Resistance of soft winter wheat (Triticum aestivum L.) varieties cultivated in the Tambov region to tan spot (Pyrenophora tritici-repentis)

The Tambov region is part of the Central Black Earth region with highly developed grain production. In the structure of cultivated area, grains make up to 50-55 % of arable land. Productivity, gross yield and quality of grain in the region vary significantly and are determined by many factors, including damage to plants by fungal pathogens. The fungus Pyrenophora tritici-repentis is the causative agent of tan spot, or yellow spot, a dangerous disease of wheat that progresses rapidly in grain-producing countries. The introduction of disease-resistant varieties into grain production is an economically beneficial and environmentally friendly method of plant protection that increases the efficiency of chemical and agrotechnical measures. In this work, when studying the P. tritici-repentis population racial composition in the Tambov region, five races of the pathogen were identified for the first time. Races producing PtrToxC predominated, and races with the ToxA gene encoding exotoxin were less common. For the first time, eight wheat varieties were revealed that were highly resistant to the phytopathogen in field and laboratory conditions, molecular screening also confirmed resistance to PtrToxA. The purpose of the work was to investigate the race composition of Pyrenophora tritici-repentis isolates from the Tambov population of 2022, to assess the resistance of winter common wheat varieties cultivated in the Tambov region to the yellow spot pathogen, and to identify their dominant/recessive allele of the Tsn1 gene. A set of 28 varieties of winter common wheat ( Triticum aestivum L.) comprised 20 varieties approved for use since 2022 (Antonivka, Bezenchukskaya 380, Biryuza, Dominanta, Don 93, Donera, Donskoy Surpriz, Zvonnitsa, Izyuminka, Inna, Lipetskaya Zvezda, Lgovskaya 4, Mironovskaya 100, Mironovskaya 808, Moskovskaya 39, Moskovskaya 40, Moskovskaya 56, Odesskaya 200, Sintetik, Skipetr), the remaining 8 varieties (Kosovitsa, Kruiz, Laguna, Latynevka, L'govskaya 167, Prestizh, Proza, Spartak) are not approved for zonal use. The resistance of wheat varieties to P. tritici-repentis was assessed in lab tests in 2022 using common methods. The infectious material was collected in 2022 in the Tambov region. From 19 affected samples of winter bread wheat, 68 monoconidial isolates of P. tritici-repentis were purified on the V4 nutrient medium. The response of wheat seedlings to inoculation with a suspension of P. tritici-repentis was assessed on days 5-6. With a set of differentiators, the Glenlea variety and the lines 6B365, 6B662 as identifiers of the toxins PtrToxA, PtrToxC and PtrToxB, the racial composition of the P. tritici-repentis population was identified based on the response of the leaves (necrosis/chlorosis) to the pathogen invasion. In 2020-2022, field assessments of wheat variety resistance were performed at the stationary site (the Central Russian branch of Michurin Federal Scientific Center, Tambov District, Tambov Province) under natural infection. Genomic DNA was extracted from leaves of 5-day-old wheat seedlings using the standard CTAB/chloroform procedure. DNA concentration was normalized to 30 ng/μl for PCR. Isolates were screened for the dominant Tsn1 or recessive tsn1 alleles using primers Xfcp623F/Xfcp623R. Among the Pyrenophora tritici-repentis isolates from winter bread wheat of the Tambov Province, three races were common, of which race 4 did not produce the toxins PtrToxA, PtrToxB and PtrToxC, race 3 produced the toxin PtrToxC, and race 1 did not produce PtrToxA and PtrToxC. Races 8 (PtrToxA, PtrToxB and PtrToxC) and 2 (PtrToxA) were classified as rare. We did not find races 5 (PtrToxB), 6 (PtrToxB and PtrToxC) and 7 (PtrToxA and PtrToxB) in the population. Race 3, producing the ToxC gene encoded exotoxin, was the most abundant in the P. tritici-repentis population of the Tambov Province; races producing PtrToxA were less frequent. Practically, seven varieties, the Lipetskaya Zvezda, Moskovskaya 56, Moskovs