Estimated at approximately $43 billion annually, the cultivated soybean Glycine max (L.) Merr., is the second most valuable crop in the United States. Soybeans account for 57% of the world oil-seed production and are utilized as a protein source in products such as animal feed. The value of a soybean crop, measured in seed quality and quantity, is negatively affected by biotic and abiotic stresses. This research is focused on resistance to biotic disease stress in soybean. In particular, we are working on the Phytophthora soja (P. sojae) and Soybean Mosaic Virus (SMV) systems. For each of these diseases, we are working to develop superior soybean germplasm that is resistant to the devastating economic impacts of pathogens. The majority of this research is focused on screening for novel sources of P. sojae resistance with core effectors to identify resistance genes (R-genes) that will be durable under field conditions. Four segregating populations and two recombinant inbred line (RIL) populations have been screened with core effectors. Effector-based screening methods were combined with pathogen-based phenotyping in the form of a mycelium-based trifoliate screening assay. One RIL population has been screened with virulent P. sojae mycelium. Disease phenotyping has generated a preliminary genetic map for resistance in soybean accession PI408132. The identification of novel R-genes will allow for stacking of resistance loci into elite G. max cultivars. The second project covered in this dissertation describes the validation of the SMV resistance gene Rsv3. Utilizing a combination of transient expression and homology modeling; we provide evidence that Glyma14g38533 encodes Rsv3. / Ph. D. / Estimated at approximately $43 billion annually, the cultivated soybean <i>Glycine max</i> (L.) Merr., is the second most valuable crop in the United States. Soybeans account for 57% of the world oil-seed production and are utilized as a protein source in products such as animal feed. The value of a soybean crop, measured in seed quality and quantity, is negatively affected by pathogens and other stressors. This research is focused on resistance to pathogen disease stress in soybean. In particular, we are working on the <i>Phytophthora soja</i> (<i>P. sojae</i>) and <i>Soybean Mosaic Virus</i> (SMV) systems. For each of these diseases, we are working to develop superior soybean lines that are resistant to the devastating economic impacts of these pathogens. The majority of this research is focused on screening for new sources of <i>P. sojae</i> resistance, using certain pathogen virulence proteins called core effectors, to identify resistance genes (<i>R</i>-genes) that will be durable under field conditions. Four segregating populations and two recombinant inbred line (RIL) populations have been screened with core effectors. Effector-based screening methods were combined with pathogen-based phenotyping in the form of an assay that involved the use of <i>P. sojae</i> to infect detached soybean leaves. One RIL population has been screened with virulent <i>P. sojae</i>. Disease screening has generated a preliminary genetic map for resistance in soybean accession PI408132. The identification of novel <i>R</i>-genes will allow for stacking of resistance genes into elite <i>G. max</i> cultivars that can be grown by farmers. The second project covered in this dissertation describes the validation of the SMV resistance gene <i>Rsv3</i>. Utilizing a combination of a molecular assay and protein prediction software; we provide evidence that the soybean gene Glyma14g38533 encodes <i>Rsv3</i>.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/77857 |
| Date | 24 May 2017 |
| Creators | Davis, Colin Lee |
| Contributors | Crop and Soil Environmental Sciences, Saghai-Maroof, Mohammad A., McDowell, John M., Zhao, Bingyu, Li, Song |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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