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Dissertation
Genetic diversity, population structure, and signatures of selection in wheat populations
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000002474
Handle:
https://hdl.handle.net/2376/121090
Abstract
There is an enduring concern about loss of crop genetic diversity. Common wheat went through major genetic bottlenecks during polyloidization, domestication, and modern plant breeding. We assessed changes in genetic diversity and population structure of the Pacific Northwest (PNW) and the U.S. wheat populations from 1850s to current day. We did not find long-term loss of single nucleotide polymorphisms (SNPs) gene diversity. In the PNW, spring varieties had peak diversity in 1970-99 but hard red spring (HRS) varieties had reduced diversity in 2000-19. For the U.S. population, comparison between pre-1961 and post-1961 varieties showed a slight increase in SNP gene diversity of spring varieties and no change in winter varieties. Genetic diversity is crucial for continued breeding gains but use of diverse landraces in breeding is difficult due to linkage drag. A wide cross between a landrace and an adapted parent is followed by multiple backcrosses to the adapted parent to restore adaptedness. This practice reduces the possibility to evaluate potentially novel and useful alleles that exist in landraces. Linkage-blocks that confer adaptation have repeatedly been selected by breeders and are likely to exhibit signatures of selection. Identification of linkage-blocks associated with adaptation could help breeders restore adaptedness without using multiple backcrosses and therefore incorporate and evaluate more novel alleles from landraces. We used three extended haplotype homozygosity (EHH) based statistics to report putative adaptation-associated linkage-blocks selected in U.S. regional and state wheat populations.
As stripe rust pathogen races evolve, novel resistance genes are needed for breeders to develop new resistant varieties. PI119350, a spring landrace from Turkey was rated highly resistant to stripe rust in Pullman and Mt. Vernon, WA. It was also resistant to stripe rust pathogen races Pstv-14 and Pstv-37, but not to Pstv-40, suggesting it could be Yr10, Yr24, Yr32, or a novel resistance gene. Quantitative trait locus analysis showed the resistance gene to be associated with the microsatellite marker psp3000, a diagnostic marker for Yr10 on chromosome 1B. Both the donor of Yr10 gene (PI178383) and PI119350 were collected from Turkey. Therefore, the QTL in PI119350 is probably Yr10 and not novel.
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Details
- Title
- Genetic diversity, population structure, and signatures of selection in wheat populations
- Creators
- Sajal Ratna Sthapit
- Contributors
- Deven R See (Advisor)Scot H Hulbert (Committee Member)Timothy D Murray (Committee Member)Kevin Murphy (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Plant Pathology, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 253
- Identifiers
- 99900606955901842
- Language
- English
- Resource Type
- Dissertation