Heterosis and combining ability in a diallel among eight elite maize populations

Crossing maize (Zea mays L.) genotypes obtained from different sources could result in better utilisation of hybrid vigor. Such heterotic response is poorly exploited in the drought-stressed areas of Ethiopia, due to problems in adaptation of some of introduced materials. This study was conducted to determine the heterosis and combining ability of eight elite maize genotypes. The eight parents were selected based on per se and top-cross performance. The parents were crossed in diallel fashion. The resulting crosses and their parents were evaluated in a randomised complete block design with three replicates at three locations for two years in Ethiopia. The combined analysis of variance showed that the mean square due to genotypes and general combining ability (GCA) were significant (P=0.01) for all the six traits studied. However, the mean square due to specific combining ability (SCA) was significant for days to tasselling, days to silking, plant height, and grain yield. The magnitude of GCA was higher than the SCA in all the cases indicating that additive gene action was more important than non-additive in the inheritance of these traits. Mid-parent heterosis occurred in varying degrees for the different traits. It was in the range of -11.6 to 21.9% for grain yield. DTP-2 C4 and Melkasa 92 DTP1 had significant and positive GCA for days to tasselling, days to silking, plant height, and grain yield. Hence, these parents can be used to develop intermediate maturing varieties while AW-8047 significantly reduced (had negative GCA for) tasselling, silking, and plant height without affecting grain yield indicating that AW-8047 can be used as source population to develop early varieties. RÉSUMÉ Le croisement des génotypoes de maïs obtenus des differentes sources pourraient aboutir à une meilleures utilisation de la vigeur des hybrides. La réponse hétérotique est pauvrement exploitée dans les régions à stress de séchéresse en Ethiopie, suite aux problèmes d'adaptation de quelques materiels introduits. Cette étude a été conduite pour déterminer l'hétérosis et l'efficacité de combinaison de huit génotypes élites de maïs. Les huit parents ont été séléctionnés sur base des caractères intrénsiques et la performance supérieure des croisés . Les parents ont été croisés selon le modèle diallèle. Les croisés et leurs parents ont été évalués dans un dispositif des blocs complètement randomisés avec trois répétitions dans trois localités pendant deux ans en Ethiopie. L'analyse combinée de la variance a montré que le carré moyen des génotypes et l' efficacité générale à la combinaison (GCA) étaient signifacatifs (