Dwarfing genes not only reduce the height of triticale plants, but also have pleiotropic effects on important agronomic traits. An important task for breeding is to evaluate the effects of gibberellin responsive (GAR) and gibberellin-insensitive (GAI) dwarfing genes in one genotype. In the greenhouse experiment, we evaluated the effects of the GAI gene Rht-B1b of wheat and the GAR gene Ddw1 of rye on height and the main agronomic traits in two connecting populations derived from crossing Ddw1 donors (cv. ‘Mudrets’ and cv. ‘Valentin 90’) with a Rht-B1b donor (cv. ‘Dublet’). The results show a strong decrease in height under the influence of Ddw1 in both populations by more than 30%. In this case, Rht-B1b in the presence of Ddw1 does not lead to a significant decrease in the height of the spring triticale; thus, this is not likely to be included in breeding programs in order to further reduce the height in the presence of Ddw1 in the spring triticale germplasm. However, Ddw1 reduces the 1000 grain weight, while Rht-B1b increases the grain number per spike and grain number per spikelet. Thus, our studies have demonstrated the negative effect of Ddw1 on spring triticale productivity of the main spike in the greenhouse experiment, which can be partially compensated by Rht-B1b.
Background Plant height is an important wheat trait that is regulated by multiple genes, among which Rht is of the utmost value. In wheat, Rht-B1p (=Rht17) is a mutant allele of the Rht gene that encodes for a DELLA-protein and results in the development of gibberellin-insensitive plants with a dwarfing phenotype. The pleiotropic effects of dwarfing genes on yield are highly dependent on both the genetic background and the environmental conditions. In Russia, the Central Non-Black Earth Region and Krasnodar Krai are two economically important regions that require differing management for sustainable wheat production for food, feed and industry. The purpose of our study was to compare the pleiotropic effects of Rht-B1p on the main valuable agronomic traits in the F3:4 families of the spring bread wheat Chris Mutant/Novosibirskaya 67 in the genetic background of Vrn-B1a/vrn-B1 (spring/winter phenotype) and Ppd-D1a/Ppd-D1b (insensitivity/sensitivity to photoperiod) alleles in a field experiment in Moscow and Krasnodar Krai. Results Plant height was reduced on average by 21 cm (28%) and 25 cm (30%), respectively; Ppd-D1a slightly strengthened the dwarfing effect in Moscow and mitigated it in Krasnodar Krai. Grain weight of the main spike was reduced by Rht-B1p in Moscow and to lesser extent in Krasnodar; Ppd-D1a and Vrn-B1a tended to partially compensate for this loss in Krasnodar Krai. Thousand grain weight was reduced on average by 5.3 g (16%) and 2.9 g (10%) in Moscow and Krasnodar Krai, respectively, but was partially compensated for by Ppd-D1a in Krasnodar Krai. Harvest index was increased due to Rht-B1p by 6 and 10% in Moscow and Krasnodar Krai, respectively. Rht-B1p resulted in a delay of heading by 1–2 days in Moscow. Ppd-D1a accelerated heading by 1 day and 6 days in Moscow and in Krasnodar Krai, respectively. Conclusions Rht-B1p could be introduced into wheat breeding along with dwarfing genes such as Rht-B1b and Rht-D1b. Special attention should be paid to its combination with Ppd-D1a and Vrn-B1a as regulators of developmental rates, compensators of adverse effects of Rht-B1p on productivity and enhancers of positive effect of Rht-B1p on harvest index.
Reducing plant height improves lodging resistance and helps to obtain high grain yield under various environmental conditions. So far, the introduction and maintenance of the dwarfing allele of the Ddw1 gene is the most effective height-reducing genetic approach in rye and triticale breeding programs. However, the dominance of the dwarfing Ddw1 allele makes it difficult to select against heterozygous lines for further breeding based on plant phenotype. To assist breeders in the identification of the allele status of the Ddw1 gene, we developed a cleaved amplified polymorphic sequence (CAPS) marker that requires basic equipment and can be easily applied. The CAPS marker was tested on two F2 segregating populations of triticale, and the test showed the association of the Ddw1 genotype with plant height. The application of the marker for marker-assisted selection (MAS) for rye and triticale is discussed in detail.
Triticale is a relatively new crop which still possesses serious drawbacks that can be significantly improved by breeding. The dwarfing genes proved to be very useful in the development of new lodging resistant and productive cultivars of winter triticale. The aim of our research was to assess the effect of the Ddw1 dwarfing gene from rye on the agronomic valuable traits in spring triticale. The Ddw1 effect was studied in the greenhouse experiment in segregating the F2:3 population and in the field of F3:4 and F4:5 families derived from crossing winter triticale ‘Hongor’ (Ddw1Ddw1) and spring triticale ‘Dublet’ (ddw1ddw1). As a result, in all three generations, a strong decrease in plant height was demonstrated that was accompanied by a decrease in grain weight per spike and 1000-grain weight. In field experiments, a decrease in spike length and increase in spike density and delay in flowering and heading were observed. As a result of decrease in culm vegetative weight due to Ddw1, the harvest index measured in F4:5 increased. The spike fertility and number of grains were not affected by Ddw1. The comparison of Ddw1 in rye, winter, and spring triticale, and the possible role of Ddw1 in improving spring triticale are discussed.
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