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Bjornsdottir, Snaedis [1], Thorsson, Aegir Thor [2], Sveinsson, Saemundur [3], Anamthawat-Jonsson, Kesara [4].

Molecular cytogenetic evidence indicating evolutionary relationship between American lymegrass species and their Eurasian and Asiatic relatives.

The genus Leymus Hochst. (lymegrass) comprises about 50 polyploid perennial grass species in the wheat tribe Triticeae. Leymus has its distribution over the temperate regions of the Northern Hemisphere. In the present study, we investigated three species from western North America, L. cinereus, L. innovatus and L. triticoides, in comparison with three species from Eurasia and Central Asia, L. chinensis, L. multicaulis and L. racemosus. We used the molecular cytogenetic method of fluorescence in situ hybridization (FISH) to identify the Ns genome, with an aim to trace evolutionary relationships among these Leymus species. In this context, we looked into Psathyrostachys Nevski (the diploid genus with Ns genome), the ancestor of Leymus. We isolated Ns specific DNA sequences from two Psathyrostachys species to be used as probes in FISH experiments. Two repetitive sequence families were obtained: PshA (five 384-745 bp DraI plasmid clones) from Ps. huashanica (China) and PsjD (six 570-625 bp ScaI clones) from Ps. juncea (Russia). The sequence analysis showed over 90% homology within family. Southern blot experiments were performed using PshA and PhjD probes to hybridize to DraI digested total genomic DNA of the Leymus and Psathyrostachys species under study, against reference species including barley, rye and wheat. Both probes hybridized only to Psathyrostachys and Leymus, confirming that they are Ns genome specific sequences. Among the Ns species, however, the two probes showed differential hybridization. While PshA is present in American Leymus species, PsjD is prevalent among Eurasian/Asiatic species. FISH experiments revealed chromosomal location of PshA and PsjD. The PshA family was localized in 22 subtelomeric heterochromatic blocks in Ps. huashanica (diploid, 2n=14): on both arms of ten chromosomes and one arm of two chromosomes. This PshA was also localized to about 22 blocks in L. innovatus (tetraploid, 2n=28) and the other American species. The PsjD family was localized in 14 subtelomeric heterochromatic blocks of Ps. juncea (diploid, 2n=14): on both arms of four chromosomes and one arm on six chromosomes. The same pattern was detected in FISH experiments of PhjD on L. multicaulis and other Eurasian/Asian species. We conclude that the American Leymus species under study are allotetraploid containing half of its Ns genomes deriving from Ps. huashanica, which has a restricted distribution in NW China. On the other hand, the Eurasia/Asian species appear to be allotetraploid containing half of its Ns genomes deriving from, or related to, Ps. juncea, which occurs in their distribution range.

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1 - University of Iceland, Life and Environmental Sciences, Askja, Sturlugata 7, Reykjavik, IS-102, Iceland
2 - The Icelandic Centre for Research (RannĂ­s), Borgartun 30, Reykjavik, IS-105, Iceland
3 - Icelandic Food and Biotech R&D (Matis), Vinlandsleid 12, Reykjavik, IS-113, Iceland
4 - University Of Iceland, Institute Of Life And Environmental Sciences, Askja - Sturlugata 7, Reykjavik, 101, Iceland

Ns genome

Presentation Type: Poster
Session: P2, Macroevolution Posters
Location: Virtual/Virtual
Date: Tuesday, July 20th, 2021
Time: 5:00 PM(EDT)
Number: P2MC002
Abstract ID:178
Candidate for Awards:None

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