Responses of different arabica coffee (Coffea arabica L.) clones to varied environmental conditions

Different improved coffee arabica crosses having resistance to coffee berry disease and leaf rust, plus a standard cultivar, were grown under a range of environmental conditions in a series of field trials in Kenya. The effects of location and year of production and their interactions with the clones were determined for berry yield. These data were used to estimate and compare methods of analysis of GEI. An AMMI model, joint regression model and ANOVA with repeated measurements were used to investigate these interactions. The results indicated the relative effects of the clones and the environmental conditions, with Meru being the location where there was greatest discrimination between the clones, probably because it was better suited for coffee. Clones, environments and joint regressions combined accounted for 31.20% of the interaction, leaving a residual of 68.80%. Significant residual mean squares showed the relationship between clones and environments not to be strictly linear, thus indicating that regression analysis did not always provide good estimates of individual clonal performance across environments. High correlations were obtained between mean yield and regression coefficients and between ecovalence and mean square deviations as well as the coefficient of determination. Results showed that the improved clones surpassed the standard cultivar both in terms of yield and stability. Different analyses of the various aspects of genotype response enabled the 21 clones to be classified into different similarity groups based on their performance and phenotypic stability as measured by various stability parameters and the use of biplots from the AMMI analysis.