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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.

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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.

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Genetic resistance to net form of net blotch in the international barley differential Canadian Lake Shore (CLS) was characterized and mapped. A doubled haploid (DH) population generated from a cross between CLS and susceptible cultivar Harrington was evaluated at the seedling stage using eight diverse Pyrenophora teres f. teres ( Ptt ) isolates and at the adult stage in the field using natural inoculum. To effectively map the CLS resistance, comparative marker frequency analysis (MFA) was performed using 8,762 polymorphic DArT-seq markers, where ‘resistant’ and ‘susceptible’ groups each comprised 40 DH lines displaying the most extreme phenotypes. Five DArTseq markers were consistently detected in eight disease assays, which was designated qPttCLS and deemed to harbor the locus underpinning CLS resistance. Four of these markers were present onto the barley DArTseq physical map and spans a region between 398203862 and 435526243 bp which were found to consist several genes involved in important plant functions such as disease response and signaling pathways. While MFA only detected the 3H region, genetic analyses based on segregation patterns were inconsistent, suggesting complex inheritance or variation in phenotypic expression of qPttCLS , particularly in the field. This study represents progress toward connecting Ptt pathotype surveys with the corresponding resistance genes in barley differentials. The markers associated with qPttCLS are useful for marker-assisted selection in breeding programs.