The dissertation theoretically summarizes and practically solves an important scientific task, which consists in improving the methodological aspects of comprehensive evaluation of winter bread wheat genotypes based on the combination of yield and grain quality indicators. The regularities of yield formation and grain quality indicators of winter bread wheat varieties and breeding lines depending on the sowing dates (September 26, October 5, and October 16) and preceding crops (corn, sunflower, soybean, mustard, green manure) in environments of the central part of the of Ukrainian Forest Steppe have been established. The efficiency of using different sowing dates after different preceding crops to differentiate and select winter bread wheat genotypes according to yield, stability and quality indicators has been proven.
In environments of the central Ukrainian Forest-Steppe, it was experimentally proven for the first time that sowing at different dates after different preceding crops contributes to the differentiation of winter bread wheat varieties and breeding lines in terms of yield and a complex of quality indicators. The efficiency of experimental data analysis when using GGE and GYT biplot graphic models is shown. There were determined the part in sum square for the factors genotype, hydrothermal conditions, sowing date, preceding crop and their interactions in variation of yield and grain quality indicators of winter bread wheat varieties and breeding lines. The grain quality indicators that are maximally determined by the genotype as compared to other influencing factors for the effective management of breeding process have been identified. The strength of the relationship between yield and grain quality indicators of winter bread wheat varieties and breeding lines was determined.
The practical significance of the dissertation work lies in the improvement of methodical approach to the evaluation of breeding material of winter bread wheat based on the combination of yield and grain quality indicators to differentiate varieties and breeding lines and to select the most promising of them. On the basis of this approach, the breeding line Lutescens 37519 has been selected; it was transmitted to the Ukrainian Institute of Plant Varieties Studying and Protection for the State Qualification Examination as the new winter bread variety wheat MIP Vidznaka. Valuable genetic sources of winter bread wheat with high yield, high grain quality indicators and their combination have been identified, which were transferred to the institutions of the Ministry of Education and Science of Ukraine, the National Academy of Agrarian Sciences of Ukraine and the agricultural enterprise. The optimal sowing dates after various preceding crops were determined to obtain the maximum yield in combination with high grain quality indicators of varieties and breeding lines of winter bread wheat in the conditions of the central Forest-Steppe of Ukraine.
The dissertation analyzes the current state of research on the formation of yield and of grain quality indicators depending on abiotic and anthropogenic factors. Urgent, insufficiently researched questions regarding the differentiation of winter bread wheat genotypes by yield and a set of grain quality indicators for such preceding crops as sunflower, corn, soybean, mustard, which occupy significant crop areas in Ukraine and therefore are one of the main preceding crops, have been identified for winter wheat. Depending on the preceding crop and the weather conditions of cropping season, the sowing dates vary significantly, which in turn calls for the need to study their efficiency after the mentioned above preceding crops for selecting varieties and breeding lines with an optimal combination of yield, stability, and grain quality indicators.
It has been experimentally proven that the use of different sowing dates after different preceding crops is an effective approach in the organization of genotype-environmental tests, which allows identifying genotypes being specifically adapted to certain conditions (preceding crops and sowing dates) and with a relatively higher level of stability when sowing in different dates after various preceding crops. It is advisable to use such approach at the final stage of selection to identify the best genotypes, as well as to develop the basic elements of crop management practice for newly-created varieties. The results obtained are of great importance for increasing the efficiency of breeding work with winter wheat and for the agricultural production of Ukraine as a whole.
