Effects of dwarfing wheat (Triticum aestivum L.) and rye (Secale cereale L.) genes in spring triticale segregating population as studied in pot trials

The urgent problem of triticale lodging may be reliably overcome by introgression of dwarfing genes into triticale cultivars. Notable, both wheat and rye dwarfing genes can reduce the height of triticale plants. Therefore, a single contribution of various dwarfing genes and their additive effects in triticale which is an intergeneric hybrid still remain intriguing in fundamental aspects and important for breeding practice. In our study, rye dwarfing gene Ddw1 has been transferred into spring triticale. Then we have hybridized winter triticale cv. Avanguard ( Ddw1 Ddw1 Rht-B1a Rht-B1a ) with spring triticale cv. Solovei Kharkovskii ( ddw1 ddw1 Rht-B1b Rht-B1b ) and used F2 seeds to reveal the mechanism of inheritance of the studied dwarfing genes Ddw1 and Rht-B1b and to determine the effect of the dwarfing alleles on economically valuable traits in the segregating population of spring triticale. Under the greenhouse conditions, 273 plants of the spring type of the segregating population F2 were grown to individually estimate plant height, the number and length of internodes, spikelet length and number per spike, spike density, grain weight, grain number and 1000-grain weight per the main spike. Each plant was also genotyped by PCR using the markers of the Ddw1 and Rht-B1 allelic state. To investigate inheritance patterns, the dominant and additive effects of genes were calculated. The second task was achieved by comparing plants homozygous for wild-type alleles ( ddw1 and Rht-B1a ) and short-stem alleles ( Ddw1 and Rht-B1b ) with estimation of both independent effect of each genes and their interlocus interaction. Using statistical methods (Fisher F -criterion, Mann-Whitney U- test, and Spearman rank correlation coefficient ρ), we found the significance of the differences and associations between phenotypic traits and genotype. Our studies have shown that the effects of the Ddw1 and Rht-B1b are somewhat different from those in wheat. The Ddw1 statistically significant affects plant height (by reducing up to 40 %, p = 0.05), manifesting itself as a partially dominant allele. The Rht-B1b results in a decrease in the spring triticale plant height but less than the Ddw1 gene does (only up to 20 %, p = 0.05). Hence, the Rht-B1b allele is proven to be partially recessive. In the presence of gene Rht-B1b a kernel weight increases from 1.4 g to 1.7 g (by 21.4 %) due to higher spike density and fertility. The Ddw1 gene introgression leads to a 16.7 % decrease (p = 0.05) in the total grain weight per spike (from 1.8 g to 1.5 g) due to a 9.6 % decrease (p = 0.05) in the 1000-grain weight (from 45.7 g до 41.3 g). In general, the Ddw1 and Rht-B1b genes affect the studied traits as antagonists. In summary, a combination of two dwarfing genes, Ddw1 from rye and Rht-B1b from wheat, makes it possible to maximize yield of dwarf spring triticale plants and is promising for breeding.