The section Multicaulia is the largest clade in the genus Hedysarum L. (Fabaceae). Representatives of the sect. Multicaulia are valuable plants used for medicinal and fodder purposes. The taxonomy and phylogeny of the sect. Multicaulia are still ambiguous. To clarify the species relationships within sect. Multicaulia, we, for the first time, explored repeatomes of H. grandiflorum Pall., H. zundukii Peschkova, and H. dahuricum Turcz. using next-generation sequencing technologies and a subsequent bioinformatic analysis by RepeatExplorer/TAREAN pipelines. The comparative repeatome analysis showed that mobile elements made up 20–24% (Class I) and about 2–2.5% (Class II) of their repetitive DNAs. The amount of ribosomal DNA varied from 1 to 2.6%, and the content of satellite DNA ranged from 2.7 to 5.1%. For each species, five high confident putative tandem DNA repeats and 5–10 low confident putative DNA repeats were identified. According to BLAST, these repeats demonstrated high sequence similarity within the studied species. FISH-based mapping of 35S rDNA, 5S rDNA, and satDNAs made it possible to detect new effective molecular chromosome markers for Hedysarum species and construct the species karyograms. Comparison of the patterns of satDNA localization on chromosomes of the studied species allowed us to assess genome diversity within the sect. Multicaulia. In all studied species, we revealed intra- and interspecific variabilities in patterns of the chromosomal distribution of molecular chromosome markers. In H. gmelinii Ledeb. and H. setigerum Turcz. ex Fisch. et Meyer, similar subgenomes were detected, which confirmed the polyploid status of their genomes. Our findings demonstrated a close genomic relationship among six studied species indicating their common origin and confirmed the taxonomic status of H. setigerum as a subspecies of H. gmelinii as well as the validity of combining the sect. Multicaulia and Subacaulia into one sect. Multicaulia.

Hedysarum grandiflorum samples were collected from 7 natural populations of the Volgograd, Samara and Lugansk People's Republic and the features of seed reproduction were studied under ex situ and in vitro conditions. The optimal temperature for seed germination and the dependence of germination and seed vigor on the storage were revealed. We observed the maximum germination rate in the scarified seeds of H. grandiflorum of 2018 collection and it was equal to 70%.It was found that the seed germina-tion and seed vigor are low and quickly decrease with years of storage, while their scarification allows to increase these indicators. It is noted that the relatively low germination of the studied seeds is leveled by the rather high productivity of species in general. The optimal mode of sterilization of H. grandiflorum seeds was experimentally determined - 10% Lysofornin® 3000 solution for 5 minutes. The percentage of sterile seedlings was 60%.

The application of isolated plant tissue and organs is getting more and more actual along with traditionalplant ex situ conservation methods. The peculiarities of hormon regulation of morphogenesis have been established fora Hedysarum razoumovianum cultivation. Optimal concentrations of growth regulators for stages of induction of explantdevelopment, microshoots regeneration and their rooting have been chosen. The development of reproduction plantsmethods is the basis of gene pool preservation.

The paper presents the results of studying the population structure of rare species Hedysarum argyrophyllum Ledeb., H . cretaceum Fisch., H . gmelinii Ledeb., H . grandiflorum Pall. and H . razoumowianum Fisch. et Helm in the Volga and Ural regions. The study area covers Volgograd, Samara, Saratov, the southern part of the Ulyanovsk and the western part of the Orenburg Regions and the Republic of Bashkortostan. 10 coenopopulations of Hedysarum argyrophyllum , 18 coenopopulations of H . cretaceum , 410 coenopopulations of H . gmelinii , 1800 coenopopulations of H . grandiflorum , 1400 coenopopulations of H . razoumowianum were examined. The work was carried out in 2000-2021 using population-ontogenetic methods. The studied representatives are rare, their population characteristics are subject to changes under the influence of anthropogenic factors. Species have sufficient potential for self-recovery of natural populations. The ontogenetic spectra of populations are similar in their parameters; the dominant fraction of individuals is the generative one. Common features are the fluctuation type of population dynamics and ontogenetic structure of model representatives, relatively low demographic characteristics, weak ability for self-maintenance and self-recovery of populations under anthropogenic load. Anthropogenic load leads to a decrease in the number of individuals, their density and the gradual aging of populations.