A description of Taraxacum zajacii J. & P. Marciniuk, a new species of T. sect. Palustria in Poland is given. Taraxacum zajacii is a pentaploid (2n = 40). Morphologically, the new species is closest to the T. subalpinum/T. neterophilum group.Taraxacum sect. Palustria includes 131 mostly apomictic species, markedly different in their karyology. Sexually reproducing diploids are represented in the section by only two rare Mediterranean species, Taraxacum raii and T. tenuifolium. The apomictic taxa form a series of polyploids, from common triploids (2n = 24) and tetraploids (2n = 32) to rare pentaploids (2n = 40) and very rare hexaploids (2n = 48) represented by only two species, which are T. ranunculus and T. flos-lacus (Kirschner & Štěpánek 1998, Tikhomirov 2003, Aquaro et al. 2008. In Poland, T. sect. Palustria includes 23 exclusively apomictic species with 15 triploids, six tetraploids and two pentaploids (Marciniuk et al. 2010b, Marciniuk 2012.A large population of a distinct taxon which, after morphological and karyological studies, appeared to be a new species was found in 2008. The description of this species is given in this paper.Morphometric analyses were made on herbarium materials collected in the field and on cultured live plants. In total, 100 individuals and herbarium specimens were analysed.For karyological studies, seeds collected from the cultured plants were germinated on moistened filter paper in Petri dishes. Three-to four-day-old seedlings were incubated in 8-hydroxychinoline for 4 h at room temperature. Then they were rinsed in distilled water and fixed in 96% ethanol/ glacial acetic acid (3:1) for 24 h. The fixed material was stained in 2% acetic orcein for 3-4 days at room temperature. The stained seedlings were rinsed in 45% acetic acid, then heated to a boiling point over a flame. For slide preparation, root tip meristems were cut off and squashed in a drop of 45% acetic acid, dry-iced, air-dried and mounted in Entellan. The chromosomes were counted during the mitotic metaphase and photographed using a Nikon Eclipse 80i microscope equipped with a monochrome CCD camera.
The genus Taraxacum is taxonomically complicated due to apomixis. Therefore, there are significant differences in knowledge of regional Taraxacum-Floras among European countries. Similarly, some taxa are well characterised with well-known distribution, whereas some ones are known e.g. from a single locality. Taraxacum scanicum of section Erythrosperma is one of the most common microspecies of this section in Europe. Recently, this taxon was split into three microspecies. In this study we map the distribution of three described taxa of this group in Poland, i.e. T. scanicum s.s., T. prunicolor and T. cristatum. The survey showed that T. scanicum has a similar distribution as T. prunicolor in Poland. This is in contrast with the hitherto known distribution of both taxa. T. cristatum was found at a single locality that is quite distant from the distribution in southern central Europe. We also provide with new morphological characteristics of achenes and pollen for T. scanicum s.s. and T. prunicolor
Measurements of the pollen size in 5 species of Taraxacum sect. Palustria at three levels of ploidy: 2n = 3x = 24 (T. paucilobum), 2n = 4x = 32 (T. vindobonense, T. trilobifolium), 2n = 5x = 40 (T. mendax) and one taxon of unknown number of chromosomes 2n = ? (T. portentosum) are presented in this paper. Obtained results indicate a lack of distinct positive correlation between the pollen size and ploidy in the studied group of plants. Distinct relationship was, however, found between ploidy and the range of pollen size and shape variability. Most variable were the pollen grains of triploid T. paucilobum and the least -those in pentaploid T. mendax. Ranges of pollen variability in tetraploid T. trilobifolium and T. vindobonense and in T. portentosum of unknown number of chromosomes showed intermediate values.
The object of this work was to analyze the karyotype structure of Rumex thyrsiflorus using differential fluorescent methods of chromosome staining (C-banding/DAPI and CMA3/DA/DAPI) and molecular sex markers. The results obtained were compared with data on the structure of the sex chromosomes and autosomes in R. acetosa, a model species in studies of sex determination and sex chromosome evolution in plants with an XX/XY1Y2 system. A high level of similarity was found in the sex chromosome structure of the 2 species, along with small differences in their autosomal complexes. It suggests that differentiation of these 2 closely related species was not accompanied by major structural changes within their sex chromosomes. Molecular tests, however, revealed differences in the composition of male-specific repetitive sequence RAYSII, occurring in the Y1 chromosome. Amplification of this sequence showed the presence of a single product (∼700 bp) in R. acetosa and of 2 products (∼600 bp and ∼700 bp) in R. thyrsiflorus. The longer product (∼700 bp) was also revealed in R. arifolius, another species closely related to R. acetosa. The shorter DNA fragment, characteristic of R. thyrsiflorus, differed from the common product by of a large indel with a length of 110 bp. This fragment may serve as a species-specific molecular marker useful in taxonomical and population studies as well as in further research on the sex chromosome differentiation in R. thyrsiflorus.
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