New Chromosome Numbers in Scorzonera, subgenera Podospermum and Pseuodopodospermum (Cichorieae, Asteraceae)

Abstract

Somatic chromosome numbers of seven Scorzonera L. species collected from different localities in Iran were counted. Except for S. mucida with 2n=28, the other species exhibited a somatic number of 2n=14. The chromosome numbers support the basic number (x=7) of Scorzonera. The chromosome numbers in S. tunicata, S. kandavanica, S. persepolitana, S. mucida, and S. raddeana are reported for the first time. Chromosome numbers in S. luristanica and S. songorica are different from those of the previous reports.

The genus Scorzonera L. (Asteraceae, Cichorieae, Scorzonerinae), with approximately 175 species belonging to the subtribe Scorzonerinae Dumort. of the tribe Cichorieae is widely spread among the arid regions of Eurasia and North Africa (Bremer 1994, Mabberley 2008, Norouzi et al. 2016). The genus is represented by 56 species in Iran (Rechinger 1977, Safavi et al. 2013, Safavi 2016), of which 20 species are endemic for the flora of Iran. Therefore, Iran is an important center of diversity for Scorzonera. Nazarova (1997) conducted the most comprehensive cytological study on Scorzonera and reported the karyotype analysis of 22 species as well as reviewed previous chromosome numbers mentioned in Scorzonera. Considering recent papers, chromosome numbers have been determined for 14 Iranian species (Safavi 1999, Ghasemi et al. 2015, Bordbar et al. 2019). Therefore, in cytogenetic terms, the species belonging to the Scorzonera have been insufficiently studied. The present study aims to expand chromosomal information, which may play a positive role in resolving the taxonomical problems of this genus.

Materials and methods

The cytological investigations were based on the least of five metaphase cells of the 1–5 individual(s) from localities in Iran, including the following taxa: Scorzonera mucida Rech. f. Aell. & Esfand., S. tunicata Rech. f. & Koeie, S. raddeana C. Winkl., S. kandavanica Reh. f., S. luristanica Reh. f., S. songorica (Kar. & Kir.) Lipsch. &Vassilcz and S. persepolitana Boiss. Table 1 presents their localities. We followed the broadly defined classification of Scorzonera (Rechinger 1977).

Table 1. Name of the plant species, locality information.

Taxon	Locality information, Altitude, Longitude-latitude, and Voucher no.
Subgen. Pseuodopodospermum (Lipsch. & Krasch.) Lipsch.
S. mucida Rech. f. Aell. & Esfand.	Iran, SE, NE Kerman, Deh Bala village, 1978 m, N30°19′18″, E57°12′51.4″, 31.V.2015, Bordbar and Makki 3000 (MIR)
S. tunicata Rech. f. & Koeie	Iran, NE, Khorassan, 32 km from Birjand to Qa’en, 1991 m, N33°08′76.7″, E59°17′15.6″, 07.V.2015, Mirtadzadini 2158 (MIR)
S. raddeana C. Winkl.	Iran: S, Fars, the pass between Estahban and Niriz (old road), 1918 m, N29°08′39.8″, E54°07′27.2″, 03.V.2016, Mirtadzadini, Attar and Ra’i 2157 (MIR)
Subgen. Podospermum (DC) Lipsch.
S. kandavanica Reh. f.	Iran: N, 6 km from Lowshan to Jirandeh, 1007 m, N36°40′41.4″, E49°34′10.0″, 20.V.2016, Mirtadzadini 2212 (MIR)
S. luristanica Reh. f.	Iran: W, Kermanshah, between Quriqala and Paweh, 1803 m, N34° 57′ 28.9″, E46°26′46.5″, 26.V.2016, Mirtadzadini, Attar and Ra’I, 2213 (MIR)
S. songorica (Kar. &Kir.) Lipsch. & Vassilcz	Iran: S, Kerman, on the road of Golbaf, near Abolfazl Mosque, 14.IV.2016, Mirtadzadini 2247 (MIR)
S. persepolitana Boiss.	Iran: North, 7 km from Zanjan to Bijar, 1669 m, N36°38′37.8″, E48°26′22.7″, 22.V.2016, Mirtadzadini 2215 (MIR)

The ripe achenes were obtained from plants that were conserved and deposited in the herbarium of Shahid Bahonar University of Kerman (MIR). Mitotic chromosome preparations were obtained from the root tips of germinating seeds on a wet filter paper in Petri dishes at room temperature. Root tips of 1–2 cm were cut off and pretreated with 0.2% α-monobromonaphthalene at 4°C for 8 h, then they were fixed in a fresh Carnoy fixative (3 : 1, ethanol : glacial acetic acid) for 24 h and stored at 4°C until use. The root tips were washed in distilled water to remove the fixative, hydrolyzed in 1 M HCl for 5–7 min at 60°C and stained in aceto-iron haematoxylin for 24 h at 30°C according to Bordbar et al. (2017). Squashing was gently carried out in a drop of 45% acetic acid on a slide glass. Using an Olympus BH-2 microscope equipped with a digital camera, the best mitotic metaphases of at least five cells in each plant were photographed.

Results and discussion

Figure 1 presents Mitotic-metaphase chromosome plates of the examined species. The results are presented below based on the subgeneric position of species according to Rechinger (1977).

Fig. 1. Metaphase chromosomes of Scorzonera. A) S. mucida, B) S. tunicata, C) S. raddeana, D) S. kandavanica, E) S. luristanica, F) S. songorica, G) S. persepolitana. Scale bar=10 µm.

Subgen. Pseuodopodospermum (Lipsch. & Krasch.) Lipsch.

S. mucida is endemic to Iran and widely distributed all over the country (Rechinger 1977). The chromosome number of this species was determined to be 2n=28 (Fig. 1A). This is the first chromosome count for this taxon.

S. tunicata is endemic to the north-east of Iran, Afghanistan, and Pakistan. This species possessed 2n=14 chromosomes (Fig. 1B). The chromosome number of this taxon is presented for the first time.

S. raddeana is distributed in Iran, Afghanistan, and Turkmenistan (Kopet Dagh region). The somatic chromosome number is 2n=14 (Fig. 1C). This is the first chromosome count for this species.

Subgen. Podospermum (DC) Lipsch.

S. kandavanica is endemic to Iran and is found in a limited area in the north of Iran. Our record of 2n=14 (Fig. 1D) for this taxon is presented here for the first time.

S. luristanica is endemic to Iran and Iraq. It possessed 2n=14 chromosomes (Fig. 1E).

S. songorica is distributed in Central Asia, Afghanistan, and Iran. The chromosome number in this species showed 2n=14 (Fig. 1F).

S. persepolitana is endemic to Iran and distributed in many parts of Iran. 2n=14 is the first report for this species (Fig. 1G).

The current study presents the chromosome numbers for seven Iranian species of Scorzonera. Five of the counts are new to science and two are in disagreement with the previous reports (Table 2). The basic chromosome numbers reported in Scorzonera are x=6 and x=7 (Nazarova 1997, Safavi 1999, Winfield et al. 2006, Ghasemi et al. 2015). The basic number of x=10 reported in S. intricata is a rare number (Bordbar et al. 2019). It seems this species is an autotriploid species with the chromosome number of 2n=3x=21, and the chromosome number of 2n=20 is due to an aneuploidy event which is normal in triploid species. In this study, the basic chromosome number of seven species supports x=7. Among the Iranian Scorzonera species, the chromosome numbers of S. luristanica and S. songorica were reported as 2n=12 (Safavi 1999). In our study, these species had a chromosome number of 2n=14, which might suggest intraspecific variation in chromosome number.

Table 2. Previous and the present reported chromosome numbers of Scorzonera, subgenera Podospermum and Psuodopodospermum

Taxon	2n	Source of reference
Subgen. Psuodopodospermum
S. leptophylla (DC.) Krasch. & Lipsch.	14	Nazarova (1980)
S. mucida	28	This study
S. phaeopappa (Boiss.) Boiss.	14	Safavi (1999)
S. tunicata	14	This study
S. turkeviczii Krasch. & Lipsch.	14, 28	Nazarova (1980, 1997)
S. raddeana	14	This study
Subgen. Podospermum
S. armeniaca (Boiss. & Huet.) Boiss.	14	Nazarova (1975, 1980, 1997), Safavi (1999)
S. cana (C. Meyer) O. Hoffm.	14	Nazarova (1980), Kuzmanov and Georgieva (1983), Vitek et al. (1992), Dobea et al. (1997), Dimitrova (1999)
	28	Papanicolaou (1984)
S. kandavanica	14	This study
S. laciniata L.	14	Nazarova (1975, 1980), Safavi (1999), Vogt and Aparicio (1999)
S. luristanica	12	Safavi (1999)
	14	This study
S. meyeri (C. Koch) Lipsch.	14	Nazarova (1975, 1980)
S. persepolitana	14	This study
S. songarica Lipsch. & Vass.	14	Nazarova (1990)
S. songorica	12	Safavi (1999)
	14	This study

Therefore, by comparing our study with the previous studies with following the subgeneric classification used in the monographic study of the genus (Lipschitz 1964), Flora Iranica (Rechinger 1977), and flora of Iran (Safavi et al. 2013), we conclude that subgen. Podospermum and Pseuodopdospermum have somatic chromosome numbers of 2n=14 and 2n=28 and the basic chromosome number of x=7. However, the chromosome number variation in Scorzonera is low (mostly 2n=14), more extensive karyologic and genomic data are required to solve the chromosome evolution and, the taxonomic and phylogenetic relationships among Scorzonera species.

Acknowledgment

We would like to thank the Iran National Science Foundation (INSF) for their support.

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