The application of Vavilov's approaches to the phylogeny and evolution of cultivated species of the genus Avena L.

The central problem that Vavilov was investigating was the overall concept of global plant genetic resources. The theoretical basis of this concept consisted of the law of homologous series in variation, research on the problem of species as a system, botanical and geographical bases of plant breeding, and the key theory of the centers of origin of cultivated plants. The VIR global collection of plant genetic resources collected by Vavilov and his associates from all over the world reflects the fullness of botanical, morphological and genetic diversity, and can be used for historical, evolutionary, phylogenetic and applied breeding research aimed at unlocking the potential of all the collection material. The whole diversity of cultivated oats, as was proved by Vavilov, had originated from segetal weeds. This process can be clearly traced in Spain on the example of the cultivated diploid species A. strigosa, A. abyssinica in Ethiopia, A. byzantina in Turkey and Iran, and on segetal forms of A. sativa. The studies of the morphological features as a whole do not yield a complete picture of the evolutionary and systematic status of some oat species and forms. The methods and approaches that use DNA markers and genomic technologies, and are promising for the study of oat polymorphism and phylogeny have been actively researched recently. A number of works devoted to the molecular aspects of the evolution and phylogeny of the genus Avena have recently appeared. The research uses various markers of genes, gene regions, intergenic spacers (internal and external), both nuclear and chloroplast and mitochondrial, genomic approaches and other modern methods. On the basis of a comprehensive study of the complete intraspecific diversity from different zones of the distribution range of cultivated oat species as well as on the basis of an analysis of data on the geography of forms and species distribution ranges, it was established that the process of hexaploid species formation also took place in the western part of the Mediterranean, and subsequently, when moving eastward, these forms started occupying all the vast spaces in the region of the Southwest Asian center, forming a large intraspecific diversity of wild forms and weedy ones in transit to cultivated hexaploid oat species. An analysis of the intraspecific diversity of landraces has specified the centers of morphogenesis of all cultivated oat species. The phylogenetic analysis of the representative intraspecific diversity of cultivated and wild Avena species carried out using next generation sequencing (NGS) showed that diploid species with A-genome variants are in fact not primary diploids, but a peculiar Mediterranean introgressive hybridization complex of species that sporadically enter into interspecific hybridization. It was established that the tetraploid cultivated species A. abyssinica had most likely originated from the wild A. vaviloviana. An analysis of the ways of A. sativa and A. byzantina domestication showed that the most widespread ribotype of the A. sativa hexaploid was inherited from A. ludoviciana, and the second most widespread one, from A. magna, while A. byzantina has two unique ribotype families, most likely inherited from an extinct oat species or a still undiscovered cryptospecies.

Naked barley: taxonomy, breeding, and prospects of utilization.

This review surveys the current state of taxonomy, origin, and utilization prospects for naked barley. The cultivated barley Hordeum vulgare L. incorporates the covered and naked barley groups. Naked barleys are divided into six-row naked barley (convar. сoeleste (L.) A. Trof.) and two-row naked barley (convar. nudum (L.) A. Trof.). The groups include botanical varieties differing in the structural features of spikes, awns, floret and spikelet glumes, and the color of kernels. The centers of morphogenesis for naked barley are scrutinized employing archeological and paleoethnobotanical data, and the diversity of its forms. Hypotheses on the centers of its origin are discussed using DNA marker data. The main areas of its cultivation are shown, along with possible reasons for such a predominating or exclusive distribution of naked barley in highland areas. Inheritance of nakedness and mechanisms of its manifestation are considered in the context of new data in genetics. The biochemical composition of barley grain in protein, some essential and nonessential amino acids, ß-glucans, vitamins, and antioxidants is described. Naked barley is shown to be a valuable source of unique combinations of soluble and insoluble dietary fibers and polysaccharides. The parameters limiting wider distribution of naked barley over the world are emphasized, and breeding efforts that could mitigate them are proposed. Pathogen-resistant naked barley accessions are identified to serve as promising sources for increasing grain yield and quality. Main stages and trends of naked barley breeding are considered and the importance of the VIR global germplasm collection as the richest repository of genetic material for the development of breeding is shown.

Resistance of oat breeding lines to grain contamination with Fusarium langsethiae and T-2/HT-2 toxins.

Fusarium disease of oats reduces yield quality due to decreasing germination that is caused by the contamination of grain with mycotoxins produced by Fusarium fungi. The aim of this study was to characterize the resistance of naked breeding lines of oats to fungal grain infection and to contamination with T-2 and HT-2 toxins. Thirteen naked oat breeding lines and two naked varieties, Nemchinovsky 61 and Vyatskiy, as well as a husked variety Yakov, were grown under natural conditions in the Nemchinovka Federal Research Center in 2019-2020. The contamination of grain with fungi was determined by the mycological method and real-time PCR. The analysis of mycotoxins was carried out by ELISA. In oats, Alternaria (the grain infection was 15-90 %), Cochliobolus (1-33 %), Cladosporium (1-19 %), Epicoccum (0-11 %), and Fusarium (3-17 %) fungi prevailed in the grain mycobiota. The predominant Fusarium species were F. poae (its proportion among Fusarium fungi was 49-68 %) and F. langsethiae (29-28 %). The highest amounts of F. langsethiae DNA ((27.9-71.9) × 10-4 pg/ng) and T-2/HT-2 toxins (790-1230 µg/kg) were found in the grain of husked oat Yakov. Among the analysed naked oat lines, the amount of F. langsethiae DNA varied in the range of (1.2-42.7) × 10-4 pg/ng,and the content of T-2/HT-2 toxins was in the range of 5-229 µg/kg. Two oat breeding lines, 54h2476 and 66h2618, as well as a new variety, Azil (57h2396), can be characterized as highly resistant to infection with Fusarium fungi and contamination with mycotoxins compared to the control variety Vyatskiy.

Dynamics of the genetic diversity of oat varieties in the Tyumen region at avenin-coding loci.

Molecular and biochemical markers are used to analyze the intraspecific genetic diversity of crops. Prolamin-coding loci are highly effective for assessing this indicator. On the basis of the Laboratory of Varietal Seed Identification of the State Agrarian University of the Northern Trans-Urals, 18 varieties of common oat included in the State Register of Selection Achievements in the Tyumen Region from the 1930s to 2019 were studied by electrophoresis in 2018-2019. The aim of the work was to study the dynamics of the genetic diversity of oat varieties at avenin-coding loci. For the analysis, 100 grains of each variety were used. Electrophoresis was carried out in vertical plates of 13.2 % polyacrylamide gel at a constant voltage of 500 V for 4.0-4.5 h. It was found that 44.4 % of the varieties are heterogeneous, each consisting of two biotypes. For three loci, 20 alleles were identified, 10 of which were detected for the first time. The allele frequency of avenin-coding loci varied with time. In the process of variety exchange, alleles that are characteristic of varieties of non-Russian origin were replaced by alleles present in domestic varieties and then in the varieties developed by local breeding institutions. The following alleles had the highest frequency in Tyumen varieties: Avn A4 (50.0 %), A2 (25.0 %), Avn B4 (50.0 %), Bnew6 (37.5 %), Avn C1 (37.5 %), C2 and C5 (25.0 %). These alleles are of great value as markers of agronomically and adaptively important characters for the region in question. The amount of genetic diversity of oats varied with time from 0.33 in 1929-1950 to up to 0.75 in 2019. The high value of genetic diversity in modern breeding varieties of the Scientific Research Institute of Agriculture of the Northern Trans-Urals and an increase in this indicator over the past 20 years are associated with the use of genetically heterogeneous source material in the breeding process. This allowed obtaining varieties with high adaptive potentials in the natural climatic conditions of the region.

[Comparative cytogenetic analysis of hexaploid Avena L. species].

Using C-banding method and in situ hybridization with the 45S and 5S rRNA gene probes, six hexaploid species of the genus Avena L. with the ACD genome constitution were studied to reveal evolutionary karyotypic changes. Similarity in the C-banding patterns of chromosomal and in the patterns of distribution of the rRNA gene families suggests a common origin of all hexaploid species. Avena fatua is characterized by the broadest intraspecific variation of the karyotype; this species displays chromosomal variants typical of other hexaploid species of Avena. For instance, a translocation with the involvement of chromosome 5C marking A. occidentalis was discovered in many A. fatua accessions, whereas in other representatives of this species this chromosome is highly similar to the chromosome of A. sterilis. Only A. fatua and A. sativa show slight changes in the morphology and in the C-banding pattern of chromosome 2C. These results can be explained either by a hybrid origin of A. fatua or by the fact that this species is an intermediate evolutionary form of hexaploid oats. The 7C-17 translocation was identified in all studied accessions of wild and weedy species (A. sterilis, A. fatua, A. ludoviciana, and A. occidentalis) and in most A. sativa cultivars, but it was absent in A. byzantina and in two accessions of A. sativa. The origin and evolution of the Avena hexaploid species are discussed in context of the results.

[Comparative analysis of diploid species of Avena L. using cytogenetic and biochemical markers: Avena pilosa M. B. and A. clauda Dur].

The diploid oat species containing the Cp genome - Avena pilosa and A. clauda - were studied using C-banding, fluorescence in situ hybridization with probes pTa71 and pTa794, and electrophoresis of grain storage proteins (avenins). Species with the C genome differed considerably from the species of the A genome group in the karyotype structure, heterochromatin type and distribution, relative positions of the 45S and 5S rRNA gene loci, and avenin patterns. These facts confirmed that the C genome had diverged from the ancestral genome before the radiation of the various A genome. Presumably, further evolution of the A -and C genome species occurred separately.

[Comparative analysis of diploid species of Avena l. using cytogenetic and biochemical markers: Avena canariensis baum et fedak and A. longiglumis dur].

The diploid oat species containing the A genome of two types (Al and Ac) were studied by electrophoresis of grain storage proteins (avenins), chromosome C-banding, and in situ hybridization with probes pTa71 and pTa794. The karyotypes of the studied species displayed similar C-banding patterns but differed in size and morphology of several chromosomes, presumably, resulting from structural rearrangements that took place during the divergence of A genomes from a common ancestor. In situ hybridization demonstrated an identical location of the 45S and 5S rRNA gene loci in Avena canariensis and A. longiglumis similar to that in the A. strigosa genome. However, the 5S rDNA locus in A. longiglumis (5S rDNA1) was considerably decreased in the chromosome 3A1 long arm. The analysis demonstrated that these oat species were similar in the avenin component composition, although individual accessions differed in the electrophoretic mobilities of certain components. A considerable similarity of A. canariensis and A. longiglumis to the Avena diploid species carrying the As genome variant was demonstrated.

[A comparative cytogenetic study of the tetraploid oat species with the A and C genomes: Avena insularis, A. magna, and A. murphyi].

Differential C-banding of chromosomes and in situ hybridization with the probes pTa71 and pTa794 were used for a comparative cytogenetic study of the three tetraploid oat species with the A and C genomes: Avena insularis, A. magna, and A. murphyi. These species were similar in the structure and patterns of C-banding of several chromosomes as well as in the location of the loci 5S rRNA genes and main NOR sites; however, they differed in the number and localization of minor 45S rDNA loci as well as in the morphology and distribution of heterochromatin in some chromosomes. According to the data obtained, A. insularis is closer to A. magna, whereas A. murphyi is somewhat separated from these two species. Presumably, all the three studied species originated from the same tetraploid ancestor, and their divergence is connected with various species-specific chromosome rearrangements. The evolution of A. murphyi is likely to have occurred independently of the other two species.

[Genomic structure of the autotetraploid oat species Avena macrostachya inferred from comparative analysis of the ITS1 and ITS2 sequences: on the oat karyotype evolution during the early stages of the Avena species divergence].

To examine the genomic structure of Avena macrostachya, internal transcribed spacers, ITS1 and ITS2, as well as nuclear 5.8S tRNA genes from three oat species with AsAs karyotype (A. wiestii, A. hirtula, and A. atlantica), and those from A. longiglumis (AlAl), A. canariensis (AcAc), A. ventricosa (CvCv), A. pilosa, and A. clauda (CpCp) were sequenced. All species of the genus Avena examined represented a monophyletic group (bootstrap index = 98), within which two branches, i.e., species with A- and C-genomes, were distinguished (bootstrap indices = 100). The subject of our study, A. macrostachya, albeit belonging to the phylogenetic branch of C-genome oat species (karyotype with submetacentic and subacrocentric chromosomes), has preserved an isobrachyal karyotype, (i.e., that containing metacentric chromosomes), probably typical of the common Avena ancestor. It was suggested to classify the A. macrostachya genome as a specific form of C-genome, Cm-genome. Among the species from other genera studied, Arrhenatherum elatius was found to be the closest to Avena in ITS1 and ITS structure. Phylogenetic relationships between Avena and Helictotrichon remain intriguingly uncertain. The HPR389153 sequence from H. pratense genome was closest to the ITS1 sequences specific to the Avena A-genomes (p-distance = 0.0237), while the differences of this sequence from the ITS1 of A. macrostachya reached 0.1221. On the other hand, HAD389117 from H. adsurgens was close to the ITS1 specific to Avena C-genomes (p-distance = 0.0189), while its differences from the A-genome specific ITS1 sequences reached 0.1221. It seems likely that the appearance of highly polyploid (2n = 12-21x) species of H. pratense and H. adsurgens could be associated with interspecific hybridization involving Mediterranean oat species carrying A- and C-genomes. A hypothesis on the pathways of Avena chromosomes evolution during the early stages the oat species divergence is proposed.

[Cytogenetic analysis of diploid Avena L. species containing the as genome].

Cytogenetic examination showed that three diploid oat species containing the As genome are highly similar in karyotype structure and chromosome C-banding patterns. Avena strigosa is more similar to A. wiestii, while A. hirtula is to an extent separated from the two species, differing in the C-banding pattern of chromosome 6. The karyotypes of all three species harbor a small acrocentric chromosome, which is absent from diploid oat species containing other variants of the A genome. The results made it possible to assume genome specificity of the rearrangement resulting in this chromosome.

[Interspecific crosses in Avena L. species]. / Mezhvidovye skreshchivaniia v rode Avena L.

Problems of crosses between various oat species are considered with regard to establishing their taxonomic positions and genomic compositions of individual species. The evolution of the genus and approaches to the search for the diploid and tetraploid ancestor of the hexaploid species are considered. Use of wild oat species in breeding is demonstrated. The results of studies of the gene pool of wild oat species are presented. These studies were performed at the Vavilov All-Russian Plant Breeding Institute with the purpose of solving problems of phylogeny and practical breeding.