Degree
Doctor of Philosophy (PhD)
Department
Plant Pathology and Crop Physiology
Document Type
Dissertation
Abstract
Global rice production continues to face significant challenges from destructive diseases such as bacterial panicle blight (BPB) and sheath blight (ShB) disease of rice caused by Burkholderia glumae and Rhizoctonia solani, respectively. This study presents a comprehensive investigation into the virulence regulation of B. glumae through in-depth characterization of the regulatory factor, QsmR. Molecular and microscopy revealed that QsmR plays a crucial role not only in the expression of virulence factors but also in regulation of the pathogen's overall physiological state. Furthermore, candidate molecules with high affinity to QsmR were predicted and identified, which modulated the toxoflavin production. These findings offer promising insights into the potential of targeting QsmR for antivirulence-based disease management strategies in rice. In response to rising global temperatures and increasingly unpredictable environmental conditions that accelerate pathogen evolution, this study also identified emerging bacterial pathogens affecting rice in Louisiana and the United States. Specifically, Pantoea ananatis and Xanthomonas sacchari were confirmed as causal agents of bacterial leaf blight and panicle blight. Their emergence underscores the need for ongoing pathogen surveillance and rapid characterization to mitigate the risks posed by newly evolving threats in rice growing areas especially in the USA. Despite the continued reliance on conventional chemical control and host genetic resistance, these strategies alone remain insufficient due to environmental concerns and the limited availability of resistant rice cultivars. Thus, this research evaluated a range of seed-priming agents including the biological control agent A257, its mutant derivative A257ΔqsmR, and other materials such as BTH (1 mM) and chitosan. These treatments, especially the A257, were validated as effective in suppressing BPB and ShB under both field and greenhouse conditions across three consecutive years (2022–2024), offering sustainable and practical alternatives for disease control. Finally, transcriptomic analysis elucidated the molecular mechanisms underlying the disease-suppressive effects of A257. Seed priming with A257 induced a primed state in rice, resulting in transcriptional reprogramming and activation of defense-related pathways associated with resistance to BPB. These findings demonstrate the capacity of A257 to elicit durable and broad-spectrum resistance, providing new insights into the defense mechanisms operative in rice panicles during pathogen attack.
Date
7-15-2025
Recommended Citation
Bruno, Jobelle S., "INTEGRATED APPROACHES TO UNDERSTANDING AND MANAGING RICE DISEASES: PATHOGEN CHARACTERIZATION, HOST RESISTANCE, AND SUSTAINABLE CONTROL STRATEGIES" (2025). LSU Doctoral Dissertations. 6866.
https://repository.lsu.edu/gradschool_dissertations/6866
Committee Chair
Ham, Jong
DOI
10.31390/gradschool_dissertations.6866