Variability and genetic control of the “seedlings-earing” interphase period in spring barley under water deficit

Abstract

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 P1 F1 P2 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 F1 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.
 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 F1 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 F2. Svarozhych can be used as a source to reduce the “seedlings-earing” interphase period, while Bohun can lengthen it