Grain yield of maize (Zea mays) in the tropics is generally low and information on combining ability among tropical maize inbred lines has not been reported for West Africa. This study was conducted to estimate combining abilities of maize inbred lines developed for West Africa. Crosses obtained from ten inbreds including five of tropical origin (A) and five of temperate x tropical origin (B) were evaluated in three environments of forest-first and -second seasons, and savanna. For the forest, yields of A x A crosses were significantly better than those of A x B which in turn were significantly higher than those of B x B. In the savanna, A x B crosses tended to be better than A x A which in turn seemed better than B x B, although these differences were not significant. Average grain yields of all 45 crosses in the three environments were 3.30 t ha-1 for the forest-first season, 3.61 t ha-1 for the forest-second season and 8.05 t ha-1 for the savanna, showing the greatest yield advantage of maize yield in the savanna. GCA effect was significant in all environments, whereas SCA effect was significant only in the savanna. Furthermore, all the five A type inbreds had positive GCA effects for grain yield in the two forest environments, while three A and two B inbreds had positive effects in the savanna. SCA effects appeared to be the major factor for the high yield potential in the savanna, particularly with A x B crosses. Data obtained from this study show clearly the environmental advantage of maize cultivation in the savanna belt of West Africa and the efficacy of the US Corn Belt germplasm after introduction of tropical adaptation and biotic resistance for the tropics.

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