Optimization of methods for assessing the resistance of winter rye to snow mold in natural and artificial infection backgrounds

Snow mold is an economically important and progressive disease of winter rye caused by several species of low temperature fungi (ascomycetes and basidiomycetes) and fungal-like organisms (oomycetes), with yield losses of up to 30–50 %. The aim of this work is to improve methods for field evaluation of winter rye resistance to snow mold, both under artificial infestation and natural conditions. The research was carried out in 2019–2024 in the Republic of Tatarstan. Since 2021, the most aggressive strains of pink (Microdochium nivale), grey (Typhula incarnata) and speckled (T. ishikariensis) snow mold pathogens collected in the Volga Federal District have been used for artificial infection. The experiment involved 60 winter rye samples, including cultivars bred by Tatar Research Institute of Agriculture, FRC Kazan Scientific Center of RAS. For a more accurate assessment of the degree of damage and identification of resistant genotypes, a detailed 9-point scale was developed, with 1 − no damage and 9 − complete damage. Under natural conditions, the average damage point ranged from 2.41 to 5.15, while under artificial infestation it was significantly higher, from 4.48 to 8.40. Most winter rye cultivars showed a moderate to moderately susceptible type of reaction on a natural background in four out of 5 years of observation. The frequency of susceptible samples on the artificial infection background reached 96 % in 2024. The use of artificial infection backgrounds allows snow mold damage to be assessed independently of weather conditions and speeds up the breeding process, providing an objective assessment of genotype resistance. As a result of research, the methodology for establishing autonomous infection backgrounds has been optimized. It involves the selection of a site with a long snowmelt period and flat relief, the use of inoculum containing virulent strains of pathogens characteristic of the region and a special method of introducing the pathogen.