Purpose. To reveal the nature of the inheritance of apricot color of the ray flowers of the sunflower and the type of interaction of genes causing different colors. Methods. Field experiment, genetic analysis. The statistical validity of the results was evaluated using Pearson’s criterion. Results. We conducted crosses of the ‘KG13’ line as the source of the sign of apricot color with sunflower lines that had yellow, orange and lemon colors of the ray flowers. In the first generation, from crossing the ‘KG13’ line with five lines, which had a yellow color, only a yellow color of ray flowers was observed. In the second generation, a 3 : 1 split was observed: three-quarters with yellow flowers and one with apricot flowers. Line ‘KG13’ was crossed with three lines (‘HA298’, ‘SL2966’, ‘LD72/3’), which had an orange color of flowers. In the first generation, orange flowers were observed; in the second gene­ration, splitting was recorded: three-quarters of offsprings with orange-colored flowers and one-quarter with apricot flowers. The line ‘KG13’ was crossed with ‘KG107’ and ‘ZL678’, which had lemon-colored flowers. The resulting plants of the first generation had a yellow coloration of ray flowers. In the second generation, five classes of plants by coloration of ray flowers were obtained: yellow, orange, apricot, lemon, lemon-apricot in the ratio 6 : 4 : 3 : 2 : 1. According to these data, the genes of lemon and apricot color have a complementary effect, the homozygous state of orange allele is epistatic to the recessive homozygote of the lemon-colored gene. The ‘KG108’ line with a combination of genes responsible for apricot and light yellow color has its own light apricot color and in crossings with a yellow colored line in the second generation gives splitting in the ratio 9 : 3 : 3 : 1. Conclusions. It was revealed that the apricot color of the ray flowers of the sunflower line ‘KG13’ is due to the homozygous state of the allele of the same gene whose second allele causes an orange color in the lines ‘NA298’, ‘SL2966’ and ‘LD72/3’. The complementary action of alleles responsible for apricot and lemon, as well as apricot and light yellow coloration of ray flowers was determined. A case of epistasis of homozygotes along the allele controlling the orange color over the recessive homozygote of the gene, which is controlled by the lemon color in the crossing combination ‘ZL678’ / ‘KG13’, was revealed.

A stabilizing (directed) selection has created a donor of short stem for winter rye (Secale cereale L.), plant height of which ranged from 50 to 60 cm. The plant height kept symmetry of its distribution curve and the frequency accumulation in central classes (positive excess). For the first time a symbolic designation to new short-stem related Hl-2Hl-2 allele and the donor name (Gnome 2) were proposed. 28 years of stabilizing selection showed that 57% of overall genetic variability of plant height resulted from adaptive genes available for directed selection by phenotype, and 43% from dominant and epistatic factors that predetermines the expression heterosis effect. Gnome 2 donor proved to have genetic additive correlation between the pants height and number of flows per ear, ear length, weight of seeds per plant , 100 seeds weight per plant; to have reverse correlation with ear density seeds weight per ear. The height of original parent components have displayed direct additive correlation with number of flowers per ear and reverse with the ear density. The additive correlation component directly exposes «genuine» impact of parental plants on the expression of the characteristics indicated among the offspring Productive bushing of parental plants, seed weight per plant directly, and seed size (100 seeds weight) indirectly, respectively, influence the height of offspring pants. The reverse additive correlation between the parents height and 100 seeds weight in the offspring is caused by pleiotropic effect of the genes impact thus enabling to combine the desirable characteristics in one genotype. Productive bushing is by 54% due to the impact of general genetic factors among the above, in particular, 30% due to that additive, 24 due to non-additive factors. The concept of genetic improvements for productive bushing of the Gnome 2 rye implies utilization of additive effect through the directed selection, as well as application of breeding techniques for controlling the effect of heterosis caused by the genes of dominant and epistatic impact. The selection paradigm requires simultaneous genotypes selection with immediate examination of the selection results by offspring while in parallel to develop inbred lines, combining these afterwards evaluating general and specific combining ability by productive bushing. It is also to be noted that the productive bushing essentially depends on the environmental conditions, which significantly corrects the implementation of productivity potent, thereby the issue of agronomical conditions aimed at extending the expression of characteristic in question remains.

The use of regression analysis for estimation of inbred lines is a breeding - oriented method, as it indicates scientifically grounded stages of the further breeding studying of these lines and a strategy of their use. Admissible levels of inbred depression of agriculturally valuable characters are limited in lines of the Verkhnyachka and Lgov geneplasms by two - three generations of self - pollinations, which testifies to the necessity "to keep" the characters of sufficient basis. Linearity of changes of values of the characters with the advancing of inbreeding shows the absence of epistasis or the weakness of their effects which makes suitable the use of an additive-dominant model for determining breeding-genetical value of inbred lines with the aim of their purposeful hybridization for obtaining genetically determined heterosis in F1.