F₁ plants were characterized by maroon color, i.e. in phenotypic expression they differed in more intense anthocyanin coloring than both parental forms resembling the complementary effect of non-allelic genes (Table 1).

In F₂ plant, it was observed a clear splitting into four phenotypic classes:

1) Plants with maroon coloring of all parts (stem, leaf, flower and box);

2) Plants with anthocyanin coloring L-2 type (stem, leaf, flower, box);

3) Plants with anthocyanin coloring of L-3 type (stem, venation of the leaf is colored, the flower is unpainted, the box is green);

4) Plants with green coloring of all parts (stem, leaf, unpainted flower, green box).

Their ratio corresponded to 9:3:3:1, in absolute numbers 84:25:30:11, χ² = 0.36, Р = 0.95.

Analysis of backcross plants F_b, F₁ (L-2 × L-3) × L-3 and F₁ (L-3 × L-2) × L-3 and F₁ (L-3 × L-2) × L-105 confirms the reliability of obtained results in F₂ (Table 1).

Fact of the complementary effect manifestation of anthocyanin color genes is proved by the analysis of the data in Table 1, revealing the phenoclass ratio 2:2 (1:1), where the first phenotype of maroon color is the result of the presence of both dominant alleles of the anthocyanin color gene with the genotype R_pr_pR_st^vr_st^v, R_pr_pR_st^vR_st^v, R_pR_pR_st^vr_st^v. If there is no dominant allele in the genotype of any R_p or R_sl^v, phenotypically, respectively, from the genotype will appear in plants of the L-3 or L-2 type. Recessive homozygosity for both r_pr_pr_st^vr_st^v genes will contribute to the phenotype of plants with green coloring.

The final evidence was given by the backcross results F₁ (L-2 × L-3) × L-105. At the same time, four phenoclasses were obtained at F_b, F₁ (L-2 × L-3) × L-105:

1) Maroon; 2) L-3 type; 3) L-2 type; 4) plants with green coloration as L-105 line. The appearance of plants with maroon color is the result of the formation of the genotype R_pr_pR_st^vr_st^v, L-2 type R_pr_pr_st^vr_st^v, L-3 type r_pr_pR_st^vr_st^v and green plants r_pr_pr_st^vr_st^v, in 1:1:1:1 ratio.

In our previous studies [2] [3], the question was emphasized on the possibility of digenic control of the anthocyanin color of a cotton plant.

In contrast to previous studies, this article presents the results of genetic analysis, indicating a complementary interaction of genes involved in the genetic control of genes of plant anthocyanin pigmentation.

The cleavage in F₂ due to the complementary interaction of the genes involved in the genetic control of the anthocyanin color of the plant can give the following genetic explanations:

Thus, on the basis of genetic analysis, it can be argued that L-2 and L-3 differ in the allelic state of anthocyanin coloring genes R_p - r_p, R_st^v, - r_st^v, dominant alleles in one genotype act complementary and cause the appearance of maroon color.

Data on the content of “a” and “b” chlorophylls in the parent and hybrid forms are shown in Table 2. L-2 in terms of the content of the sum of chlorophylls “a” + “b” has an indicator of X = 1.32 ± 0.11 and for “a” X = 0.8 ± 70.11, for “b” X = 0.39 ± 0.16. For L-3, these indicators are slightly higher than for L-2, “a” + “b” X = 1.70 ± 0.37, “a” 1.16 ± 0.11, and for “b” 0.62 ± 0.15.

In F₁ plants L-2 × L-3, “a” + “b” amount is 2.21 ± 0.11, which indicates the heterosis effect –hp = 3.68. According to chlorophyll “a”, –1.37 ± 0.35 is relatively weak heterosis, hp = 2.50. According to chlorophyll “b” 0.79 ± 0.33, where hp = 2.54, the effect of heterosis is also observed.

Interesting results were obtained for F_b (L-2 × L-3) × L-3, where all plants turned out to be anthocyanin-colored: the content of chlorophylls “a” + “b” –1.96 ± 0.17, according to “a” 1.44 ± 0.16, a dominance effect is observed, and heterosis, respectively, hp = 0.01 and 2.00.

Regularity is observed for chlorophyll “b” 0.50 ± 0.05, high variability, hp = –2.62, that is, the effect of negative heterosis is observed, over dominating compared to F₁ and L-3.

The reason for these phenomena is revealed by analyzing the content of chlorophyll in the population F₂, L-2 × L-3 (in one family of F₂ plant).

According to the table, in F₂ there is a wide range of variability in the content of chlorophylls “a” + “b”, that ranges from 0.25 to 2.25, with an average value of the trait X = 1.21 ± 0.45, with V = 8.06. If we consider separately the inheritance of the content of chlorophyll “a” and “b”, we can see that they have a kind of genetic control and regularity. The inheritance of chlorophyll “a” is as follows. The indicator of this trait, in the parent forms, L-2, X = 1.32 ± 0.14, with V = 6.24, in L-3 X = 1.70 ± 0.37, V = 8.31. In F2 plant – trait fluctuations range from 0.25 to 1.75 at X = 0.87 ± 0.18, at V = 7.74. And the chlorophyll “b” indicator, in the parent form L-2, X = 0.39 ± 0.16, V = 5.87, in L-3, from 0.25 to 0.75 X = 0.62 ± 0.15, V = 4.21. In F₂ plant, indicator of this trait was at X = 0.32 ± 0.11, V = 4.67%.

Obtained data indicate that the sign of the content of both chlorophyll “a” and chlorophyll “b” have different genetic controls and therefore they have different degrees of variability in F₂ (Table 2).

In order to identify the significance of anthocyanin coloration in the inheritance of indicators of “a” and “b” chlorophylls, we carried out a separate analysis of the inheritance of this trait against the background of the color of the plant. In F₂ plants with a darker anthocyanin color, in 32 plants, the total amount of chlorophylls “a” + “b” ranges from 0.25 to 2.25, X = 1.08 ± 0.10, V = 9.77. On chlorophyll “a”, the fluctuations of the indicator are from 0.25 to 1.75, at X = 1.14 ± 0.13, V = 7.26%, and on chlorophyll “b”, from 0.25 to 1.25, at X = 0.52 ± 0.11, V = 8.05. The same indices for 6 F₂ plants with anthocyanin coloration with a phenotypic expression of the type of coloration L-2, chlorophyll “a” + “b” ranged from 0.75 to 1.25, at X = 1.14 ± 0.14, V = 8 44, chlorophyll “a” ranges from 0.25 to 1.25, at X = 0.81 ± 0.23, V = 5.52, and chlorophyll “b” X = 0.67 ± 0.19, V = 4.81. In 3 plants with anthocyanin coloration, type L-3, “a” + “b” ranges from 0.75 to 1.25, at X = 1.62 ± 0.10, V = 13.02, while the content of chlorophyll “a” ranges from 1.25 to 1.75, X = 1.74 ± 0.15, V = 15.30 “b” X = 0.35, ± 0.16, V = 9.05. In 3 green plants, the content of chlorophylls “a” + “b” ranges from 0.75 to 1.25, X = 0.97 ± 0.22, V = 9.60%. Chlorophyll “a” fluctuates from 0.25 to 0.75, X = 0.67 ± 0.14, V = 6.95%, and chlorophyll “b”, X = 0.39 ± 0.08, V = 5.46%.

Thereby, analysis of inheritance of “a” + “b” chlorophylls content in the total for F₂ plant with dark burgundy anthocyanin coloration is on average 1.08 ± 0.10, V = 9.77%, for F₂ plants with anthocyanin coloration (L-2 type), 1.14 ± 0.14, V = 8.44%, for F₂ with anthocyanin color, type L-3, much higher than 1.62 ± 0.10, V = 13.02. In the new phenotype of F₂-plant with a green color, this indicator is lower 0.97 ± 0.22, V = 9.60. If we closely monitor the inheritance of chlorophylls “a” + “b” in the four phenotypic classes, the highest chlorophyll content in plants of L-3 type, then a plant of L-2 type, then plants F₂ with maroon color, and a new phenotype with green color (Table 2).

When one considers the inheritance of the trait against the background of chlorophylls “a” or “b”, one can see that the content of chlorophyll “a” in the parent L-2 and L-3 lines have significant differences in the average. For L-2 line, this indicator is 0.87 ± 0.11, for L-3 1.16 ± 0.11, for chlorophyll “b” they also have differences for L-2 0.39 ± 0.16, and L-3 0.62 ± 0.15. Therefore, in F₂ plants with anthocyanin coloration, on average, they are much higher in terms of their sum “a” + “b”, respectively 1.08 ± 0.10, 1.62 ± 0.10 in a plant with green coloration 0.97 ± 0.22, significantly less. According to the content of chlorophyll “a” of F₂ plants, colored individuals averaged 1.14 ± 0.13, type L-2 0.81 ± 0.23, type L-3 1.74 ± 0.15, and the plant had a green color 0.67 ± 0.14. Here, L-3 type is significantly different with the best twice as high levels of chlorophyll “a”.

As for chlorophyll “b,” F₂ plants with maroon pigmentation are 0.52 ± 0.11, L-2 type 0.67 ± 0.12, L-3 type 0.35 ± 0.16, and new phenotype with green color 0.39 ± 0.08.

According to the data on F₂, the best indicators for chlorophyll content in individuals with anthocyanin pigmentation of L-3 type, both in the sum of “a” + “b” and individually, the content of “a” and “b” of chlorophylls are higher.

Obtained data allow making a conclusion either about the linkage of genes determining the content of chlorophylls in the chromosome linkage group, where R_st^v gene is localized or the pleiotropic effect on the formation of both chlorophyll “a” and “b”. This is evidenced by the low content of chlorophyll in the F₂ plant with a green color characterizing the recessive homozygous state of r_pr_p и r_st^vr_st^v genes, especially r_st^v gene in genotype.