Identifier

etd-11072014-104549

Degree

Master of Science (MS)

Department

Plant Pathology and Crop Physiology

Document Type

Thesis

Abstract

Bacterial panicle blight, caused by Burkholderia glumae, is a major bacterial disease of rice in Louisiana. This bacterium contains several virulence factors required for disease development such as toxoflavin, lipase and flagella. In a genome-wide search for regulatory factors related to the virulence of B. glumae, tepR was identified as a negative regulator for toxoflavin production and found to encode a sigma 54-dependent response regulator. TepR is homologous to LuxO, a quorum-sensing signaling component of Vibrio spp. A markerless tepR deletion mutant of B. glumae 336gr-1, LSUPB401, produced more toxoflavin and showed higher lipase and protease activities compared to the wild type, 336gr-1. The phenotype of mutant LSUPB401 was complemented by a functional tepR clone, confirming that tepR is a novel negative regulator for toxoflavin production in B. glumae. In addition, LSUPB401 was more aggressive than the wild type in causing symptoms on rice panicles and onion bulb scales. However, LSUPB401 lost flagellar motility and hypersensitive reaction, suggesting positive roles of tepR in those phenotypes. These findings suggest that TepR promotes the cellular functions for initial host colonization. Ten bacterial strains showing antagonistic activities against B. glumae in an in vitro assay were detected from several thousand bacterial isolates obtained from the root region of rice grown at the Rice Research Station, Crowley, Louisiana. Those bacteria were identified as Bacillus, Paenibacillus and Pseudomonas based on the 16S rDNA sequences. Some isolates suppressed bacterial panicle blight significantly in both greenhouse and field conditions, therefore, are potential candidates for further biocontrol studies.

Date

2014

Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Committee Chair

Ham, Jong Hyun

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