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United States Department of Agriculture

Agricultural Research Service

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Location: Cereal Crops Research

2011 Annual Report

1a. Objectives (from AD-416)
The objectives of this cooperative research project are: 1) identify tan spot and Stagonospora nodorum blotch resistance genes in wheat, 2) determine the chromosomal locations of the resistance genes, and 3) identify or develop markers suitable for marker-assisted selection of the resistance genes.

1b. Approach (from AD-416)
A recombinant inbred (RI) population derived from a cross between the resistant wheat landrace Salamouni and the susceptible Canadian variety Katepwa will be developed for the identification and mapping of novel resistance genes. The RI population will be genotyped with molecular markers, and linkage maps representing all 21 wheat chromosomes will be assembled. The population of RI lines will be screened for reaction to multiple races of the tan spot fungus and isolates of S. nodorum. The phenotypic data will be regressed on the molecular marker data to identify quantitative trait loci (QTL) associated with resistance. Genomic regions harboring significant QTL will be targeted for saturation mapping to identify and/or develop user-friendly PCR-based markers tightly linked to the QTL for marker-assisted selection.

3. Progress Report
The RI population derived from the parental wheat lines Salamouni and Katepwa was completed, and seed of each of the 121 RI lines was increased. Each line of the population was evaluated for reaction to ToxB, which is a toxin produced by the fungus that causes the disease tan spot. By evaluating each line and determining if they were sensitive or insensitive to ToxB, we were able to determine the chromosomal location of the Tsc2 gene, which is the gene that governs sensitivity to ToxB. The Tsc2 gene mapped to the short arm of wheat chromosome 2B. Next, we identified molecular markers that mapped near the Tsc2 gene, and we developed new markers based on previously determined DNA sequences of genes on chromosome 2B, to saturate the region of the genetic map containing the Tsc2 gene. This allowed us to make detailed comparisons of the wheat chromosomal region containing the Tsc2 gene with syntenic regions of the rice and Brachypodium genomes, which then allowed us to develop more markers that were more tightly linked to the Tsc2 gene. We showed that one marker very tightly linked to Tsc2 will be useful as a tool for marker-assisted selection against the Tsc2 gene, which would result in higher levels of tan spot resistance. ADODR monitoring included personal visitation, email correspondence, and telephone discussions.

4. Accomplishments

Last Modified: 05/24/2017
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