Characteristics of perspective wheat cultivars, admitted to cultivation in the Lower Volga region of the Russian Federation, based on resistance to perynophorosis and tan spot pathogens

Annual monitoring of the phytosanitary condition of wheat crops in the Saratov region evidences the active development of leaf spots and the accumulation of their infectious potential. Pyrenophora tritici-repentis is the causative agent of pyrenophora, or tan spot, and one of the dangerous wheat diseases. Bipolaris sorokiniana is the causative agent of spot blotch, a potentially dangerous wheat disease. In this work, as a result of field and laboratory assessment of 20 varieties of bread wheat ( Triticum aestivum L.) cultivated in the Lower Volga region, samples resistant to the pathogen of tan spot, as well as moderately resistant to the pathogen of spot blotch, were identified for the first time. The results of identification of the Tsn1 / tsn1 gene allele using the molecular marker Xfcp623 showed that among the studied wheat samples, the Tsn1 gene was predominant in winter wheat varieties. For the first time, statistically significant differences were revealed between the average values of field phytopathological estimates of resistance to P. tritici-repentis among varieties from different resistance groups (RR, R, MS and S).The purpose of the study is to assess the resistance of winter and spring bread wheat varieties ( Triticum aestivum L.) cultivated in the Lower Volga region to tan spot and spot blotch pathogens and to identify the dominant/recessive allele of the Tsn1 gene in plants. The work examined 13 varieties of winter bread wheat (Gostianum 237, Lutescens 230, Saratovskaya 8, Guberniya, Mironovskaya 808, Donskaya bezostaya, Saratovskaya 90, Zhemchuzhina Povolzhya, Saratovskaya 17, Kalach 60, Podruga, Anastasia, Sosedka) and 7 varieties of spring bread wheat (Favorit, Prokhorovka, Yugo-Vostochnaya 2, Saratovskaya 70, Saratovskaya 73, Belyanka, Lebedushka). Of these, 16 varieties were approved for use in 2022. Sosedka is a promising variety of winter bread wheat; Gostianum 237, Lutescens 230, Saratovskaya 8 are the Saratov selection varieties of winter bread wheat produced in the first half of the 20th century. Field trials were carried out in 2020-2022 in the breeding nursery of the Federal Center of Agriculture Research of the South- East Region (Saratov). The response of wheat varieties to natural infection by a local population of the yellow spot pathogen was assessed under field conditions using a modified and extended Saari-Prescott scale. In lab tests, plant leaves were infected with P. tritici-repentis and B. sorokiniana . The inoculum consisted of a mixture of several fungal isolates from plant infectious material 2022 from the Saratov ( P. tritici-repentis , ToxA ), and Leningrad ( B. sorokiniana ) regions and the Republic of Kazakhstan ( P. tritici-repentis , ToxB ) obtained from the collection of the All-Russian Research Institute of Plant Protection. For phytopathological assessment of P. tritici-repentis , a scoring scale was used that characterizes the development degree of necrosis and chlorosis. When assessing the resistance of wheat to spot blotch caused by B. sorokiniana , we used a scale developed at the All-Russian Research Institute of Plant Protection. Genomic DNA was isolated from leaves of 5-day-old wheat seedlings using the standard CTAB/chloroform method. After quantification, the DNA concentration was normalized to 30 ng/μl for subsequent PCR. Screening for the presence of a dominant or recessive gene allele ( Tsn1 or tsn1 ) in the the varieties was carried out using PCR with primer pairs Xfcp623F/Xfcp623R (ZAO Evrogen, Russia). The proportion of varieties resistant to P. tritici-repentis isolates capable of producing toxins encoded by the ToxA and Tox B genes was 40 %, to the isolate with ToxA - 55 %, with Tox B - 60 %. The proportion of varieties with moderate resistance to Bipolaris sorokiniana was only 15 %. The genotypes of three winter bread wheat varieties (Gostianum 237, Mironovskaya 808, Podruga) and 5 genotypes of spring bread wheat (Favorit, Prokhorovka, Saratovskaya 70, Sarat