Date of Graduation

5-2019

Document Type

Thesis

Degree Name

Master of Science in Plant Pathology (MS)

Degree Level

Graduate

Department

Plant Pathology

Advisor/Mentor

Clemencia Rojas

Committee Member

Ken Korth

Second Committee Member

Vibha Srivastava

Third Committee Member

Ioannis Tzanetakis

Keywords

Bacteriology, Biological Control, Burkholderia, Microbiology, Plant Pathology, Rice

Abstract

Burkholderia glumae is the causal agent of the emerging disease, Bacterial Panicle Blight of rice, a serious disease that can significantly decrease yield and poses a threat to rice production worldwide. This thesis is concerned with searching for a biological control agent to control this disease. Plant associated microbes are a good source of beneficial bacteria which can be exploited for use as a biological control agent. It is possible that the microbiomes of cultivars which are known to be more resistant to plant pathogens may contain more microbes which inhibit those pathogens and therefore could be used as biological control agents in agriculture. This thesis can be divided into two parts, part one which is concerned with identifying inhibitory bacteria from the moderately resistant rice cultivar Jupiter and from the Rojas Lab collection, and part two which is concerned with identifying the mode of control these inhibitory bacteria use against B. glumae. The hypotheses for part one are that there are different rice associated bacteria present on the susceptible cultivar Bengal and the moderately resistant cultivar Jupiter, and that the rice associated bacteria unique to Jupiter add to its resistance to the pathogen. The hypotheses for part two are that the inhibitory bacteria identified in part one use either competition or antibiosis to inhibit B. glumae. These hypotheses were tested using a variety of experiments including microbiome isolation, inhibition assays, plant inoculations and inhibitory compound isolation experiments to find bacteria which could control B. glumae, and to discover their mechanisms of inhibition. Though the bacteria isolated from Bengal and Jupiter were comprised of different bacterial strains, the Jupiter-specific bacteria were not particularly good at inhibiting the growth of the pathogen. Two strains of bacteria from the Rojas lab collection, Burkholderia cenocepacia and Pseudomonas fluorsecens, however were found to be very successful at inhibiting the growth of B. glumae and successfully reduced symptoms of infection in vivo. Furthermore it was found that these two bacterial strains do in fact control B. glumae through the production of inhibitory compounds.

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