The Volga region is one of the main grain-producing regions of Russia. Wheat stem rust caused by Puccinia graminis f. sp. tritici is among the most destructive fungal diseases of wheat. Recently, its harmfulness has increased in the Volga region. In this regard, an analysis of the resistance and diversity of the Sr genes in the Russian wheat cultivars is necessary. In this work, 126 wheat cultivars (including 23 durum wheat cultivars and 103 bread wheat cultivars) approved for use in the Volga region were evaluated for their resistance to two samples of P. graminis f. sp. tritici populations from different Volga region areas at the seedling stage. Specific DNA primers were used to identify resistance genes (Sr2, Sr24, Sr25, Sr26, Sr28, Sr31, Sr32, Sr36, Sr38, Sr39, and Sr57). Highly resistant cultivars (30 from 126) were identified. In bread wheat cultivars, the genes Sr31 (in 19 cultivars), Sr24 (in one cultivar), Sr25 (in 15 spring wheat cultivars), Sr28 (in six cultivars), Sr38 (in two cultivars), and Sr57 (in 15 cultivars) and their combinations—Sr31 + Sr25, Sr31 + Sr38, Sr31 + Sr28, Sr31 + Sr57, Sr31 + Sr28 + Sr57, and Sr31 + Sr24—were identified. The obtained results may be used to develop strategies for breeding rust-resistant cultivars.

Tan spot caused by Pyrenophora tritici-repentis (Died.) Drechsler, in recent years, occupies an increasingly large area on the territory of Russia. Due to the wide distribution and economic significance of this disease, the search for resistant plants to the pathogen is relevant. This paper presents the results of a field assessment for 2017–2019 of 34 regionally distributed winter wheat varieties of Russian selection for resistance to P. tritici-repentis in the North Caucasus region of Russia. Field resistance - the development of the disease up to 30% against the background of artificial infection for three years was shown by 20.5% of the studied varieties. Wheat varieties were assessed for resistance to isolates of tan spot identified as races 1, 3, and 4 in the greenhouse at the seedling stage. The number of resistant accessions for each race was different and ranged from 12 to 20. The 12 varieties showed resistance to race 1, 14 varieties to race 3, 20 varieties to race 4. This research showed that the resistance to tan spot of studied varieties was race-specific. A functional allele of the susceptibility gene Tsn1 to P. tritici-repentis isolates, producing the toxin Ptr ToxA, was diagnosed by PCR method. Of the analyzed 34 varieties, 13 had a dominant allele of the Tsn1 (Tsn1+), and 21 had a recessive allele in the tsn1tsn1 homozygous state. All Tsn1+ varieties, and most varieties with recessive alleles tsn1tsn1, were susceptible to tan spot in the field. Varieties Dolya, Gurt, Lebed and Sila, which showed field resistance, had the tsn1tsn1 genotype. The expected reaction of varieties with different allelic composition of the Tsn1 gene to inoculation with the isolate of race 1, according to the generally accepted model of “gene-to-gene” interaction, did not coincide with that observed in reality, which confirms the results obtained by other authors. Research results demonstrate the effect of weather conditions on the susceptibility of wheat varieties to tan spot. In years with higher humidity and higher average air temperatures, the susceptibility response to the disease was observed in more varieties than in drier years. The studies show that the main part (79.5%) of winter wheat varieties of Russian selection widely zoned in the North Caucasus region of Russia are susceptible to P. tritici-repentis. Varieties that have been resistant to the pathogen in the adult phase in the field for three years and to the pathogen races in which the recessive allele of the tsn1 gene has been identified may be of interest as sources of resistance for developing new disease-resistant varieties.

A total of 57 introgression lines and 11 cultivars of spring bread wheat developed by All-Russian Institute of Plant Protection and cultivated in the Volga Region were analyzed. The lines were obtained with the participation of CIMMYT synthetics, durum wheat cultivars, direct crossing with Agropyron elongatum (CI-7-57) and have introgressions from related species of bread wheat, namely translocations from Ag. elongatum (7DS-7DL-7Ae#1L), Aegilops speltoides (2D-2S), Ae. ventricosum (2AL-2AS-2MV#1), Secale cereale (1BL-1R#1S), 6Agi (6D) substitution from Ag. intermedium and triticale Satu. Cultivars and lines were assessed for resistance to Saratov, Lysogorsk, Derbent and Omsk stem rust pathogen populations (Puccinia graminis f. sp. tritici), and analyzed for the presence of the known Sr resistance genes using molecular markers. The analysis of the cultivars’ and lines’ resistance to the Saratov pathogen population in the field, as well as to Omsk, Derbent and Lysogorsk populations at the seedling stage, showed the loss of efficiency of the Sr25 and Sr6Agi genes. The Sr31 gene remained effective. Thirty one wheat lines out of 57 (54.4 % of samples) were resistant to all pathogen populations taken into analysis. The Sr31/Lr26, Sr25/Lr19, Sr28, Sr57/Lr34 and Sr38/Lr37 genes were identified in the introgression lines. The Sr31/Lr26 gene was identified in 19 lines (33.3 % of samples). All lines carrying the 1RS.1BL translocation (Sr31/Lr26) were resistant to all pathogen populations taken into analysis. The Sr25/Lr19 gene was identified in 49 lines (86 %). The gene combination Sr31/Lr26+ Sr25/Lr19 was identified in 15 lines (26.3 %). The gene combinations Sr38/Lr37+Sr25/Lr19, Sr57/Lr34+Sr25/Lr19 and Sr31/Lr26+Sr25/Lr19+Sr28 were identified in 3 introgression lines. These three lines were characterized by resistance to the pathogen populations studied in this work. The Sr2, Sr24, Sr26, Sr32, Sr36 and Sr39 genes were not detected in the analyzed wheat lines.

The aim of this research is to develop for the Russian Federation Non-Cher nozem Zone competitive prototypes of winter wheat cul tivars with several genes for resistance to stem rust (in clu ding race Ug99) based on new sources of resistance with the use of molecular markers. The individual plants and then lines of winter common wheat with several effective genes for resistance to race Ug99 of stem rust were selected by means of marker assistant selection out of hybrid combinations from the crossing of new donors of resistance to this dangerous disease. The development of initial material was based on the use of new sources of resistance to race Ug99 of stem rust from VIR and “Arsenal” collections. Three accessions of winter wheat (wheat-aegi lops-rye line 119/4-06rw, cv. Donskaya Polukarlikovaya, line GT 96|90 from Bulgaria) and one accession of spring wheat (line 113/00i-4 with genetic material from Aegilops triuncialis), which supplemented and contrasted each other in such economically valuable features as plant height, number of days before heading, resistance to powdery mildew and leaf rust, were selected for hybridization and backcrossing. To accelerate the breeding process, resistant genotypes with Sr genes were selected with the use of molecular markers. As a result the lines of winter common wheat with a set of economically valuable features and the presence of two-four genes for resistance to stem rust in homozygote state were created. The spectrum of the stem rust gene combinations in the created lines differs from the gene combinations in the parental accessions involved in the crossing and is associated with the direction of the selections conducted by the marker assisted selection method. We discovered more than 20 different combinations of the Sr2, Sr22, Sr31, Sr32, Sr36, Sr39, Sr40 and Sr47 genes in winter wheat lines. The combination of Sr22 and Sr32 in homozygote state was most often found. The genotypes with a set of economically valuable features approximating or surpassing the standard cultivar of winter wheat Moskov skaya 39 were selected for further testing in breeding nurseries of the Moscow region. The developed initial material is intended for use in selection of winter wheat cultivars resistant to stem rust in different grain-sowing regions of the Russian Federation. This will serve as a barrier for spread of new races of Puccinia graminis and will raise the resistance of selected cultivars to local populations of stem rust.

Anticipatory wheat breeding for pathogen resistance is key to preventing economically significant crop losses caused by diseases. Recently, the harmfulness of a dangerous wheat disease, stem rust, caused by Puccinia graminis f. sp. tritici, was increased in the main grain-producing regions of the Russian Federation. At the same time, importation of the Ug99 race (TTKSK) is still a possibility. In this regard, the transfer of effective resistance genes from related species to the bread wheat breeding material followed by the chromosomal localization of the introgressions and a marker analysis to identify known resistance genes is of great importance. In this work, a comprehensive analysis of ten spring bread wheat introgressive lines of the Federal Center of Agricultural Research of the South-East Region (L657, L664, L758, L935, L960, L968, L971, L995/1, L997 and L1110) was carried out. These lines were obtained with the participation of Triticum dicoccum, T. timopheevii, T. kiharae, Aegilops speltoides, Agropyron elongatum and Secale cereale. In this study, the lines were evaluated for resistance to the Ug99 race (TTKSK) in the Njoro, Kenya. Evaluation of introgression lines in the field for resistance to the Ug99 race (TTKSK) showed that four lines were immune, two were resistant, three were moderately resistant, and one had an intermediate type of response to infection. By cytogenetic analysis of these lines using fluorescent (FISH) and genomic (GISH) in situ hybridization, introgressions from Ae. speltoides (line L664), T. timopheevii (lines L758, L971, L995/1, L997 and L1110), Thinopyrum ponticum = Ag. elongatum (2n = 70) (L664, L758, L960, L971, L997 and L1110), as well as introgressions from T. dicoccum (L657 and L664), T. kiharae (L960) and S. cereale (L935 and L968) were detected. Molecular markers recommended for marker-oriented breeding were used to identify known resistance genes (Sr2, Sr25, Sr32, Sr1A.1R, Sr36, Sr38, Sr39 and Sr47). The Sr36 and Sr25 genes were observed in lines L997 and L1110, while line L664 had the Sr39+Sr47+Sr25 gene combination. In lines L935 and L968 with 3R(3D) substitution from S. cereale, gene resistance was presumably identified as SrSatu. Thus, highly resistant to both local populations of P. graminis and the Ug99 race, bread wheat lines are promising donors for the production of new varieties resistant to stem rust.