N. TSENOV and D. ATANASOVA
Dobrudzha Agricultural Institute, BG - 9520 General Toshevo, Bulgaria
TSENOV, N. and D. ATANASOVA, 2015. Influence of environments on the amount and stability of grain yield in the modern winter wheat cultivars. II. Evaluation of each variety. Bulg. J. Agric. Sci., 21: 1128–1139
Aims: The large number of wheat cultivars developed in Bulgaria requires evaluation of yield variation in the grain production regions of Bulgaria. The analysis on the interaction of the cultivar with the growing conditions was used to make a specific evaluation of each cultivar for its ecological plasticity and stability.
Methods: Cultivars grown in the farmers’ fields 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. Multiple statistical methods and approaches were applied to evaluate the adaptability of each cultivar by grain yield against the background of the complex genotype x environment interaction. A number of parameters and indices were calculated using several types of software (STABLE, GEST98, GGE biplot 6.5, JMP 10) to find out the variation and correlations among the cultivars.
Key results: Significant variations of grain yield were found among the investigated cultivars regardless of their specific response to the year conditions and the location. The interaction genotype x environments was significant 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 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.
Conclusions: The percent of variation caused by the environment was significant 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 (first quality group), Galateya, Slaveya (second quality group) and Todora, Kristal and Pryaspa (third quality group). Cultivars Sadovo 1 and Pobeda were most affected by the environment, which was not a typical behavior of cultivars used as checks.