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The aim of the study was to assess the size and stability of grain yield of a group of varieties grown in different conditions of the country. The study included a total of forty samples of winter common wheat, developed by Agronom breeding company. The field experiment was conducted in three typical grain production locations of the country: Dobrich, Trastenik and Straldja, in the period 2017-2019. All aspects of the interaction of varieties with environmental conditions were analyzed using two statistical programs PBSTAT and GEA-R. Through their application, 16 different parameters were calculated, through the ranks of which stability was assessed. The data obtained from the individual parameters were subjected to direct comparison with the modules of the programs GenStat 15, JMP 14 and GGE Biplot 6.3, which have a visual representation of the results for the level of yield and stability of each cultivar. The stability of only the varieties with higher yield than the check cultivar was monitored. Their stability was monitored and measured through all software products before a conclusion was made about its level. The share of genotype and its interaction with environment was only about 20% of the total variation. The conditions in the individual locations have a significant impact on the yield performance, which causes a strong change in the yield in the individual varieties. It causes a drastic change in the rank of the yield by locations. Against the background of strong G x E interaction, only six varieties have been identified: ABC Aldo, ABC Grosso, ABC Lombardya, ABC Klausius, ABC Zigmund and ABC Navo, whose average yields were proven to be higher than those of the check variety LG Avenue. Their high productive potential was realized to a degree that guarantees high stability in changing conditions of the used regions. Current statistical models were effective in quickly and efficiently determining all possible levels of combination between genotype yield and stability. The newly created varieties showed higher stability than the already established ones, as their productivity was at a much higher level. Breeding, accompanied by ecological tests of many advanced lines, shows that it was possible to combine high yields with relatively high stability with enough varieties for successful zoning throughout the country. [ABSTRACT FROM AUTHOR]

Aims: In order to determine the effect of the characters, which are in high correlation with grain yield under contrasting conditions of growing, the nature of the interaction of the cultivar with the growing conditions was analyzed. Methods: Bulgarian wheat cultivars were investigated during four successive years at five locations within the country. The locations were chosen to cover the variety of soils and climate in all grain-production regions of Bulgaria. The complex interaction of the genotype with the environment was analyzed in relation to three characters - grain yield, and two characters (date to heading and number of grains per spike) with determining effect on it. Different statistical approaches were used to analyze the interaction of these characters with the environment and their effect on grain yield. Key results: The genotype x environment interaction was significantly high according to the factor year, as well as to the factor location of testing. The interaction year x location was low and insignificant. The variation determined in this experiment through principal component analysis reached third level, which complicated the assessment of the individual cultivars by two of the three investigated characters. Only with date to heading predominant linear interaction of the genotype with the environment was observed, which allowed determining of the cultivars' stability by this character. Conclusions: Grain yield can be correctly evaluated against the background of contrasting environmental conditions, through characters in positive correlation with it. In our case, these were the date to heading and the number of grains per spike. Each of the investigated characters revealed different nature and direction of the genotype's interaction with the environment. It is possible, through the established regularities, to objectively evaluate the cultivars which differ from the group mean. It is demonstrated how the stability of the grain yield is related to the stability of another two characters in the same cultivars. [ABSTRACT FROM AUTHOR]

Situation and aims. This investigation was carried out with the aim to determine the suitability of some Ukrainian wheat cultivars for improvement of the productivity of the Bulgarian ecotype of winter wheat. The economic traits and properties of promising breeding lines from crosses between them were studied. The focus was on the breeding possibilities of compromise combining early maturation with grain yield. Methods. A total of 50 genotypes were investigated: 40 of them were lines (from 4 hybrid combinations), 8 parental lines and several standard cultivars for comparison. Data were obtained from competitive varietal trials after growing for several successive years. The main traits directly or indirectly related to productivity were analyzed. The combination of earliness with the other economic traits and indices is discussed from the point of view of the combining ability of the early parents involved in the combinations. Key results. Although each studied combination involved an early parent, it was found that early forms were obtained with the participation of cultivars Obriy and Mironovskaya 29. The percent of early lines was highest in the combinations with their participation. In the crosses involving Albatros odeskiy and Mironovskaya 27, the productivity of the early lines was lower than the productivity of the parental lines. Cultivar Obriy was most promising for breeding work, especially for combining early heading with higher grain yield through high values of number of productive ears and grain size. Conclusions. Cultivars Albatros odeskiy and Obriy were most suitable for obtaining higher productivity in combination with earliness. The deriving of lines with earlier date to heading and higher productivity from the early cultivars Mironovskaya 29, Galateya and Enola was completely successful. By using specific cultivars, there is the possibility to combine high yield with earliness but within the limits of the specific parental cultivars for each individual combination. [ABSTRACT FROM AUTHOR]

Numerous common wheat varieties have been developed in Bulgaria, which when grown under variable environments, the magnitude of the grain yield is influenced by them. In order to determine the reasons for such variations the effect of the growing conditions on grain yield from the winter wheat cultivars with the highest distribution in production were investigated. The cultivars were investigated during four successive years at twelve different locations in Bulgaria with contrasting environmental components such as soil and climate. The phenotypic response of the cultivars was followed with a focus on the size of the yield and the direction of variation within the group of cultivars as a result of each factor: season, location of growing, genotype, and their complex interactions. The collected data were analyzed with the help of several well-known statistical software, (Statistica 7, Statgraphics XV, Jmp 10), which provided sufficient information on the genotype x environment interaction. Significant differences were found among the investigated cultivars by grain yield regardless of their specific response to the year conditions and the location. The genotype x environment interaction was significantly high and non-linear. This means that under changeable environments the different cultivars react differently and can therefore be grouped according to the grain yield stability and plasticity they demonstrated. This is very clear from the significantly high values of heterogeneity of variation. The principal component analysis showed that the dispersion of grain yield was of three-component type, PC1 being only about 1/3 of the total variation of the character, while PC2 and PC2 formed about 50 % from this variation. Within a wide ecological network of 12 locations in Bulgaria a significant genotype x environment interaction was established for grain yield in four successive years. The direct influence of the investigated factors, through their correlations with grain yield, showed the highest effect of the year (r=0. 476*), followed by the location (r=0.208*), the value of the genotype was the lowest and negative (r=-0. 194*). This normal distribution of the data on grain yield was combined with linear and non-linear type of interaction of the groups of cultivars with the year conditions, the location and their interaction as factors of influence; this made the analysis on the adaptability of each cultivar very difficult. [ABSTRACT FROM AUTHOR]

One of the main tasks of the contemporary breeding programs is developing of varieties characterized with high production potential and stability of grain yield under different growing environments. The aim of this investigation was to evaluate the yield stability of contemporary bread wheat cultivars grown in five successive years of contrasting meteorological conditions. The trial was carried out at DAI during 2007- 2011. The focus of investigation was on the grain yield from common winter wheat. The analysis of variances (ANOVA) undoubtedly revealed the significant interaction of the genotype with the environment The parameters of stability were calculated and the final evaluation of each cultivar included its grain yield according to the method of Kang (1998). Cultivars Zlatitsa and Korona realized the highest production potential during the investigated period. Relatively highest grain yield stability was demonstrated by cultivars Slaveya, Zlatitsa, Iveta, Aglika, Bolyarka and Dragana. Cultivars with high quality genetic potential such as Iveta, Lazarka and Aglika possessed excellent combination of high and stable grain yield significantly higher than the standard cultivar Pryaspa which belongs to third group of grain quality [ABSTRACT FROM AUTHOR]

Recurrent drought periods of varying duration often cause extensive crop damage and affect wheat production in Southern Europe. This study compares biochemical and ultrastructural responses of four wheat ( Triticum aestivum L.) cultivars to long-term field drought, and their contribution to final grain yield. Gel electrophoresis and immunoblotting analyses combined with transmission electron microscopy and grain yield evaluation were employed to assess drought susceptibility of the wheat cultivars. Two of them behaved as drought-tolerant, the other two presented as drought sensitive. Enhanced degradation of Rubisco large subunit (RLS), Rubisco small subunit (RSS) and Rubisco activase (RA) accompanied by an increased protease activity and reduced levels of heat shock proteins (HSP70) and dehydrins (DHNs) were associated with drought sensitivity. Drought tolerance coincided with relatively stable or increased HSP70 and DHN contents, and unchanged/higher levels of RLS, RSS and RA. Sensitive cultivars were more vulnerable to ultrastructural damages, showing obvious degradation of chloroplast membrane systems and depletion of leaf starch reserves. These drought responses affected yield potential, as tolerant cultivars gave higher yield under intense drought. Thus, our results provide additional insights into the complexity of plant drought responses, identifying multiple interacting traits that may serve as indirect selection criteria for wheat drought tolerance. [ABSTRACT FROM AUTHOR]