ARS | Publication request: Discovery and molecular mapping of a new gene conferring resistance to stem rust, Sr53, derived from Aegilops geniculata and characterization of spontaneous translocation stocks with reduced alien chromatin

Submitted to: Chromosome Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2011
Publication Date: July 1, 2011
Citation: Liu, W., Rouse, M.N., Friebe, B., Jin, Y., Gill, B., Pumphrey, M. 2011. Discovery and molecular mapping of a new gene conferring resistance to stem rust, Sr53, derived from Aegilops geniculata and characterization of spontaneous translocation stocks with reduced alien chromatin. Chromosome Research. 19(5):669-682.

Interpretive Summary: This study reports the discovery and molecular mapping of a resistance gene transferred from a wild relative of wheat, Aegilops geniculata, that is effective against wheat stem rust. Two populations were developed and used for genetic mapping to identify markers linked to the resistance gene. Further molecular and cytogenetic characterization resulted in identification of nine spontaneous recombinants with shortened Ae. geniculata chromosome segments. Three of the wheat-Ae. geniculata recombinants had 20%-30% proximal segments from the wild species translocated to chromosome 5DL of wheat; the other six are recombinants having shortened segments of the original resistance gene donor. All recombinants were confirmed to be genetically compensating on the basis of genomic in situ hybridization and molecular marker analysis. These recombinants between wheat and Ae. geniculata will provide another source for wheat stem rust resistance breeding and for physical mapping of the resistance locus and crossover hotspots between chromosomes of wheat and Ae. geniculata.

Technical Abstract: This study reports the discovery and molecular mapping of a resistance gene effective against stem rust races RKQQC and TTKSK (Ug99) derived from Aegilops geniculata (2n=4x=28, UgUgMgMg). Two populations from the crosses TA5599 (T5DL-5MgL.5MgS)/TA3809 (ph1b mutant in Chinese Spring background) and TA5599/Lakin were developed and used for genetic mapping to identify markers linked to the resistance gene. Further molecular and cytogenetic characterization resulted in identification of nine spontaneous recombinants with shortened Ae. geniculata segments. Three of the wheat-Ae. geniculata recombinants (U6154-124, U6154-128 and U6200-113) are interstitial translocations (T5D.5DL-5MgL-5DL), with 20%-30% proximal segments of 5MgL translocated to 5DL; the other six are recombinants (T5DL-5MgL.5MgS) have shortened segments of 5MgL with fraction lengths (FL) of 0.32-0.45, compared to FL 0.55 for the 5MgL segment in original translocation donor, TA5599. Recombinants U6200-64, U6200-117 and U6154-124 carry the stem rust resistance gene Sr53 with the same infection type as TA5599, the resistance gene donor. All recombinants were confirmed to be genetically compensating on the basis of genomic in situ hybridization and molecular marker analysis with chromosome 5D- and 5Mg-specific SSR/STS-PCR markers. These recombinants between wheat and Ae. geniculata will provide another source for wheat stem rust resistance breeding and for physical mapping of the resistance locus and crossover hotspots between wheat chromosome 5D and chromosome 5MgL of Ae. geniculata.