African Journals Online
African Crop Science Journal

The Journal of Tropical Crop Science and Production
VOLUME 9 NUMBER 3, 2001
Abstracts

SEGREGATION FOR SEED WEIGHT, POD LENGTH AND DAYS TO FLOWERING FOLLOWING A COWPEA CROSS 

B. EWA UBI,* H. MIGNOUNA¹ and G. OBIGBESAN² 
International Institute of Tropical Agriculture (IITA), PMB 520, Ibadan, Nigeria 
¹Department of Crop Science, University of Calabar, Calabar, Nigeria 
²Department of Agronomy, University of Ibadan, Ibadan, Nigeria

(Received 11 October, 1999; accepted 31 March, 2001) 

ABSTRACT

Field studies were conducted to evaluate the segregation of the F3 (early generation) and F6 (late generation) families for seed weight, pod length and days to flowering among cowpea inter-sub-specific crosses. A wide range of segregants were provided in this cross and families were highly significantly different in the three agronomic traits studied. The continuous distributions observed for these traits studied in both generations confirms the quantitative nature of inheritance for these traits. Broad sense heritability estimates ranged from 47.8 to 91.1%. Estimates of genetic advance ranged from high to low and were consistent in both generations for all the traits. The F3 and F6 generations were not significantly different in all the three agronomic traits. Intergeneration correlations ranging from 0.35 to 0.49 also revealed strong associations between traits measured in the two generations. A no significant drop was observed between F3 mean and the corresponding F6 mean. This suggests the existence of a good measure of additive and possibly of additive x additive components of variance (which alone are fixable through subsequent inbreeding) although some amount of dominance and duplicate epistasis (which are non-fixable) may also be operative. The results of this study indicate that selection in early generations for superior types is feasible. 

Key Words: Agronomic traits, early generation, late generation, Vigna unguiculata 

RÉSUMÉ

Des études en champs ont été conduites pour évaluer la ségrégation des familles en F3 (jeune génération) et F6 (génération avancée) quant au poids des graines, la longueur de la gousse et le nombre de jours à la floraison chez des sous-espèces de niébé croisées. Une large gamme de lignées ségrégantes était introduite dans ces croisements et les familles utilisées étaient sensiblement différentes pour les trois caractères agronomiques étudiés. Les distributions continues observées pour ces caractères étudiés au sein des deux générations confirment la nature quantitative du patrimoine héréditaire pour ces caractères. Les estimations générales d'héritabilité se rangeaient entre 47,8 et 91,1%. Les estimations de transferts génétiques allaient des plus basses aux plus élevées et elles étaient constantes au sein des deux générations pour tous les caractères étudiés. Les corrélations entre générations s'est rangées entre 0.35 et 0.49 et montrées aussi les fortes associations entre les caractères mesurés pour les deux générations. Un déclin non significatif était observé entre la moyenne de F3 et son correspondant de F6. Ceci suggère l'existence d'une bonne mesure additive et peut-être de l' additive x additive composante de la variance (fixable pendant le croisement ultérieur) même si certains traits de dominance et de double épistasies (non fixables) pourraient être opérationnels. Les résultats de cette étude montre qu'une sélection parmi les jeunes générations de races supérieures est faisable.

Mots Clés: Caractéristiques agronomiques, jeune génération, génération avancée









HETEROSIS AND COMBINING ABILITY IN A DIALLEL AMONG EIGHT ELITE MAIZE POPULATIONS

M. NIGUSSIE and H. ZELLEKE ¹
Nazret Research Centre, P. O. Box 436, Nazareth, Ethiopia
¹Alemaya University of Agriculture, P.O. Box 138, Dire Dawa, Ethiopia

(Received 3 April, 2000; accepted 12 March, 2001) 

ABSTRACT

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