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 F 1 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 F 1 hybrids for specific combining ability.

The magnitude of genetic expression and associations among traits are important for the prediction of response to selection in diverse environments and provide the basis for planning and evaluating breeding programs. In this regard, a cross classification mating design was used to produce hybrid sorghum populations, which were evaluated in a randomized completed block design with three replications at four environments in Northern Cameroon. Data on grain yield, days to anthesis, plant height, inflorescence length, threshing percentage and seed mass were collected and subjected to statistical genetic analyses. Significant genotype × environment interaction effects were observed for all traits. Genetic variance was essentially attributed to additive gene effects, with dominance variance for grain yield being negligible. However, the reverse was observed for threshability. Genetic variance components were much higher for plant height and grain yield than for days to anthesis, seed mass and threshability. Heritability estimates for plant height and inflorescence length were high (77 and 54 percent respectively) while the estimates for grain yield and threshability were low (14 and 5 percent respectively). Grain yield had positive genotypic correlation with most of the traits. Days to anthesis were negatively correlated with vegetative and reproductive traits. These results suggest that improvement of days to anthesis, plant height, and inflorescence length should be faster because of higher heritabilities and greater phenotypic variation. However, selection for earliness and reduced plant height would not be possible without hampering grain yield. Selecting for yield primary components namely inflorescence length and seed weight would be effective for increasing production. In addition, optimizing agronomic practices and improved experimental design would increase the selection efficiencies.

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Seventy-five sorghum hybrids and twenty parental lines were evaluated for two consecutive years at two locations. Our objective was to compare relative stability of grain yields among hybrids and parental lines. Mean grain yields and stability analysis of variance, which included linear regression coefficient (bi) and deviation from regression (S 2 d) were used to determine relative stability. Genotypes x environment interactions were significant. Significant hybrids x environment interactions were also detected. Hybrids and parental lines had significantly different regression coefficients, as indicated by hybrid-environment (linear) mean squares. Hybrids showed significantly higher mean yield compared with parental lines and the yield advantage generally increased with increasing environmental yield potential. Hybrids bi values were significantly higher (0.02-2.14) than for parental line (-0.82-1.52). Deviations from regression for hybrids were higher than those of parental line. Crosses between hybrids ICSA 38 x Damougari, and ICSA 39 x Damougari produced the highest grain yields. Their bi values were not significantly different from unity, but S 2 d estimates were significantly greater than zero. Thirteen hybrids recorded bi values close to unity, small S 2 d and grain yields higher than the mean of all the hybrids. Based on our findings it is apparent that in the dry land agriculture of west Africa, selection of hybrids for superior yields across environments should be emphasized first, and then the relative stability of these hybrids over environment should be determined.