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Browsing Theses and Dissertations by Author "Afshar, Zaki, author"

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    Characterization and molecular mapping of stripe rust resistance in a Denali/Hatcher winter wheat doubled haploid population
    (Colorado State University. Libraries, 2019) Afshar, Zaki, author; Haley, Scott D., advisor; Byrne, Patrick F., committee member; Broders, Kirk D., committee member
    The majority of global wheat (Triticum aestivum L.) production is subject to infection by the stripe rust pathogen (Puccinia striiformis Westend. f. sp. tritici Erikss.). The evolution of new stripe rust races appears to be occurring more rapidly than in the past, causing significant economic loss through yield reduction and increased use of fungicides. A combination of all-stage resistance and high-temperature adult plant (HTAP) resistance in new cultivars may provide complete resistance or serve to reduce disease incidence, thus providing a greater overall level of protection. In addition, knowledge of the form of resistance present in a particular cultivar may help to minimize fungicide use with cultivars that show early-season infections prior to initiation of HTAP resistance. A doubled haploid population (n=210) developed from a cross between winter wheat cultivars 'Hatcher' (PI 638512) and 'Denali' (PI 664256) was developed and characterized for response to stripe rust during 2018 and 2019 at Fort Collins, CO and Rossville, KS. A high density genetic linkage map consisting of 4,441 single nucleotide polymorphism markers derived via genotyping by sequencing was used to identify markers for stripe rust resistance in this population. Four quantitative trait loci (QTL) for infection type (IT) and disease severity (DS) (QYr.csu-1B, QYr.csu-3A, QYr.csu-3B, and QYr.csu-7B) were found to contribute to stripe rust resistance. Among the resistance QTL, QYr.csu-1B and QYr.csu-3A iii were the most consistent for single environments and combined across environments and accounted for 9.6-16.3% and 10.1-14.4% of phenotypic variation, respectively. QYr.csu-3B showed a stronger effect than QYr.csu-7B and was detected in more than one environment. Flanking markers for all the identified QTL, especially for QYr.csu-1B and QYr.csu-3A, will be useful to develop wheat cultivars with more effective and durable resistance to stripe rust.