Genotype by Environment Interaction in Maize Variety Performance Across Nigerian Agro-Ecological Zones

This study analyses genotype by environment interaction in maize variety performance across Nigerian agro-ecological zones, quantifying the relative importance of G×E effects on yield variability and identifying stable high-yielding genotypes for specific environments. Genotype by environment interaction is a central challenge in crop improvement and variety recommendation in Nigeria, where diverse agro-ecological conditions mean that varieties optimal in one zone may perform poorly in another. Understanding G×E structure is essential for efficient variety release targeting and for identifying broadly adapted genotypes. This study uses yield data from multilocation trials of 20 maize genotypes conducted across 12 environments spanning the Sahel, Sudan savanna, Guinea savanna, forest, and mangrove zones from 2019 to 2022, provided by IITA and national research partner data from Kano, Sokoto, Katsina, Kaduna, Niger, Benue, Enugu, Lagos, Rivers, and Borno States. AMMI analysis, GGE biplot methodology, and Eberhart-Russell stability analysis are applied to decompose yield variation into genotypic, environmental, and G×E interaction components. Findings reveal that G×E interaction accounts for 31 percent of total yield variation, comparable to the main genotype effect of 28 percent, confirming the importance of environment-specific variety targeting. GGE biplot analysis identifies three mega-environments: the northern zone, the Middle Belt, and the southern humid zone, with distinctly superior varieties for each. No genotype is broadly adapted across all three mega-environments. The study contributes an original G×E analysis for Nigerian maize and recommends mega-environment-specific variety release policies.

Keywords: genotype by environment interaction, maize varieties, AMMI analysis, GGE biplot, Nigeria.