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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Cereal Crops Improvement Research » Research » Research Project #447467

Research Project: Genetic Analysis and Characterization of Genes Governing Disease Susceptibility in Wheat

Location: Cereal Crops Improvement Research

Project Number: 3060-21000-046-038-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Feb 1, 2025
End Date: Jan 31, 2026

Objective:
The objectives of this cooperative research are to: Identify candidate genes for the wheat Snn2 gene governing susceptibility to the disease septoria nodorum blotch; 2) Validate Snn2 candidate genes using mutagenesis and genetic complementation.

Approach:
For objective 1, a biparental recombinant mapping population segregating for susceptibility to SNB conferred by the Snn2 gene will be evaluated to determine the precise position of Snn2 on chromosome 2D. One parent, the hexaploid wheat line BR34, lacks the Snn2 gene, and the second parent, line BG301, harbors a functional allele of Snn2. At least 5,000 recombinant gametes will be evaluated to develop a high-resolution map of the Snn2 locus and identify flanking DNA markers. The physical size and make-up of the DNA segment between the flanking markers will be subjected to bioinformatic analyses to identify models of candidate genes in the wheat lines with sequenced genomes. Sequence comparisons of gene models among SNB-resistant and susceptible lines will be conducted to identify the most plausible candidate genes. For objective 2, the candidate genes identified in objective 1 will be validated using mutagenesis and genetic complementation by transformation. For mutagenesis, approximately 1,000 seeds of the Snn2-containing line BG301 will be exposed to 0.35% v/v ethyl methanesulfonate (EMS), grown under standard greenhouse conditions, and harvested to obtain the M2 generation. M2 families will be screened for reaction to the pathogen-produced necrotrophic effector SnTox267, which is recognized by Snn2 leading to necrosis. Insensitive plants lacking the ability to exhibit necrosis will be considered Snn2-disrupted mutants and subjected to comparative sequence analysis of the candidate genes identified in objective 1. The second line of validation will include the transformation of the candidate genes in the wheat line BR34, which does not contain a native copy of Snn2. Appropriate GRF-GIF-containing vectors will be used to clone a genomic segment of the candidate genes containing the native promotor and transformed into BR34 using the Agrobacterium-mediated gene transfer method. Putative transformed plants will be evaluated for reaction to SnTox267 to determine if they harbor the functional Snn2 gene.