In uence of Environments on The Amount and Stability of Grain Yield in The Modern Winter Wheat Cultivars II. Evaluation of Each Variety

Cultivars grown at the farmers’ Şelds were selected and tested for three consecutive years at eight locations in Bulgaria, which were representative for the entire territory of the country and had contrasting soil and climatic conditions for crop growing. SigniŞcant variations of grain yield were found among the investigated cultivars regardless of their speciŞc response to the year conditions and the location. The interaction genotype x environments was signiŞcant and high, and was of non-linear type. The changeable environmental conditions caused different reactions of the cultivars, which allowed dividing them into groups according to the plasticity and stability they demonstrated. The variation in this experiment determined through Principal Component Analysis (PCA reached level four, which is comparatively rare for this trait. On the whole, PC1 had low value (49%), while PC2 was high (16%). There were several cultivars with very high PC2 values, exceeding several times the values of their respective PC1. The percent of variation caused by the environment was signiŞcant for grain yield under the conditions of Bulgaria. The investigated cultivars differed not only by grain yield but also by their plasticity and stability under changeable environments, the percent of the genotype effect being about 12 % for the entire experiment. It was found that each cultivar can give high grain yield at high ecological stability regardless of its genetic potential for quality. Best balance between grain yield and stability was found in cultivars Aglika, Demetra, Iveta (Şrst quality group), Galateya, Slaveya (second quality group) and Todora, Kristal and Pryaspa (third quality group)