Thesis Title

Biological Control of Grapevine Crown Gall and Differential Screening of Suppression Subtractive Libraries to Identify Powdery Mildew-Induced Grape Genes

Author

Le Chang

Date of Graduation

Summer 2006

Degree

Master of Science in Plant Science (Agriculture)

Department

College of Agriculture

Committee Chair

Laszlo Kovacs

Keywords

trifolitoxin, biological control, crown gall, grape, powdery mildew, SSH, defense-related gene

Subject Categories

Plant Sciences

Abstract

Trifolitoxin (TFX), a peptide antibiotic, is a promising candidate biopesticide which has in vitro control activity against the crown gall pathogen Agrobacterium vitis. I examined the applicability of TFX-producing bacteria to prevent grapevine root infection by A. vitis. I tested the interaction between four TFX-producing bacterial strains and three pathogenic A. vitis strains by applying TFX-producing bacteria to the roots of grapevines and by introducing the A. vitis strains to the soil in which the vines were grown. Following a growing season and a dormancy period, I identified only one vine which became infected with A. vitis. The results did not allow me to determine if trifolitoxin is effective against A. vitis, and indicated that this experimental system requires further improvement. Powdery mildew (PM) is an economically important pathogen of grapevine, but little is known about the molecular basis of the disease. I performed the differential screening of three subtracted libraries wihch were previously constructed of PM-treated grape leaves. Escherichia coli clones, each carrying a plasmid with a unique cDNA molecule, were transferred to nylon membranes, and their plasmid DNA was immobilized. The membranes were then hybridized with radio-labeled positive and negative SSH probes, and differentially expressed genes were selected based on their different signal intensity on autoradiograph. Of the 2880 clones tested, 106 were found to represent PM-responsive genes. These clones were PCR-amplified, sequenced, and the putative function of the corresponding genes was determined. This annotation indicated that 106 genes represented a broad range of physiological functions, among which defense and senescence were predominant.

Copyright

© Le Chang

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