Gene Action and Combining Ability for Yield and Panicle Traits in Sorghum under Semi-arid Conditions of Kenya
Naaman Arodi *
Department of Plant Sciences & Crop Protection, University of Nairobi, P.O. Box 29053–00625, Nairobi, Kenya.
Kahiu Ngugi
Department of Plant Sciences & Crop Protection, University of Nairobi, P.O. Box 29053–00625, Nairobi, Kenya.
*Author to whom correspondence should be addressed.
Abstract
Aims: To determine the nature of gene action and combining ability governing yield and panicle traits in sorghum (Sorghum bicolor L.) under semi-arid conditions of Kenya and to identify parental lines and cross combinations of potential value for breeding.
Study Design: A North Carolina Design II mating scheme was evaluated in a randomised complete block design with three replications.
Place and Duration of Study: KALRO Kiboko Sub-Centre, Makueni County, Kenya, during the 2020/2021 long and short rainy seasons.
Methodology: Two elite sorghum inbred lines (IESV23006DL and IESV23010DL) and two landraces (Redswazi and Wheatland) were crossed to generate four progenies. The progenies and parental checks were evaluated for days to 50% flowering, plant height, panicle length, panicle width, panicle yield, ear exsertion and seed set. Analysis of variance and combining ability analyses were conducted using GenStat 15th Edition.
Results: Significant genotypic variation (P ≤ .05) was detected for days to 50% flowering, plant height and panicle yield. General combining ability effects were significant for several traits, and the GCA/SCA variance ratio exceeded one for panicle length, panicle width and panicle yield, whereas it was below one for days to 50% flowering and plant height. IESV23010DL showed significant negative GCA effects for days to flowering and plant height, while Redswazi showed a positive GCA effect for panicle yield. Significant SCA effects were detected for days to flowering in IESV23006DL × Redswazi and IESV23010DL × Redswazi, and for panicle length in IESV23010DL × Wheatland.
Conclusion: Both additive and non-additive genetic effects contributed to variation in the evaluated traits. The results indicate that selection may be useful for traits with a relatively greater GCA contribution, while hybrid evaluation may be useful where non-additive effects are relatively more important. The identified parental materials and crosses warrant further evaluation across environments before use in breeding programmes.
Keywords: Sorghum, gene action, combining ability, general combining ability, specific combining ability, North Carolina Design II, panicle traits, yield, semi-arid environments, Kenya