Disease resistance. Stem and Leaf Rust Resistance.

Sr39 / Lr35

Contributed by J. Douglas Procunier

Agriculture & AgriFood Canada

References

1. Development of a molecular marker for rust resistance genes Sr39 and Lr35 in wheat breeding lines. Gold J, Harder D, Townley-Smith F, Aung T, Procunier J. In: Electronic Journal of Biotechnology, 1999, 2: (1).

Polymorphic DNA bands were identified between a near iso-isogenic line of wheat carrying both stem (Sr39) and leaf (Lr35) rust resistance genes and the recurrent line Thatcher (Tc) which lacks these genes. Both resistance genes are located on a translocated chromosomal segment derived from Aegilops speltoides and thus are genetically linked. The primers used to generate polymorphic bands were 3'-anchored inter-simple sequence repeat primers which identified genomic microsatellites with a repeated motif of 3 nucleotides in length. The primers were used singly to amplify genomic segments which were flanked by inversely orientated, closely spaced, identical microsatellite sequences. One of the polymorphic bands, a 900 base pair band, was completely linked to the Sr39 and Lr35 rust resistance genes in the segregating population used in this study. After cloning and sequencing this polymorphic band, the inter-simple sequence repeat marker was converted to a sequence characterized amplified region marker by designing primer sets which amplify a single, easily resolved band from DNA of plants with Sr39/Lr35 genes. This marker is present in six wheat lines carrying the Sr39 and Lr35 genes on the translocated chromosome segment from Ae. speltoides. The marker has facilitated efforts to breed Canada Prairie Spring and Canada Western Extra Strong lines with these rust resistance genes.

2. Transfer to hexaploid wheat of linked genes for adult-plant leaf rust and seedling stem rust resistance from an amphiploid of Aegilops speltoides x Triticum monococcum. Kerber ER, Dyck PL. In: Genome, 1990, 33: 530-537.

3. Virulence in Puccinia recondita f. sp. tritici isolates from Canada to genes for adult-plant resistance to wheat leaf rust. Kolmer JA. In: Plant Disease, 1997, 81: 267-271.

Sixty-seven isolates of Puccinia recondita f. sp. tritici collected in Canada were tested for virulence to adult plants of Thatcher near-isogenic wheat lines with leaf rust resistance genes Lr13, Lr22a, Lr34, Lr35, and Lr13 and Lr34 combined. All of the isolates had low infection type to the Thatcher lines with Lr22a and Lr35. All isolates had lower infection type and lower rust severity on the Thatcher line with Lr34 compared with Thatcher. The isolates were polymorphic for virulence to the Thatcher line with Lr13, many isolates were completely virulent to this line, and other isolates produced very low or intermediate avirulent infection type. On the Thatcher line with Lr13 and Lr34 combined, many isolates had infection type and rust severity similar to the Thatcher line with Lr34, while other isolates had lower infection type and rust severity compared with the single-gene lines with Lr13 or Lr34. Fifteen isolates with low intermediate, and high infection type to adult plants with Lr13 were tested for infection type on seedling plants of the Thatcher lines with resistance genes Lr13, Lr22a, Lr34, Lr35, and Lr37, and on Thatcher lines with Lr13 paired with seedling resistance genes. Most isolates were completely virulent to seedling plants with Lr13 and Lr22a. Plants with Lr37 expressed seedling resistance to all isolates tested. Seedling plants with Lr34 had lower infection types to all isolates compared with Thatcher. Seedlings with Lr35 had high infection types to most isolates. with varying amounts of chlorosis. The Thatcher lines with Lr13 plus seedling resistance genes were most resistant to the isolates that had very low infection types on adult plants with

4. 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.

5. Registration of P8810-B5B3A2A2 white-seeded spring wheat germplasm with Lr35 leaf and Sr39 stem rust resistance. . Knox RE, Campbell HL, DePauw RM, Clarke JM, Gold JJ. In: Crop Science, 2000, 40: 1512-1513.