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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 transfer Lr39 and Lr54 leaf rust resistance genes into triticale from Aegilops tauschii and Ae. kotschyi, respectively. 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. Before inoculation, each plant was screened using molecular cytogenetics and molecular markers linked to leaf rust resistance genes. 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 to triticale cv. Bogo plants. It was shown, that Lr39 gene did not increase the leaf rust resistance level of triticale cv. Bogo.

Lr46/Yr29/Pm39 (Lr46) is a gene for slow rusting resistance in wheat. The aim of the study was to analyze the miRNA expression in selected common wheat cultivars carrying resistance genes, Lr46 among others (HN Rod, Pavon‘S’, Myna‘S’, Frontana‘S’, and Sparrow’S’) in response to leaf rust infection caused by Puccinia triticina Erikss. In the Pavon ‘S’, Myna ‘S’, Frontana‘S’, and Sparow‘S’ varieties a product with a length of 242 bp has been identified, which is specific to the Xwmc44 marker linked to the brown rust resistance gene Lr46. In the next step, the differences in the expression of microRNA (miR5085 and miR164) associated with the Lr46 gene, which is responsible for different resistance of selected wheat cultivars to leaf rust, were examined using emulsion PCR (ddPCR). In the experiment, biotic stress was induced in mature plants by infecting them with fungal spores under controlled conditions in a growth chamber. For analysis the plant material was collected before inoculation and 6, 12, 24, and 48 h after inoculation. The experiments also showed that plant infection with Puccinia triticina resulted in an increase in miR164 expression in cultivars carrying the Lr46 gene. The expression of miR164 remained stable in a control cultivar (HN ROD) lacking this gene. This has proved that miR164 can be involved in leaf rust resistance mechanisms.

Recently, leaf rust and yellow rust caused by the fungi Puccinia triticina Erikss. and P. striiformis Westend f. sp. tritici Eriks and Henn are diseases of increasing threat in triticale (× Triticosecale Wittmack, AABBRR, 2n = 6x = 42) growing areas. The use of genetic resistance is considered the most economical, effective and environmentally friendly method to control the disease and minimize the use of fungicides. Currently, breeding programs mainly relied on race-specific Lr and Yr genes (R), but new races of the rust fungi frequently defeat resistance. There is a small group of genes that causes partial type of resistance (PR) that are characterized by a slow epidemic build up despite a high infection type. In wheat slow rusting resistance genes displayed longer latent periods, low infection frequencies, smaller pustule size and less spore production. Slow rusting Lr46/Yr29 gene, located on chromosome 1B, is being exploited in many wheat breeding programs. So far, there is no information about slow rusting genes in triticale. This paper showed significant differences between the results of identification of wheat molecular markers Xwmc44 and csLV46G22 associated with Lr46/Yr29 in twenty triticale cultivars, which were characterized by high levels of field resistance to leaf and yellow rust. The csLV46G22res marker has been identified in the following cultivars: Kasyno, Mamut and Puzon. Belcanto and Kasyno showed the highest resistance levels in three-year (2016–2018), leaf and yellow rust severity tests under post-registration variety testing program (PDO). Leaf tip necrosis, a phenotypic trait associated with Lr34/Yr18 and Lr46/Yr29 was observed, among others, to Belcanto and Kasyno, which showed the highest resistance for leaf rust and yellow rust. Kasyno could be considered to have Lr46/Yr29 and can be used as a source of slow rust resistance in breeding and importantly as a component of gene pyramiding in triticale.