Combining ability and heterosis estimation in elite sorghum [Sorghum bicolor (L) Moench] inbred lines under moisture stress conditions

Abstract

he most important prerequisite in crop improvement is the selection of suitable parents, which could combine well and produce desirable hybrids. However, lack of potential parents and hybrids, limited genetic variation, narrow genetic base and information on the genetic components are the most important limiting factors for sorghum yield improvement under moisture stress. Therefore, the present study was conducted to determine the combining abilities, heterosis, mean yield performance and 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 cropping season of 2018/19. Combined analysis of variance revealed highly significant differences due to genotypes for all studied traits over locations, which indicates the availability of substation genetic variation among genotypes. Based on general combining ability analysis, inbred line 3 and 4 were identified as best general combiners for both days to flowering and plant height traits whereas inbred line 2 and 7 were identified as best general combiners for stay green traits. 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 nonadditive 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. The maximum grain yield was obtained from a hybrid 4x14 (6.32 t/ha) followed by hybrid 8x15(5.92 t/ha), 1x15 (5.88 t/ha), 13x14 (5.78 t/ha) and 6x15 (5.57 t/ha) with the average value of 5.0 tones/ha which had higher mean value than the mean of the parents and the check. Among the hybrids, 8x15 recorded maximum heterosis (112.41%) over the mid parents, hybrid 1x15 revealed maximum heterosis (68.71%) over the better parent whereas 4x14 recorded maximum grain yield with (30.71%) heterosis over the standard check for grain yield. The two heterotic groups were identified based on their specific combining ability effects and also three heterotic groups were identified based on their general combining ability effects to develop superior hybrids from broad base and suitable parents. Finally, based on mean yield performance, heterotic response, combining ability estimates and nature of gene action for grain yield and its components, inbred lines 4, 9, 10, 11, 12, 13 and the hybrid crosses 4x14, 8x15, 1x15, 11x14, 11x15, 13x14, 6x15 were found to be the most promising and potential varieties which could be exploited commercially after critical evaluation for their superiority and yield stability across the locations over years.