Goal of the research was to study the genetic diversity of bread winter wheat cultivars resistance to brown rust in the conditions of natural infection background north-eastern Forest-steppe of Ukraine and the formation of a working genotypes collection to create a new breeding material.

The material for research was the varieties of bread winter wheat, listed in the StateRegister of Plant Varieties suitable for dissemination in Ukraine in 2012. The field experiments were conducted on the experimental field of Sumy National Agrarian University during 2012-2014. The experience was carried out on the plots of 1 m² area by SH-1 manual seeder in three-dimensional repetition. Plots were located in the repetitions by systematic method. Testing the varieties resistance to brown rust was fulfilled by the common methods on the natural infection background. The degree of pathogen resistance was determined visually on flag leaf by 9-rating immunological scale adopted in the COMECON countries.

According to the results of our study, the varieties were divided by the degree of resistance into 5 groups according to the scale. Analyzing the obtained results it had been revealed that the minimum index was in the group of varieties which were amenable to pathogens and amounted to 3,1 points, and the maximum index was in the group with a very high resistance – 8,6points.

The coefficient of variation in all groups did not exceed 10%, that indicated insignificant variability of the index. Relatively low coefficient of variation (of 1,1%) was seen in the first group, where the varieties had a very high resistance. That index was the highest (4,7%) one in the five groups.

Having considered the error band, significant deviation was revealed between the third, the fourth and the fifthgroups with the first and the second ones, and between the first, the second and the third groups with the fourth one, because they did not overlap each other. The varieties of the first group had the highest average arithmetical value of the resistance index (8,4 points). The lowest index was observed in the fifth group, where the degree of resistance was favorable (3,4 points). Such varieties as Smuglyanka, Kalynova, Er 24220 were extremely resistant, Kryzhynka, Remeslivna, Myronivska 65, Zolotokolosa, Vesnyanka and Er 24210 varieties were of high resistance. They can be used for creating a new breeding material as a source of resistance to the brown rust pathogen.

Analyzing the indicators of resistance to brown rust, it had been revealed that the maximum pathogen indexes were observed in the varieties with 1AL/1RS translocation, and minimum – in the varieties that did not contain translocations.

The coefficient of variation in the varieties with wheat-rye translocation was less than 10%, that indicated insignificant variability, and in the varieties that did not contain translocations was greater than 20%. Therefore, variability was significant.The error band revealed significant deviations of the varieties, that did not contain translocations and the varieties with wheat-rye translocation, as they did not overlap each other. The analyzed data had shown that the varieties with wheat-rye translocation were more resistant to brown rust, because they contained introgressive genes from rye.

In 2012-2014 growing years weather conditions contributed to the development of the brown rust pathogen, which suggested the possibility of evaluating the resistance of varieties on the natural infection background.

Such varieties as Smuglyanka, Kalynova, Er 24220 were extremely resistant. Kryzhynka, Remeslivna, Myronivska 65, Zolotokolosa, Vesnyanka and Er 24210 ones were of high resistance. They can be used for creating a new breeding material as a source of resistance to the brown rust pathogen.

The varieties with wheat-rye translocation were more resistant to brown rust, because they contained introgressive genes from rye.

Key words: winter wheat, immunity, cultivars, resistance genes, brown rust.