Leaf rust caused by
Puccinia triticina (Pt) is one of the most dangerous diseases causing significant losses in common wheat crops. In adult plants resistant to rust, a horizontal adult plant resistance (APR) type is observed, which protects the plant against multiple pathogen races and is distinguished by greater persistence under production conditions. Crucial pleiotropic slow-rust genes such as
Lr34,
Lr46,
Lr67, and
Lr68, in combination with other genes of lesser influence, continue to increase durable resistance to rust diseases. Based on our previous results, we selected four candidate genes for
Lr46 out of ten candidates and analysed them for expression before and after inoculation by
P. triticina. As part of our study, we also investigated the expression patterns of miRNA molecules complementary to
Lr34 and the candidate genes. The aim of the study was to analyse the expression profiles of candidate genes for the
Lr46 gene and the
Lr34 and
Lr67 genes responsible for the differential leaf-rust resistance of hybrid forms of the F1 generation resulting from crosses between the Glenlea cultivar and cultivars from Polish breeding companies. In addition, the expression of five miRNAs (tae-miR9653b, tae-miR5384-3p, tae-miR9780, tae-miR9775 and tae-miR164), complementary to
Lr34, and selected candidate genes were analysed using stem-loop RT-PCR and ddPCR. Biotic stress was induced in adult plants by inoculation with
Pt fungal spores, under controlled conditions. Plant material was collected before and 6, 12, 24, and 48 h after inoculation (hpi). Differences in expression patterns of
Lr34,
Lr67, and candidate genes (for
Lr46) were analysed by qRT-PCR and showed that gene expression changed at the analysed time points. Identification of molecular markers coupled to the
Lr genes studied was also carried out to confirm the presence of these genes in wheat hybrids. qRT-PCR was used to examine the expression levels of the resistance genes. The highest expression of
Lr46/Yr29 genes (
Lr46-Glu2,
Lr46-RLK1,
Lr46-RLK2, and
Lr46-RLK3) occurred at 12 and 24 hpi, and such expression profiles were obtained for only one candidate gene among the four genes analysed (
Lr46-Glu2), indicating that it may be involved in resistance mechanisms of response to
Pt infection.
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