Object: improvement of immunological approaches to sunflower breeding by developing an evaluation system for determining resistance of starting material and sunflower hybrids created on its basis to major pathogens; peculiarities of manifestation of major diseases; inheritance patterns of resistance levels and reaction norms of F1-F2 hybrids for affection by pathogens; formation of collections, creation of sunflower lines and F1 hybrids of with genetically determined resistance to downy mildew, Phomopsis and Gray Mold (Botrytis cinerea). Objectives: theoretical justification of methodological fundamentals of sunflower breeding for resistance to major pathogens, improvement of immunological approaches in the crop breeding and their practical use in breeding programs. Methods: general-scientific, specific (field, laboratory), statistical. Novelty: For the first time in Ukraine, the degree of variability of the pathogenic complex of sunflower under arid and wet conditions of cultivation years was determined, and association of frequencies of their manifestation was analyzed. Methodological fundamentals of the sunflower breeding process for resistance to diseases were theoretically rationalized, and ways of their optimization were practically outlined by using interval estimates of the root-mean-square deviation (CI) or the least significant difference (CI LSD0.5) as a system for determining immunological characteristics of sunflower genotypes, depending on the infection level, with taking into account weather conditions and dynamics of disease spreading from year to year. The baseline levels of infectious backgrounds were determined by intensity of development of Phomopsis and Gray Mold (Botrytis cinerea) at 25.0% and 100.0% of their prevalence, respectively, and at 34.0% of affected plants for downy mildew. The genetic diversity of sunflower was expanded by creating 45 lines-carriers of resistance genes (Pl6) to virulent races (races 730 and 732) of the causative agent of downy mildew. These lines are also resistant to the causative agents of stem canker and gray rot and a basis for generating genetically protected hybrids for the next 3-5 years. Results: the methodology of formation of sunflower collections of different uses (trait, working collections) was developed; a scale for assessing resistance of sunflower to downy mildew, which, unlike the existing one, ranks accessions according to their resistance scores with singling out immune ones and takes into account the affection range with determination of the statistical increment, addition of which determines the margin of a successive group of resistance. The method of evaluation and differentiation of starting material for sunflower breeding by resistance to necrotrophic diseases was improved as a system for determining immunological characteristics of accessions, depending on infection level. Twenty sunflower hybrids with high resistance (9 points) to downy mildew and tolerance (7 points) to stem canker and gray rot pathogens with a set of valuable economic features were created. Valuable starting material (45 lines) for sunflower breeding, which combine resistance to pathogens of downy mildew, stem canker and gray rot with a number of agronomical features was created. Degree of Implementation: The scientific results have been used in the breeding programs of the Laboratory of Sunflower Breeding and Genetics of the Plant Production Institute named after VYa Yuriev of NAAS, the Institute of Oil Crops of NAAS and in the educational processes of Odessa, Sumy and Kharkiv National Agrarian Universities. The hybrids created are grown in Ukraine on the area of about 250,000 hectares, giving yields of 2.3-2.8 t/ha in production conditions. Eleven certificates of authorship for sunflower hybrids have been received. Scope of implementation: scientific institutions of NAAS and the Ministry of Agrarian Policy and Food of Ukraine, higher educational establishments, agrarian enterprises of Ukraine.
