ARTÍCULO

Investigation of the meiotic behavior in some Echinops L. (Asteraceae) species from Iran

BEHNAZ ALIJANPOOR¹, MASOUMEH SAFAEISHAKIB² & HAMIDEH JAVADII³

¹ Research Center of Agriculture and Natural Resource of Tehran Province, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran
² Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
³ Assistant Professor, Gene Bank of Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization, Tehran, Iran

ORCID iD. B. ALIJANPOOR: https://orcid.org/0000-0002-9698-2592, M. SAFAEISHAKIB: https://orcid.org/0000-0002-3557-0287, H. JAVADII: https://orcid.org/0000-0002-5805-6539

Author for correspondence: B. Alijanpoor (b.alijanpoor@gmail.com)

Editor: S. Garcia

ABSTRACT
Investigation of the meiotic behavior in some Echinops L. (Asteraceae) species from Iran.— Echinops L., is a genus of Asteraceae and contains ca. 76 species in Iran. The current investigation was performed on six species and nine populations including E. cephalotus, E. chorassanicus, E. elebursessis, E. leiopolycerus, E. ritroides and E. robustus. Chiasma frequency and distribution, chromosomal association and segregation were analyzed for meiotic characters. Meiotic irregularities, unreduced chromosomes and other related abnormalities were observed in the studied species. Chromosome stickiness, laggard chromosomes as well as frequent tripolar and multipolar cell formation due to anaphase I and II failure were observed.
KEY WORDS: Echinops; meiotic irregularities and abnormalities; unreduced pollen grains.

RESUMEN
Investigación sobre el comportamiento meiótico en varias especies de Echinops L. (Asteraceae) de Irán.— Echinops L., es un género de Asteraceae y contiene ca. 76 especies en Irán. La investigación actual se basa en seis especies y nueve poblaciones, incluidas E. cephalotus, E. chorassanicus, E. elebursessis, E. leiopolycerus, E. ritroides y E. robustus. La frecuencia y distribución de quiasmas, la asociación cromosómica y la segregación han sido analizadas para caracteres meióticos. En las especies estudiadas se han observado irregularidades meióticas, cromosomas no reducidos y otras anomalías relacionadas. Se observan también adherencia cromosómica, cromosomas rezagados, así como frecuentes formaciones de células tripolares y multipolares debido a fallos en la anafase I y II.
PALABRAS CLAVE: Echinops; granos de polen no reducidos; irregularidades y anomalías meióticas.

CONTENIDOS

INTRODUCTIONTop

Echinops L., belongs to family Asteraceae Bercht. & J. Presl, subfamily Carduoideae Cass. ex Sweet., tribe Cardueae Cass. (Cynareae Lam. & DC., Echinopsinae) (Susanna et al., 2006Susanna, A., Garcia-Jacas, N., Hidalgo, O., Vilatersana, R. & Garnatje, T. 2006. The Cardueae (Compositae) revisited: Insights from ITS, trnL-trnF, and matK nuclear and chloroplast DNA analysis. Annals of the Missouri Botanical Garden 93: 150–171. https://doi.org/10.3417/0026-6493(2006)93[150:TCCRIF]2.0.CO;2 ). Characters like compound inflorescence and single-flowered capitula congested into secondary inflorescences appearing as spherical or oval heads are the exceptional and diagnostic characteristics in this tribe. The taxa of this genus are mostly perennial with few annuals (Petit, 1997Petit, D. P. 1997. Generic interrelationships of the Cardueae (Compositae): A cladistic analysis of morphological data. Plant Systematics and Evolution 207: 173–203. https://doi.org/10.1007/BF00984388). Echinops encompasses approximately 120 species (Bobrov, 1997Bobrov, E. G. 1997. Echinops L. In: Shishkin, B. K. & Bobrov, E. G. (Eds.), Flora of the USSR 27. Bishen Singh Mahendra Pal Singh, Dehra Dun & Koeltz Scientific Books, Koenigstein: 1–70.; Susanna & Garcia-Jacas, 2007Susanna, A. & Garcia-Jacas, N. 2007. III. Tribe Cardueae Cass. (1819). In: Kadereit, J. W. & Jeffrey, C. (Eds.), The families and genera of vascular plants 8. Flowering plants: Eudicots. Asterales. Springer, Berlin & Heidelberg: 123–146. https://doi.org/10.1007/978-3-540-31051-8) occurring in the north and tropical Africa, the Mediterranean basin, and temperate habitats in Eurasia up to central Asia and north-eastern China. The Caucasus and the Middle East are the two regions where most species grow (Bobrov, 1962Bobrov, E. G. 1962. Echinops L. In: Shishkin, B. K. & Bobrov, E. G. (Eds.) Flora of the USSR 27. Academy of Sciences of the USSR, Moscow & Leningrad: 1–54.; Jäger, 1987Jäger, E. J. 1987. Arealkarten der Asteraceen-Tribus als Grundlage der ökogeographischen Sippencharakteristik. Botanische Jahrbücher fur Systematik, Pflanzengeschichte und Pflanzengeographie 108: 481–497.; Meusel & Jäger, 1992Meusel, H. & Jäger, E. J. 1992. Vergleichende Chorologie der Zentraleuropäischen, Band Flora III. Gustav Fischer, Stuttgart. https://doi.org/10.1002/fedr.19941050520; Susanna & Garcia- Jacas, 2009Susanna, A. & Garcia-Jacas, N. 2009. Cardueae (Carduoideae). In: Funk, V. A., Susanna, A., Stuessy, T. F. & Bayer, R. J. (Eds.), Systematics, Evolution, and Biogeography of Compositae. IAPT, Vienna: 293–313.; Sánchez-Jiménez et al., 2010Sánchez-Jiménez, I., Lazkov, G. A., Hidalgo, O. & Garnatje, T. 2010. Molecular systematics of Echinops L. (Asteraceae, Cynareae): A phylogeny based on ITS and trnL-trnF sequences with emphasis on sectional delimitation. Taxon 59: 698–708. https://doi.org/10.1002/tax.593003 ). For the Flora Iranica area almost 76 species were recorded in five sections (Rechinger, 1979Rechinger, K. H. 1979. Compositae III-Cynareae. In: Rechinger, K.H. (Ed.) Flora Iranica 139a. Akademische Druck und Verlagsanstalt, Graz: 1–85.) and subsequently Mozaffarian (2002Mozaffarian, V. 2002. [Systematic studies of Echinops L. (Asteraceae) in Iran]. PhD Thesis, Tehran University [in Persian]. , 2006Mozaffarian, V. 2006. A taxonomic survey of Echinops L. Tribe Echinopeae (Asteraceae) in Iran: 14 new species and diagnostic keys. The Iranian Journal of Botany 11: 197–239., 2008aMozaffarian, V. 2008a. [Compositae: Anthemideae and Echinopeae]. In: Assadi, M., Maassoumi, A. & Mozaffarian, V. (Eds.) Flora of Iran 59. Research Institute of Forests and Rangeland, Tehran: 262–391 [in Persian]. , bMozaffarian, V. 2008b. Four new plant species from Ilam province, Iran. The Iranian Journal of Botany 14: 87–94. ) and Mozaffarian & Ghahreman (2002aMozaffarian, V. & Ghahreman, A. 2002a. A new species of Echinops L. (sect. Oligolepis Bunge) from Iran. Pakistan Journal of Botany 34: 23–35. , bMozaffarian, V. & Ghahreman, A. 2002b. Three new species of Echinops (Compositae, Cynareae) from Iran. Botanical Journal of the Linnean Society 140: 181–186. https://doi.org/10.1046/j.1095-8339.2002.00063.x) added 19 new species of this genus to the treaty. About 50 species of Echinops are endemic to Iran. Hence, Iran is one of the most important diversification centers of this genus in the world (Montazerolghaem et al., 2017Montazerolghaem, S., Susanna, A., Calleja, J. A., Mozaffarian, V. & Rahiminejad, M. R. 2017. Molecular systematics and phylogeography of the genus Echinops (Compositae, Cardueae-Echinopsinae): focus on the Iranian centre of diversification. Phytotaxa 297: 101–138. https://doi.org/10.11646/phytotaxa.297.2.1).

In Asteraceae, the chromosome number ranges from n = 2 to n = 114 (Funk et al., 2005Funk, V. A., Bayer, R. J., Keeley, S., Chan, R., Watson, L., Gemeinholzer, B., Schilling, E., Panero, J. L., Baldwin, B. G., Garcia-Jacas, N., Susanna, A. & Jansen, R. K. 2005. Everywhere but Antarctica: using a supertree to understand the diversity and distribution of the Compositae. Biologiske Skrifter 55: 343–374. ) and high ploidy levels are present. Cytological investigations of Echinops have been mostly focused on chromosome number and karyotype analysis (Strid & Franzen, 1981Strid, A. & Franzen, R. 1981. In: Löve, A. (Ed.), Chromosome number reports LXXIII. Taxon 30: 829–842.; Moore, 1982Moore, D. M. 1982. Florn Biropaeci. Cambridge Press, London.; Goldblatt & Johnson, 1983Goldblatt, P. & Johnson, D. E. (Eds.) 1983. The family of Asteraceae. Index to plant chromosome number. Missouri Botanical Garden, St. Louis.; Ghaffari, 1999Ghaffari, S. M. 1999. Chromosome studies in the Iranian Asteraceae II. The Iranian Journal of Botany 8(1): 91–104. ; Sheidai et al., 2000Sheidai, M., Nasirzadeh, A. & Kheradnam M. 2000. Karyotypic study of Echinops (Asteraceae) in Fars Province, Iran. Botanical Journal of the Linnean Society 134: 453–463. https://doi.org/10.1111/j.1095-8339.2000.tb00542.x; Garnatje et al., 2004aGarnatje, T., Vallès, J., Garcia, S., Hidalgo, O., Sanz, M., Canela, M. A. & Siljak-Yakovlev, S. 2004a. Genome size in Echinops L. and related genera (Asteraceae, Cardueae): karyological, ecological and phylogenetic implications. Biology of the cell 96: 11–124. https://doi.org/10.1016/j.biolcel.2003.11.005, bGarnatje, T., Vilatersana, R., Susanna, A., Vallès, J. & Siljak-Yakovlev, S. 2004b. Contribution to the karyological knowledge of Echinops L. (Asteraceae, Cardueae) and related genera. Botanical Journal of the Linnean Society 145: 337–344. https://doi.org/10.1111/j.1095-8339.2003.00280.x; Sánchez-Jiménez et al., 2012Sánchez-Jiménez, I., Hidalgo, O., Canela, M. A., Siljak-Yakovlev, S., Šolić, M. E., Vallès, J. & Garnatje, T. 2012. Genome size and chromosome number in Echinops (Asteraceae, Cardueae) in the Aegean and Balkan regions: technical aspects of nuclear DNA amount assessment and genome evolution in a phylogenetic frame. Plant Systematics and Evolution 298: 1085–1099. https://doi.org/10.1007/s00606-012-0618-4 ). Chromosome numbers in Echinops range from 2n = 26 (E. gmelini Turcz) (Sánchez-Jiménez et al., 2009Sánchez-Jiménez, I., Pellicer, J., Hidalgo, O., Garcia, S., Garnatje, T. & Vallès, J. 2009. Chromosome numbers in three Asteraceae tribes from inner Mongolia (China), with genome size data for Cardueae. Folia Geobotanica 44: 307–322. https://doi.org/10.1007/s12224-009-9043-z) to 2n = 36 (E. transcaucasicus Iljin). Most of the reported chromosome numbers are 2n = 28, 30, 32, 34 and 36 (Ghaffari, 1999Ghaffari, S. M. 1999. Chromosome studies in the Iranian Asteraceae II. The Iranian Journal of Botany 8(1): 91–104. ; Sheidai et al., 2000Sheidai, M., Nasirzadeh, A. & Kheradnam M. 2000. Karyotypic study of Echinops (Asteraceae) in Fars Province, Iran. Botanical Journal of the Linnean Society 134: 453–463. https://doi.org/10.1111/j.1095-8339.2000.tb00542.x; Alijanpoor et al., 2019aAlijanpoor, B., Azizi, H., Mashayekhi, S. & Alijanpoor, M. 2019a. Karyotype analysis and new chromosome number reports of the genus Echinops L. (Asteraceae, Cardueae) from Iran. Iranian Journal of Botany 25: 49–55. https://doi.org/10.22092/ijb.2019.119245, bAlijanpoor, B., Azizi, H., Mashayekhi, S., Fallah, L. & Khodayari, H. 2019b. Karyological study of six Echinops L. species (Asteraceae: Cardueae) from Iran. Biharean Biologist 13: 66–70. ).

The main aim of this survey is to study the meiotic behavior and the pollen grain morphology in some Echinops species.

MATERIAL AND METHODSTop

Plant material

Floral buds of nine populations from six Echinops species were collected from Tehran and Alborz slope regions (April to August 2012) in different natural habitats. Voucher specimens are deposited in the herbariums IRAN (Iranian Research Institute of Plant Protection) and HSBU (Herbarium of Shahid Beheshti University), details are presented in Table 1. Species were identified based on Flora Iranica (Rechinger, 1979Rechinger, K. H. 1979. Compositae III-Cynareae. In: Rechinger, K.H. (Ed.) Flora Iranica 139a. Akademische Druck und Verlagsanstalt, Graz: 1–85.) and compared with the specimens deposited at these herbaria.

Meiotic studies

For the meiotic analysis, young flower buds, collected from at least 10 plants, were randomly selected. After being fixed in a mixture of ethanol and glacial acetic acid in a volume ratio (3:1) for 24 h, these were subsequently transferred to 70% ethanol for 24 h and stored at 5^°C until use. Meiocytes were prepared by squashing anthers and stained with acetocarmine (1%). Chromosome numbers were determined for a minimum of 100 metaphase/diakinesis pollen mother cells (PMCs), and 500 anaphase and telophase cells were analyzed for data collection from freshly prepared slides (Sheidai et al., 1999Sheidai, M., Saeed A. M. & Zehzad B. 1999. Meiotic studies of some Aegilops (Poaceae) species and populations in Iran. Edinburgh Journal of Botany 56: 405–419. https://doi.org/10.1017/S0960428600001359, 2002Sheidai, M., Koobaz, P., Termeh, F. & Zehzad, B. 2002. Phenetic studies in Avena species and populations of Iran. Journal of Sciences, Islamic Republic of Iran 13: 19–28.). Bright field images were obtained using an Olympus BX-60 microscope (Olympus, Tokyo, Japan).

Pollen grain analysis

Pollen fertility and size frequencies were analyzed through stain ability tests using 2% acetocarmine: 50% glycerin (1:1) for about 30 min (Sheidai et al., 2010Sheidai, M., Alijanpoor, B. & Khayyami, M. 2010. Contribution to cytology of genus Salvia L. (Lamiaceae) in Iran. Caryologia 63: 405–410. https://doi.org/10.1080/00087114.2010.10589753). Up to 1000 pollen grains were examined. Round complete pollen grains with stained nuclei were taken as apparently fertile while shriveled and unstained pollens were considered as infertile.

Statistical analyses

Student’s t-test analysis for the purpose of significant difference in mean total and relative chiasma frequency was performed. One-way analysis of variance (ANOVA) was applied with Duncan test to decide the contrasts between different Echinops species. The Pearson coefficient of correlation was applied to address the relationship between pollen fertility, anaphase, and telophase laggard chromosomes with extra chromosomes. In order to group the nine populations showing similar meiotic behavior, WARD and different methods of cluster analyses, including single linkage, UPGMA as well as ordination based on principal components analysis (PCA) were utilized (Sheidai et al., 2002Sheidai, M., Arman, M. & Zehzad, B. 2002. Chromosome pairing and B-chromosomes in some Aegilops (Poaceae) species and populations from Iran. Caryologia 55: 263–273. https://doi.org/10.1080/00087114.2002.10589286 ). For this analysis, at least 50 larger pollen grains and 50 smaller pollen grains were randomly measured. For the statistical analyses SPSS v16, and PAST v4.06b were used.

RESULTSTop

Meiotic abnormalities

The genus Echinops was studied cytogenetically, with chromosome counts 2n = 2x = 32 and 34. In E. ritroides (Haraz), many unreduced pollen grains (2n) were observed. Laggard chromosomes, anaphase and telophase II failure, chromosomes stickiness, abnormal tripolar, micronucleus, and quadrivalent formation were also observed. In E. eleborensis (Haraz), abnormal metaphase I/II, laggard, metaphase II failure, multipolar (tetrapolar and triad) were detected. In E. cephalotes, (Qarchak population), anaphase I/II failure, telophase failure, micronucleus, syncyte, multipolar, and normal pollen grains were seen, however, compared to the population of Khojir two meiotic characters such as anaphase II laggards and metaphase I stickiness were not observed. In E. chorassanicus (Polour population), anaphase I/II, metaphase I stickiness, laggard, and tripolar abnormalities were identified. While in the E. chorassanicus (Kamard) population anaphase I laggards and metaphase I stickiness were not observed. In E. leiopolycerus (Kamard population), metaphase I stickiness, telophase II failure, with variation in shape and size of unreduced pollen grains, was created. In E. leiopolycerus (Abali population), metaphase I/II anaphase II failure, syncyte, micronucleus, triad, tetrapolar, unreduced pollen grain with variation in shape and size revealed. Finally, in E. robustus (Qom) species all meiotic characters were gained except anaphase II laggard percentage (Table 2). The meiotic traits investigated in this study include terminal chiasmata/bivalent, intercalary chiasmata/bivalent, total chiasmata/bivalent, ring bivalent/cell, rod bivalent/cell, size of normal pollen grains (μm), and unreduced pollen grains (μm). Also, chromosomal abnormalities related to the behavior in metaphase I/II telophase I/II, laggard, anaphase II failure, telophase II failure, stickiness, micronucleus, diffuse, meiotic irregularities like tripolar and multipolar were studied [Fig. 3 (1–27)]. Duncan’s test presented a significant difference p < 0.05 in meiotic characteristics such as mean number of terminal chiasmata/bivalent (TXN), mean number of intercalary chiasmata/bivalent (IXN), mean number of total chiasmata/bivalent (TOXN) and size of normal pollen grain (NP) among the species and populations studied (Table 3).

Ploidy level and chiasma frequency

Among Echinops species, the highest mean number of terminal chiasmata and total chiasmata (31.25, 26.01) occurred in E. robustus (Qom population) and E. cephalotes (Khojir population), respectively, while the lowest mean number of the total, intercalary and terminal chiasmata was obtained in E. elbursensis (Emamzadeh Hashem), E. robustus (Qom) and E. cephalotes (Khojir) (4.45, 16.44 and 3.12, respectively) (Table 2). This study showed that mostly rod and ring shapes of diakinesis chromosomes process in meiosis-I metaphase. Additionally, pollen fertility showed >0.90%. The correlation test showed no significant correlation between relative total, terminal and intercalary chiasmata as well as ring and rod bivalents with change in chromosome number. Cluster analysis UPGMA and ordination according to principal components analysis (PCA) of meiotic characters generated similar outcomes (Figs. 1 and 2).

Figure 1. PCA plot analysis of meiotic data in the Echinops species and populations studied. The first component includes E. cephalotes (Khojir), E. cephalotes (Qarchak), and E. elbursensis (E-hashem). Other species such as E. robustus (Qom), E. ritroides (Abali), E. chorassanicus (Kamard), E. chorassanicus (Polour), E. leiopolycerus (Kamard) and E. leiopolycerus (Abali) belong to the second component. [View full size] [Descargar tamaño completo]

Figure 2. Cluster analysis (single linkage) of meiotic characters in Echinops species studied. [View full size] [Descargar tamaño completo]

Unreduced pollen grain formation

Pollen grains sizes of all six species were measured. The large pollen grains (unreduced pollen grains) were obtained in E. leiopolycerus (Abali population) (107.23 μm) and smaller pollen grains (normal) were from E. ritroides (Abali population) (44.44 μm) (Table 2). The pollen fertility of all species was more than 90%. It should be noted that a variety of shapes (oval and triangular) and size of pollen grains were also observed in studied species. Student’s t-test analysis disclosed a significant difference (p < 0.05) for the size between the larger and smaller size pollen grains in all species of Echinops [Fig. 3 (15, 20, 26)].

Figure 3a. (1–12) Echinops cephalotes (Khojir): (1), anaphase I; (2), syncyte; Qarchak population: (3), micronuclei formation (arrow); (4), diakinesis; (5), variation in shape and size of pollen grain (n, 2n, normal & infertile); E. chorassanicus (Polour): (6), diakinesis; (7), metaphase I stickiness; (8), leptotene; Kamard population: (9), telophase II (abnormal); (10), pollen grain (n, 2n); E. leiopolycerus (Kamard): (11), laggard (arrows); (12), metaphase II and laggard (arrow) [View full size] [Descargar tamaño completo]

Figure 3b. (13–27) Echinops cephalotes (Khojir): (13), diakinesis; Abali population: (14), anaphase II stickiness; (15), pollen grain (n, 2n); E. elbersensis (E-hashem): (16), diakinesis; (17), irregular tetrapolar; (18), failure anaphase I stickiness; (19), irregular tetrapolar; (20), pollen grain variation in shape (oval and triangular); E. robustus (Qom): (21), diakinesis; (22), failure anaphase I; (23), multipolar; (24), pollen grain (n, 2n); E. ritroides (Abali): (25), diakinesis; (26), pollen grain (n, 2n); (27), tetrapolar. Scale bar = 10 μm. [View full size] [Descargar tamaño completo]

DISCUSSIONTop

In the previous work of Sheidai et al. (2000) the chromosome number of E. leiopolyceras 2n = 30 was reported. Similarly, for E. ritrodes, the chromosome number was reported as 2n = 32 (Ghaffari, 1999Ghaffari, S. M. 1999. Chromosome studies in the Iranian Asteraceae II. The Iranian Journal of Botany 8(1): 91–104. ; Sheidai et al., 2000Sheidai, M., Nasirzadeh, A. & Kheradnam M. 2000. Karyotypic study of Echinops (Asteraceae) in Fars Province, Iran. Botanical Journal of the Linnean Society 134: 453–463. https://doi.org/10.1111/j.1095-8339.2000.tb00542.x). However, recent work of Alijanpoor et al. (2019bAlijanpoor, B., Azizi, H., Mashayekhi, S., Fallah, L. & Khodayari, H. 2019b. Karyological study of six Echinops L. species (Asteraceae: Cardueae) from Iran. Biharean Biologist 13: 66–70. ) did not support the previous results, pointing to 2n = 32 for E. leiopolyceras and 2n = 34 for E. ritrodes. These contradictions might be explained by aneuploidy, dysploidy or unstable chromosome number in Echinops species.

In two meiotic cells of E. ritroides a ring quadrivalent was observed, but it was not considered in the final analysis due to its low frequency. Such quadrivalents may be formed due to heterozygote translocations among two pairs of chromosomes (Sheidai et al., 2010Sheidai, M., Alijanpoor, B. & Khayyami, M. 2010. Contribution to cytology of genus Salvia L. (Lamiaceae) in Iran. Caryologia 63: 405–410. https://doi.org/10.1080/00087114.2010.10589753), conversely many univalent cases were observed in E. elbursensis. Dendrograms (Figs. 1 and 2) produced similar results which confirm previous reports (Rechinger, 1979Rechinger, K. H. 1979. Compositae III-Cynareae. In: Rechinger, K.H. (Ed.) Flora Iranica 139a. Akademische Druck und Verlagsanstalt, Graz: 1–85.; Mozaffarian 2008bMozaffarian, V. 2008b. Four new plant species from Ilam province, Iran. The Iranian Journal of Botany 14: 87–94. ) pointing toward the show close affinity between E. chorassanicus population and E. leiopolyceras population. E. robustus and E. ritrodes species are placed very close in the same clade. Comparatively, E. elbursensis remain closely related to E. cephalotes populations (Figs. 2 and 3). Chromosomal stickiness occurred in the early stages of prophase to the end of the meiotic stage in most of the studied species. Except for E. elbursensis, other species had unreduced pollen grains. However, in E. retroides its percentage was high (Table 2).

Some meiotic irregularities include laggard, anaphase, telophase II failures, stickiness, tripolar, and micronucleus, resulting in the formation of tripolar cells variation in pollen grain size with unreduced pollen grain (Bahattacharya, 1978Bhattacharya, S. 1978. Study of some Indian members of the genus Salvia with references to the cytological behaviour. Cytologia 43: 317–324. https://doi.org/10.1508/cytologia.43.317; Sheidai et al., 2010Sheidai, M., Alijanpoor, B. & Khayyami, M. 2010. Contribution to cytology of genus Salvia L. (Lamiaceae) in Iran. Caryologia 63: 405–410. https://doi.org/10.1080/00087114.2010.10589753; Alijanpoor & Safaeishakib, 2022Alijanpoor, B. & Safaeishakib, M. 2022. Cytomixis and meiotic abnormal behavior related in some species of the genus Salvia L. (Lamiaceae) from Iran. Acta Scientifica Malaysia (ASM) 6: 34–37. https://doi.org/10.26480/asm.02.2022.34.37). In E. ritroides (2n = 2x = 34) from the Abali population, about fifty percent of unreduced pollen grains were obtained. However, in this species some 2n = 32 cells were observed in meiosis. The main reason for this phenomenon is the presence of abnormalities, especially quadrivalents. On the other hand, there is a high level of stickiness observed in this species. Therefore, unreduced pollen grains with a variety of shapes (oval and triangular) in the studied species have been shown here [Fig. 3 (20)]. Moreover, tripolar and multipolar cell formations as meiotic irregularities can be due to anaphase I and II abnormality (Sheidai & Bagheri-Shabestarei, 2007Sheidai, M. & Bagheri-Shabestarei, E. S. 2007. Cytotaxonomy of some Festuca species and populations in Iran. Acta Botanica Croatica 66: 143–151.) [Fig. 3 (18, 22)]. Meiotic cells with double chromosome number of chromosomes may be due to syncyte formation and lack of anaphase separation. Moreover, in accordance with some reports, phenomena like cytomixis (the migration of the nuclei from one cell to another through special intercellular channels), anaphase failure and multipolar cell formation could be responsible for unreduced gamete formation in some plant species (Sheidai & Fadaei, 2005Sheidai, M. & Fadaei, F. 2005. Cytogenetic studies in some Bromus L. species section Genea Dum. Journal of genetics 84: 189–194. https://doi.org/10.1007/BF02715845; Sheidai & Bagheri-Shabestarei, 2007Sheidai, M. & Bagheri-Shabestarei, E. S. 2007. Cytotaxonomy of some Festuca species and populations in Iran. Acta Botanica Croatica 66: 143–151.). Abnormal meiosis behavior seems to be one of the reasons for infertility in pollen grains.

CONCLUSIONSTop

This accurate cytological study of Echinops species displayed that chromosome stickiness and anaphase failure, leading to meiocytes with double chromosome numbers and multipolar cells, might be considered as the possible mechanisms of the unreduced pollen grain shape.

ACKNOWLEDGEMENTSTop

The authors thank the Research Center of Agriculture and Natural Resource of Tehran Province “Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran” for the financial support for this study.

REFERENCESTop