Disease resistance. Leaf and stripe rust resistance

Lr37-Yr17-Sr38

References

1. Cytogenetic studies in wheat XIV. Location of rust resistance genes in VPM1 and their genetic linkage with other disease resistance genes in chromosome 2A. Bariana HS, McIntosh RA. In: Genome, 1993, 36: 476-482

Inheritance studies showed that the VPM1-derived seedling resistances to stem rust, stripe rust, leaf rust, and powdery mildew were controlled by single genes; the genes for rust resistance were designated Sr38, Yr17, and Lr37, respectively, whereas the gene for resistance to powdery mildew was postulated to be Pm4b. Sr38, Yr17, and Lr37 were shown to be closely linked and distally located in the short arm of chromosome 2A. They showed very close repulsion linkage with Lr17 and were genetically independent of other genes known to be located in chromosome 2A. Previously unmapped, Yr1 appeared to be distally located in the long arm of chromosome 2A.

2. Obtention des bles tendres resistants au pietin-verse par croisements interspecifiques bles X Aegilops. Maia N. In: C. R. Acad. Agric. Fr., 1967, 53: 149-154.

3. The genetic analysis of two interspecific sources of leaf rust resistance and their effect on the quality of common wheat. Dyck PL, Lukow OM. In: Canadian Journal of Plant Science, 1988, 68: 633-639.

4. McIntosh RA, Wellings CR, Park RF. In: Wheat Rusts, an Atlas of Resistance Genes Melbourne, Australia, CSIRO, 1995.

5. Identification of molecular markers for the detection of the yellow rust resistance gene Yr17 in wheat. Robert O, Abelard C, Dedryver F. In: Molecular Breeding,1999, 5:167-175.

The Yr17 gene, which is present in many European wheat cultivars, displays yellow rust resistance at the seedling stage. The gene introduced into chromosome 2A from Aegilops ventricosa was previously found to be closely linked (0.5 cM) to leaf and stem rust resistance genes Lr37 and Sr38, respectively. The objective of this study was to identify molecular markers linked to the Yr17 gene. We screened with RAPD primers, for polymorphism, the DNAs of cs. Thatcher and the leaf rust-resistant near-isogenic line (NIL) RL 6081 of cv. Thatcher carrying the Lr37 gene. Using a F₂ progeny of the cross between VPM1 (resistant) and Thesee (susceptible) the RAPD marker OP-Y15(580) was found to be closely linked to the Yr17 gene. We converted the OP-Y 15(580)RAPD marker into a sequence characterized amplified region SCAR). This SCAR marker(SC-Y15) was linked at 0.8+/-0.7 cM to the Yr17 resistance gene. We tested the SC-Y15 marker over a survey of 37 wheat cultivars in order to verify its consistency in different genetic backgrounds and to explain the resistance of some cultivars against yellow rust. Moreover, we showed that the Xpsr150-2Mv locus marker of Lr gene described by Bonhomme et al.[6] which possesses A. ventricosa introgression on the 2A chromosome was also closely linked to the Yr17 gene. Both the SCAR SC-Y15 and Xpsr150-2M markers should be used in breeding programmes in order to detect the cluster of the three genes Yr17, Lr37 and Sr38 in cross progenies.

6. Resistance gene analogs within an introgressed chromosomal segment derived from Triticum ventricosum that confers resistance to nematode and rust pathogens in wheat. Seah S, Spielmeyer W, Jahier J, Sivasithamparam K, Lagudah ES. In: Molecular and Plant Microbe Interactions, 2000, 13: 334-341.

A resistance (R) gene-rich 2S chromosomal segment from Triticum ventricosum contains a cereal cyst nematode (CCN; Heterodera avenae) R gene locus CreX and a closely linked group of genes (Sr38, Yr17, and Lr37) that confer resistance to stem rust (Puccinia graminis f. sp. tritici), stripe rust (P. striiformis f. sp. tritici), and leaf rust (P. recondita f. sp. tritici) when introgressed into wheat. The 2S chromosomal segment from T. ventricosum is further delineated in translocations onto chromosome 2A of bread wheat, where the rust genes are retained but not the CreX gene. Using these critical genetic stocks, we have isolated family members of R gene analogs that are associated with either the 2S segment from T. ventricosum carrying the CreX locus or the rust genes. Derivatives of the Cre3 candidate R gene sequence and a rice (Oryza sativa) R gene analog that mapped to the 2S homologous chromosome groups in wheat were used to isolate related gene sequences from T. ventricosum that contain a nucleotide binding site-leucine rich repeat domain. The potential of these gene sequences as entry points for isolating candidate genes or gene family members of the CreX or rust genes and their further applications to plant breeding are discussed.

7. PCR assays for the Lr37-Yr17-Sr38 cluster of rust resistance genes and their use to develop isogenic hard red spring wheat lines Helguera M, Khan IA, Kolmer J, Lijavetzky D, Zhong-qi L, Dubcovsky J. In: Crop Science, 2003, 43:1839-1847

Rust resistance genes Lr37, Sr38 and Yr17 are located within a segment of Triticum ventricosum chromosome 2NS translocated to the short arm of bread wheat chromosome 2AS. Characterization of this chromosome segment with 13 RFLP markers indicated that the 2NS translocation replaced approximately half of the short arm of chromosome 2A (distal 25-38 cM). The objective of this study was to develop PCR assays based on RFLP marker cMWG682 to facilitate the transfer of this cluster of rust resistance genes into commercial wheat cultivars. DNA sequence was obtained from the A, B, D and N-alleles of cMWG682 and was used to design N-allele specific primers. The 2NS fragment amplified by PCR primers co-segregated with the presence of the RFLP-2NS band in all backcross populations. A cleaved amplified polymorphic sequence (CAPS) was used to develop a marker for the 2A-allele. This marker can be used to differentiate homozygous and heterozygous plants carrying the 2NS translocation in the final cycle of backcross introgression or in screenings for homozygous plants in segregating populations. Finally, a third PCR assay was developed using TaqMan ® technology as a high-throughput alternative for selection of the 2NS/2AS translocation in large segregating populations in breeding programs that have access to real time PCR equipment. These molecular markers were used to develop four hard red spring isogenic lines homozygous for the 2NS chromosome segment. One of the isogenic lines, derived from 'Anza', did not show the expected resistance in spite of the presence of all the RFLP markers for the 2NS chromosome segment. Analysis of F₁ hybrids suggested that a suppressor of the Lr37 gene is present in Anza. These isogenic lines will provide a valuable tool to test the effects of the large 2NS translocation on quality and agronomic performance.