STABILITY ANALYSIS OF YIELD OF POTATO GEN OTYPES IN RIO-GRANDE-DO-SUL

The objective of this work was to compare the amount of genotype-envir onment (GE) interaction described by using the additive main effects a nd multiplicative interaction (AMMI) model and the analysis of linear regression (LR), and to compare the yield stability of potato (Solanum tuberosum L.) genotypes. Ten genotypes were evaluated in 34 environme nts (local, cultivation period and year combinations) in Rio Grande do Sul, Brazil, in 1994 and 1995. The sum of squares (SS) for the regres sions accounted for only 19.5% of the interaction SS, whereas the firs t principal component (PC1) of the analysis of the principal component s accounted for 44.6% of the interaction SS. The SS of PC1 was more th an twice the combined SS of all three regressions (jointed, genotypic and environmental). Therefore, the AMMI analysis was more efficient in describing the GE interaction than the LR. The cultivar Monte Bonito is unstable, but has the highest yield; 'Baronesa' is moderately stabl e and has high yield; 'Santo Amor' and 'Trapeira' are the most stable, with yield above average; 'Macaca' and 'Cristal' are the most unstabl e, with yield below average; 'Atlantic' is unstable and has low yield.