Wheat breeders must effectively maintain and manage existing genetic diversity in
order to continue the development of superior genotypes. It is therefore fundamental
that the genetic relationships and diversity within the germplasm pools be thoroughly
characterized and understood. Recently, DNA-based markers have provided powerful
tools for genetic diversity analysis. This study investigates the usefulness of nuclear
and chloroplast simple sequence repeat (SSR) markers in characterizing Pacific
Northwest wheat (Triticum aestivum) breeding germplasm, and explores the patterns
of genetic relatedness revealed by these markers. The 15 chloroplast SSRs were
effective in differentiating between B-type, D-type, and barley (Hordeum vulgare)
cytoplasms. Genetic distance estimates were determined for each pair of lines studied
and analyzed using UPGMA clustering. The markers revealed five plastomic types
within the B-type cytoplasm studied. Several lines of wheat in this germplasm,
including important PNW cultivars like Madsen, were found to contain D-type
cytoplasm rather than the B cytoplasm of wheat. Nuclear SSR assays using 24 markers
revealed three major clusters of germplasms: PNW soft white winter wheat, Western
European-derived lines, and Great Plains accessions, as well as two clusters of more
distantly related lines and genetic stocks. The primary defining characteristic of these
clusters was regional adaptation. Subgroups of these major groups often clustered
together on the basis of pedigree and market class. When nuclear and chloroplast SSR
data was combined in analysis, the primary defining characteristic of the dendrogram
became the type of cytoplasm rather than regional adaptation, with secondary
divisions based on pedigree relationships. Cultivars released prior to 1950 were found
to have a minimum of 20% of alleles in common for nuclear and chloroplast data
combined, despite being unrelated via pedigree information. Heterogeneity was 2.3%
for all marker/variety combinations. Overall, these sets of markers were found to be
effective in characterizing the genetic relatedness of PNW wheat breeding germplasm. / Graduation date: 2003
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/31500 |
| Date | 18 December 2002 |
| Creators | Edwards, Melanie Love |
| Contributors | Riera-Lizarazu, Oscar, Peterson, C. James |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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