Abstract:
Sorghum is an important cereal crop grown primarily in arid and semi-arid climates with a wide range of adaptability to various agro-ecological conditions of Ethiopia. However, the limited availability of improved varieties and the low production potential of landraces have constrained sorghum production in Ethiopia and a little information is available on combining ability, heterosis, and gene action for locally adapted sorghum landraces. Therefore, the research was undertaken to generate information on combining abilities, heterosis, and gene action governing the quantitative traits for yield and its related traits. The experimental materials consisted of fifty-six parents, one hundred eight F1 progenies produced by Line x Tester mating design, and five standard checks, which makes a total of 169 entries planted by using simple lattice design with two replications at Melkassa and Miesso in main cropping season of 2020/2021. The yield and yield-related traits of the combined analysis of variance revealed highly significant (P≤0.01) variation due to genotypes for all traits over locations, which indicated the existence of sufficient genetic variability and potential for selection of genotypes with high performance for agronomic traits. From the mean performance, high grain yields were obtained from the hybrids ATX2783 x IS38312(6.67t/ha), ATX2783 x ETSL100383 (6.40t/ha), ATX2783 x ETSL100007(6.21t/ha), ATX2783 x ETSL101152(6.16t/ha) and ATX623 x IS38341(5.82t/ha) with the overall value of 4.32t/ha, which was greater than the mean value of the parents and the checks. The result of line x tester analysis of variance for pooled combining ability revealed that the mean square due to GCA of lines showed highly significant (P≤0.01) variation for all studied traits, and also mean square due to GCA of testers showed highly significant (P≤0.01) variation for days to flowering, days to maturity, plant height, leaf width, number of productive tillers, panicle length, stay green and thousand kernel weight. The mean square due to SCA of lines x testers interactions exhibited highly significant (P≤0.01) variation for all characters studied, except number leaf per plant and leaf width. A total of twenty-two parental lines showed positive and highly significant (P≤0.01) GCA effects for grain yield, and the contributions of GCA of lines and testes were 59.22% and 0.04% to the total cross variances for grain yield, respectively. Whereas, twenty-one and eleven cross combinations exhibited highly significant (P≤0.01) and significant (P≤0.05) positive SCA effects for grain yield, respectively, and it contributed 40.74% to a total cross variance for grain yield. Variance due to sca was higher than gca and the ratio of variance of general to specific combing ability was less than unity for all the traits studied indicating the preponderance of non-additive gene action governing in the inheritance of these traits. Based on the SCA effects of grain yield, male lines were classified into two heterotic groups aligned to the different cytoplasmic systems of testers. Among the crosses, ATX2783 x ETSL100829 recorded the highest heterosis (242.12%) over the mid parents, hybrid ATX2783 x ETSL100978 revealed the highest heterosis (191.01%) over the better parent, whereas ATX2783 x IS38312 recorded highest grain yield with 81.43 and 40.00% heterosis over the best check ESH-5 and Argity, respectively. The information generated in this study will be used for future sorghum breeding programs and hence, additio nal information needs to be generated by evaluating the genotypes at multi-locations.