Stem rust resistance gene Sr32

Sr32 is a gene effective against the Ug99 and related strains of Puccinia graminis sp. tritici. It is responsible for a low infection type 1+ to 2C. Sr32 was derived from Aegilops speltoides and translocated to hexaploid wheat. However, it has not been employed in wheat breeding programs because the large Sr32-carrying translocations also contained genes with deleterious effects or were present in genetic backgrounds unsuitable for breeding (1,2).

Mago et al. (3) crossed the translocation line C82.2 (+ Sr32) with the wheat line ‘Angas ph1bph1b’.  After selection and backcrossing a set of recombinant lines with wheat cultivars ‘Angas’, ‘Aroona’ or ‘Westonia’, they obtained several lines with small alien translocations carrying  Sr32 on the short arm of chromosome 2D.

Marker for Sr32

Mago et al (3) developed two dominant PCR markers for Sr32 that are useful for breeding programs: csSr32#1 and csSr32#2.

Primers sequences:

csSr32#1

csSr32#1-F      5'- GGT TTG GTG GCA ACT CAG GT -3'

csSr32#1-R      5'- CAT AAG CCA AAG AGG CAC CA -3'

PCR conditions:

  • Denaturing step: 95°C, 2 min
  • Amplification step (30 cycles):
    • 95°C, 30 sec
    • 58°C, 30 sec
    • 72°C, 40 sec
  • Extension step: 72°C, 5 min

csSr32#2

csSr32#2-F       5'- CAA ATG AAT AGA AAA ACC CGT GCT -3'

csSr32#2-R       5'- CAC ACA CTG TTT TCC GTT GC -3'

PCR conditions:

  • Denaturing step: 95°C, 2 min
  • Amplification step (30 cycles):
    • 95°C, 30 sec
    • 60°C, 40 sec
    • 72°C, 50 sec
  • Extension step: 72°C, 5 min

Expected products

The PCR products were separated on 2% agarose gels. csSr32#1 and csSr32#1 amplified products of 184-bp and 152-bp, respectively, on several lines carrying Sr32, while none of them produced amplificaton in lines missing Sr32.

Conditions presented here should be considered only as a starting point of the PCR optimization for individual laboratories.

References

1. Wheat rusts: an atlas of resistance genes. McIntosh RA, Wellings CR, Park RF. 1995. CSIRO Publications, Victoria.

2. Characterization of wheat-alien translocations conferring resistance to diseases and pests: current status. Friebe B, Jiang J, Raupp WJ, McIntosh RA, Gill BS. In: Euphytica, 1996, 91:59-87. DOI:10.1007/BF00035277.

3. Development of wheat–Aegilops speltoides recombinants and simple PCR-based markers for Sr32 and a new stem rust resistance gene on the 2S#1 chromosome. Mago R, Verlin D, Zhang P, Bansal U, Bariana H, Jin Y, Ellis J, Hoxha S, Dundas I. In:Theoretical and Applied Genetics, 2013, 126:2943-2955. DOI: 10.1007/s00122-013-2184-8

Tags

stem rust resistance