Combining ability studies in tropical sorghum (Sorghum bicolor (L.) Moench)

Sorghum varieties grown in West Africa usually have low production potential. Information on combining ability of diverse open-pollinated cultivars and gene pools is needed for efficient choice of breeding methods and parental materials to use in developing breeding programs to increase production. Twenty parental lines including 15 restorers and 5 male-sterile A-lines were mated. The 20 parents were sampled from elite germplasm available for cultivar development in the region. Combining ability studies were conducted on these parents along with their F1 hybrids for grain yield, days to anthesis, plant height, inflorescence length, threshing percentage, and seed mass in 2 years and in two locations. Each location-year combination was considered as an environment. For each trait, general combining ability (GCA) and specific combining ability (SCA) effects were estimated using the line-tester method of analysis. Highly significant GCA effects of males were found for all traits under study. Significant SCA was detected in all traits except inflorescence length. From the ratio of general combining ability to specific combining ability non-additive gene action was predominant for most traits. Parental lines with good performance per se and good performance in crosses for most agronomic traits included: ICSA 902 NG, NR 71182-2, NR 71182-3, CS 144, and Damougari. Both additive and non-additive gene effects are involved in variations observed among crosses. Hybrid breeding could contribute to sorghum improvement in the dry land agriculture of West Africa. Importance of genotype-environment interaction underlines the necessity of evaluating breeding materials under broad range of conditions. The various traits studied can be improved through breeding procedures using a range of different intra-population and inter-population selection procedures. In hybrid breeding procedures, testing of parent lines for general combining ability should be supplemented by evaluation of individual F1 hybrids for specific combining ability