Abstract
Abstract The topcross method for assessing combining abilityis more economical and less laborious compared to diallel analysis, and also allows the breeder to obtain quite valuable information about the inbred material. In this research, the determination of the general (GCA) and specific (SCA) combining ability of barley (Hordeum vulgare L.) hybridsin two regions of Kazakhstan contrasting in soil and climatic conditions,the role of additive and non-additive genes in the determination of thetraits understudyhas beenrevealed. It is concluded thatthe predominance of additive gene interactions in the control of the traits understudyin theconditions of the Aral Sea region indicates the possibility of effective selection already in the F 2 generation, and in the piedmontzone of the Almaty region, due to the high determination of these traits by dominant genes, it is necessary to differentiate the populations of hybrids, starting from the first generation and further selection shall be carried out in several cycles until the achievement of homozygosity of loci carrying dominant genes. Consequently, the genetic contribution of the additive and non-additive effects of genes to the determination and inheritance of the studied traits significantly depends on the conditions of growing the genotypes of spring barley. Of greatest practical interest are the varieties Rihane, WI2291/Roho/WI2269 from the International Center ICARDA and the variety-tester Odessa 100 (Odessa Selection and Genetic Institute, Ukraine) with high GCA and SCA effects, little dependent on growing conditions, which are recommended to be used as reliable donors in breeding programs.