Nenka M. Expression of Combining Ability in Sugar Beet Sterility Maintainers Subject to Genotype and Environmental Factors

3. The thesis deals with studying regularities of combining ability of the female hybrid component, response of hybrids to regulated environmental factors (mineral fertilization background and growing space), as well as with development of methods for selection of the best high adaptive genotypes according to complex agronomic traits against breeding agro backgrounds feature various combinations of environmental factors. Studied are five sterility maintainers, five their CMS analogues, and twenty simple sterile hybrids as female components based on CMS, improved is their identification by genetic value. For the first time the features of inheritance and combining ability variation according to elements of productivity and specificity of genotypes reaction due to changeable environmental factors have been studied. It is shown that genotype features in breeding lines completely reveal themselves against extended growing space. It was established that according to sowing qualities of seeds elements it is possible to take off inbreeding depression by using a female component as simple sterile hybrid component. Revealed is specifics of changes in the structure and share of its components in female component of hybrids at phenotypic level in genetic control of agronomic traits and their manifestations in changing environment. Proved is the feasibility of using simple sterile hybrids as female components with high combining ability, improved sowing qualities, environmental sustainability against regulated environmental factors while creating high adaptive hybrids of sugar beet based on CMS. Created are five high adaptive hybrids exceeding group's performance standard by 9.5...10.7 %. Keywords: sugar beet; sterility maintainers; CMS lines; simple sterile hybrids; breeding background; environmental sustainability and plasticity.