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dc.contributor.authorFrazier, Taylor Priceen_US
dc.date.accessioned2017-07-08T06:00:31Z
dc.date.available2017-07-08T06:00:31Z
dc.date.issued2016-01-14en_US
dc.identifier.othervt_gsexam:6864en_US
dc.identifier.urihttp://hdl.handle.net/10919/78320
dc.description.abstractSwitchgrass is a C4 perennial grass that is currently being developed for use as a second generation lignocellulosic biofuel crop. For switchgrass to be fully utilized as a bioenergy crop, large-scale plantings of elite switchgrass germplasm, possibly in monoculture, are likely to occur. This practice may increase the selection pressure on plant pathogens, such as switchgrass rust, which could result in devastating disease epidemics. The identification and deployment of quantitative trait loci (QTLs) and major plant disease resistance genes (R) in switchgrass breeding programs could offer broad spectrum and durable disease resistance in commercial switchgrass cultivars. 'Alamo', a lowland cultivar, is generally resistant to switchgrass rust whereas 'Dacotah', an upland cultivar, is highly susceptible. I hypothesized that major R genes and/or QTLs were contributing to the differences in disease phenotypes of these two cultivars. In this dissertation, bioinformatics and molecular biology approaches were employed to dissect the genetic mechanisms underlying switchgrass rust disease resistance. Novel pseudo-F2 mapping populations were created from a cross derived from 'Alamo' and 'Dacotah'. RNA-sequencing of the pseudo-F2 progenies of 'Alamo' x 'Dacotah' was used to construct a genetic linkage map and to identify potential QTLs correlating with disease resistance. In addition, a homology-based computational method was used to identify 1,011 potential NB-LRR R genes in the switchgrass genome (v 1.1). These potential R genes were characterized for polymorphism and expression differences between 'Alamo' and 'Dacotah'. Moreover, I found that some NB-LRR genes are developmentally regulated in switchgrass. One of the major objectives of switchgrass breeding programs is to develop cultivars with improved feedstock quality; however, changes in the components of the plant cell wall may affect disease resistance. I hypothesized that genetically modified switchgrass plants with altered cell wall components will respond differently than the wild-type to switchgrass rust. Transgenic switchgrass plants overexpressing AtSHN3, a transcription factor with known functions in epicuticular wax accumulation and cell wall deposition, were created. I found that AtSHN3-overexpressing transgenic switchgrass lines were more susceptible than wild-type plants in their response to switchgrass rust. Overall, the results of this dissertation provide a platform for elucidating the molecular mechanisms underlying resistance of switchgrass to switchgrass rust. These findings will help breeders create switchgrass cultivars with improved disease resistance, and will ultimately allow switchgrass to be used for sustainable biomass production.en_US
dc.format.mediumETDen_US
dc.publisherVirginia Techen_US
dc.rightsThis Item is protected by copyright and/or related rights. Some uses of this Item may be deemed fair and permitted by law even without permission from the rights holder(s), or the rights holder(s) may have licensed the work for use under certain conditions. For other uses you need to obtain permission from the rights holder(s).en_US
dc.subjectSwitchgrassen_US
dc.subjectPanicum virgatumen_US
dc.subjectBiofuelen_US
dc.subjectSwitchgrass Rusten_US
dc.subjectDisease Resistanceen_US
dc.subjectNB-LRRen_US
dc.subjectGene Expressionen_US
dc.subjectSNPsen_US
dc.subjectRNA-sequencingen_US
dc.subjectMolecular Markeren_US
dc.subjectSHN3en_US
dc.subjectLigninen_US
dc.subjectCelluloseen_US
dc.titleA Comprehensive Analysis of Rust Disease Resistance in the Bioenergy Plant Switchgrass (Panicum virgatum L.)en_US
dc.typeDissertationen_US
dc.contributor.departmentHorticultureen_US
dc.description.degreePh. D.en_US
thesis.degree.namePh. D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineHorticultureen_US
dc.contributor.committeechairZhao, Bingyuen_US
dc.contributor.committeememberSaghai-Maroof, Mohammad A.en_US
dc.contributor.committeememberVeilleux, Richard E.en_US
dc.contributor.committeememberSchmale, David Garner Burtonen_US


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