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Population dynamics and induced resistance in biological control by Lysobacter enzymogenes strain C3
The spatial and temporal pattern of colonization by Lysobacter enzymogenes strain C3 was investigated on tall fescue at the scale of individual leaf segments and whole leaves. A high degree of nonuniformity in colonization by C3 was found along the length of the grass leaves when populations of C3 was examined at the leaf segment scale. The aggregation of C3 populations on leaf surfaces became more evident as population levels started to decline. When C3 populations were examined at the whole leaf scale, a uniform pattern of colonization was predominant over the course of the experiment while C3 population sizes were highly variable among leaves. The relationship of C3 population sizes to germination of B. sorokiniana conidia was also determined. Inhibition of Bipolaris conidial germination was inversely related to the C3 population numbers on the same leaf when Bipolaris conidia were deposited onto treated leaves shortly after C3 application. However, there was no dose-response relationship when pathogen inoculation was delayed by at least 1 day. In this study, induced resistance was found to be another mechanism of action by C3 in addition to chitinolysis. Induced resistance elicited by C3 resulted in arrested germination of B. sorokiniana conidia on the phylloplane, in addition to reduced development of leaf spot. When applied to tall fescue leaves, heat-killed cells, which retained no direct antifungal activity, were effective in inducing the pathogen-inhibitory effect. Application of live or heat-killed cells of C3 to tall fescue leaves resulted in localized resistance expressed within 1 day of the elicitor treatment. Treatment of roots resulted in systemic resistance expressed in the foliage following a delay of over 5 days. Induced resistance by C3 was not pathogen or host specific. It was effective against B. sorokiniana in wheat and against R. solani in tall fescue. In tall fescue, treatments with C3 were associated with significant increases in peroxidase activity over the control, supporting the hypothesis that C3 can elicit a host response. Similar results were found with certain PGPR strains and the chemical inducer Benzothiadiazole (BTH). ^
Agriculture, Plant Pathology
Kilic, Ozlem, "Population dynamics and induced resistance in biological control by Lysobacter enzymogenes strain C3" (2002). ETD collection for University of Nebraska - Lincoln. AAI3059952.