Genotype x Environment Interaction and Yield Stability in Improved Rice varieties (Oryza sativa L.) Tested Over Different Locations in Western Oromia, Ethiopia

Eleven rice genotypes were evaluated at 6 environments in Western Ethiopia during 2015 and 2016 main cropping season. The objective of the study was to determine the magnitude of genotype x environment interaction and performance stability in the rice genotypes. The study was conducted using a randomized complete design with 3 replications. Genotype x environment interaction and yield stability were estimated using the additive main effects and multiplicative interaction and site regression genotype plus genotype x environment interaction bi plot pooled analysis of variance for grain yield showed significant (P<0.01) to significant (P<0.05)  differences among  genotypes, environment, genotype x environment interaction effects. This indicates that genotypes differentially respond to the change in test environments or the test environments differentially discriminated the genotypes or both. Environment accounted for 69.39%, of the total yield variation, genotype for 8.50% and genotype x environment for 3.90%, indicating the need for spatial and temporal replication of the trials.  Regression and AMMI analysis were employed in order to determine the stability of genotypes. The two models regression analysis and AMMI revealed similar result in that Adet and Hidassie  were stable and widely adapted genotypes. Adet and Hidassie varieties were the most stable and high yielding genotype and was therefore recommended for commercial production in the western Ethiopia upland rice  growing areas. Keyword s : Rice, genotype x environment interaction, stability parameters, yield