Kirchuk Y. Breeding improvement of bread winter wheat by combining different genetic systems of leaf rust resistance for the conditions of the steppe zone of Ukraine

In the conditions of southern Ukraine, the breeding value of collection and breeding material for resistance to leaf rust was first investigated depending on the presence of genetic systems of different ecological and geographical origin. The effectiveness of combining the studied genetic systems in one genotype to create breeding material with durable resistance to this disease was revealed. The research on the peculiarities of inheritance of the trait of winter wheat resistance to leaf rust in populations of F2 hybrids from crosses of parental components with different levels of resistance was further developed. Collection and breeding samples of winter wheat with genetic systems of leaf rust resistance of different ecological and geographical origin were used as material for the study. The collection material of different origins was analysed for adult and juvenile resistance. It was found that the most effective sources in terms of the average resistance rate were genotypes belonging to the groups "Institutions of the NAAS system" and "Western Europe" with an average juvenile resistance rate of 6.5 and 5.2, and adult plant resistance rate of 7.2 and 7.4 points, respectively. The effects of resistance sources of different origin on yield and resistance to leaf rust during ontogeny were studied on the material of recombinant lines of the final stage of breeding. It was found that the genetic systems "Lr34", "Western Europe" and "Translocation (1BL/1RS) + Lr34 + Western Europe" were the most effective in terms of average resistance during ontogeny (juvenile and adult) and yield. The regularities of inheritance of the trait of resistance to leaf rust in hybrid populations F2, from crossing of parental components with different genetic systems of control of this trait, contrasting in the level of its expression, were investigated. The polygenic character of inheritance of resistance to leaf rust was established, which corresponded to different types of gene interaction, depending on their combination in a separate group of crosses. The degree of phenotypic dominance in F2 populations ranged from negative dominance (Д-) to positive superdominance (НД+). The highest percentage of resistant lines was achieved when combining the following genetic systems (Serbia-Odesa + Lr34) + "Phyto", (Aeg. СL) + "Phyto", (Aeg. СL) + (Serbia-Odesa + Lr34) and Serbia-Odesa + Phyto in which inheritance was by the type of positive heterosis (PD+). The effect of resistance genes of Western European origin and the Lr34+ gene block on resistance to leaf rust in winter wheat lines from simple and triple crosses in different generations was studied. A clear tendency to increase the level of resistance in lines where at least one parent had the Lr34+ gene was found, regardless of the crossing scheme. This pattern can be traced both in the early generations of hybrids (F4) and in later generations (F12). Genotypes with Lr- genes from parents from Western Europe in their pedigree showed significantly higher average leaf rust resistance grades both in early generations (F4) and at the final stage of selection (F12). The study of the effects of combining different genetic systems on the main economically valuable traits in the creation of breeding material with pyramidal resistance showed that the most effective combinations of genetic systems for ensuring a high resistance level while maintaining the main economically valuable traits in winter bread wheat lines at the optimal level are the combinations Western Europe + Serbia-Odesa and Translocation (1BL/1RS) + Lr34 + Western Europe + Serbia-Odesa. A special scheme of the breeding process was developed to increase the efficiency of work on the creation of winter bread wheat genotypes with durable resistance. It was used to obtain a new source material for breeding with pyramids of leaf rust resistance genes, the presence of which was verified by PCR analysis.