Disease resistance. Leaf and stripe rust resistance

Lr37-Yr17-Sr38

Background information

A long chromosomal fragment (25-38 cM) containing three rust resistance genes was translocated between the short arms ofTriticum ventricosum 2NS and the bread wheat chromosome 2AS (1). This segment includes three disease resistance genes: Lr37, Yr17 and Sr38 conferring resistance to leaf rust (Puccinia triticina Eriks), stripe rust (Puccinia striiformis West. f. sp. tritici) and stem rust (Puccinia graminis Pers. f.sp. tritici Eriks. & E. Henn.) respectively.

The 2NS fragment was first introgressed into wheat cultivar VPM1 (2) and later it was transferred to other commercial cultivars like Madsen and Thatcher (3,4,5,6). Recently, Helguera et al. found thatLr37 was not functional in Anza-Lr37, suggesting the presence of a supressor factor (7).

Rust races virulent to Lr37 and Yr17 resistance genes have been already identified (5). However, these genes still provide resistance to a wide range of races and can be used in combination with other rust resistance genes.

Methods

Helguera et al. (7) developed PCR markers for this fragment. The detailed protocols can be found in the methods section. The 2NS chromosome segment does not recombine with the bread wheat chromosomes, and therefore the three resistance genes are transferred together and are completely linked to markers developed within the 2NS segment. However, occasional recombination events cannot be ruled out and the final products should be tested with the pathogen to confirm the introgression of resistance genes. Until now, we have not observed a single recombination event between the markers and the resistance genes.

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. [abstract]

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. [abstract]

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. [abstract]

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. [abstract]