Theoretical justification of the possibility to select perspective individuals in cultivar populations of self-pollinators on the example of soybean

Breeding practice shows that soybean cultivars developed by synthetic breeding methods are submitted for the state variety testing in the F10-F11 generation. But the newly bred cultivars are not completely homozygous. The studies were related to the determination of the frequencies of formation of atypical and suitable for selection promising individuals in soybean cultivars developed by synthetic breeding methods. The studies were carried out in 2019-2020 at the central experimental base of V.S. Pustovoit AllRussian Research Institute of Oil Crops, Krasnodar. In the experiments, we used cultivars of our own breeding: Selena, Puma, Vita, Irbis, Bars, Barguzin and Sayana with a total age of 11-15 years from the year F1 hybrids were obtained. To confirm the practical possibility of isolating individuals differing from the phenotypic varietal norm in varietal populations, a complete examination of the crops of all studied soybean cultivars was carried out. In the fields of all cul-tivars, individuals were identified that differed from the varietal norm phenotypically. Mostly, the isolated individuals were distinguished by an increased plant height, a more powerful habit, an increased number of beans per plant, and resistance to lodging. The facts of the detection of atypical individuals with improved morphological traits in soybean cultivars of different ages confirm the possibility of individual selection of plants in varietal populations based on morphometric traits. The statistical dynamics of a decrease in heterozygous individuals in increasing generations in a hybrid self-pollinating population in terms of the n-number of paired genes, by which the parental forms can hypothetically differ, were calculated using the modified formula of S. Borojevic (1984). It was found that the frequency of formation of phenotypically different individuals in varietal populations of soybeans depends on the total age of the cultivar. The frequency of the formation of morphologically different individuals decreases with an increase in the number of generations of the cultivar. Individual selection of individuals with positive phenotypic differences from the varietal norm can be recommended as an additional source of promising and practically homozygous starting material for accelerated analytical breeding of soybean.