New sources and donors with high potential for complex resistance to especially dangerous diseases for wheat breeding

The development and introduction into production of new wheat varieties with complex resistance to diseases is an urgent task of modern breeding. This work is the first to identify samples resistant to the main pathogens of septoria blotch, tan spot, spot blotch, leaf and stem rust during comprehensive field and laboratory evaluations of 18 spring soft wheat breeding lines originated at the Central Russian branch of Michurin Federal Scientific Center, and 25 hybrids and varieties of soft wheat of domestic and foreign breeding. Using molecular markers, a recessive allele tsn1 , providing resistance to the ToxA toxin, was detected in more than 20 wheat samples. Samples carrying the recessive allele snn1 , providing resistance to the Tox1 toxin, were identified. The work objective was an immunological assessment of soft wheat breeding material resistance to leaf-stem diseases and identification of genes for resistance to phytopathogen toxins. Immunological tests of soft wheat (Triticum aestivum L.) samples were carried out in 2021-2023 at a stationary site of the Michurin Central Russian branch of the Federal Scientific Center located in the north-eastern part of the Central Black Earth Region (Tambov District, Tambov Province). The material for immunological studies in infectious nurseries were 18 breeding lines of spring soft wheat from the Central Russian branch of the Michurin Federal Scientific Center 1/16-5-1, 1/16-5-2, 3/16-5, 3/16-20, 5/16-2-1, 5/16-2-2, 5/16-20, 6/16-2-1, 6/16-2-2, 12/16-4, 1/16-2, 1/16-3, 5/16-1, 5/16-5, 5/16-2, 10/16-1, 11/16-5, 17/16-1 and 25 hybrids and varieties of soft wheat of domestic and foreign selection 31213 (USA), 31228 (USA), 31306 (USA), 34950 (USA), 49851 (USA), 55196 (USA), 51289 (USA), 51829 (USA), 55199 (USA), 30287 (Mexico), 32164 (Mexico), 31821 (Mexico), 347071 (Mexico), 31765 (CIMMYT), 31964 (CIMMYT), 33832 (CIMMYT), 33402 (Brazil), 3515 (Argentina), 63325 (France), 34984 (Peru), 30579 (ICARDA), Biora (Russia), Lutescens 537 (Russia), Estivum 614 (Russia), 54208 (Russia) (the work provides sample numbers from the catalog of the Michurin Federal Scientific Center). To evaluate wheat samples with septoria tritici blotch (Zymoseptoria tritici, Parastagonospora nodorum , P. pseudonodorum) and leaf rust (Puccinia triticina) pathogens, an artificial infection load was created in field conditions. Plant damage by the tan spot (yellow leaf spot, Pyrenophora tritici-repentis) was evaluated under natural infection. Laboratory evaluation with artificial infection load of leaf and stem rust (P. triticina , P. graminis ) pathogens was performed 8-10 days after inoculation. For laboratory evaluation of resistance/susceptibility to spot blotch, a spore mixture of fungal isolates from the collection of the All-Russian Research Institute of Plant Protection (St. Petersburg-Pushkin) was used as an inoculum (Z. tritici , P. nodorum , P. pseudonodorum , Septoria triticicola). In addition, in lab tests, the leaves of collection wheat samples were infected with isolates of P. tritici-repentis (ToxA) and B. sorokiniana. The inoculum of each fungal species contained a mixture of several isolates obtained in 2022 from the VIZR collection. The P. tritici-repentis material was collected in the Saratov Province, B. sorokiniana in the Leningrad Province. Genomic DNA was isolated from the leaves of 5-day-old wheat seedlings using the standard CTAB/chloroform method. After quantitative assessment, DNA concentration was normalized to 30 ng/μl for PCR. Wheat samples were examined for the presence of Tsn1/tsn1 , Snn1/snn1 genes. A number of breeding lines and hybrid forms had high resistance to the main spot blotch pathogens Z. tritici (1/16-5-1, 1/16-5-2, 3/16-5, etc.), P. nodorum (6/16-2-2, 12/16-4, 1/16-2, etc.), P. pseudonodorum (6/16-2-2, 12/16-4, 1/16-3, etc.) and S. triticicola (3/16-5, 11/16-5, 17/16-1, etc.). In field and laboratory tests most of the studied samples (95-100 %) showed high resistance to leaf and stem rust. A number of breeding lines and hybrids were resistant to the causative agent of tan spot ( P. triticina-repentis ) (1/16-5-1, 3/16-5, 3/16-20, etc.). Some lines and hybrids were resistant to the causative agent of spot blotch ( B. sorokiniana ) (5/16-2-1, 5/16-2-2, 6/16-2-2, etc.). In the studied wheat breeding material, genes for resistance to two important toxins of phytopathogens ToxA and Tox1 were identified. The recessive allele tsn1 , providing resistance to the ToxA toxin, was identified in more than 20 wheat samples. These are two varieties (Biora, Lutescens 537), 9 selection lines (1/16-5-1, 1/16-5-2, 3/16-20, 5/16-20, 1/16-3, 5/16-1, 5/16-5, 10/16-1, 17/16-1) and 13 hybrid lines 31228, 34950, 55196, 55199 (USA); 30287, 31821, 347071 (Mexico); 31765, 31964 (CIMMYT); 33402 (Brazil); 63325 (France); 34984 (Peru); 54208 (Russia).