Multi-environment evaluation and stability analysis of early-maturing drought-tolerant tropical maize (Zea mays L.) hybrids using AMMI and GGE models

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Introduction: Adaptability and stability analysis play a key role in genotype selection under Genotype x Environment Interaction (GEI) for identification of suitable genotypes adapted to target environments. Methods: The current study analyzed GEI for stability and adaptability of drought-tolerant three-way hybrids using the additive main effect, multiplicative interaction (AMMI) and Genotype main effect, and genotype x environment interaction (GGE) models. Grain yield data used for the analysis was recorded from the trial conducted during 2018 and 2019 for two (wet) seasons, at six test environments; with three environments in Iringa district, two environments in Kongwa district (Dodoma region), and one environment in Kiteto district (Manyara region) using alpha lattice design. The field and agronomic management of the trial was standard at all test environments; data collected from environments that were not affected by drought were analyzed as optimal while that from environments which were slightly affected by drought were analyzed as moderate stress and the rest from severely drought affected sites were analyzed under severe stress. Results: Differences for grain yield were not significant (P<0.05) between maize hybrids analyzed under optimal conditions but significantly different when analyzed under moderate and severe stress conditions. Grain yield heritability estimates of 0.7 and 0.6 under optimal and moderate drought conditions, respectively, indicate strong genetic control of grain yield. Several hybrids outperformed commercial checks by up to 20% under drought stress. Grain yield for the 10 top performing hybrids ranged from 8 to 7.4; 6.7 to 4.6 and 3.1 to 0.9 t ha-1 under optimal, moderate and severe stress, respectively, which was better than SAWA, the drought tolerant check. The genotype main effect (G) and environment main effect (E) were highly significant (p<0.001) for grain yield; however, G × E effects were not significant. Ranking sites based on power of discriminating genotypes and representativeness, NGUMBI was the highly discriminating site, while IGULA was the most representative. MLALI and KIHOROGOTA were identified as the core test sites within the second quadrant. Discussion: Based on AMMI and GGE models, we identified stable and widely adapted hybrids and those with specific adaptation for deployment in semi-arid regions of Tanzania.

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