Virulence of Puccinia triticina in the North Caucasus region of Russia

Aim of study: To analyze the structure of P. triticina populations by a virulence survey in the North Caucasus region of Russia from 2011 to 2015. Area of study: The North Caucasus region is a leading grain production region in Russia where wheat leaf rust causes losses in yield. Material and methods: Uredinial samples of leaf rust were collected in all agro-climatic zones of the North Caucasus on the production sites of winter wheat and on the plots of official state trials. Single uredinial isolates (a total of 564) were tested for virulence with 41 'Thatcher' near isogenic lines with Lr resistance genes. Main results: Clones virulent to Lr9, Lr42, Lr47 and Lr50 were not found. Isolates virulent to the Lr19, Lr24, Lr29, Lr41, Lr43 + 24, Lr45, Lr52 genes were characterized by low frequencies. The 564 fungal isolates studied were represented by 564 virulence phenotypes, the majority of them with a virulence complexity from 9 to 19. A high level of intrapopulation fungus diversity in virulence was noticed during the whole period of research (Shannon diversity index from 2.994 to 3.314). The differences in the frequencies of virulences in the years of research were small (Rogers distance from 0.001 to 0.160). Research highlights: Due to the fact that the North Caucasus region is a zone of epiphytotic danger and high variability of the P. triticina population, the analysis of the genetics of the fungus population is important for the strategy of varietal distribution in the region and development of rust-resistant varieties.