Evaluation of the resistance to P. triticina of Bulgarian common and durum wheat cultivars under controlled conditions and in infection field

During 2018 - 2020, in the infection field of Dobrudzha Agricultural Institute - General Toshevo, Bulgaria, 34 common winter wheat and 5 durum wheat cultivars were tested for resistance to leaf rust (P. triticina). The response of the common wheat cultivars to the P. triticina pathotypes predominant in this period was studied under controlled conditions, at seedling stage. The full set of pathotypes from the pathogen population identified during the respective year of study was taken out to the infection field to achieve a maximum rate of infection accumulation on the standard susceptible cultivar Michigan amber. The field parameters final disease severity (FSD), average coefficient of infection (ACI) and resistance rate were estimated. The type of resistance of the studied cultivars was determined. The results showed that at seedling stage most of the cultivars had compatible, susceptible reaction to the P. triticina pathotypes used in the study. Under the conditions of the infection field, 7.7 % of the cultivars exhibited high level of resistance (VR). Cultivar Zhana responded with stable resistance (R), and the cultivars with this type of resistance constituted 2.6%. Moderate resistance (MR) was registered in 5.1% of the tested cultivars. With very resistant to resistant reaction (VR - R) responded 18% of the cultivars. Resistant to moderately resistant (R - MR) was the reaction of 43.6% of the investigated cultivars, and 12.8% reacted within the range of high to moderate resistance (VR - MR). Some cultivars demonstrated variation of resistance within a wider range. The cultivars, which were within the range of highly resistant to moderately susceptible (VR - MS) constituted 5.1%, as well as those within the range moderately resis-tant to moderately susceptible (MR-MS). In some cultivars, such as Merilin, the level of resistance remained the same as in the previous years, regardless of the variations in the pathogen population, while in other cultivars, such as Karina, Enola and Lazarka, the resistance varied over years. All cultivars with stable resistance under the conditions of the infection field (from high to moderate), can be used in the breeding programs as parental components for the development of varieties resistant to leaf rust.