Molecular identification of triticale introgression lines carrying leaf rust resistance genes transferred from Aegilops kotschyi Boiss. and Ae. tauschii Coss.

Triticale (× Triticosecale Wittmack) is a commercial hybrid harboring wheat (Triticum sp.) and rye (Secale cereale L.) genomes. The limited genetic diversity of this crop resulted in the collapse of fungal disease resistance. Leaf rust disease, caused by Puccinia triticina Eriks., is reported to reduce the triticale yield significantly (more than 30%). There is a need to enlarge the genetic variability of this crop including leaf resistance genes. The main aim of this research was to evaluate the leaf rust resistance of the offspring of translocation lines of triticale carrying chromatin of Ae. tauschii and Ae. kotschyi. A reaction of seedlings of 200 plants of two triticale-Aegilops translocation lines (Bogo-2Dt.2R and Sekundo-2Sk.2R) was compared after inoculation with a natural mixture of P. triticina races, specific to triticale in controlled condition. Before inoculation, each plant was screened using molecular cytogenetics and molecular markers linked to leaf rust resistance genes. The presence of Aegilops chromosome segments was confirmed using genomic in situ hybridization (GISH). Lr39 and Lr54 leaf rust resistance genes were identified using Xgdm35 and S14 molecular markers, respectively. After inoculation, a significant improvement of resistance severity was observed in Sekundo-2Sk.2R in comparison with triticale cv. Sekundo plants. The resistance level of Bogo-2Dt.2R did not differ compared with triticale cv. Bogo plants. It was shown that Lr39 gene did not increase the leaf rust resistance level of triticale cv. Bogo.

Development and Cytomolecular Identification of Monosomic Alien Addition and Substitution Lines of Triticale (×Triticosecale Wittmack) With 2Sk Chromosome Conferring Leaf Rust Resistance Derived From Aegilops kotschyi Boiss.

Alien chromosome introgression has become a valuable tool to broaden the genetic variability of crop plants via chromosome engineering. This study details the procedure to obtain monosomic addition and monosomic substitution lines of the triticale carrying 2Sk chromosome from Aegilops kotchyi Boiss., which harbors Lr54 + Yr37 leaf and stripe rust-resistant gene loci, respectively. Initially, A. kotschyi × Secale cereale artificial amphiploids (2n = 6x = 42 chromosomes, UUSSRR) were crossed with triticale cv. "Sekundo" (2n = 6x = 42, AABBRR) in order to obtain fertile offspring. Cyto-molecular analyses of five subsequent backcrossing generations revealed that 2Sk chromosome was preferentially transmitted. This allowed for the selection of monosomic 2Sk addition (MA2Sk) lines of triticale. Finally, the 2Sk(2R) substitution plants were obtained by crossing MA2Sk with the nullisomic (N2R) plants of triticale. The presence of 2Sk chromosome in subsequent generations of plants was evaluated using SSR markers linked to Lr54 + Yr37 loci. Disease evaluation of the monosomic 2Sk(2R) substitution plants for the reaction to leaf and stripe rust infection were carried out under controlled conditions in a growth chamber. The results showed significant improvement of leaf rust resistance severity of monosomic substitution plants compared with control ("Sekundo"). In contrast, the introgression of the Lr54 + Yr37 loci did not lead to improvement of stripe rust resistance. In summary, the creation of monosomic addition and monosomic substitution lines of triticale is the starting point for the precise and guided transfer of Lr54 + Yr37 loci. The results showed that the developed materials could be exploited for the development of triticale varieties with resistance to leaf rust.

Development of Triticale × Wheat Prebreeding Germplasm With Loci for Slow-Rusting Resistance.

There is a growing interest in breeding and production of hexaploid triticale (× Triticosecale Wittmack ex A. Camus) in European Union and in the world. It is reported that triticale can be an alternative to wheat (Triticum aestivum L.) for livestock feed production and has a potential to become preferred industrial energy crop. Fungal diseases, mainly leaf and stripe rusts, are the limiting factors of triticale growth and yield. Geneticists and breeders are now focusing on accumulation of the major genes for durability of rust resistance. Slow-rusting genes Lr34/Yr18 and Lr46/Yr19 are being exploited in many wheat breeding programs. This type of horizontal resistance is reported to be effective over space and time. Classical breeding techniques supported by marker-assisted selection (MAS) are the main tools in breeding programs. The aim of this study was to assess the possibility of transfer of slow-rusting genes from resistant genotypes of wheat into hexaploid triticale through cross-hybridizations. A total of 5,094 manual pollinations were conducted between two triticale cultivars Fredro and Twingo and 33 accessions of common wheat, which were reported as sources of slow-rusting resistance genes. The investigation of the slow-rusting gene transmission was performed using both molecular markers analyses and genomic in situ hybridization (GISH). In total, 34 F1 hybrid plants were obtained, and 29 of them carried both slow-rusting loci. Therefore, these hybrids may be used for triticale prebreeding program.