The success of a plant breeding program greatly depends on the right choice of parents for hybridization and the gene action of different economic traits. Genetic variation is a key component in broadening gene pools in any given crop population and is critical to the success of yield improvement program. However, limited genetic variation and lack of potential parents and hybrids are the most limiting factors for improvement of sorghum in the moisture stress areas. Therefore, the study was conducted to estimate the combining abilities and determine gene action governing the quantitative traits for yield and its components using line x tester mating design. The experimental materials consisted of fifteen parents along with their twenty six hybrids and one standard check. The experiment was laid out using alpha lattice design with two replications at Mieso and Kobo during the main cropping season of 2019. For all of the traits studied, the combined analysis of variance indicated highly significant variations due to genotypes, indicating the presence of considerable genetic variation among genotypes. Inbred lines 3 and 4 were selected as the best general combiners for both days to flowering and plant height traits, while inbred lines 2 and 7 were identified as the best general combiners for stay green traits, based on general combining ability analysis. Thousand seed weight showed best general combiners in inbred line 6, 10 and 12. The hybrid crosses 4x14, 8x15 and 11x14 were identified as best specific combiners for grain yield while hybrid 1x15 was best specific combiner for days to flowering, days to maturity, panicle length, panicle width and thousand seed weight. The estimates of general and specific combining ability revealed the preponderance of non-additive gene action since the ratio of general combining ability to specific combining ability was less than unity for all the traits under study except for plant height. Eventually, Inbred lines 4, 9, 10, 11, 12, 13 and hybrid crosses 4x14, 8x15, 1x15, 11x14, 11x15, 13x14, 6x15 were found to be the most promising and potential genotypes that could be exploited commercially after critical evaluation for superiority and yield stability across locations over years, based on combining ability estimates and nature of gene action for grain yield and its components.

Keywords: General combining ability; Specific combining ability; Gene action; Sorghum; Hybrid; Drought