Analyzing genotype-environment interactions and identifying stable and high-yielding stay-green sorghum (Sorghum Bicolor [L.] Moench) genotypes using different stability models

This research sought to develop high-yielding, stable, and drought-tolerant stay-green sorghum genotypes by comprehensively evaluating Genotype Environment Interaction (GEI). Fifteen stay-green sorghum genotypes were assessed across three locations over three years in a randomized complete block design with three replications. Significant genetic variation was observed among genotypes for all evaluated traits, indicating substantial potential for genetic improvement. Environmental factors profoundly influenced genotype performance, and GEI significantly impacted key traits such as Days to Heading, Days to Maturity, and Thousand Seed Weight, particularly Days to Heading, suggesting the presence of distinct mega-environments. The average grain yield across all locations was 4.14 t ha-1. ETSC 300552 (G1) recorded the highest yield. The observed substantial yield variations across environments and strong GEI confirmed the critical need for multi-environment testing in cultivar development. AMMI analysis revealed highly significant main effects for genotype, environment, and their interaction on sorghum grain yield, underscoring considerable genetic differences and varied performance across environments. The first two interaction principal component axes accounted for 49.6% of the total GEI variation. The Environment contributed a dominant 27% of the total sum of squares, compared to only 10% from genotype, highlighting the overwhelming influence of environmental factors on sorghum grain yield and the necessity of Multi-Environment Trials (MET) for identifying stable, high-yielding genotypes. The "which-won-where" polygon view from GGE biplot analysis effectively elucidated genotype-environment relationships, explaining 59.39% of the total variation and identifying three distinct mega-environments. Within the first mega-environment (E3, E8, E7), G1, G5, G7, and G14 performed best, with G1 identified as the winning genotype. Analysis of grain yield alongside 16 stability parameters identified G1 and G7 as the most stable genotypes. Specifically, G1 exhibited low deviation from regression, low Wi² and σ² _i values, and a low coefficient of environmental variation (13.6), all while maintaining a high grain yield. This combination of attributes positioned G1 as a highly desirable genotype with broad adaptability. The stability parameter θ₀ exhibited a strong positive correlation with grain yield, making it an excellent indicator of both high performance and stability. Furthermore, through direct matrix ranking, G1 was ranked first by farmers, aligning with the scientific findings. Based on its consistently superior performance, high stability, and positive farmer evaluation, G1 was officially approved by the Ethiopian variety releasing committee for national release.