Khablak S. Genetic control of root development in Arabidopsis thaliana (L.) Neynh.

This thesis presents the results of long-term studies on the genetic control of morphogenesis of the root system in A. thaliana that are of interest for the development of theoretical basics of the plant root system genetics and its applications aimed at creating varieties and hybrids that use mineral elements of soil and fertilizers efficiently. The role of the SHR1, SСR1, WOL1, COB1, LIT1, SAB1 and GPA1 genes in the root system formation was established, on the basis of which it was proven that the root system transition from one type to another is genetically determined and depends on the genes regulating the activity of root apical meristem and functioning of pericycle cells. The influence of auxin-, cytokinin- and ethylene-induced mutations on the degree of root branching that causes root system to reduce or increase the root branching order was revealed. The character of the SHR1, GPA1 and COB1 gene interaction effect on root system features that is produced by the type of independent action of genes was determined. The peculiarities of the RHD3, RHD4, CEN1 and SAR1 gene interaction effect on the nature of root hair form formation that is produced by the type of gene complementary action when each of the genes is characterized by its own specific effect were established. The influence of the signal system of plant development regulation on the gene interaction when inheriting root system features was revealed. The character of the GPA1 and SLR1, CTR1 and ALF3 gene interaction effect on root system features that is produced by the type of recessive epistasis in ratio of 9:3:4 was determined. The role of the Etr1-1 and Etr2-1 dominant mutations of the ETR1 and ETR2 genes in heterosis that consists in the mutant gene domination in the F1 hybrids over the wild-type gene was established. The peculiarities of inheritance of the root system features with the SHY2 and MSG1, NPH4 and IAR2, ETR1 and ETR2 gene interactions that determine the polymeric character of the gene actions were determined. On the basis of relationship between plant signal system and gene interaction when inheriting the features, a concept of the gene interaction mechanism was improved. An understanding of heterosis phenomenon nature was deepened, and genes that cause advantage of the F1 hybrids over the parental forms in heterozygous state were found. The presence of genetic polymorphism on the basis of root nutrition and adaptation to mineral nutrition stresses was identified in different nutrition patterns of plant mutant strains with root development disorder, based on which the necessity of controlled breeding by changes in the level of features associated with the effective use of nutrients from soil and fertilizers by plants was justified. The breeding directions for cultivated plants in creation of varieties and hybrids, more sensitive to fertilizer elements, with specified parameters of mineral nutrition that allows to improve the evaluation of breeding material and breeding were established. The understanding of using the economically valuable feature of “root branching” in plant breeding was broadened that ensures the root system flexibility in response to changing environmental conditions, providing a breeder with a specific tool for creation of varieties and hybrids of the cultivated plants that are well adapted to soil conditions and capable of absorbing and using nutrients of soil and fertilizers effectively. The directions of searches for donor plants with high adaptation to unfavorable environmental factors that increase the degree of root branching were determined.