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Abstract 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 programs. However, limited genetic variation and a lack of potential parents and hybrids are the most limiting factors for improving sorghum in moisture-stressed areas.Therefore, this study was conducted to estimate the combining abilities and determine the gene action governing the quantitative traits for yield and its components using a 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 performedusing an 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 genotype, 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 was greatest for general combiners in inbred lines 6, 10 and 12. The hybrid crosses 4x14, 8x15 and 11x14 were identified as the best specific combiners for grain yield, while the hybrid 1x15 was the mostspecific 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 nonadditivegene 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, and 13 and hybrid crosses 4x14, 8x15, 1x15, 11x14, 11x15, 13x14, and 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 the years, based on combining ability estimates and the nature of gene action for grain yield and its components.
Begna et al. (Wed,) studied this question.