The stability of varieties is an important element of the integrated protection of flax from
The purpose of the research is to characterize the varieties of long-legged flax included in the State Register of Breeding Achievements in terms of resistance to fusarium wilt, rust, anthracnose and pasmo. The research was conducted in 2018-2020 in vegetative, laboratory and field conditions at the All-Russian Research Institute of Flax (currently: A separate division Research Institute of Flax). As an object of research, we used varieties of flax-long-legged flax included in the State Register of Breeding Achievements of the Russian Federation for 2018-2020. Methods. The studies were carried out using modern mycological and phytopathological methods. Laboratory, vegetation and field experiments were conducted according to the All-Russian Research Institute of Flax methods. Results and practical significance. Among the studied 66 varieties, 56.1 % were highly resistant and resistant genotypes to fusarium wilt and 58.3 % - to rust. The specific weight of the Flax Institute varieties for this period was 34.8 %. High resistance to rust and fusarium wilt was characterized by the VNIIL selection varieties: Universal, Diplomat, Alexim, Dewdrop, Zaryanka, Aleksandrit. For the first time, scientists of the Flax Institute have created varieties of flax-long-legged (Diplomat and Tonus) resistant to three diseases: rust, fusarium wilt and anthracnose, and the Caesar variety-to four diseases. All varieties, with the exception of Diplomat and Tonus, a selection of the Flax Institute, were susceptible to anthracnose. The Grant variety of the selection of the Republic of Belarus and the Caesar variety were resistant to pasmo by 59.7 %, the rest were characterized by resistance to damage by 27.8-42.0 %. Scientific novelty. The characteristics of the resistance of the varieties included in the State Register of Breeding Achievements of the Russian Federation are comprehensively described on infectious and provocative backgrounds using natural and synthetic populations of pathogens diseases of flax. Varieties with group resistance to 2, 3, and 4 diseases are identified. The use of flax varieties resistant to the most economically dangerous diseases in flax crops will reduce the infectious potential and its accumulation in nature.