Plant Science & Landscape Architecture Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/2797

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    IDENTIFYING HIGHLY CONSERVED PATHOGENICITY GENES IN CHESTNUT BLIGHT AND POWDERY MILDEW FUNGI AS TARGETS FOR NOVEL FORMS OF HOST RESISTANCE
    (2019) Levine, Bruce Jonathan; Xiao, Shunyuan; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A bioinformatic search of the genomes of chestnut blight fungus, Cryphonectria parasitica (Cp), and the Arabidopsis powdery mildew fungus, Golovinomyces cichoracearum (Gc), yielded six suspected pathogenicity genes with homologues in both species. Deletion of these genes by homologous gene replacement was attempted in Cp, with one success, TG4. The TG4-knockout strain showed changes in phenotype and reduced fungal virulence against chestnut. TG4 appears to be a promising target for host-induced gene silencing (HIGS) in transgenic American chestnut. The use of homologues from genetically tractable species like Cp can help overcome the obstacles to performing reverse genetics on intractable, biotrophic fungi such as Gc. Experiments underway involving the silencing and ectopic overexpression of the Gc homologues of the target genes provide a rapid method to study Cp genes, including to screen additional candidate genes as future targets for HIGS.
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    INTEGRATED PEST MANAGEMENT OF FUSARIUM HEAD BLIGHT IN SOFT RED WINTER WHEAT
    (2011) Reed, Elizabeth; Grybauskas, Arvydas; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Fusarium head blight (FHB), caused by Fusarium graminearum, is a destructive disease of the soft red winter wheat grown in the Mid-Atlantic region. Management of FHB focuses primarily on foliar fungicides or cultivar resistance. The purpose of this research was to examine how type II resistance (resistance to spread of the pathogen) is affected by multiple infections along the spike. The combination of type II resistance and fungicide as a way to manage FHB was evaluated in both the greenhouse and field settings. Finally, the role of increased foliage density in an integrated pest management program that included fungicide and cultivar resistance was also evaluated. Multiple infections occurring along a single wheat spike can overwhelm the type II resistance present in some cultivars. The combination of type II resistance and fungicide was the best management practice for FHB than either alone. Foliage density did not improve FHB disease ratings.