Abstract
A meiotic study was performed on 21 populations of 17 Cirsium species growing in Iran. The species of C. spectabile, C. congestum, C. strigosum, C. ciliatum, C. osseticum, C. aduncum, C. haussknechtii, C. turkestanicum, C. echinus, C. obvallatum, C. libanoticum, C. alatum, C. echinus, C. obvallatum, C. libanoticum, C. hygrophilum and C. arvense had 2n=2x=34 chromosome number, while the species of C. lappaceum, C. vulgare and C. elodes showed 2n=4x=68. The chromosome numbers of C. spectabile, C. strigosum, C. haussknechtii, C. lappaceum, C. turkestanicum and C. libanoticum are new to science and a new polyploidy level (4x) has been reported for C. elodes. The ANOVA test revealed significant differences for chiasma frequency and chromosome pairing among the species studied and the Pearson coefficient of correlation determined showed significant positive correlation between intercalary chiasmata and the mean number of quadrivalents. Although diploid species and populations are expected to form only bivalents in metaphase I, quadrivalents were formed in C. arvense, C. ciliatum, C. congestum, C. echinus, C. strigosum and C. libanoticum possibly due to the occurrence of heterozygote translocations. Interestingly enough, tetraploid species of C. lappaceum did not form any quadrivalents showing diplontic behavior. The occurrence of large pollen grains (possibly 2n pollen grains) was observed along with smaller (normal) pollen grains in species and populations showing tripolar cells. Cytological characteristics may be used in species delimitation in Cirsium but may not be used in sectional delimitation of the genus.
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