Genetic control of parameters of harvest structure elements in the corn diallel complex

The article discusses the results of the use of diallel analysis in the study of self-pollinated maize lines. The average values of the elements of the structure of the grain yield in self-pollinated lines, as well as the average group indicators of hybrids, are noted. The effects of the general and dispersion of the specific combinative ability of lines are revealed. The ranking of the average group values of hybrids by the weight of the cob was carried out, which made it possible to arrange the lines in the following sequence: CL 7 < X 46 < SE 19 < Od 28 < KS 25 < LV 32 < Bg 1266 < Om 255 < Uk12 D 2 < RSK 25 < Om 232 < Mk 130 U < RSK 3 s< RSK 7 < RN 26 < Mk 11. In 2016-2019 A significant influence on the manifestation of the weight of the cob, the weight of the grain from the cob, the yield of grain, the number of grains in a row and the grains on the cob of the paratypical component of the dispersion (E) was noted.


Introduction
One of the directions in the study of maize breeding material is the study of the combinational ability of lines and the determination of the components of the genetic control of economically valuable parameters [3][4]. The use of a diallel crossing scheme, unlike other methods for studying combinational ability (topcross, polycross, free cross-pollination), is more laborious [9;13;15]. However, this method allows obtaining the most accurate information about the general and specific combinational ability [4;7;11]. The most convenient for diallel analysis are quantitative indicators, which, with a relatively simple measurement, are an important component in the formation of an integral indicator of plant yield [1;6]. Determining the overall combining ability by the weight of the cob, grain yield, the number of grains on the cob is an important part of the work that helps to identify promising lines that can produce high-yielding hybrids [5].

Materials and methods
The studies were carried out in 2016-2019 on the experimental field of the FGBNU RosNIISK "Rossorgo" in accordance with the methodology [2]. The climate of the region is characterized as sharply continental. The HThC amounted to 0.48 in 2016, -1.05 in 2017, 0.61 in 2018, and 0.56 in 2019. The soil of the experimental plot is southern low-humus, medium-thick, heavy loamy chernozem. The experiment included simple hybrids (120 combinations) obtained according to the diallel scheme of 16 homozygous lines (method 2, Griffing model 1). Repetition -three times. The accounting area of the plot is 7,7 m 2 ; plot length 5.5 m. Plant density (45 thousand plants/ha).  14]. The combination ability of the samples was determined according to the II method of B. Griffing [16]. Genetic analysis of the components of the genetic dispersion was carried out according to B.I. Hayman [17]. Data processing was carried out using the computer program Agros-2.09.

Results and Discussion
To increase the productivity potential of corn hybrids, it is necessary to analyze quantitative traits that affect grain yield and other economically valuable traits. In this case, special attention should be paid to the elements of productivity. The elements of the yield structure are correlated with grain yield, although they make an unequal contribution to the formation of plant productivity (table 1). A similar conclusion is given in other studies [8]. Correlation analysis of averaged data for 2016-2019 revealed a close relationship between grain yield and cob weight (r = 0.96), and grain weight per cob (r = 0.99). For 2016-2019 the weight of 1 cob in self-pollinated lines varied from 50.1 g to 91.5 g (table 1). The average group values of hybrids varied from 118.1 g to 142.9 g. The weight of grain per cob varied within the limits: 35.8-71.6 g for lines, 92.3-110.4 g according to the average group values of hybrids. Ranking according to the average values of the cob mass made it possible to arrange the lines depending on the following sequence: CL 7 < RSK 25 < RN26 < Uk12D2 < MK 130 U < Om 255 < X46 < RSK 7 < LV32 < MK 11 < YuV 19 < Bg1266 < KS 25 < Om232 < Od 28 < RSK 3. The distribution of the average group indicators of hybrids revealed a shift in the location of the lines: CL 7 < X 46 < YuV 19 < Od 28 < KS 25 < LV 32 < Bg 1266 < Om 255 < Uk12 D 2 < RSK 25 < Om 232 < Mk 130 U < RSK 3 < RSK 7 < РН 26 < Mk 11. Ranking according to the average values of grain weight from the cob in the lines and according to the average group values of hybrids revealed minor deviations in a similar sequence.
In terms of grain yield from the cob, the parameter varied from 66.5% to 79.4% for the lines and from 76.7% to 79.4% for the average group values of hybrids. The hybrids with the participation of lines RSK 7, YuV 19, RSK 25, RSK 3, Uk 12 D 2 showed the highest percentage of grain yield.
On average, over the years of the study, differences were noted between the lines in the number of grains in a row and the number of grains on the cob. The largest number of grains in the row was noted in the lines Uk 12 D 2, YuV 19, LV 32, Om 255, RSK 7. The hybrids with these forms also showed the largest number of grains in the row.
The results of the analysis of the combinational ability of self-pollinated maize lines, carried out according to the diallel scheme, indicate a low value of the effects of GCA on the traits "cob weight" and "grain weight per cob" in line CL 7. A high effect of GCA was noted in line Mk11. (table 2). The remaining forms according to these parameters were characterized by the average value of the GCA Using the method of diallel crosses, one can also establish the nature of the inheritance of quantitative traits and obtain information about other genetic properties of the analyzed forms (about the additive effects of genes, the degree and direction of dominance of genes that control the development of traits, about the ratio of frequencies of dominant and recessive genes in a certain locus) [8 ]. In the experiment, there is a negative correlation between the value of the trait and dominance in parental lines in terms of: cob weight r= -0.60 (df=10), grain weight from the cob r= -0.51 (df=11), grain yield from the cob r = -0.73 (df=13), the number of grains in the row r= -0.24 (df=10). A positive correlation was noted between the number of grains on the cob and dominance.  (table 4). The ratio √H 1 /D according to these parameters is greater than one (1.35-9.40), which indicates a positive effect of overdominance. The obtained data confirm the conclusions of other researchers [12].
According to the yield of grain from the cob, significant indicators of the component characterizing the additive effect of genes (D) and insignificant values of the dominance components were noted. The value of the √H 1 /D component (0.78) indicates the effect of incomplete dominance. The difference between the overall average trait in all offspring (ml1) and the average parental forms (ml0) for the studied traits is positive, which indicates that dominance in all parameters is directed towards parental forms with a greater severity of the trait, which is confirmed by h > D.
The values of the H 2 /4H 1 ratio for the studied traits are significantly less than the theoretical value (0.25), which indicates an uneven distribution of alleles with positive and negative effects. Analysis of the components indicates that 9-11 genes or groups of genes influence the manifestation of the cob mass and grain mass, and the manifestation of the number of grains in a row is controlled by 7 genes. Insignificant values of the H 2 component in terms of grain yield and the number of grains on the cob do not allow one to reliably determine the number of genes that affect the manifestation of traits. In

Conclusion
The use of diallel analysis makes it possible to determine the components of genetic dispersion and evaluate the self-pollinated maize lines included in the working collection. As a result of the assessment of self-pollinated maize lines for combination ability by elements of the grain yield structure, high effects of GCA and SCA dispersion were noted in the following cross components: RN 26, Bg 1266, Mk 11, RSK 7. These lines can be used to identify promising hybrid combinations and obtain synthetic populations. It is expedient to use the CL 7 lines with low GCA when highlighting individual valuable combinations. A significant influence of the components of dominance (H 1 , H 2 ) was established, and also that dominance is directed towards parental forms with a greater severity of the trait.