In the eastern U. S. and other wheat growing areas of the world, powdery mildew is a major constraint to the production of wheat. Currently, the most effective and economical means of control is to use resistant cultivars. Unfortunately, the diversity of the pathogen population enables the pathogen to overcome new resistance genes, often within several seasons of commercial deployment. Surveys to determine the virulence of the population to a set of resistance genes have been performed in many areas of the world. Often, differential frequencies of virulence at varying geographic areas are extended to infer a putative population structure. Due to selective pressure, virulence frequencies are poorly suited to high-resolution analysis of population structure and results may reflect regional cultivar choices and not underlying population phylogeny. A collection of 206 single-ascospore derived powdery mildew isoaltes were utilized to determine virulence frequencies at varying locations in the eastern U. S. Primers were developed to amplify coding sequences in order to assess single nucleotide polymorphisms within this population, which allowed allowed analyses of the distribution of presumably neutral genetic variation. Dendrograms based on Nei?s standard genetic distance (Gst) indicated clustering of virulence frequencies into northern and southern subpopulations, with North Carolina as the putative boundary between groups. DNA sequence based AMOVA analysis using groups derived from Hudson?s sequence based subdivision test (Snn) support this conclusion. Tests for population richness indicate greater haplotype diversity in Virginia and Delaware; a result with several possible explanations based on the known history of North American wheat cultivation.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-01032008-214715 |
| Date | 24 January 2008 |
| Creators | Parks, Wesley Ryan |
| Contributors | J. Paul Murphy, Ignazio Carbone, Christina Cowger |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-01032008-214715/ |
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