Immunity and plant protection UDC 632.4:632.938.1:57.053:577.19:635.262 doi: 10.15389/agrobiology.2016.5.722rus doi: 10.15389/agrobiology.2016.5.722eng GENETIC STRUCTURE OF REGIONAL POPULATIONS OF Mycosphaerella graminicola (Septoria tritici), THE SEPTORIA LEAF BLOTCH AGENT OF WHEAT E.V. PAKHOLKOVA, N.N. SAL’NIKOVA, N.A. KURKOVA All-Russian Research Institute of Phytopathology, Federal Agency of Scientific Organizations, 5, Institute, pos. <...> Bol’shie Vyazemy, Odintsovskii Region, Moscow Province, 143050 Russia, e-mail pakholkova@vniif.ru Acknowledgements: The authors thank Dr. S.B. Goodwin (USDA-ARS, Crop Production and Pest Control Research Unit, Small Grain Fungal Disease Laboratory, USA) for kindly providing seeds of the wheat varieties with known resistance genes Stb1-Stb8. <...> Supported financially by International Science and Technology Center (ISTC, Kazakhstan) Received February 26, 2016 A b s t r a c t Mycosphaerella graminicola (anamorph Septoria tritici), the causal agent of septoria tritici blotch (STB) of wheat, is dominating species in Septoria/Stagonospora complex on crops in the main grain-producing areas of Russia. <...> Resistance to STB may be either quantitative (horizomtal) or isolate-specific (vertical). <...> The genfor-gen interaction in the «wheat―M. graminicola» pathosystem has been demonstrated by genetic analysis; therefore, the aviability of resistance genes in the host proposes the existence of specific virulence genes in the pathogen. <...> The relative frequency of virulence genes within a geographic region may be calculated as a fraction of the isolates expressing this virulence genes from the overall number of isolates used in the study. <...> The purpose of the present study was to estimate the virulence genes in populations of M. graminicola from different geographic regions of Russia on the basis of a genfor-gen relationship, using the cultivars with known resistance genes, i.e. Bulgaria 88 (Stb1), Oasis (Stb1), Veranopolis (Stb2), Israel 493 (Stb3), Tadinia (Stb4), CS/Synthetic 7D (Stb5), Flame (Stb6), Estanzuela Federal (Stb7), W7984 (Stb8). <...> A total of 47 isolates from the North-Caucasian region, 66 isolates from the Central-Chernozem region, 29 isolates from the Volga region, 64 isolates from the Central region, and 34 isolates from the North-West region were tested under greenhouse and grows chamber conditions. <...> The virulence was estimated on seedlings at two-leaf stage, using two parameters <...>