Phylogeny and maternal donors of Elytrigia Desv. sensu lato (Triticeae; Poaceae) inferred from nuclear internal-transcribed spacer and trnL-F sequences

Comparative Characterization of Pseudoroegneria libanotica and Pseudoroegneria tauri Based on Their Repeatome Peculiarities

Pseudoroegneria species play an important role among Triticeae grasses, as they are the putative donors of the St genome in many polyploid species. Satellite repeats are widely used as a reliable tool for tracking evolutionary changes because they are distributed throughout the genomes of plants. The aim of our work is to perform a comparative characterization of the repeatomes of the closely related species Ps. libanotica and Ps. tauri, and Ps. spicata was also included in the analysis. The overall repeatome structures of Ps. libanotica, Ps. tauri, and Ps. spicata were similar, with some individual peculiarities observed in the abundance of the SIRE (Ty1/Copia) retrotransposons, Mutator and Harbinger transposons, and satellites. Nine new satellite repeats that have been identified from the whole-genome sequences of Ps. spicata and Ps. tauri, as well as the CL244 repeat that was previously found in Aegilops crassa, were localized to the chromosomes of Ps. libanotica and Ps. tauri. Four satellite repeats (CL69, CL101, CL119, CL244) demonstrated terminal and/or distal localization, while six repeats (CL82, CL89, CL168, CL185, CL192, CL207) were pericentromeric. Based on the obtained results, it can be assumed that Ps. libanotica and Ps. tauri are closely related species, although they have individual peculiarities in their repeatome structures and patterns of satellite repeat localization on chromosomes. The evolutionary fate of the identified satellite repeats and their related sequences, as well as their distribution on the chromosomes of Triticeae species, are discussed. The newly developed St genome chromosome markers developed in the present research can be useful in population studies of Ps. libanotica and Ps. tauri; auto- and allopolyploids that contain the St genome, such as Thinopyrum, Elymus, Kengyilia, and Roegneria; and wide hybrids between wheat and related wild species.

Characterization of the complete chloroplast genome of Elymus alashanicus (Keng) S. L. Chen, and its phylogenetic analysis

Elymus alashanicus (Keng) S. L. Chen, a herbaceous plant endemic to China, plays a crucial role in the local ecosystems. In this study, we sequenced and characterized the complete chloroplast (cp) genome of E. alashanicus, which is 135,072 bp in length and arranged in a circular form. The cp genome includes a pair of inverted repeats (IRa and IRb) of 20,813 bp each, separated by a large single-copy (LSC) region of 80,678 bp and a small single-copy (SSC) region of 12,768 bp. The cp genome contains 130 genes, including 83 protein-coding genes, 39 tRNA genes, and eight rRNA genes. Phylogenetic analysis revealed that E. alashanicus is closely related to Elymus breviaristatus and Campeiostachys dahurica var. tangutorum in current sampling. Our findings provide valuable insights into the cp genome of E. alashanicus, which could contribute to further studies on the evolution and conservation of this species.

Polymorphism of ITS sequences in 35S rRNA genes in Elymus dahuricus aggregate species: two cryptic species?

Nuclear ribosomal internal transcribed spacer (ITS) sequences were sequenced for 23 species and subspecies of Elymus sensu lato collected in Russia. The Neighbor-Net analysis of ITS sequences suggested that there are four ribotypes called Core Northern St-rDNA, Core Southern St-rDNA, Northern dahuricus St-rDNA and Southern dahuricus St-rDNA. The Core Southern variant of St-rDNA is closely related to rDNA of diploid Pseudoroegneria stipifolia (PI 313960) and P. spicata (PI 547161). The Core Northern St-rDNA is closely related to rDNA of P. cognata (PI 531720), a diploid species of Kyrgyzstan carrying StY variant of the St genome. The Core Northern St-rDNA is widespread among the Elymus species of Siberia and the Far East, including Yakutia and Chukotka. The Core Southern St-ribotype is typical of southern Elymus and Pseudoroegneria of the South Caucasus, Primorye, Pakistan, and South Korea. The Northern dahuricus St-ribotype and Southern dahuricus St-ribotype are derivatives of the Core Northern and Core Southern St-ribotypes, correspondingly. Both of them were found in all four studied species of the E. dahuricus aggregate: E. dahuricus Turcz. ex Griseb., E. franchetii Kitag., E. excelsus Turcz. ex Griseb. and Himalayan E. tangutorum (Nevski) Hand.-Mazz. In other words, there are at least two population groups (two races) of the Elymus dahuricus aggregate species that consistently differ in their ITS-sequences in Siberia, the Far East and Northern China. Each contains all morphological forms, which taxonomists now attribute either to different species of E. dahuricus aggr. (E. dahuricus sensu stricto, E. franchetii, E. tangutorum, E. excelsus) or subspecies of Campeiostachys dahurica (Turcz. ex Griseb.) B.R. Baum, J.L. Yang et C.C. Yen. At the moment it is unknown if there are any morphological differences between plants carrying either Northern or Southern dahuricus rDNA. Probably, they are cryptic species, but it is certain that if differences in morphology between the two races exist, they are not associated with signs that are now considered taxonomically significant and are used to separate E. dahuricus s. s., E. franchetii, E. tangutorum, and E. excelsus.