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Bacterial bioluminescence: a tool to study host-pathogen interactions between Brassica oleracea and the bacterial phytopathogen Xanthomonas campestris pv. campestris in black rot of cabbage

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Title:Bacterial bioluminescence: a tool to study host-pathogen interactions between Brassica oleracea and the bacterial phytopathogen Xanthomonas campestris pv. campestris in black rot of cabbage
Authors:McElhaney, Rosemarie
Date Issued:1991
Abstract:Black rot of cabbage, caused by the bacterial pathogen Xanthomonas campestris pv, campestris, is a very serious disease, which results in significant crop losses worldwide. Gene technology has provided a unique marker, bacterial bioluminescence, to trace the movement of bacteria in an infected plant and their spread in the field without interrupting the disease process. Xanthomonas campestris pv. campestris strain G-171 was tranformed to the bioluminescent strain 171LIIH-7 in a mating with Escherichia coli HB101 harboringplasmidpUCD607. The plasmid carries the genes for bioluminescence and four antibiotic resistance loci. Stability of the plasmid-borne genes as well as expression of pathogenicity and virulence were confirmed in serial passage through agar plates and cabbage seedlings. Southern hybridization patterns and other in vitro tests suggest that the genes for bioluminescence and antibiotic resistances are integrated into the chromosome. Growth of the transconjugant at different temperatures and with various nitrogen compounds was compared to that of the wild type strain in liquid culture, and showed that the two strains behave similarly except for a temperature sensitivity for 171LIIH-7 above 30 C. Once it was determined that the transconjugant stably expressed bioluminescence and pathogenicity, the applicability of the bioluminescence marker to studies of black rot of cabbage was examined. The effect of host nutrition on disease progression and severity was investigated by growing Brassicaoleracea seedlingswith varying amounts of different nitrogen sources, potassium, and phosphorus. In situ movement of the bacteria in infected seedlings was monitored with X-ray film. It was determined that insufficient amounts of nitrogen increased disease, but that amounts above those required for optimum plant growth reduced disease. No significant effects on disease severity were observed from varying the amounts of potassium and phosphorus fertilization; however, when phosphorus was omitted, disease development was greatly inhibited. The transconjugant was also used to confirm disease transmission via roots and to examine transmission by whiteflies. The bioluminescent pathogen was transmitted through the roots in one out of ten seedlings, which were grown in potting mix containing black rot infected cabbage leaves. The pathogen was traced from a location in the root system into the leaves with X-ray film. The role of whiteflies in the spread of black rot of cabbage was not determined in this study, because white flies did not transmit the pathogen to healthy seedlings.
Description:Thesis (Ph. D.)--University of Hawaii at Manoa, 1991.
Includes bibliographical references (leaves 94-102)
x, 102 leaves, bound ill. (some col.) 29 cm
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: Ph.D. - Botanical Sciences (Plant Pathology)

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