Abstract
The karyological analyses of 11 species, one taxon of which is endemic of Oxytropis (Fabaceae), distributed in Turkey were examined in this study. Among these taxa, the chromosome numbers were as follows: 2n = 16 in Oxytropis kotschyana, O. pallasii, O. pilosa, O. savellanica, O. persica, O. albana, O. argyroleuca, O. aucheri, O. karjaginii, O. lupinoides; and 2n = 96 in O. lazica. The karyotype analysis of taxa belonging to the genus Oxytropis was performed using Image Analysis System (Bs200Pro).
1. Introduction
Oxytropis DC. is considered the most closely related genus to Astragalus L. in its gross morphology. These two genera co-exist in the same environment and habitats. Although it differs from Astragalus only in keel petal (pointed versus obtuse) and pod septum (arising from adaxial suture versus abaxial), it was never considered in Astragalus after its separation by De Candolle (Citation1802). Recent molecular studies based on nrDNA ITS and chloroplast trnL intron data (Wojciechowski et al. Citation1999; Wojciechowski Citation2005) have demonstrated that Oxytropis is monophyletic and not nested within Astragalus sensu stricto, but forms a separate clade within the large Astragalean clade. It has also been shown that Oxytropis is a sister group of Astragalus which has Eurasian origin (Ranjbar et al. Citation2010). Based on cytological (Ledingham Citation1957, 1960) and morphological evidence, it has been suggested that Oxytropis evolved in Eurasia (Chaudhary et al. Citation2008). The genus Oxytropis has been revised by Karaman Erkul and Aytaç (Citation2013) who reduced its species to 11 and considered only one species as endemic to Turkey.
Cytogenetic studies of the genus Oxytropis are mostly based on the chromosome number. The somatic chromosome number of the genus has been found to be 2n = 16, 24, 32, 48, 56, 58, 64, 80, 94, 96, 98 (Gurzenkov Citation1973; Belaeva and Siplivinsky Citation1976; Rostovtseva Citation1977; Krogulevich Citation1976, Citation1978; Kovanda Citation1978; Engelskjon Citation1979; Moraldo and Valva Citation1980; Krasnoborov et al. Citation1980; Zhukova and Petrovsky Citation1980; Andreev Citation1981; Astanova and Abdusaljamova Citation1981; Dawe and Murray Citation1981a, 1981b; Strid and Franzen Citation1981; Petrovsky and Zhukova Citation1981; Löve and Löve Citation1982; Pogan Citation1982; Yurtsev and Zhukova Citation1982; Zhukova Citation1983; Krasnikova et al. Citation1983, Citation1984; Gurzenkov and Pavlova Citation1984; Rostovtseva Citation1984; Strid and Andersson Citation1985; Ashraf and Gohil Citation1986; Krusheva Citation1986; Probatova and Sokolovskaya Citation1986; Rudyka Citation1986; Jurtsev Citation1988; Yan et al. Citation1989; Zhang and Ma Citation1989; Lavrenko et al. Citation1990; Zakharjeva Citation1990; Jahan et al. Citation1994; Starlinger et al. Citation1994; Stepanov Citation1994; Wang et al. Citation1994; Zhang et al. Citation1994; Gu and Sun Citation1996; Pavlova Citation1996; Gervais et al. Citation1997; Favarger Citation1997; Aedo et al. Citation1998; Filippov et al. Citation1998; Gervais and Blondeau Citation1999; Zhu and Ohashi Citation2000; Yan et al. Citation1995, 2000; Volkova et al. Citation2003). Several cytological publications have been written about Fabaceae family in recent years (Martin et al. Citation2008; Pedro and Delgado-Salinas Citation2009; Hejazi et al. Citation2010; Sepet et al. Citation2011).
Karyological knowledge needs to be used in conjunction with other sources of data to achieve a better understanding of the cytologic relationship of Oxytropis taxa, leading to their natural classification. In this study, meristematic root tips were obtained from all species of the genus for karyotype analysis. As well as the underlying somatic chromosome numbers, the chromosome data obtained by Image Analysis System were used to analyze chromosome morphology.
2. Materials and methods
The specimens were collected and identified by SKE and ZA. Localities of the plant material used in this study and collectors are shown in Table .
Table 1. The studied taxa and their collection locations.
The karyological study of the genus Oxytropis within the taxa was conducted on the meristematic cells of root tips. The root cells, grown in the dark at room temperature, were laid into α-mono-bromonaphthalene solvent and kept for 16 h in the refrigerator during the pretreatment procedure. Afterwards, the root tips were fixed in 3:1 absolute alcohol, glacial acetic acid and stored in a refrigerator in 70% alcohol. The root tips were painted at room temperature in 1N HCl with 2% aceto-orcein for 2 h. The mitotic metaphase cells determined under a light microscope were transferred to a computer. Finally, karyological analyses of the taxa were conducted with Image Analysis System (Bs200Pro; http://www.bab.com.tr/prgdis.php?prog_id=bssito&dilsec=1).
Chromosomes were classified using the nomenclature of Levan et al. Citation(1964). Karyotype analyses of mitosis metaphase were obtained for 10 different root tips from each taxa.
3. Results
The chromosome number and karyomorphology of Oxytropis kotschyana, O. pallasii, O. pilosa, O. savellanica, O. persica, O. albana, O. lazica, O. argyroleuca, O. aucheri, O. karjaginii, and O. lupinoides were determined. Detailed morphological characteristics of the somatic chromosomes are given in Figure . The idiogram of taxa is shown in Figure . The characteristics of somatic chromosomes in studied taxa are given below.
Figure 1. Mitotic metaphase chromosomes of Oxytropis. (a) O. kotschyana; (b) O. pallasii; (c) O. pilosa; (d) O. savellanica; (e) O. persica; (f) O. albana; (g) O. lazica; (h) O. argyroleuca; (i) O. aucheri; (j) O. karjaginii; (k) O. lupinoides. Bar: 10 μm.
Figure 2. Idiograms of Oxytropis taxa. (a) O. kotschyana; (b) O. pallasii; (c) O. pilosa; (d) O. savellanica; (e) O. persica; (f) O. albana; (g) O. lazica; (h) O. argyroleuca; (i) O. aucheri; (j) O. karjaginii; (k) O. lupinoides. Bar: 10 μm.
The somatic chromosome number of Oxytropis kotschyana was obtained as 2n = 16 (Figure. a). The chromosome length ranges between 1.56 and 3.03 μm. Chromosome arm ratios were measured as 1.29–1.65 μm and the karyotype formula is 8m. The centromeric index values varied between 3.32 and 6.71, and relative lengths ranged from 8.38 to 16.26. The haploid chromosome length is 18.66 μm. The asymmetry index is 0.0004. An ideogram of the taxon was drawn using the Image Analysis System (Figure a).
The somatic chromosome number of Oxytropis pallasii was obtained as 2n = 16 (Figure b). The chromosome length ranges between 1.41 and 2.10 μm. Chromosome arm ratios were measured as 1.31–2.13 μm and the karyotype formula is 6m+2sm. The centromeric index values varied between 4.12 and 5.67, and relative lengths ranged from 10.04 to 14.91. The haploid chromosome length is 14.07 μm. The asymmetry index is 0.0001. An ideogram of the taxon was drawn using the Image Analysis System (Figure b).
The somatic chromosome number of Oxytropis pilosa was obtained as 2n = 16 (Figure c). The chromosome length ranges between 1.53 and 2.42 μm. Chromosome arm ratios were measured as 1.00–2.16 μm and the karyotype formula is 1M+5m+2sm. The centromeric index values varied between 3.98 and 5.83, and relative lengths ranged from 10.09 to 15.98. The haploid chromosome length is 15.14 μm. The asymmetry index is 0.0002. An ideogram of the taxon was drawn using the Image Analysis System (Figure c).
The somatic chromosome number of Oxytropis savellanica was obtained as 2n = 16 (Figure d). The chromosome length ranges between 1.63 and 3.21 μm. Chromosome arm ratios were measured as 1.30–2.03 μm and the karyotype formula is 6m+2sm. The centromeric index values varied between 3.50 and 6.52, and relative lengths ranged from 8.83 to 17.37. The haploid chromosome length is 18.49 μm. The asymmetry index is 0.0005. An ideogram of the taxon was drawn using the Image Analysis System (Figure d).
The somatic chromosome number of Oxytropis persica was obtained as 2n = 16 (Figure e). The chromosome length ranges between 2.83 and 4.25 μm. Chromosome arm ratios were measured as 1.18–2.23 μm and the karyotype formula is 6m+2sm. The centromeric index values varied between 3.31 and 7.12, and relative lengths ranged from 10.33 to 15.50. The haploid chromosome length is 27.45 μm. The asymmetry index is 0.0003. An ideogram of the taxon was drawn using the Image Analysis System (Figure e).
The somatic chromosome number of Oxytropis albana was obtained as 2n = 16 (Figure f). The chromosome length ranges between 2.30 and 3.64 μm. Chromosome arm ratios were measured as 1.30–2.30 μm and the karyotype formula is 7m+1sm. The centromeric index values varied between 3.75 and 6.71, and relative lengths ranged from 9.87 to 15.59. The haploid chromosome length is 23.36 μm. The asymmetry index is 0.0003. An ideogram of the taxon was drawn using the Image Analysis System (Figure f).
The somatic chromosome number of Oxytropis lazica was obtained as 2n = 96 (Figure g). The chromosome length ranges between 0.79 and 3.50 μm. Because the chromosomes of the taxon are very small, centromeres and the type of chromosomes could not be determined and chromosome morphology of the mitotic metaphase chromosomes of taxon is investigated according to their total length. The haploid chromosome length is 84.46 μm. The asymmetry index is 0.0004. An ideogram of the taxon was drawn using the Image Analysis System (Figure g).
The somatic chromosome number of Oxytropis argyroleuca was obtained as 2n = 16 (Figure h). The chromosome length ranges between 1.65 and 2.52 μm. Chromosome arm ratios were measured as 1.17–2.00 μm and the karyotype formula is 7m+1. The centromeric index values varied between 4.31 and 6.79, and relative lengths ranged from 9.70 to 14.81. The haploid chromosome length is 17.01 μm. The asymmetry index is 0.0002. An ideogram of the taxon was drawn using the Image Analysis System (Figure h).
The somatic chromosome number of Oxytropis aucheri was obtained as 2n = 16 (Figure i). The chromosome length ranges between 1.76 and 3.30 μm. Chromosome arm ratios were measured as 1.15–1.67 μm and the karyotype formula is 7m+1sm. The centromeric index values varied between 3.25 and 6.89, and relative lengths ranged from 9.13 to 17.10. The haploid chromosome length is 19.29 μm. The asymmetry index is 0.0004. An ideogram of the taxon was drawn using the Image Analysis System (Figure i).
The somatic chromosome number of Oxytropis karjaginii was obtained as 2n = 16 (Figure j). The chromosome length ranges between 1.32 and 2.76 μm. Chromosome arm ratios were measured as 1.08–1.63 μm and the karyotype formula is 8m. The centromeric index values varied between 3.36 and 6.93, and relative lengths ranged from 7.60 to 15.82. The haploid chromosome length is 17.43 μm. The asymmetry index is 0.0006. An ideogram of the taxon was drawn using the Image Analysis System (Figure j).
The somatic chromosome number of Oxytropis lupinoides was obtained as 2n = 16 (Figure k). The chromosome length ranges between 1.77 and 3.18 μm. Chromosome arm ratios were measured as 1.24–1.68 μm and the karyotype formula is 8m. The centromeric index values varied between 3.47 and 6.65, and relative lengths ranged from 8.95 to 16.03. The haploid chromosome length is 19.84 μm. The asymmetry index is 0.0003. An ideogram of the taxon was drawn using the Image Analysis System (Figure k).
4. Discussion
It is determined that the caryotype formule of Oxytropis kotschyana, O. karjaginii, and O. lupinoides is 8m, O. pallasii, O. savellanica, and O. persica is 6m+2sm, O. albana, O. argyroleuca, and O. aucher is 7m+1sm, and O. pilosa is 1M+5m+2sm. This also indicates that chromosome morphology between species is specific to these taxa.
The shortest chromosome was 0.79 μm (O. lazica), and the longest chromosome was 4.25 μm (O. persica). O. pilosa had the smallest arm ratio (1.00), and O. albana had the largest arm ratio (2.30). According to the centromeric index, the O. aucheri had the smallest index value (3.25), and O. persica. O. karjaginii had the largest (7.12). O. pallasii had the shortest total length of haploid complement (14.07 μm), and O. persica had the longest (27.45 μm). O. pallasii had the smallest asymmetry index (0.0001), and O. karjaginii had the largest asymmetry index (0.0006).
Oxytropis differs from Astragalus by having a beak on the keel petal. The beak is very distinct at the Oxytropis taxa except O. lazica. Additionally, it is also located in the key of section Hypoglottis of genus Astragalus in the Flora of Turkey(Chamberlain and Mathews Citation1970). The chromosome number of O. lazica is determined to be 2n = 96, different from other species. O. kotschyana, O. pilosa, and O.pallasi are caulescent among Oxytropis species distributed in Turkey; the rest is acaulescent. Besides, in addition to these species, O. aucheri, O. argyroleuca, O. karjaginii, and O. lupinoides are spread over steppes, and the rest are alpine plants.
It is determined that the habitat altitude and stem structure (caulescent/acaulescent) of the Oxytropis species distributed in Turkey do not affect the somatic chromosome number, chromosome length, arm ratios, karyotype formula, centromeric index, relative lengths ratio, total haploid chromosome length, or the asymmetry index.
Acknowledgment
This work was supported by the Scientific and Technological Research Council of Turkey [TBAG-105T180 and 113Z899].
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References
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