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Erwinia Tracheiphila Pathosystem

其他書名	Vector-pathogen Interactions
出版	Pennsylvania State University, 2015
URL	http://books.google.com.hk/books?id=s5n8jwEACAAJ&hl=&source=gbs_api

註釋Cucurbitaceae is a diverse plant family that includes cultivated species in the genera Cucumis, Cucurbita, Citrullus, Lagenaria and Luffa. Within Cucurbitaceae, there is a tight association between the bacterial pathogen Erwinia tracheiphila and the required diabroticite beetle vector, Acalymma vittatum (the striped cucumber beetle). This thesis expands on prior knowledge of this tri-trophic system by providing insights into vector competence of diabroticite beetles that exist outside of the geographic range of Erwinia tracheiphila. Identification of a novel biological control agent, Pseudomonas fluorescens, targeting microbial gut interactions within the vector beetle to control Erwinia tracheiphila. Two diabroticite beetle species were selected from regions of the United States that currently do not have the causal agent of bacterial wilt of cucurbits, Erwinia tracheiphila: the western striped cucumber beetle (Acalymma trivittatum) from California and the banded cucumber beetle (Diabrotica balteata) from Florida. Based on ecological and phylogenetic similarities to Acalymma vittatum, Acalymma trivittatum could serve as a competent vector that would provide Erwinia tracheiphila a route into the western United States. Likewise, if Diabrotica balteata is also a competent vector, it would provide avenues for Erwinia tracheiphila into the southern United States. The three diabroticite species were subjected to feeding bioassays to determine transmission capabilities. Analysis of frass through polymerase chain reaction and plate culturing demonstrated presence and viability of Erwinia tracheiphila after passage through the beetles. While the results indicated that Acalymma trivittatum was able to transmit Erwinia tracheiphila, there was insufficient statistical power to compare its transmission efficiency relative to Acalymma vittatum. Diabrotica balteata was also able to transmit Erwinia tracheiphila, but due to low beetle survival rates during the course of the experiment, the sample size of the surviving beetles was too small to make statistically relevant conclusions about its vector status. Current control methods for Erwinia tracheiphila target the vector through pesticide application, but with possible geographic expansion by other vector species, an alternative strategy may be required. The bacterial wilt of cucurbit disease cycle is maintained by Erwinia tracheiphila gut colonization of the vector beetle, effectively overwintering until the next growing season. By disrupting Erwinia tracheiphila gut colonization, the number of infected vectors could be greatly reduced. This has proven to be an effective biological control approach for Erwinia amylovora (the fire blight of tree fruit pathogen) using a commercially available isolate of Pseudomonas fluorescens. In this study, I challenged isolates of Erwinia tracheiphila with an isolate of Pseudomonas fluorescens (Pf55) through in vitro plating assays and in vivo co-localization gut assays. In vitro assays confirmed that Pseudomonas fluorescens successfully inhibited Erwinia tracheiphila growth. Because Pseudomonas fluorescens was detected in the mid and hindguts of Acalymma vittatum (coinciding with the sites of Erwinia tracheiphila gut colonization), the in vitro assay results supported the hypothesis that Pseudomonas fluorescens could potentially inhibit Erwinia tracheiphila in vivo. I have shown that other diabroticite beetles can successfully transmit Erwinia tracheiphila and demonstrated the potential use of Pseudomonas fluorescens as a new method of biological control for Erwinia tracheiphila.