N. Tsenov, I. Stoeva, T. Gubatov, V. Peeva

Abstract. Breeding for grain yield and quality is central in research work on wheat in Bulgaria. Combining the two genetic systems is difficult and requires long and systematic efforts. The aim of this investigation was to analyze the ecological plasticity and stability of grain yield and quality of cultivars already in production. Such information would be valuable with a view of their proper distribution. The quality and production potential of cultivars Aglika, Slaveya and Iveta were determined applying several different approaches for analysis of the genotype x environment interaction. Data were used from several different trials involving these cultivars in a group of 33 Bulgarian varieties during two successive years at eight locations in Bulgaria. The data on the different quality indices are from trials conducted at DAI during a period of six years. The focus is on the complex evaluation of grain yield and quality with respect to their level of realization and plasticity under different combinations of environmental conditions in two groups of trials. Grain yield and its components of the three investigated varieties were significantly higher in comparison to the standards. The model cultivars Sadovo 1 and Pobeda had larger grain and higher tillering capacity although their yields were lower. Number of grains per spikes, which determines the higher productivity of the investigated cultivars, had values with 30 % higher than the values of the model varieties. The values of the indices determining wheat grain strength and bread making quality (valorimetric value, dough resistance and sedimentation) of the three cultivars were significantly higher than the values of the standard Pobeda, which confirmed their genetic potential of strong wheats. No significant variations between cultivars and standard varieties were observed for the indices test weight and wet gluten. The investigated cultivars Aglika, Slaveya and Iveta are a good breeding achievement because they successfully combine high yield with high grain quality. In this respect all three cultivars considerably exceed the level of variety Bezostaya 1, which was at the basis of the successful breeding for combining high yields with high grain quality in the recent past. Cultivar Slaveya, although well established in the group of fillers, demonstrated quality indices of strong wheat. The cultivars possess good adaptability and plasticity under changeable environments with regard to grain yield and its main components. According to the complex indicator of quality level (bread making strength index), all three genotypes demonstrated excellent plasticity and adaptability ranking first among over thirty analyzed cultivars developed in Bulgaria.