Multi-trait selection of tropical maize hybrids for combined productivity, agronomic stability, and aflatoxin resistance

Abstract

Aspergillus ear rot (ear rot) and aflatoxin contamination, caused mainly by Aspergillus flavus , threaten maize productivity, grain quality, and food safety in tropical and sub-tropical regions. Although significant breeding progress has been made, selection for resistance remains challenging due to environmental conditions, genotype × environment interaction (G×E), low heritability of resistance traits, and the need to simultaneously improve productivity. The objectives of this study were to: assess the effect of genotype, environment and G×E, examine trait relationships, and identify superior maize hybrids with favourable multi-trait performance. Eighty-three maize inbred lines were crossed with two testers using a line × tester mating design. The resultant 166 testcrosses and six checks were evaluated across four environments with two replications in each environment under artificial inoculation using a highly toxigenic A. flavus isolate (La3228). Data were analysed using linear mixed models, with variance components estimated by REML. Environmental effects were significant for aflatoxin accumulation and ear rot ( p ≤ 0.05), while hybrids differed significantly for grain yield and ear rot ( p ≤ 0.01). There was no significant G×E interaction for grain yield, aflatoxin accumulation and ear rot ( p ≥ 0.05). Broad-sense heritability estimate was high for grain yield (H 2  = 0.62), moderate for ear rot (H 2  = 0.36) and low for aflatoxin (H 2  = 0.22), indicating strong environmental influence on the expression of the resistance-related traits. Grain yield was not significantly correlated with aflatoxin accumulation (r = 0.08), suggesting that selection for grain yield may be independent of aflatoxin accumulation. However, grain yield was significantly and negatively correlated with ear rot (r = -0.20*). The first two principal components of the genotype plus genotype × environment (GGE) biplot explained 76.4% of the total variation among the selected hybrids and identified two mega-environments, revealing differential adaptation among hybrids. The sequential application of multi-trait genotype–ideotype distance index (MGIDI) and GGE biplot identified five testcrosses, En80, En74, En102, En157, and En65 combining competitive grain yield, favourable stability, and resistance-related traits. These hybrids are promising for further multi-environment evaluation for their potential contribution to the development of maize hybrids with improved productivity and reduced aflatoxin accumulation in tropical and sub-tropical regions.