Heterosis and combining ability of elite highland adapted maize (zea mays. L) inbred lines for desirable agronomic traits

Abstract

Maize (Zea mays L.) is one of the cereals that provide calorie requirements in the Ethiopian diet. The national average maize yield in Ethiopia is low and thus, knowledge of combining ability and heterosis is a prerequisite to develop high yielding maize varieties. The objective of the present study was to estimate combining ability of elite maize inbred lines for grain yield and related agronomic traits, to identify crosses with higher yield than the standard check and to determine the relationship existing between grain yield andyield related traits. A total of 36 diallel crosses generated by crossing 9 elite maize inbred lines using half diallel mating scheme and four standard checks were studied for different agronomic and yield traits during the 2017 cropping season at Ambo and Kulumsa Agricultural Research Centers. The genotypes were evaluated in alpha lattice design replicated twice in both locations. Analyses of variances showed significant mean squares due to crosses were observed for most traits studied.The highest grain yield was obtained from crosses L1 x L3, L3 x L8, L4 x L8 and L8 x L9.GCA mean squares were significant for all studied traits whereas, SCA mean squares were significant for grain yield, days to anthesis, ear per plant and ear diameter. Relatively larger GCA over SCA variances were observed in the current study for most studied traits revealed the predominance of additive gene action in controlling these traits. Inbred lines L3 and L8 were the best general combiners for grain yield, and hence are promising parents for hybrid development program. Inbred lines L2, L4, L6, L7 and L8 had negative and significant GCA effects for days to anthesis and silking. Whereas, L1, L2 and L6 showed negative and significant GCA effects for plant and ear height. Based on mean grain yield, standard heterosis and specific combining ability effects, L1 x L3, L1 x L5, L2 x L4, L2 x L7, L3 x L8, L7 x L9 and L8 x L9 are promising crosses that could be promoted for further use in maize breeding program. Grain yield revealed positive and highly significant (P<0.01) phenotypic and genotypic correlation with number of ears per plant, ear length, number of kernels per row and thousand kernel weight. The information generated from this study shall have important implications in the development of maize varieties with desirable traits’ composition for highland sub-humid agro-ecology of Ethiopia.