[PLEIOTROPIC EFFECTS OF GIBBERELLIN-SENSITIVE AND GIBBERELLIN-INSENSITIVE DWARFING GENES IN COMMON WHEAT OF THE SOUTHERN STEP REGION OF BLACK SEA].

Investigations of the pleiotropic effects of GA-sensitive (Rht8) and GA-insensitive (Rht-B1, Rht-D1) dwarfing genes and a gene that determines the response of plants to photoperiod--Ppd-D1 were carried out for three years in the southern step region of Black Sea bank on five different genetic backgrounds. It is shown that in addition to direct effects on plant height GA-sensitive and GA-insensitive dwarfing genes have pleiotropic effects on all studied traits except the number of fertile spikelets. Presence of the dwarfing genes in the genotype of tall forms led to the decrease of stem and ear length, and at the same time to the increase of ear density. The number of spikelets per spike decreased due to sterile spikelets, whereas the number of fertile spikelets did not change. There was a significant increase in the number of grains per ear as a result of increasing of spikelets in ears. The number and weight of grains did not decrease, even though the plants were characterized by a smaller number of productive stems. The presence of Rht8x allele on genetic background of variety Stepnyak resulted in a significant decrease of plants productivity. However, in combination with Ppd-D1a allele plants with Rht8x increased the potential productivity, and surpassed the parental form (Rht8a Ppd-D1b). The presence of Rht-B1e allele resulted in reduction of grain mass per spike and 1000-grain weight, increase of l/h, and left the number of grains per spike stable in comparison with Rht8c.

[Effects of dwarfing genes on the genetic background of wheat varieties of the south Ukraine region].

Effects of the Rht8c, Rht-B1b, Rht-B1e and Rht-D1b genes on the plant height of wheat have been investigated. Variations of these effects are significantly modified by genetic background and year conditions. Complex of the alleles Rht8c Rht-B1a Rht-D1b Ppd-D1a is advantageous for the conditions of the South Ukraine region. There are gene(s) in the genotypes of some varieties which significantly decrease height and are unidentified by molecular markers in our investigation.