Department of Agricultural Biology

Permanent URI for this communityhttps://hdl.handle.net/10217/100336

These digital collections include theses, dissertations, faculty publications, and datasets from the Department of Agricultural Biology. Also present is a video documentary titled Complete Harvest: The Future of Rice as Bioenergy. Due to departmental name changes, materials from the following historical departments are also included here: Bioagricultural Sciences and Pest Management; Botany; Botany and Plant Pathology; Entomology; Plant Pathology and Weed Science; Zoology; Zoology and Entomology.

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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.
Open 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.
Open Access
The impacts of high temperature on bacterial blight resistance genes in rice
(Colorado State University. Libraries, 2024) Shipp, Jennifer, author; Leach, Jan E., advisor; Argueso, Cristiana, committee member; Reddy, Anireddy, committee member
Rice is cultivated around the world and serves as a primary source of income and calories for many people. However, rice yield is threatened by the bacteria Xanthomonas oryzae pv. oryzae (Xoo), and outbreaks can be devastating to global communities. Xoo is the causal agent of bacterial blight (BB) in rice, and it proliferates in rice-growing climates. As climate change progresses, the trend of increasing BB severity may result in increased losses for growers. Disease severity, quantified through lesion lengths, increases at high temperature in rice. Previous studies indicated this pattern of increased disease phenotypes occurs even when a resistance (R) gene is present, except for one, Xa7. Our rationale for these experiments is to determine if the classification of an R gene can predict its performance against BB outbreaks. The classification of R genes in rice is a recent addition to the scope of our knowledge of plant pathology and has been the result of studies on nucleotide polymorphisms, genetic mapping, and fluorescent imaging of protein localization. Grouping the underlying mechanisms of action of individual R genes, such as the executor genes Xa7 and Xa10, allow for comparative studies to further elucidate details of their assigned classes. Not all R genes have been classified, but establishing a trend that some R genes maintain efficacy under higher temperatures would provide breeders with more tools to develop climate-friendly rice lines. This study indicates that R genes that remain effective at high temperature may be classified into the same category of executor R genes. More research is needed to determine if R gene classification predicts durability under heat stress. This study explores BB lesion lengths and Xoo colony counts at high and low temperatures. We find that at high temperature relative to low temperature, disease lesions were more severe in IR24, containing no active R gene, and in plants containing the R genes Xa21, xa5, and Xa3. Lesions were shorter in plants with Xa7 and Xa10. Additionally, under the same treatments, bacterial numbers increased to higher levels in IR24, Xa21, xa5, and Xa3. Numbers in Xa7 were reduced while numbers in Xa10 were low early in infection, but eventually increased beyond those measured at low temperature. Degree of lesion restriction did not always correspond to degree of restricted bacterial numbers, suggesting that severity of lesions may not always be a predictor of bacterial multiplication in the plant. Xa7 and Xa10 are classified as executor R genes. The mechanism of action in these genes may play a role in their durability at high temperatures. We hypothesize that the success of executor R genes may be a result of protein accumulation in the nucleus. This mechanism might be analogous to instances of temperature sensitive pathogen defense related protein accumulation, as seen in Arabidopsis. This mechanism may be induced or enhanced by the presence of reactive oxygen species (ROS) or other heat-stress related markers. More research is needed to explore the signaling between heat-stress pathways and R genes.

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Browsing Department of Agricultural Biology by Subject "abiotic stress"