BACKGROUND: Although people began to consume coffee for its stimulating effect, the demand for decaffeinated coffee is increasing and now accounts for 10% of the total amount of coffee consumed in the world. Forty-two arabica coffee genotypes originating from Ethiopia were tested to assess caffeine content variability among them, and the correlation of caffeine content with cup quality and green bean physical characteristics.

A study was conducted at Northwestern Ethiopia, during 2010 main cropping season. Fifteen maize genotypes were evaluated at four locations that differ in soil type, altitude and mean annual rainfall. The experiment was laid out in a randomized complete block design with three replications. Stability parameters that are useful tools for identification of genotypes with specific and wide adaptations, and contrasting the role played by genotype, environment and G x E interaction in multilocational variety trials were considered and analyzed. The highly significant G x E interactions indicated that genotypes performance was inconsistent across testing locations and need to be tested in several locations in order to select stable genotypes. Jibat-851, Wonchi and BHQPY-545 exhibited high mean grain yield across environments and average responsiveness with high degree of stability indicating general adaptability and thus can be recommended for north western Amhara region and for areas with similar environments. The best genotype with respect to location Adet was Gibe-1 while Wonchi was the best genotype for Merawi area. Phb-3253 performed well at Motta, while Phb-30G19 and Jibat-851 performed well at Finoteselam. Therefore, these genotypes can be recommended according to their specific adaptation area.

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Potato is one of the important crops grown in mid and high altitude areas of Ethiopia. Several potato genotypes have been introduced in different parts of this region. However, the stability and performance of these genotypes are not yet assessed. Therefore, the objective of this study was to determine the effect of genotype, environment and their interaction for tuber yield and identify stable potato genotypes. The study was conducted using eight potato genotypes in rainfed production season of years 2010 and 2011 at five potato growing locations in the region. Randomized complete block design with three replications was used for the experiment. Among the testing locations, the superior mean tuber yield (25.43 t/ha) was obtained at Adet while the inferior (13.89 t/ha) was at Injibara. Similarly, among the genotypes, CIP-396004.337 gave the highest mean tuber yield (25.66 t/ha), while CIP-395011.2 gave the lowest (17.78 t/ha). Combined ANOVA indicated that the main effects due to environments, genotypes and genotype by environment interaction were highly significant. The contribution of E, G and GEI to the total variation in tuber yield was about 47.11%, 8.83% and 44.07%, respectively. The GEI was further partitioned using GGE biplot model. The first two principal components obtained by singular value decomposition of the centered data of tuber yield explained 71.26% of the total variability caused by (G + GE). Out of these variations, PC1 and PC2 accounted 51.24% and 20.02% variability, respectively. GGE biplot view of this study identified Serinka as ideal testing location and CIP-396004.337 as ideal genotype for Amhara region in Ethiopia.

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