The study was undertaken with the objective to examine the nature and to quantify the magnitude of genotype x environment interaction effects on soybean [Glycine max (L.) Merr.] grain yield and to determine the winning genotype (s) for test environments in north western Ethiopia. The experiment was executed at four different locations of Ethiopia for two consecutive years (2007 and 2008) using thirty two genotypes including two checks. Randomized complete block design with three replicates was employed. The combined analysis of variance over environments explained soybean grain yield was significantly (p<0.001) affected by environments (25.58%), genotypes (14.87%) and genotype x environment interaction (59.55%). The result depicted differential performance of soybean genotypes at different test environments and hence the interaction was crossover type. The genotype main effect plus genotype x environment interaction (GGE) biplots were applied to analyze and visualize pattern of the interaction component. The first two principal components (PC1 and PC2) of the GGE explained 63.4% with PC1=41.6 and PC2=21.8 of the GGE sum of squares using environment standardized model. Genotypes, G13 (TGX-1998-29F), G3 (TGX-849-313D), and G7 (TGX-1889-29F) combined both high mean yield and high stability performance across the test environments and could be characterized as an ideal genotypes.
Key words: Glycine max, genotype plus genotype x environment interaction (GGE), Ethiopia, stability, yield.