Download Cytogenetic studies on Quercus L. (Fagaceae) species belonging to

CARYOLOGIA
Vol. 64, no. 3: 297-301, 2011
Cytogenetic studies on Quercus L. (Fagaceae) species belonging to
Ilex and Cerris section in Turkey
YILMAZ1,* AYKUT, EMEL USLU2 and M. TEKIN BABAÇ2
1
Department of Biology, Faculty of Science and Arts, Hitit University, 19030 Çorum, Turkey
Department of Biology, Faculty of Science and Arts, Abant Izzet Baysal University, Bolu, Turkey
2
Abstract — A detailed karyotype analyses of the five species of Quercus L. (Q. coccifera L., Q. ilex L., Q. aucheri
Jaub. & Spach, Q. cerris L. and Q. ithaburensis Decne subsp. macrolepsis (Kotschy) Hedge & Yalt.) belonging to
Ilex and Cerris section were examined. The somatic chromosome number of all studied taxa 2n = 24 was found.
The karyotypes of investigated species showed the great similarity with the chromosome length and the position
of centromere. Chromosome number and detailed karyotype of these species were first time counted from Turkey.
Key words: cerris, ilex, Karyotype analyses, Quercus, Turkey.
INTRODUCTION
The genus Quercus belongs to the family
Fagaceae which represents broad leaved species
of the nothern hemisphere. The biggest and the
best- known group of this family is the Quercus
genus with about 600 species in the world.
Turkey is one of the most important region
for Quercus genus according to species number
and distribution of species. The genus Quercus
is represented by 18 species in three sections
in Turkey (HEDGE and YALTIRIK 1982; YALTIRIK
1984). The species that were analysed in this
study belonged to different Quercus sections,
such as Quercus coccifera, Quercus ilex and
Quercus aucheri: section Ilex, Quercus cerrris and
Quercus ithaburensis: section Cerris. These two
section species are found to be more close than
those Section Quercus in recent studies (BELLAROSA et al. 2005; PAPINI et al. 2011).
The systematic relationships in the genus are
not completely clear (NIXON 1993). In other word,
oak taxonomy is still debatable, despite various
morphological, ecological, chemo-taxonomical,
*Corresponding author: e-mail [email protected]
molecular and recently cpDNA studies (BIANCO
and SCHIRONE 1985; BELLAROSA et al. 1990; NIXON
1993; BORDACS et al. 2002; DUMOLIN et al. 1995;
DUMOLIN-LAPEGUE et al. 1999; FINESCHI et al.
2002; SOLTIS et al. 1992; PETIT et al. 1997).
Especially, because of wide spread introgressive hybridization (BORAZAN and BABAÇ 2003)
the genus Quercus is one of the most problematic groups in the world. Taxonomic problems
can be solved by molecular and cytological studies but however, especially cytological studies on
oak species are still insufficient (OHRI and AHUJA
1990; ZOLDO et al. 1998). Therefore; we aimed
to identify any hybrid relations between the two
Quercus sections’ (Ilex and Cerris) member by
cytological analysis.
In this study, detailed karyotype morphology
of five species (Q. coccifera, Q. ilex, Q. aucheri,
Q. cerris, Q. ithaburensis) belonging to Ilex and
Cerris section of Quercus genus is reported.
MATERIALS AND METHODS
Acorns of five different species were collected from various sites of Turkey. Three to
five acorns from each localities of the studied
species were collected (Table 1). Acorns of
samples were germinated at 4°C in a refrigerator for karyotype studies. As a first treatment,
298
YILMAZ , USLU
and BABAÇ
Fig. 1 — Somatic chromosomes of a) Q. coccifera b) Q. ilex c) Q. aucheri d) Q. cerris e) Q.
ithaburensis.
actively growing root tips were pre-treated in
α-monobromonaphthalene for 16 hours at 4 °C,
and then, fixed for over night in 3:1 absolute
alcohol-glacial acetic acid mixture. Fixed materials were stored in 70 % alcohol at refrigerator
untill analyses. Afterwards, the root tips were
hydrolyzed in 1 N HCl for 30 minutes at 60 °C
and then stained with Feulgen stain for 2 hours.
Squashes were made in a drop of 2 % acetoorcein. The preparations were frozen in liquid
nitrogen and made permanent with Entellan.
Chromosome pairs were identified according
to the nomenclature of STEBBINS (1971). Chromosome lengths, centromeric index and the ra-
299
CYTOGENETIC STUDIES ON QUERCUS L .
Fig. 2 — Idiograms of a) Q. coccifera b) Q. ilex c) Q. aucheri d) Q. cerris e) Q. ithaburensis.
TABLE 1 — Localities, chromosome number, karyotypic description and length range of studied oaks.
Species
Q. coccifera
Locations
Somatic chromosome
Karyotypic description
number
Length range (µm)
Uşak, Hatay
2n=24
24 m.
(0.80-1.98)
Q. ilex
Zonguldak, Düzce
2n=24
24 m.
(1.07-2.05)
Q. aucheri
Aydın, İzmir, Muğla
2n=24
24 m.
(1.12-2.56)
Balıkesir
2n=24
24 m.
(0.99-2.11)
Çanakkale, Balıkesir
2n=24
24 m.
(0.90-2.06)
Q. cerris
Q. ithaburensis
tio between the largest and the smallest chromosomes (L/S) were calculated for each samples.
However, the karyotype asymmetry parameters
including centromeric index (Ic), intrachromosomic asymmetry index (A1) and interchromosomic asymmetry index (A2) were evaluated according to ROMERO ZARCO (1986).
RESULTS
Chromosomes of three species from Ilex and
two species from Cerris are investigated and
they are all found diploid with 2n=24 (Fig. 1).
Somatic chromosome number and karyotypic
description of samples are given in Table 1. The
averages of chromosomal lengths ranged from
0.80 to 2.56 µm. Among of the studied species,
Q. aucheri has the biggest chromosomes, while
Q. coccifera has the smallest chromosomes.
Karyotypic analysis of these species show that
somatic chromosomes of investigated species are
very small and similar having all median region
type chromosomes. Morphometric parameters
of species are given in Table 2.
In the comparison of five species of Quercus
according to haploid complement, Q.coccifera
has the smallest values. However, other species
have bigger haploid complements. Q. ithaburensis is the second smallest haploid complement
300
YILMAZ , USLU
among the studied species. All investigated
species showed very similar intrachromosomal
asymmetry (A1). When the results were evaluated on the basis of section for intrachromosomal
asymmetry (A1), species belonging to same section have closer A1 values. In other words, Cerris section members showed small A1 value than
those of section Ilex members (Table 2). However, in the comparison of interchromosomal
asymmetry (A2) Q. coccifera and Q. ithaburensis
had higher value than the other three species.
When the results were evaluated according to
centromeric index (Ic), species from Ilex section
have smaller Ic values than Cerris section.
Finally, it can be concluded that members of
the same section showed close morphometric
parameters.
and BABAÇ
burensis, were selected from section Cerris for
comparison. As Q. cerris is very common oak for
Turkey, Q. ithaburensis usually make hybrid with
this species (YALTIRIK 1984). The results showed
that both members of Cerris section were found
to be very close according to Ic and A1 values.
They were differentiated in regard of A2 as Q.
ithaburensis had the highest value even all among
studied species (Table 2). On the other hand,
members of Ilex section showed more variations
according to the length range of chromosomes
and haploid complements (Table 1-2). Especially
Q. coccifera showed the least haploid complement, 14.61 µm, among all the studied species.
This is important as the close species from this
section Q. aucheri, which showed the highest value according to the haploid complement, can be
differentiated from Q. coccifera (Table 2).
When Q. coccifera, Q. ilex and Q. cerris were
evaluated on the basis of chromosome number,
the same results were observed in other studies
but when other morphometric parameters were
used in the comparison like chromosome type,
haploid complement, A1 and A2 values, they are
not entirely matched (D’EMERICO et al. 19952000). Generally, this study results showed less
parametric values than Quercus species studied
by D’EMERICO et al. (1995-2000). This situation
can be reason for Quercus living in different geographical regions. Results were compared with
the other study made on Turkish Quercus species in terms of morphometric parameters like
chromosomal length, haploid complement, intrachromosomal asymmetry (A1) and interchromosomal asymmetry (A2), they are not shown
distinct values rather had quite similar values
(YILMAZ et al. 2008).
DISCUSSION
All the studied species chromosome numbers
are found 2n=24 (Fig. 1) and their idiograms
were presented in Figure 2. When the results
provided from this study are compared with
previous studies with regard to chromosome
number of the genus Quercus show similarity
(DUFFIELD 1940; STAIRS 1964; OHRI and AHUJA
1990; D’EMERICO et al. 1995-2000; ZOLDO et al.
1998; KUROKAWA and YONEZAWA 2004; YILMAZ et
al. 2008). In other word, results of study support
that the basic chromosome number of the genus
is n=12. However, the presence of chromosomal
differentiation among different oak species is reported by ZOLDO et al. (1998).
All the members of Ilex section were studied but only two species, Q. cerris and Q. itha-
TABLE 2 — Morphometric parameters of five investigated species of Quercus. L/S= largest/shortest chromosome; Ic=
centromeric index; A1= intrachromosomal asymmetry; A2= interchromosomal asymmetry. In parenthesis= standart
error of mean.
Species L/S
Haploid complement (µm)
Ic
A1
A2
Q. coccifera
2.47 (±0.21)
14.61 (±0.09)
44.80 (±0.37)
0.19 (±0.01)
0.27 (±0.10)
Q. ilex
1.91 (±0.12)
17.47 (±0.08)
44.10 (±0.35)
0.21 (±0.01)
0.20 (±0.08)
Q. aucheri
2.28 (±0.18)
19.76 (±0.11)
43.72 (±0.66)
0.22 (±0.02)
0.24 (±0.12)
Q. cerris
2.13 (±0.15)
17.33 (±0.09)
45.11 (±0.67)
0.18 (±0.02)
0.23 (±0.10)
Q. ithaburensis
2.28 (±0.18)
15.66 (±0.10)
45.40 (±0.47)
0.17 (±0.02)
0.28 (±0.10)
CYTOGENETIC STUDIES ON QUERCUS L .
Findings of this study showed clear separations
of two section members in many chromosomal
characters. But the differences are not too much.
Therefore, these species although belong to different sections, they still show parallelism with each
other. The molecular studies of section Cerris and
section Ilex were also found similar in many regions as they evolve from the common ancestor
(SIMEONE et al. 2009; BELLAROSA et al. 2005).
Distribution of Q. aucheri is restricted with
South West Anatolia and some Greek Islands. In
other word, Q. aucheri has not shown wide distribution and for this reason, it is not well known
species in the world. This is the first report of
chromosome number and detailed karyotype of
Q. aucheri. Another important point is Q. coccifera separated from Q. aucheri by having different chromosome haploid complements.
Acknowledgements — The authors thank to Biology departments of Hitit and Abant Izzet Baysal
Universities for providing financial supports.
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Received October 28th 2010; accepted September 4th 2011