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.

The high content of phenolic compounds (quercetin-3-O-glycoside, izoramnetine-3-O-glycoside, 4'-metoxykempferol-3-O-glycoside, 4'-metoxyqvercetine-3-0-glycoside, apigenine and luteoline) in flowers of Prunus cerasifera Ehrh. in comparison with Prunus armeniaca L. has been shown. That can be the reason weak susceptibility of generative organs of cherry-plum to Sclerotinia (Monilinia) laxa (Aderh et Ruhl.) Honey.

The untypical weather conditions during the extrema drought in 1993- 1994 have been described. Regularities of the accumulation and spending of the dry substance in leaves of varieties, signi ficantly different in productivity, weke considered depending on weather conditions.

In the component composition of volatile solutions determining fragrance of the flowers in apricot and cherry-plum varieties and Prunus brigantiaca Vill. x Armeniaca vulgaris Lam. hybrids there are 36 highest hydrocarbons and benzaldehyde that prevail. There are fewer amounts of the solutions which scare bees (benzaldehyde) in the fragrance of cherry-plum varieties as compared to the flowers of apricot and hybrids. At the same time, the content of tricosane, pentacosane, docosane, heneycosane, eicosane, nonadecan that probably attract bees is higher in the cherry-plum flowers than in the fragrance of apricot and hybrid flowers. The average three years yield of cherry-plum plants (Nikitska Zhovta 10,7 and Salgirskaya Rumjanaya 28,5 t/ ha) is higher than for apricot (Recolte de Schatene 0,3; Rodnik 2,9; Ananasniy Tsurupinsky 7,4 t/ha) and hybrids (8110 – 5,2; 8098 – 6,4 t/ha) that could be explained with better pollination of flowers and better fruit formation. Prevailing components of flower aroma of these plants and their possible link with yield of the objects in questions have been analyzed.

The studying results of drought resistance for 15 varieties and 6 forms of apricot in the condition of South of the Ukraine have been given. The plants with different level of drought resistance have been selected from apricot varieties and forms introduced on the South Coast of the Crimea. From the studied varieties the most drought resistance ones are: Vardaguin Vagdaas, Luchak Sumbarskiy, Sulina, LE-132. Two best apricot varieties have been recommended for use in selection on this character