Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2008
Publication Date: 1/2/2009
Citation: Zhang, Z., Friesen, T.L., Simons, K.J., Xu, S.S., Faris, J.D. 2009. Development,Identification and Validation of Markers for Mmarker-Assisted Selection Against the Stagonospora nodorum Toxin Ssensitivity Genes Tsn1 and Snn2 in Wheat. Molecular Breeding,23:35-49. Interpretive Summary: Stagonospora nodorum is a fungal pathogen of wheat that produces numerous toxins, which interact with specific genes in the wheat host to cause disease. The chromosomal locations of the host toxin-sensitivity genes Tsn1, Snn2, and Snn3, which confer sensitivity to the S. nodorum toxins ToxA, SnTox2, and SnTox3, respectively, were previously determined. In this work, we used molecular methodologies to identify and/or develop molecular markers closely associated with Tsn1 and Snn2 for use by wheat breeders in marker-assisted selection schemes. For Tsn1, we developed markers that flank the gene and delineated it to a 1.0 cM interval. For Snn2, we identified a marker that mapped 0.4 cM proximal to the gene, and we developed a new marker that mapped 3.6 cM distal to the gene. Thus, these two markers delineated the Snn2 gene to a 4.0 cM interval. Evaluation of the markers for Tsn1 and Snn2 in a diverse set of wheat genotypes validated their utility for marker-assisted selection, which is particularly efficient for removing toxin sensitivity alleles from elite germplasm and varieties.
Technical Abstract: The wheat-Stagonospora nodorum pathosystem involves a number of pathogen-produced host-selective toxins that interact with host genes in an inverse gene-for-gene manner to cause disease. The wheat intervarietal recombinant inbred population derived from BR34 and Grandin (BG population) segregates for the toxin sensitivity genes Tsn1, Snn2, and Snn3, which confer sensitivity to the toxins ToxA, SnTox2, and SnTox3, respectively. Here, we report the addition of 141 molecular markers to the BG population linkage maps, the identification and/or development of markers tightly linked to Tsn1 and Snn2, and the validation of the markers using a set of diverse wheat accessions. The BG population maps now contain 787 markers and new simple sequence repeat (SSR) markers closely linked to Snn2 on chromosome arm 2DS were identified. In an effort to target more markers to the Snn2 locus, STS markers were developed from 2DS bin-mapped ESTs resulting in the development and mapping of 36 markers mostly to the short arms of group 2 chromosomes. Together, SSR and EST-STS markers delineated Snn2 to a 4.0 cM interval. SSRs developed in related work for Tsn1 were mapped in the BG population and delineated the gene to a 1.0 cM interval. Evaluation of the markers for Tsn1 and Snn2 in a diverse set of wheat genotypes validated their utility for marker-assisted selection, which is particularly efficient for removing toxin sensitivity alleles from elite germplasm and varieties.