Location: Cereal Crops Improvement Research
Project Number: 3060-21000-046-027-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: May 1, 2024
End Date: Apr 30, 2027
Objective:
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The amendment objectives are to: 1) Validate a high-throughput marker assay for the Tsc1 gene and evaluate allelic variation and diversity in hard red spring wheat germplasm, 2) Validate Tsc1 gene function by complementation in hard red spring wheat.
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Determine allelic diversity and identify causal polymorphisms in the tan spot susceptibility gene Tsc1, 2) Develop a single nucleotide polymorphism-based marker for Tsc1 suitable for high throughput genotyping and marker-assisted selection.
The objectives of this cooperative research are to: 1) Screen diverse collections of wheat and wheat relatives for reaction to bacterial leaf streak disease to identify sources of genetic resistance; 2) Analyze segregating biparental wheat populations to determine the genetic control of bacterial leaf streak resistance; 3) Identify genetic loci associated with bacterial leaf streak resistance using DNA markers, genetic linkage mapping, and quantitative trait loci analysis.
Approach:
For objective 1, approximately 500 hard red spring wheat lines will be evaluated with the Tsc1 marker assay to determine which lines possess an allele of the gene. Among lines that possess an allele, the DNA sequence of the gene will be determined to evaluate the number of alleles and degree of diversity among the lines. Representative lines from each allelic classification, including the absent allele, will be inoculated with Pyrenophora tritici-repentis to evaluate tan spot reactions and determine associations between different allelic haplotypes and reactions to tan spot disease. This will allow the determination of causal polymorphisms within the gene and help to devise more effective assays. For objective 2, the Tsc1 genomic sequence will be transformed into the hard red spring wheat line Cadenza, which is known to lack Tsc1 and is amenable to transformation, using Agrobacterium methods that have been optimized for wheat. This experiment will validate that Tsc1 alone is sufficient to confer tan spot susceptibility.
For objective 1, collections of wheat lines will be screened for reaction to bacterial leaf streak (BLS) disease in greenhouse and field environments. The collections will include parental lines of various mapping populations, all tetraploid and hexaploid lines that have full genome sequences available, a collection of synthetic hexaploid lines, and a collection of emmer wheat lines. The lines will first be evaluated under greenhouse conditions in multiple replications. BLS resistant lines will then be evaluated under field conditions to determine if BLS resistance is expressed under both field and greenhouse environments. For objective 2, we have identified through preliminary experiments that two biparental populations of recombinant inbred lines (RILs) are segregating for reaction to BLS. One population, derived from a cross between the hard red spring wheat variety Boost and the hard red spring wheat breeding line ND830, consists of 190 RILs. The second population consists of 114 RILs derived from a cross between the synthetic hexpaploid line M6 and the hard red spring wheat Opata85. Both populations will be screened under greenhouse and field conditions to determine the inheritance of BLS resistance. For objective 3, both RIL populations will be genotyped with molecular markers to develop genetic linkage maps. BLS reaction types will be regressed on the genotypic data using QTL analysis software to identify genetic loci and linked markers associated with BLS resistance. The markers identified will be useful for tracking and introgression of the BLS resistance QTL into adapted wheat lines.