Abstract:
In Ethiopia, rice variety development program was started recently but many rice varieties were recommended for production. But recommendation of varieties and introduction of new genotypes alone might not be enough to increase rice yield. This required conducting a multi-location evaluation of varieties and identified wide to specific adaptable variety is critical steps in breeding. Therefore, this research was conducted to determine the effect of genotype (G), environment (E) and genotype x environment interaction (GEI), and stability of the rice varieties for yield and related traits and to evaluate and stratify rice testing environments in Ethiopia. Twenty rice varieties were evaluated at six sites during 2016/17 in randomized complete block design with three replications. The combined analysis of variance over environments showed significant differences among genotypes (G), environments (E) and significant effect of GEI on phenology, growth traits, yield components and grain yield of varieties. Additive Main Effects and Multiplicative Interaction (AMMI) model revealed that G, E and GEI contributed 3.03 to 33.58, 25.69 to 72.02, and 7.09 to 30.36 %, respectively, to the total sum squares of traits. The E and GEI had a higher contribution than G for most of the traits, and GEI had larger contribution than G and E to the variations of varieties for yield. The interaction principal component axis one (IPC1) and two (IPC2) contributed 37.94 to 88.85 and 8.92 to 87.13% to sum of squares of GEI, respectively. Various stability parameters were used to estimate stability of the varieties tested for grain yield. NERICA-3, Hidasse and Chewaqa varieties had 15.99, 15.7 and 15.42% higher yield than average yield of genotypes, respectively, and identified as responsive to changing environments. These varieties were AMMI selected as the first four best varieites across poor to most favorable environments and GGE biplot identified them as ideal and stable varieties suggested to be used for production across environments. NERICA-12 and ADET varieties had 12.85 and 8.29% higher yield, respectively, than average yield of varieties and identified as most stable by most of the stability parameters and considered as widely adaptable varieties. NERICA-4, NERICA-13 and Getachew varieties had 11.97, 10.83 and 5.7% yield advantages over the average yield of varieties, identified as stable varieties by most of the stability parameters and selected as the first four best varieties at poor to average environments suggested to be used in these environments. The GGE biplot identified Pawe and Tepi as most discriminating environments, Manbuk and Maitsebri identified as average environments and Woreta as representative environments that could be used as test environments to develop varieties at different stages of breeding activities. The stability parameters from ER's and AMMI models had positive and significant rank correlations with most of the stability parameters and yield and considered as sufficient to evaluate the stability of varieties for yield. In conclusion, it is suggested to conduct the experiment over seasons to certain the results due to the significant effect of GEI and its larger contribution to the variations of varieties for yield and other traits.