VARIABILITY AND GENETIC CONTROL OF THE “SEEDLINGS-EARING” INTERPHASE PERIOD IN SPRING BARLEY UNDER WATER DEFICIT

When creating cultivars with potential performance and adaptability, one should determine the roles of genotype and environmental factors in yield formation. Phenomenological and geneticbiometric methods were used for this purpose. As to the genetic control of earing time, incomplete intra-locus dominance and inter-locus additivity were determined, suggesting a possibility of selection starting from F3, with cultivar Svarozhych as a source of fast ripening and cultivar Bohun as a source that extends this period length.

and 1000-grain weight. Such features of cultivars are taken into account when one selects parents for hybridization.
At present, there extensive experimental data on the inheritance of the "seedlings-earing" interphase period in cereals. Literature review revealed that in the first-generation (F 1 ) hybrids the vegetation length was under polygenic control and could be much shorter than the more shortseason parent, equal to that in either of the parents, intermediate compared to the parents, or longer than that in the more late-ripening original cultivar [9][10].
When the genetics of the "seedlings-earing" interphase period was studied, the prevalence of an additive-dominant complex of genes in the determination of this trait was demonstrated, i.e. intra-locus dominance and inter-locus additivity were noticed. [7,[11][12][13][14]. As a rule, a partial, not complete or complete dominance, and sometimes overdominance are observed inside loci. This phenomenon is attributed both to the assortment of cultivars involved in experiments and to the meteorological conditions during the plant vegetation. The fact that the dominant genes shorten the earing time and the recessive ones extend it is very important [15][16][17][18].
Purpose and objectives. Therefore, our purpose was to determine the variability and genetic control of the "seedlings-earing" interphase period in spring barley under water deficit, to theoretically substantiate generations for selection in the diallel crossing design using cultivars bred at different breeding institutions and of different ecotypes, thereby solving the problem of shortening the spring barley breeding process.
Material and methods. The study was conducted at Donetsk State Agricultural Station of NAAS of Ukraine. In 2018-2019, hybridization was performed and over 150 grains for each combination were obtained. In 2019-2020, the field experiments were laid out; cultivars and hybrids were sown within the optimal timeframe. The plots were arranged as per a P 1 F 1 P 2 scheme. The row length was 1.5 m. A cassette seeder SKS-6-10 was used. The nutrition area was 10 cm x 20 cm. The experiments were carried out in three replications. The predecessor was black fallow.
Data were processed using the package of applications for processing genetic and breeding experiments "EliteSystems gr." developed by the PPI nd.a. V.Ya. Yuriev NAASU. Based on genetic analysis, the following Hayman parameters were determined: P3 -r (Wr + Vr;, Xpcorrelation coefficient between the sum of Wr + Vr and the mean values of traits in the parents, which characterizes the direction of dominance; P6 -(√H 1 /D) -measure the average degrees of dominance over all loci in the population; P9 -(1/4 H 2 /H 1 ) -mean value of plus or minus alleles of all loci; P13 -(√4DН 1 + F/√ 4DН 1 -F) -ratio of the total number of dominant genes to the total number of recessive genes in the parental cultivars, where D, H 1 and H 2 are components of variation attributed to genes with additive effects, dominant and recessive genes, respectively. The genetic control was assessed using Hayman graphs (dependence of Wr on Vr -respectively covariance and variance) and the parameters. In a Hayman graph, the relationship between Wr and Vr is expressed through the linear regression coefficient b y . We used these parameters, which relatively really describe the organization of a quantitative trait, as V.A. Dragavtsev did in his study (1995). The parameters of adaptability, stability of genotypes and environment as a background for yieldoriented selection were calculated by A.V. Kilchevskiy and L.V. Khotylyova's method (1997). Analysis of variance and correlation analysis were performed in compliance with B.A. Dospekhov's recommendations (1985). The GCA effects and SCA variances were calculated by V.G. Volf and P.P. Litun's method (1980) [19][20][21][22][23].
The weather in 2019-2020 was characterized by various hydrothermal indicators, favoring comprehensive assessments of starting material of spring barley for productive and adaptive potentials as well as for the "seedlings-earing" interphase period. Results and discussion. In our study, the "seedlings-earing" interphase period in the cultivars varied 42.8 days to 49.1 days in 2019 (Table 1). 1.09 1.03 -Not significant differences the "seedlings-earing" interphase period between the cultivars and F 1 hybrids and its variability, depending on the hydrothermal mode in the study years, were demonstrated by analysis of variance (Table 3). Thus, the share of the first factor (A) was 99.76% of the total variability of the trait, and the shares of genotype and genotype-environment interaction were only 0.15% and 0.07%, respectively.
The equality of the group mean values for cultivars and hybrids indicates, firstly, a intermediate type of inheritance, and secondly, the predominance of additive effects in the determination of the trait. This was confirmed by analysis of the combining ability of the cultivars in their hybrids. Table 4 shows that the share of the GCA variances was 70.8% of the total variability of the trait. Significant influence and SCA variance, the effects of allelic and non-allelic interactions were higher in a less favorable year: 18% vs. 14.5%.
Analysis of the hybrid combinations indicates that the female effect, which increases the earing time, was seen in the hybrid combinations Partner/Komandor, Komandor/Baskak, Bohun/Baskak, and Bohun/Komandor. Of the cultivars under investigation, Baskak and Svarozhych reduced the earing time, while Komandor and Bohun increased it, and the GCA effects were most pronounced in the latter (Table 5). Genetic analysis was performed by Hayman's method (Fig. 2). Evaluation of the Wr-Vr difference homogeneity using t-test revealed no epistatic interaction (t = 0.21 and 0.10 insignificant).
The regression line passes above the origin, indicating the leading role of dominance in the genetic control of the "seedlings-earing" period. This is confirmed by the indicator of medium degree of dominance (P6 = 0.76 and 0.79).
The divergence of the cultivar points along the regression line is significant, indicating the differentiation of the genotypes by the presence of dominant and recessive genes.  In 2019, Partner and Komander were in the dominant zone, Baskak, Svarozhych and Bohun -in the recessive one.

2019
In 2020, Svarozhych and Komandor were in the recessive zone, and Bohun moved from the recessive zone to the dominant one. In general, the location of the cultivars along the regression line is relatively stable. Positive correlation coefficients between Wr + Vr and Xp (P3 = 0.32 ± 40 and 0.52 ± 0.32) indicate the stability of genetic systems determining the barley earing time, but they are insignificant, indicating the dominance direction, i.e. both dominant and recessive genes can reduce or increase this trait.
In the loci that show dominance, the product of the frequencies of positive and negative alleles was asymmetric, the P9 index was 0.16 and 0.19 for the study years, respectively, i.e. not equal to 0.25, and the ratio of the total number of dominant genes to the total number of recessive ones, proceeding from the values of 1, indicates prevalence of the former. In the genetic control of the "seedlings-earing" interphase period, incomplete intra-locus dominance and inter-locus additivity were recorded.
The prevalence of the additive-dominant genes in the heredity of the "seedlings-earing" interphase period suggests a possibility of selecting desired genotypes in the early generations, starting with F 3 . Svarozhych can be used as a source to reduce the "seedlings-earing" interphase period, while Bohun can lengthen it. This trait is controlled by a single genetic system.
Conclusions. Cultivars of different ecotypes bred at different breeding institutions, with due account for their competitiveness in terms of performance, were taken as initial components.
Of crossing designs, we preferred diallel crossing for the following reasons: it allows obtaining the full range of combinatorics of the parents' genetic information. The assemblage of F 1 hybrids and parental cultivars gives a typical segregation. Starting selection, we have an idea about the trait inheritance and can determine from which generation to start it.
Positive correlation coefficients between Wr + Vr and Xp (P3 = 0.32 ± 40 and 0.52 ± 0.32) indicate the stability of genetic systems determining the barley earing time, but they are insignificant, indicating the dominance direction, i.e. both dominant and recessive genes can reduce or increase this trait. The trait is controlled by a single genetic system, so selection can be based both on dominant alleles and on recessive ones, regardless of whether or not they reduce "seedlings-earing" interphase period. One should prefer recessive alleles, because they can be manifested in F 2 .
Svarozhych can be used as a source to reduce the "seedlings-earing" interphase period, while Bohun can lengthen it.

VARIABILITY AND GENETIC CONTROL OF THE "SEEDLINGS-EARING" INTERPHASE PERIOD IN SPRING BARLEY UNDER WATER DEFICIT
Vashchenko V.V., Shevchenko A.A. Dnipro State Agrarian and Economic University, Ukraine Purpose. To determine the variability and genetic control of the "seedlings-earing" interphase period in spring barley under water deficit, to theoretically substantiate generations for selection in the diallel crossing design using cultivars bred at different breeding institutions and of different ecotypes, thereby solving the problem of shortening the spring barley breeding process. Material and methods. The study was conducted at Donetsk State Agricultural Station of NAAS of Ukraine. In 2018-2019, hybridization was performed and over 150 grains for each combination were obtained. In 2019-2020, the field experiments were laid out; cultivars and hybrids were sown within the optimal timeframe. The plots were arranged as per a P 1 F 1 P 2 scheme. The row length was 1.5 m. A cassette seeder SKS-6-10 was used. The nutrition area was 10 cm x 20 cm. The experiments were carried out in three replications. The predecessor was black fallow. Data were processed using the package of applications for processing genetic and breeding experiments "EliteSystems gr." developed by the PPI nd.a. V.Ya. Yuriev NAASU. Based on genetic analysis, the Hayman parameters were determined. Results and discussion. The "seedlings-earing" interphase period in the cultivars varied 42.8 days to 49.1 days. In F 1 hybrids, the "seedlings-earing" interphase period varied significantly, depending on crossing of cultivars of different ecotypes. Significant influence and SCA variance, the effects of allelic and non-allelic interactions were higher in a less favorable year: 18% vs. 14.5%. Analysis of the hybrid combinations indicates that the female effect, which increases the earing time, was seen in the hybrid combinations Partner/Komandor, Komandor/Baskak, Bohun/Baskak, and Bohun/Komandor. Baskak and Svarozhych reduced the earing time, while Komandor and Bohun increased it, and the GCA effects were most pronounced in the latter. Evaluation of the Wr-Vr difference homogeneity using t-test revealed no epistatic interaction (t = 0.21 and 0.10 insignificant). The regression line passes above the origin, indicating the leading role of dominance in the genetic control of the "seedlings-earing" period. This is confirmed by the indicator of medium degree of dominance. The divergence of the cultivar points along the regression line is significant, indicating the differentiation of the genotypes by the presence of dominant and recessive genes. In 2019, Partner and Komander were in the dominant zone, Baskak, Svarozhych and Bohun -in the recessive one. In 2020, Svarozhych and Komandor were in the recessive zone, and Bohun moved from the recessive zone to the dominant one. In general, the location of the cultivars along the regression line is relatively stable. In the loci that show dominance, the product of the frequencies of positive and negative alleles was asymmetric, and the ratio of the total number of dominant genes to the total number of recessive ones, proceeding from the values of 1, indicates prevalence of the former. In the genetic control of the "seedlings-earing" interphase period, incomplete intra-locus dominance and inter-locus additivity were recorded.