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Seed dormancy in barley (Hordeum vulgare L.) : comparative genomics, quantitative trait loci analysis and molecular geneticsBonnardeaux, Yumiko Graciela January 2008 (has links)
[Truncated abstract] Under prolonged wet and damp conditions, barley grain with low dormancy can germinate precociously, a condition known as preharvest sprouting that causes a number of detrimental effects in grain quality. In particular, preharvest sprouting renders the grain unsuitable for malting. The aim of this study was to take a genomics approach to identify and characterise candidate genes that could be linked to the control of seed dormancy in barley. This thesis developed a bioinformatic strategy that exploited the availability of gene sequences with functional evidence in the model species of Arabidopsis and rice. The bioinformatic strategy integrated phenotypic data (QTL data) and comparative genomics for a targeted approach in identifying candidate genes with a high probability of having a conserved function in cereals. This bioinformatic study identified two candidate genes ERA1 and ABI2 with strong evidence for a role in seed dormancy based on their function in Arabidopsis in abscisic acid (ABA) signal transduction and their co-location to seed dormancy QTLs in Arabidopsis, rice and wheat. In order to establish whether the candidate genes mapped to seed dormancy QTLs in barley, QTL analyses were performed on a double haploid population, not previously studied, developed from a cross between Stirling, a major Australian malting cultivar, and Harrington, a major Canadian malting cultivar. This cross was specifically chosen for this study, as elucidation of chromosomal regions associated with seed dormancy in the background of a malting cultivar would make a significant contribution for the malting industry. '...' Identification of a seed dormancy QTL on the long arm of 3H, in a region syntenic to the wheat chromosome locations of ESTS aligning to the ERA1 and ABI2 genes, laid the foundation for physical and genetic mapping of the candidate genes to investigate whether the genes co-located to the QTL on 3H. Physical mapping of the genes in wheat barley addition lines confirmed their positions on the long arm of 3H. Genetic mapping of the ERA1 gene was performed using a CAPS marker developed in this thesis. The genetic mapping of the ERA1 gene did not place the gene within either of the minor QTLs on 3HL, although segregation distortion may have influenced the map position of this gene. Further investigation is required to resolve the positioning of the ERA1 and ABI2 genes in relation to the 3H seed dormancy QTL. The main outcomes of this study have been 1) identification of candidate genes for further study; 2) identification of QTLs on the long arm of 3H that were previously unknown; 3) demonstration of the potential differences in dormancy that can be achieved through the use of specific gene combinations, highlighting the importance of minor genes and the epistatic interactions that occur between them and; 4) the development of a CAPS marker for the ERA1 gene, which can be used to track the gene in barley breeding programs to observe its association with important agronomic traits. This thesis also pioneered the implementation of several new technologies including multiplex-ready PCR (Hayden et al. 2008) for fluorescencebased SSR genotyping and QTLNetwork (Yang et al. 2008) for statistical analysis of QTLs. Seed dormancy is a complex trait and is likely to involve the interplay of a number of genes that have a role in other developmental and regulatory processes.
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Let the Seeds Fall Where They May: Investigating the Effect of Landscape Features on Fine-Scale Seed DispersalGrasty, Monica R. 19 May 2017 (has links)
Seed dispersal is a crucial ecological and evolutionary process that allows plants to colonize sites and expand their ranges, while also reducing inbreeding depression and facilitating the spread of adaptive genetic variation. However, our fundamental understanding of seed dispersal is limited due to the difficulty of directly observing dispersal events. In recent years, genetic marker methods have furthered our understanding of colonization and range expansion due to seed dispersal. Most investigations focus on regional scales of dispersal, due to low levels of variation in the chloroplast genome (cpDNA), which can serve as an indirect measure of seed dispersal. Here, I employ a whole-genome assay of cpDNA variation in Plagiobothrys nothofulvus to resolve variation due to patterns of seed dispersal within a 400x400 meter section of the Whetstone Savanna Preserve in Central Point, OR, USA. Whetstone is characterized by a mosaic of habitat types, including vernal pools, hummocks of dry prairie, and large Ceanothus cuneatus bushes, as well as a network of vole runways. Plagiobothrys nothofulvus grows in dense patches on hummocks within this prairie.
I found evidence of limited seed dispersal in P. nothofulvus, indicated by strong genetic structure over distances of less than 100 meters. There was little evidence that geographic distance predicts genetic distance; environmental features have a stronger influence on dispersal. Habitat preference was the strongest predictor of genetic variation in P. nothofulvus, indicating that it may be a habitat specialist in this prairie. Flower density also accounted for a significant portion of dispersal, which may be a consequence of the annual life history of P. nothofulvus resulting in seasonal turnover and lack of competition with adult plants. Least-cost-path analysis indicated that seeds are secondarily dispersed by small mammals along vole runways. Overall, I found significant evidence that landscape features influence dispersal, even at a very fine spatial scale.
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