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Background: Grasslands in the Arctic tundra undergo irreversible degradation due to climatic changes and also over-exploitation and depletion of scarce resources. Comprehensive investigations of cytogenomic structures of valuable Arctic and sub-Arctic grassland species is essential for clarifying their genetic peculiarities and phylogenetic relationships, and also successful developing new forage grass cultivars with high levels of adaptation, stable productivity and longevity. We performed molecular cytogenetic characterization of insufficiently studied pasture grass species (Poaceae) from related genera representing two neighboring clades: 1) Deschampsia and Holcus; 2) Alopecurus, Arctagrostis and Beckmannia, which are the primary fodder resources in the Arctic tundra. Results: We constructed the integrated schematic maps of distribution of these species in the northern, central and eastern parts of Eurasia based on the currently available data as only scattered data on their occurrence is currently available. The species karyotypes were examined with the use of DAPI-banding, multicolour FISH with 35S rDNA, 5S rDNA and the (GTT)9 microsatellite motif and also sequential rapid multocolour GISH with genomic DNAs of Deschampsia sukatschewii, Deschampsia flexuosa and Holcus lanatus belonging to one of the studied clades. Cytogenomic structures of the species were specified; peculiarities and common features of their genomes were revealed. Different chromosomal rearrangements were detected in Beckmannia syzigachne, Deschampsia cespitosa and D. flexuosa; B chromosomes with distinct DAPI-bands were observed in karyotypes of D. cespitosa and H. lanatus. Conclusions: The peculiarities of distribution patterns of the examined chromosomal markers and also presence of common homologous DNA repeats in karyotypes of the studies species allowed us to verify their relationships. The obtained unique data on distribution areas and cytogenomic structures of the valuable Arctic and sub-Arctic pasture species are important for further genetic and biotechnological studies and also plant breeding progress. [ABSTRACT FROM AUTHOR]

We visualized the Feulgen-stained nuclei and chromosomes of fossilized leaves of Metasequoia occidentalis (syn. M. disticha) from West Siberia dated to 29–33 million years old. There are about 22 metacentric chromosomes in somatic anaphase cells. The karyotype of the fossil plant is similar to the modern species M. glyptostroboides. Metasequoia was widespread in middle and high latitudes of Eurasia and North America during the Cretaceous but is represented nowadays by the single relict species, M. glyptostroboides , in central China. • The fossil Metasequoia leaf cells carry nuclei with Feulgen-positive material. • In each of the nucleolus, there is an unstained area similar to the nucleolus vacuole. • There are about 22 metacentric chromosomes in somatic anaphase cells. • The karyotype of the fossil plant is similar to the extant species Metasequoia. [ABSTRACT FROM AUTHOR]