Genotype-by-environment Interaction and Yield Stability Analysis of Egyptian Cotton (Gossypium Barbadense L.)

Genotype-by-environment interaction (GEI) poses a significant challenge to achieving consistent cotton yield across diverse agro-ecologies. This study aimed to quantify the components of yield variation, identify stable high-yielding genotypes, and delineate mega-environments within the Nile Delta for efficient cultivar deployment. Seven cotton genotypes (four advanced lines and three commercial cultivars) were evaluated across six environments, generated from three locations over two growing seasons (2023 and 2024). Data were analyzed using combined analysis of variance, Additive Main Effects and Multiplicative Interaction (AMMI), and Genotype plus Genotype-by-Environment (GGE) biplot models. The combined ANOVA revealed that GEI was the predominant source of variation, accounting for 47.12% of the total sum of squares, followed by environmental (32.91%) and genotypic (19.97%) effects. AMMI analysis identified 'Line 1' and 'Line 4' as highly stable genotypes. The GGE biplot effectively categorized the test environments into three distinct mega-environments (MEs): a favorable ME (Kafr El-Sheikh) where 'Line 1' performed best; a moderate-stress ME (Damietta) where 'Line 4' excelled; and a high-stress ME (El-Sharkia) where the commercial cultivar 'Giza 94' showed superior stability. These findings provide a robust framework for strategic cultivar recommendation and breeding targeted at specific agro-ecological zones in the Nile Delta, which can enhance yield stability and regional productivity.