans ATCC
10231, Enterococcus faecalis ATCC 29212, Escherichia
coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853,
Staphylococcus aureus (ATCC 25923, ATCC 29213, ATCC
33591, ATCC 33592, ATCC 43300, ATCC BAA 976),
and S. epidermidis ATCC 12228. Ten clinical isolates of
antibiotic-sensitive as well as antibiotic-resistant S. aureus
strains (SA1, SA2, SA3, SA4, SA5, SA6, SA7, SA8, SA9,
SA10) were provided by University Hospital in Motol
(Prague, Czech Republic). Microorganism cultures were
stored in MHB at 4 °C until use. Prior to antimicrobial
tests, microorganisms were re-cultured at 37 °C for 24 h
(48 h for C. albicans).
Assessment of minimum inhibitory concentrations (MICs)
MICs were determined by the broth microdilution method
using 96-well microplates modified according to previous
recommendations for effective assessment of the antiinfective potential of natural products [27, 28]. An aliquot
of 100 μl of two-fold serial dilutions of each extract was
prepared in MBH, equilibrated with Tris-buffered saline, in concentrations ranging 4–512 μg/ml. For inoculum standardization, the turbidity of the bacterial
suspension was adjusted to 0.5 McFarland standard
(1.5 × 108 CFU/ml) using Densi-La-Meter II (Lachema,
Czech Republic) spectrophotometric device. This bacterial suspension was inoculated into each well, and
plates were incubated at 37 °C for 24 h (48 h for C.
albicans). Microorganism growth was measured as turbidity recorded at 405 nm using the Multiscan Ascent
Microplate Reader (Thermo Fisher Scientific, Waltham,
MA). The MIC was calculated as the lowest concentration that showed ≥ 80 % reduction of microbial growth
compared to extract-free growth control. Antibiotics
Teka et al. BMC Complementary and Alternative Medicine (2015) 15:286
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Table 1 Ethnomedicinal use profile of tested medicinal plants, parts used, route of administration (ROA) and dried residue plant
extract yield
No.
Botanical name [Family]
Local name
Part used
Ethnomedicinal
use (Local name)
ROA
Yield (%)
Collected site
Voucher no.
1
Apodytes dimidiata E.
Mey. ex Arn.
[Icacinaceae]
Wendemu, Gefe
Bark
Cholera (Ye-dengiya-qar)
Oral
29
08°09.349′ N
At-85
038°19.713′ E
2227 m a.s.l.
2
Asparagus africanus
Lam. [Asparagaceae]
Yefur ded
Bersama abyssinica
Fresen. [Melianthaceae]
Hureta
Leaf
Herpes zoster
Topical
21
08°01.370′ N
At-176
038°21.219′ E
2031 m a.s.l.
3
Seed
Dandruff, wound, skin
burn, scabies
Topical
33
08°15.799′ N
At-15
037°46.261′ E
1793 m a.s.l.
4
5
6
Cucumis ficifolius A.
Rich. [Cucurbitaceae]
Hulgerecho, Yafer
geranger, Yale tay,
Adeni debaqula
Root
Gladiolous abyssinicus
(Brongn. ex Lemaire)
Goldblatt & de Vos
[Iridaceae]
Enzerziye
Bulb
Guizotia schimperi
Sch. Bip. ex Walp.
[Asteraceae]
Mocho
Lippia adoensis Hochst.
ex Walp. var. adoensis
[Verbenaceae]
Kessie
Abdominal pain,
abdominal bloating,
jaundice (Qoya), anthrax
(Shem-itere), indigestion
Oral
Toothache
Topical
17
08°02.189′ N
At-157
038°31.220′ E
1826 m a.s.l.
41
08°08.024′ ′N
At-132
037°55.70′ E
2065 m a.s.l.
Leaf
Wound, dandruff
Topical
32
08°01.370′ N
At-45
038°21.219′ E
2031 m a.s.l.
7
Leaf
Toothache, abdominal
pain, diarrhea, indigestion
Oral, Topical
22
08°02.189′ N
At-59
038°31.220′ E
1826 m a.s.l.
8
Olinia rochetiana A.
Juss. [Oliniaceae]
Tife
Pavonia urens Cav.
[Malvaceae]
Menatef
Bark
Toothache
Topical
37
08°08.024′ N
At-93
037°55.70′ E
2065 m a.s.l.
9
Leaf
Diarrhea, indigestion,
excess vomiting
Oral
25
08°07.924′ N
At-191
038°21.969′ E
2143 m a.s.l.
10
Premna schimperi Engl.
[Lamiaceae]
Teqoqi
Pittosporum viridiflorum
Sis [Pittosporaceae]
Hunbosho
Leaf
Toothache
Topical
31
08°08.380′ N
At-122
038°20.445′ E
2143 m a.s.l.
11
Leaf
TB, pneumonia
Oral
34
07°43.752′ N
At-251
038°06.954′ E
2002 m a.s.l.
12
Polygala sadebeckiana
Gurke [Polygalaceae]
Shime yeter chiza,
Felfel, Qiteriye,
Root
Sida rhombifolia L.
[Malvaceae]
Badefacha
Root
Anthrax, toothache,
indigestion
Oral, Topical
Abdominal pain,
amoebiasis
Oral
57
08°15.799′ N
At-112
037°46.261′ E
1793 m a.s.l.
13
15
08°01.370′ N
At-13
038°21.219′ E
2031 m a.s.l.
14
Solanum incanum L.
[Solanaceae]
Embuay
Fruit
Dandruff, anthrax,
tonsillitis, wound
Oral, Topical
45
08°08.024′ N
037°55.70′ E
2065 m a.s.l.
At-155
Teka et al. BMC Complementary and Alternative Medicine (2015) 15:286
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Table 1 Ethnomedicinal use profile of tested medicinal plants, parts used, route of administration (ROA) and dried residue plant
extract yield (Continued)
15
Thunbergia ruspolii
Lindau [Acanthaceae]
(Endemic)
Yangacha qomet
Root
Abdominal pain
Oral
22
Leaf
Abdominal pain, general
malaise (Michi)
Oral
16
Cholera, abdominal
pain, hemorrhoids
Oral
08°08.024′ N
At-124
037°55.70′ E
2065 m a.s.l.
Root
ciprofloxacin, oxacillin, teteracycline and tioconazole
were used as positive controls. Oxacillin and teteracycline
were used as markers for methicillin and tetracycline
resistance, respectively. Solvents used did not inhibit bacterial growth at concentrations tested. We used S. aureus
ATCC 29213 as a quality-control strain for antibiotic
susceptibility. Results reported in this study are expressed
as the mode of MICs obtained from three independent
experiments that were assayed in triplicate.
Results
Extracts from leaves of four species (Asparagus africanus,
Guizotia schimperi, Lippia adoensis var. adoensis, Premna
schimperi) showed activity against some of the tested
microorganisms (Table 2). The extracts were active against
C. albicans, E. faecalis and S. aureus at a concentration
between 128 and 512 μg/ml. Guizotia schimperi, L.
33
adoensis var. adoensis and P. schimperi showed activity
against E. faecalis and S. aureus (MIC range from 128 to
512 μg/ml), whereas A. africanus inhibited growth of E.
faecalis (MIC = 512 μg/ml). Candida albicans was susceptible to G. schimperi and L. adoensis var. adoensis at highest
concentrations only (MIC = 512 μg/ml). Gram-negative
bacteria (E. coli and P. aeruguinosa) were resistant to all
ethanol extracts tested in this study.
The ethanol extract of G. schimperi, which showed
strong activity against E. faecalis and S. aureusas as compared with other plant extracts, was subjected to further
antibacterial analysis against 16 standard and clinical isolates of staphylococcal strains. The clinical isolates were
resistant to either oxacillin (MIC ≥ 4 μg/ml) or tetracycline
(MIC ≥ 16 μg/ml). Three isolates (SA2, SA3 and SA9)
were resistant to both antibiotics, and can be considered
as multidrug-resistant strains. Strong antibacterial activity
Table 2 Minimum inhibitory concentration (MIC) of the medicinal plant species extracts
MIC (μg/ml)
Enterococcus faecalis
ATCC 29212
Staphylococcus aureus
ATCC 25923
Escherichia coli
ATCC 25922
Pseudomonas aeruguinosa
ATCC 27853
Candida albicans
ATCC 10231
Apodytes dimidiata
–
Asparagus africanus
512
–
–
–
–
–
–
–
–
Bersama abyssinica
–
–
–
–
–
Cucumis ficifolius
–
–
–
–
–
Gladiolous abyssinicus
–
–
–
–
–
Guizotia schimperi
128
128
–
–
512
Lippia adoensis var. adoensis
256
256
–
–
512
Olinia rochetiana
–
–
–
–
–
–
–
–
–
–
Pavonia urens
–
–
Premna schimperi
512
512
Pittosporum viridiflorum
–
–
–
–
–
Polygala sadebeckiana
–
–
–
–
–
Sida rhombifolia
–
–
–
–
–
Solanum incanum
–
–
–
–
–
Thunbergia ruspolii
–
–
–
–
–
ATB
0.5a
0.5a
0.015a
0.125a
0.5b
ATB Antibiotics used as positive control
a
Ciprofloxacin
b
Tioconazole
“–” No inhibition (MIC > 512 μg/ml)
Teka et al. BMC Complementary and Alternative Medicine (2015) 15:286
Page 5 of 7
was observed for G. schimperi extract against all strains
tested at concentrations of 128–256 μg/ml (Table 3).
Moreover, this extract showed higher antibacterial activity
for tests against S. aureus ATCC 33591, ATCC 33592,
SA3 and SA5 strains (128–256 μg/ml) than oxacillin
(512 μg/ml). The same MIC values (128 μg/ml) were
obtained for G. schimperi extract as for tetracycline in the
test against ATCC 33592.
exhibiting higher activity (MIC ≤ 256 μg/ml) than oxacillin (MIC = 512 μg/ml). Togan et al. [32] described possible
differences in susceptibility patterns between standard and
clinical strains, in which clinical strains may represent
current isolates responsible for clinical disease and spread
of resistance.
To the best of our knowledge, no studies related to antimicrobial activity of G. schimperi (synonym of G. scabra
subsp. schimperi) have been published previously. This
annual weed named “Mocho” by the local people is very
close taxonomically to G. abyssinica and G. scabra [24]. It
is most likely the wild progenitor of G. abyssinica,
cultivated for its edible seeds and known for its medicinal
uses [33]. Chemical analysis of essential oils from G.
scabra leaves collected from Rwanda has characterized
germacrene-D, limonene and diterpenes as the principal
constituents. These components have been shown to
exhibit several medicinal properties [34, 35]. From a chemotaxonomic point of view, different plant species in a
genus often share similar chemical components [36]. In
view of these facts, the inhibition exhibited by G. schimperi
against standard and clinical isolates in particularly at
comparable concentration to standard antibiotics is very
promising for phytomedicine development, so phytochemical investigation of G. schimperi leaves is needed to identify
their antimicrobial active constituents.
Antimicrobial analysis of L. adoensis var. adoensis
extract showed activity against C. albicans, E. faecalis
and S. aureus. However, no activity against E. coli or P.
aeruginosa. In other studies, petroleum ether, chloroform, acetone and methanol extracts of L. adoensis var.
adoensis showed significant activity against E. coli and P.
aeruginosa [17] but were inactive against C. albicans
[16]. Wasihun et al. [17] reported presence of secondary
metabolites of L. adoensis responsible for its antimicrobial activity. The latter authors further showed that,
non-polar fractions have relatively better antimicrobial
activity compared to polar fractions. Motamedi et al.
[37] report that solubility of active principles in plant
materials varies according to extraction solvent used,
which may relate to differences in antimicrobial effect of
plant extracts [38]. Hence, the extraction solvents used in
this study could have caused variation in the antimicrobial
activity results.
Asparagus africanus extracts showed activity against E.
faecalis. Asparagus spp. contain steroidal saponins as
major bioactive constituents besides others including,
such as flavonoids, resins and tannins [39]. Our results
could reflect the bioactive constituents mentioned above.
Madikizela et al. [40] applied the broth microdilution
method and reported A. africanus ethanol extract as
inactive against S. aureus, which complements our results. We found that P. schimperi inhibited growth of E.
faecalis and S. aureus. Habtemariam et al. [19]reported a
Discussion
The extracts tested in the present study revealed the
potential of traditional medicinal plants in searching for
novel pharmaceuticals. We explored 15 plants used in the
Gurage and Silti Zones of Ethiopia. Gram-positive bacteria
were more sensitive to the medicinal plant extracts tested
than Gram-negative bacteria, consistent to previous
findings [29, 30]. The G. schimperi extract inhibited all
standard and clinical isolates of S. aureus tested. The latter
bacterium has been stated as one of the leading causes of
human infections, causing significant nosocomial illness,
generally via hospital-acquired infections [31]. It occurs
commonly in Ethiopia, and shows high levels of resistance
to commonly-used antibiotics [2]. In this study, antibacterial activity was most pronounced against ATCC
33591, ATCC 33592, SA3 and SA5, with G. schimperi
Table 3 In vitro anti-staphylococcal activity of Guizotia schimperi
extracts and of antibiotics oxacillin and tetracycline
MIC (μg/ml)
Standard strains
Oxacillin
Tetracycline
Extract
ATCC 12228
0.5
64
128
ATCC 29213
0.5
0.5
128
ATCC 33591
512
64
128
ATCC 33592
512
128
128
ATCC 43300
16
0.25
256
ATCC BAA 976
16
0.25
128
SA1
16
0.25
128
SA2
64
16
256
SA3
512
32
128
SA4
16
0.25
128
SA5
256
0.25
256
SA6
0.5
8
256
SA7
1
16
128
SA8
16
0.125
128
SA9
128
64
256
SA10
0.5
0.25
128
Clinical isolates
SA1-SA10 = resistant if MIC ≥ 4 μg/ml for oxacillin, ≥ 16 μg/ml for tetracycline [47]
MIC Minimum inhibitory concentration, ATCC American type culture collection,
SA Staphylococcus aureus
Teka et al. BMC Complementary and Alternative Medicine (2015) 15:286
novel diterpene in leaves as active against S. aureus,
which might explain the antibacterial activity of P. schimperi
in our study.
Extracts of Solanum incanum fruit (methanol, hexane
and chloroform) tested by disc diffusion and broth dilution
techniques showed no activity against E. coli, S. aureus and
P. aeruginosa [41], matching our findings. Alamri and
Moustafa [42] applied agar well diffusion to test ethanol
extracts of S. incanum fruit, and found it very active against
S. aureus, with less activity against P. aeruginosa and E. coli.
In a similar study, phenolic compounds were isolated from
S. incanum fruits, which could be responsible for inhibition
of S. aureus [42]. Concentration of active principles in
plants may vary with climate and across geography [15].
Moreover, different methodologies may contribute to differences in antibacterial activity, particularly in the case of our
S. incanum fruit extracts.
In the present study, some of the plant species tested on
antimicrobial activity showed no inhibition within the applied concentration ranges. Known medicinal plants, such
as Apodytes dimidiata (bark), Olinia rochetiana (bark)
and Polygala sadebeckiana (root), have been claimed to be
medicinally useful by local communities of the study area
and in previous scientific studies [29, 30, 43]. The methanol extracts of O. rochetiana bark exhibited antiviral
activity against measles virus [43], whereas the anticancer
agent, camptothecine, was isolated from the bark of A.
dimidiata [44]. For P. sadebeckiana, apart from the ethnomedicinal uses reported by Hailemariam et al. [45] in
Ethiopia (the root being used to cure liver disease, abdominal distention and snake bite), no information was found
on its medicinal use and antimicrobial effects. It is further
also possible that ethanol extract, plants that showed no
inhibition, is only active at higher concentrations than the
starting concentration (512 μg/ml) used in our study. In
general, the disparities between our findings and others
may result from differences in chemical composition of
extracts, effects of secondary metabolites including antiviral properties [46], geographic variation in antimicrobial
properties, or methodological considerations. Scientific
testing of medicinal properties thus need to consider these
diverse factors, such that application of different testing
methods and extraction solvents is important. Regarding
species that resulted inactive in this study, despite strong
claims of medicinal value, further analyses are needed
before more conclusions can be drawn.
Conclusions
The present study revealed the potential of some traditional
medicinal plants to be used as sources of antimicrobials.
The usefulness of these plants, in particular of G. schimperi,
should be confirmed through further phytochemical and
toxicity analyses.
Page 6 of 7
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
AT performed field data collection, carried out the main experimental work
and prepared first draft of the paper. JR and LK designed the experiment. All
authors read and approved the final manuscript.
Acknowledgements
We are grateful to University of Gondar (UoG), Ethiopia, for sponsoring the
study. The Research and Graduate Programs Office, Addis Ababa University
(AAU) is acknowledged for funding costs of field work. We would also like to
thank the local communities and informants for their support and for
sharing their knowledge on medicinal plant use. We are grateful to the staff
of the National Herbarium, Addis Ababa University, for their kind cooperation
in allowing us use of herbarium facilities. We are also indebted to the
Bijzonder Onderzoeksfonds (BOF), Ghent University (UGent), for providing
the travel grant for the laboratory work in Prague, Czech Republic. Czech
University of Life Sciences (CULS), Laboratory of Ethnobotany and
Ethnopharmacology, is deeply acknowledged for providing laboratory
facilities. Last but not least, we would like to thank Prof. Townsend Peterson
(University of Kansas Biodiversity Institute) for comments that greatly
improved the manuscript.
Author details
1
Laboratory for Tropical and Subtropical Agriculture and Ethnobotany,
Department of Plant Production, Faculty of Bio-Science Engineering, Ghent
University, Coupure links, 653-9000 Ghent, Belgium. 2Department of Plant
Biology and Biodiversity Management, College of Natural Sciences, Addis
Ababa University, P.O. Box 3434, Addis Ababa, Ethiopia. 3Department of Crop
Sciences and Agroforestry, Faculty of Tropical AgriSciences, Czech University
of Life Sciences Prague, Kamycka 129, 165 21 Prague 6-Suchdol, Czech
Republic.
Received: 1 May 2015 Accepted: 13 August 2015
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