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Document Type

Dissertation - University Access Only

Award Date

2013

Degree Name

Doctor of Philosophy (PhD)

Department / School

Plant Science

First Advisor

Xingyou Gu

Abstract

Pre-harvest sprouting (PHS) is a worldwide problem in wheat production. Seed dormancy provides cereal crops with resistance to PHS. This research was conducted to explore the genetic potential of Aegilops tauschii-derived synthetic hexaploid wheat (SHW) as a new source of seed dormancy genes and to identify quantitative trait loci (QTL) for seed dormancy. Four SHW-derived segregating populations were evaluated for the genetic variability of seed dormancy measured by kernel germination and spike sprouting rates. Spike sprouting rate was lower than kernel germination rate, indicating the presence of germination inhibitors in the covering tissues. Both year and line effects were significant, with the former much greater than the latter, in each of the four populations. Heritability estimates were 0.32-0.53 for kernel germination percentage or 0.32-0.56 for kernel germination index in the four populations across years. Genotypic correlation (0.646-0.794) between kernel germination and spike sprouting rates was higher than phenotypic (0.480-0.636) and environmental (0.149-0.521) correlations in 2007, 2009, and 2010, suggesting that shared genetic factors play a major role in regulating dormancy with kernels and spikes. A population of 186 doubled haploid lines was used to construct a framework linkage map covering 21 chromosomes to identify seed dormancy QTL. A total of 19 putative QTL for seed dormancy were detected on 5A, 4 B, and 4 D chromosomes. Six QTL were detected in more than one year, and 7 QTL were associated with more than one of the parameters. These QTL accounted for 3.3-28.6% of the phenotypic variance. Both parental lines contributed the dormancy-enhancing alleles to 7 and 12 QTL, respectively. Eight QTL were involved in 6 pairs of digenic epistasis, which could be grouped into three types. Five QTL were involved in genotype-by-year interactions. Both of the epistasis and G-by-E analyses demonstrated the importance of evaluating seed dormancy genes/QTL in the genetic background of local cultivars under the local environmental conditions for multiple years. In addition, two future research directions, i.e. pyramiding seed dormancy-enhancing alleles and comparative research on seed dormancy genes among wheat and model plants, were discussed based on preliminary data collected during the period of the dissertation project.

Library of Congress Subject Headings

Wheat--Seeds--Dormancy
Wheat--Preharvest sprouting
Wheat--Genome mapping
Wheat--Genetic engineering

Description

Includes bibliographical references (pages 105-128)

Format

application/pdf

Number of Pages

158

Publisher

South Dakota State University

Rights

In Copyright - Educational Use Permitted
http://rightsstatements.org/vocab/InC-EDU/1.0/

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