A new leaf rust resistance gene Lr79 mapped in chromosome 3BL from the durum wheat landrace Aus26582

Abstract

A new leaf rust resistance gene Lr79 has been mapped in the long arm of chromosome 3B and a linked marker was identified for marker-assisted selection. Aus26582, a durum wheat landrace from the A. E. Watkins Collection, showed seedling resistance against durum-specific and common wheat-specific Puccinia triticina (Pt) pathotypes. Genetic analysis using a recombinant inbred line (RIL) population developed from a cross between Aus26582 and the susceptible parent Bansi with Australian Pt pathotype showed digenic inheritance and the underlying loci were temporarily named LrAW2 and LrAW3. LrAW2 was located in chromosome 6BS and this study focused on characterisation of LrAW3 using RILs lacking LrAW2. LrAW3 was incorporated into the DArTseq map of Aus26582/Bansi and was located in chromosome 3BL. Markers linked with LrAW3 were developed from the chromosome survey sequence contig 3B_10474240 in which closely-linked DArTseq markers 1128708 and 3948563 were located. Although bulk segregant analysis (BSA) with the 90 K Infinium array identified 51 SNPs associated with LrAW3, only one SNP-derived KASP marker mapped close to the locus. Deletion bin mapping of LrAW3-linked markers located LrAW3 between bins 3BL11-0.85-0.90 and 3BL7-0.63. Since no other all stage leaf rust resistance gene is located in chromosome 3BL, LrAW3 represented a new locus and was designated Lr79. Marker sun786 mapped 1.8 cM distal to Lr79 and Aus26582 was null for this locus. However, the marker can be reliably scored as it also amplifies a monomorphic fragment that serves as an internal control to differentiate the null status of Aus26582 from reaction failure. This marker was validated among a set of durum and common wheat cultivars and was shown to be useful for marker-assisted selection of Lr79 at both ploidy levels.

Genome‐Wide Association Study of a Worldwide Collection of Wheat Genotypes Reveals Novel Quantitative Trait Loci for Leaf Rust Resistance

“…Seedling resistance, also known as all-stage resistance, confers resistance to only certain races (race-specific) with a high degree; however, a shift in the virulence of the pathogen population can easily overcome seedling resistance (Kolmer, 2005(Kolmer, , 2013. Lr72 (Herrera-Foessel et al, 2014), Lr76 (Bansal et al, 2017), and Lr79 (Qureshi et al, 2018) are some examples of genes for seedling resistance to LR reported recently. On the other hand, APR is normally detected after the seedling stages, confers resistance to multiple races (nonrace-specific), provides a moderate level of resistance, and has been found to be more durable (Kolmer, 1996(Kolmer, , 2013McIntosh et al, 1995).…”

Genetic analysis of Aegilops tauschii-derived seedling resistance to leaf rust in synthetic hexaploid wheat

“…The most effective, economical, and environmentally sound means of controlling this disease is the deployment of resistant wheat cultivars. To date, formally designated leaf rust resistance genes have been catalogued at 76 loci (Lr1-Lr79;McIntosh et al 2013McIntosh et al , 2017Qureshi et al 2018). The release of cultivars with resistance based upon single major resistance genes leads to the emergence of pathotypes with matching virulence.…”

Transcriptome Analysis Based on Lr19-Virulent Mutants Strain Provides Clues for the Pathogenicity-Related Genes and Effectors of Puccinia Triticina

“…To date, over 80 genes conferring leaf rust resistance derived from Triticum aestivum wheat cultivars, wild wheat, grass species, and durum wheat have been identi ed and designated as Lr1 to Lr79 [2]. Among them, only Lr9, Lr19, Lr24, Lr34, Lr37, Lr38, Lr46, Lr47, Lr51, Lr53, and Lr68 confer effective resistance to leaf rust currently.…”