Research of genetic similarity of Poa nemoralis L.and Рoa palustris L. (Роасеае), based on ETS of 18S-26S NR DNA sequence data.

An attempt of phylogenetic reconstruction of section Stenopoa Dumort. (genus Poa L.), based on classic morphological and ecologo-geographycal methods, has revealed a lot of controversial points, which can be settled by using of the molecular methods, as alternative method of research. The relationship of both mesomorphic species (Poa nemoralis L. and Р. palustris L.), which are supposed to be situated on the base of the main branches of phylogenetic tree of section, is one of the main problems of section phylogeny. These species are very similar both in their morphology and habitus, and the difference between them is much less, then the difference between their xeromorphic derivates. Nevertheless, this difference does not express the degree of relationship, but may be caused by convergent similarity. The genetic differentiation of these species should be searched for eliciting of their divergence, and, consequently, their position in the section system. As far as ITS1 and ITS2 sequences are known to not reveal the differences between P. nemoralis and P. palustris, the attempt of its revealing , based on ETS (external transcribed spacer) has been made. The ETS region, located between 18S and 26S of nuclear ribosomal DNA was sequenced in 10 representatives of P. palustris and one sample of P. nemoralis in order to evaluate their genetic similarity. Since the ETS region of P. nemoralis had already been investigated, our search was concentrated on P. palustris. The resulting ETS matrix contains the 570 base pairs. Comparison of the nucleotide sequences has showed a high similarity of ETS areas of P. nemoralis and P. palustris, however, some differences, implicit and explicit, has been revealed. Obvious differences were found in positions of nucleotides 44, 537, 538 and 562. Basically there were transitions. In one case the transversion was reported at position 538. In this position in P. nemoralis was R, which may mean adenine or guanine, whereas all P. palustris had cytosine at this area. Finally in position 44 in P. nemoralis was found deletion, whereas P. palustris had adenine. Position 136 is quite interesting as well: P. nemoralis has cytosine here, the samples 3, 5, 7 of P. palustris shows an adenine in this position, whereas in the other samples this position falls out as a whole, ie both transversion and deletion take place. Some implicit differences were found as well. Thus, in position 43 P. palustris had cytosine, whereas P. nemoralis - M, that may mean both cytosine, and thymine; in position 161 P. palustris had guanine, whereas P. nemoralis - S, which may mean both guanine and cytosine. Nevertheless, these seem to be the mistakes of identification of nucleotides, and, in general, such comparisons are not quite proper, because P. nemoralis was represented by only one sample, however, it may give a notion on the genetic similarity between species. Comparison of our data with ones, obtained from GenBank, has confirmed the close genetic similarity of P. palustris, not only with P. nemoralis, but also with P. glauca, with P. laxa subsp. flexuosa (Sm.) Hyl., (which is supposed to be derived from the hybridization P. laxa and P. glauca), and even with P. lettermanii Vasey (sect. Abbreviatae Nannf. еx Tzvel.). Тhe search has revealed the weak variability of this region. The studies have shown that ETS region has proved to be too conservative for the investigation of relationships between quite close species of Stenopoa. Thus, other methods should be tried for this purpose.

Keywords

Authors

References