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

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 (H2 = 0.62), moderate for ear rot (H2 = 0.36) and low for aflatoxin (H2 = 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.