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Theses and Dissertations

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Browsing Theses and Dissertations by Subject "abiotic stress"

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    Buffering the effects of a changing climate: Salsola tragus as a potential source of stress tolerance genes
    (Colorado State University. Libraries, 2024) Lemas, John M., author; Gaines, Todd, advisor; Brown, Cynthia, committee member; Henriksen, James, committee member
    The tumbleweed Salsola tragus is an allotetraploid C4 weedy member of the Salsola polyploid complex. Commonly referred to as Russian thistle, it develops a thorny habit during inflorescence, and commonly separates at an abscission layer near the soil to form a tumbleweed. This species is economically important to all land use types and is especially impactful in the Northwestern United States where it affects spring cereal production. The International Weeds Genomics Consortium recently completed a fully annotated reference genome assembly for each of the sub genomes in the somatic cells of this allotetraploid. Polyploids, in general, are overrepresented in the most troublesome weeds globally, and Salsola tragus is no exception. Recurrent formation of polyploids, increased activity of transposable elements, and increased mutation rates that follow genome duplication may lead to the de novo formation and selection of novel highly adapted alleles over time. We utilized the reference genome assembly for this species to align a stress-response transcriptome to investigate how this species responded to two selected abiotic stressors. Many expected response pathways are represented, including response to stress phytohormones, sodium-proton antiporters, calcium exchangers, and cold-responsive binding factors. In addition, several uncharacterized proteins were differentially overexpressed in the shoot and root tissues of this species. Identified genes from this species may present novel alleles for osmotic and temperature stress tolerance. Uncharacterized genes may represent novel stress response genes and can be used to improve the provided reference annotation for this species. These genes of interest may provide the scientific community with additional genomic resources to bolster crop production in this era of climate change.
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    ItemOpen Access
    Characterization of Sorghum bicolor genotypes under varying water regimes
    (Colorado State University. Libraries, 2019) Person, Taylor, author; Jahn, Courtney E., advisor; Byrne, Pat, committee member; Gaines, Todd, committee member
    Agriculture is the largest consumer of fresh water, accounting for 70% of use globally. The availability of water is expected to decrease in future climate models. It is imperative to develop crop varieties with improved performance under targeted limited water environments. One approach to address this aim is capitalizing on inherent variability for drought tolerance traits in crops. Depending on the nature of water stress and other environmental factors, specific root morphology, shoot morphology, and the harvest index are selectable traits that can distinguish performance of different genotypes in crops. These aforementioned parameters discriminate relative water-stressed performance in many studied crop species. Among these is sorghum (Sorghum bicolor), a grain crop adapted to many different environments, particularly where limited rainfall is an agricultural constraint. The specific objectives of the following thesis were to 1) characterize the morphology of a sorghum recombinant inbred line (RIL) population (n = 430) of Sorghum bicolor for response to varying moisture regimes and 2) evaluate 10 selected genotypes for below-ground morphology in the greenhouse and field for response to varying moisture regimes. This population expresses a wide range of phenotypes in response to varying moisture regimes in panicle weight, shoot weight, harvest index, plant height, stem diameter, tillering and days to flowering. Ten selected RILs, including the two population parents, BTx623 and IS3620C, represent the population distribution and respond uniquely to different moisture environments. When subjected to drought stress and subsequent recovery when re-watered in the greenhouse, root system response varied at both time points. Root system and stem size are indicators of this response and vascular tissue variation may play a role in these varied responses. In the field, the root system of these ten RILs, as quantified by crown root angle, had a tendency to grow more vertically than horizontally under dryland conditions while high moisture environments showed no association with root system orientation. Taken together, this study provides foundational knowledge on above and below-ground responses of RIL population BTx623 X IS3620C to varying moisture environments.