Estimation of Combining Ability and Gene Actions in Maize for Grain Yield and Selected Agronomic Traits under Contrasting Soil Nitrogen Conditions

Background: High cost, cropping pressure on soil and climate change are currently posing constraint to maize production in Africa. Development of, and genetic studies on adapted varieties of the crop might be useful to overcome the challenge.

Aim: To determine combining ability and gene actions of the maize inbred lines in their crosses under contrasting nitrogen conditions.

Materials and Methods: 150 hybrid maize generated from 20 inbred lines were evaluated in 2014 and 2015 in low and optimal N conditions in an experiment laid out in 19 × 8 lattice design with three replicates. Days to anthesis (DTA) and days to silking (DTS) were counted. Anthesis-silking-interval (ASI) and grain yield (GY) were estimated. Plant and ear heights were measured while stay green (SG), plant aspect (PASP) and ear aspect (EASP) were scored. Analysis of variance was performed on the data collected. The general combining ability (GCA), specific combining ability (SCA) and relative contribution of GCA and SCA on progeny for agronomic performance were also estimated.

Results: Significant differences existed due to environments, genotypes, male, female and female × male for GY and other traits. Only BD74-171, BD74-179, BD74-170 and BD74-175 had significant high GCA effects for GY under low N. The BD74-128, BD74-171, TZEI188, BD74-55, TZEI1, BD74-179, BD74-175 and BD74-399 had significant GCA effects under optimal N. Only 23 of the 150 hybrids had significant high SCA in at least one of the N conditions. From these, 14 and 15 hybrids had high positive and significant SCA in low and optimal N conditions, respectively. The GCA and SCA varied for all the traits signifying prominence of both additive and non-additive genetic components.

Conclusion: Inheritance of GY, DTA, DTS and SG are governed by non-additive gene action but vice versa for PH and EH under both N conditions. Effects of male were greater than those of female in gene expression for the GY under the N conditions, but males were genetically diverse than females for the other traits in the low N condition. Effects of both male and female are important in inheritance of flowering and growth parameters under optimal N condition.