Yield Phenotypic Plasticity and Stability in Semidwarf Winter Wheat (Triticum aestivum L.) Cultivars

Based on the analysis of yield variation observed for nine semidwarf wheat cultivars tested in sixty three yield trials that covered diverse environmental conditions, we consider that, for better description of cultivar response to environments, phenotypic plasticity should include, along with the slope of Finlay-Wilkinson regression, a parameter describing the position of the regression line. The minimum yield predicted by regression at the lowest observed trial average proved to be preferable, as it has more biological sense than the regression intercept, which imply the existence of negative yields, and is more reliable than the observed minimum yield, which is based on results of only one trial. The analyzed cultivars showed large variations in these two components of plasticity, which were not correlated with one another. Yield stability, as described by the coefficient of variation was not correlated with regression slope but was significantly correlated with the minimum predicted yield. Cultivar FDL Columna combined a high regression slope with high minimum predicted yield and lower than average coefficient of variation, while cultivar FDL Consecvent had lower regression slope, combined with good minimum yield and the best yield stability. Both these cultivars had top rankings across the entire range of recorded yield levels, while other cultivars ranked at the top only at high yield levels (Ursita), or at lower yield levels (Glosa).