Stripe rust resistance gene Yr34 (synonym Yr48) is located within a distal translocation of Triticum monococcum chromosome 5AmL into common wheat

Abstract

Key messageThe stripe rust resistance geneYr34 was transferred to polyploid wheat chromosome 5AL from T. monococcumand has been used for over two centuries.Wheat stripe (or yellow) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is currently among the most damaging fungal diseases of wheat worldwide. In this study, we report that the stripe rust resistance gene Yr34 (synonym Yr48) is located within a distal segment of the cultivated Triticum monococcum subsp. monococcum chromosome 5AmL translocated to chromosome 5AL in polyploid wheat. The diploid wheat species Triticum monococcum (genome AmAm) is closely related to T. urartu (donor of the A genome to polyploid wheat) and has good levels of resistance against the stripe rust pathogen. When present in hexaploid wheat, the T. monococcum Yr34 resistance gene confers a moderate level of resistance against virulent Pst races present in California and the virulent Chinese race CYR34. In a survey of 1,442 common wheat genotypes, we identified 5AmL translocations of fourteen different lengths in 17.5% of the accessions, with higher frequencies in Europe than in other continents. The old European wheat variety “Mediterranean” was identified as a putative source of this translocation, suggesting that Yr34 has been used for over 200 years. Finally, we designed diagnostic CAPS and sequenced-based markers that will be useful to accelerate the deployment of Yr34 in wheat breeding programs to improve resistance to this devastating pathogen.

Detecting Major Introgressions in Wheat and their Putative Origins Using Coverage Analysis

“…LongReach Lancer (Supplementary Data 1). Previous studies have reported introgressions on wheat chromosomes 5AL and 7AL from T. monococcum 41 and T. boeoticum 42 , respectively, although the introgressed regions differ. In contrast, the introgression on chromosome 1AS has been described for cv.…”

“…We identified putative introgressions as regions with decreased coverage of reads from the progenitor species of the wheat subgenomes; that is, for a genomic window, the proportion covered by reads is decreased (Methods). Triticum urartu (2n=2x=14, A u ) and Aegilops tauschii (2n=2x=14, D) are the donors of the A and D subgenomes of wheat [20][21][22] , respectively, whereas the donor of the B subgenome is either not known yet or extinct 23 . Aegilops speltoides (2n=2x=14, S) is the most closely related remnant taxon to the wheat B subgenome donor [23][24][25] .…”

Detecting major introgressions in wheat and their putative origins using coverage analysis

“…LongReach Lancer (Supplementary Data 1 ). Previous studies have reported introgressions on wheat chromosomes 5AL and 7AL from T. monococcum 41 and T. boeoticum 42 , respectively, although the introgressed regions differ. In contrast, the introgression on chromosome 1AS has been described for cv.…”

“…This observation is consistent with findings of introgressions from T. monococcum in bread wheat cv. Mediterranean 41 released in 1837. We hypothesise that the introgressions found in old cultivars resulted from spontaneous natural interspecific crosses that were subsequently selected.…”

Identification and characterization of Sr22b, a new allele of the wheat stem rust resistance gene Sr22 effective against the Ug99 race group

“…T . monococcum harbours several valuable rust resistance genes, including the leaf rust resistance genes LrTM16 (Sodkiewicz and Strzembicka, 2008) and Lr63 (Kolmer and Anderson, 2010); the stripe rust resistance loci QYrtm.pau‐2A and QYrtb.pau‐5A (Chhuneja et al ., 2008) and Yr34 (Chen et al ., 2021); and the stem rust resistance genes Sr21 (Chen et al ., 2015; The, 1973), Sr22 (Gerechter‐Amitai et al ., 1971), Sr35 (McIntosh et al ., 1984), SrTm4 (Briggs et al ., 2015) and Sr60 and SrTm5 (Chen et al ., 2018a).…”