Disease resistance. Stem and Leaf Rust Resistance.
Sr39 / Lr35
Contributed by J. Douglas Procunier
Agriculture & AgriFood Canada
Background information
The wheat stem rust pathogen, Puccinia graminis Pers. f. sp. tritici Erik. & Henn., can potentially devastate wheat (Triticum aestivum L. and T. turgidum L.) crops. The stem rust resistance gene Sr39 was transferred to the hexaploid wheat cultivar Thatcher (Tc) from the wild wheat relative Aegilops speltoides L. Thatcher carries stem rust resistance genes Sr5, Sr9g, Sr12, and Sr16. Gene Sr39 is on a translocated chromosome segment, putatively 2S#2, from A. speltoides. A Tc/Sr39 line demonstrated highly resistant infection type reactions in the seedling stage to approximately 1200 isolates of P. graminis f. sp. tritici. This gene has not yet been used in wheat breeding. Also associated with the translocated Sr39 resistance is the adult plant leaf rust (P. recondita Rob. ex Desm. f. sp. tritici Eriks.) resistance gene Lr35. Lr35 is highly effective against North American populations of P. recondita f. sp. tritici. Both the Sr39 and Lr35 genes are located on the alien translocated segment and co-segregate in crosses with a recombination value of 3.0 between them. Genetic tests established that both resistance genes are on chromosome 2B of wheat.
Methods
An inter-simple sequence repeat (ISSR) marker was converted to a sequence characterized amplified region (SCAR) marker by designing primer sets which amplify a single, easily resolved band from DNA of plants with the Sr39/Lr35 genes. Experimental details are described in the PCR methods section.
Available germplasm
RL6082 is a T. aestivum cv. Thatcher (Tc) near-isogenic line carrying the partially dominant genes Sr39 and Lr35, for resistance to stem rust and leaf rust, respectively. The NIL was derived from an amphiploid of Ae. speltoides x T. monococcum L. by direct crossing and backcrosses. Six wheat lines originating from the Ae. speltoides x T. monococcum amphiploid and carrying Sr39 and Lr35 were tested for the presence of the marker. RL5711 and RL5910 were obtained from the Cereal Research Centre, Winnipeg, MB; p8810 from Dr. R. Knox ( Semi-arid Prairie Agriculture ResearchCentre, Swift Current, SK) ; and segregants of RL6082 x BW148, RL6082 x BW173 and RL6082 x MqK from the Cereal Research Centre, Winnipeg, MB.
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). [abstract]
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. [abstract]
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.