Combining Abilities and Heterotic Patterns among Early Maturing Maize Inbred Lines under Optimal and Striga-Infested...

Area of Science:

• * Agricultural Science
• * Plant Breeding
• * Genetics

Background:

• * Successful hybrid crop development relies on understanding the general combining ability (GCA) of inbred lines and specific combining ability (SCA) of hybrid combinations.
• * Early maturing maize inbred lines are vital for diverse agricultural systems, especially in challenging environments.
• * Striga, a parasitic weed, poses a significant threat to maize production in Africa, necessitating the development of resistant hybrids.

Purpose of the Study:

• * To evaluate the combining ability of thirty early maturing maize inbred lines in both optimal and Striga-infested conditions.
• * To classify these inbred lines into heterotic groups using two distinct methods: General Combining Ability Effects of Multiple Traits (HGCAMT) and Single Nucleotide Polymorphism Genetic Distance (SNP-GD).
• * To compare the effectiveness of the HGCAMT and SNP-GD methods in heterotic grouping.

Main Methods:

• * Generation of 150 single-cross hybrids from 30 maize inbred lines using the North Carolina Design II mating method.
• * Field evaluation of hybrids and local checks across optimal and Striga-infested environments in Ghana and Nigeria (2016-2017).
• * Analysis of combining ability, gene action (additive vs. non-additive), maternal effects, and heterotic grouping using HGCAMT and SNP-GD.

Main Results:

• * Grain yield inheritance was primarily governed by non-additive gene action in both environments and additive gene action across environments.
• * Non-additive gene action influenced most traits under Striga infestation, with exceptions like Striga damage rating.
• * Inbred lines TZEI 127 and TZEI 40 showed significant positive GCA effects for grain yield, indicating potential for yield improvement.
• * The SNP-GD method proved more effective for classifying the thirty maize inbred lines into heterotic groups.

Conclusions:

• * The SNP-GD method is the most adequate approach for heterotic grouping of early maturing maize inbred lines.
• * Understanding gene action and combining ability is crucial for optimizing maize hybrid development under varying environmental conditions.
• * Identifying elite inbred lines like TZEI 127 and TZEI 40 with favorable alleles can accelerate the development of high-yielding maize hybrids.