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Title: Spatio-temporal dynamics of saprophytic populations of Rhizoctonia solani Kühn
Author: Creaser, M. L.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1998
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Rhizoctonia solani is a vigorous soilborne, fungal plant pathogen that is responsible for substantial losses to many agriculturally important crops. The pathogen's destructive nature and wide host range has promoted considerable research into its taxonomy, pathology, and ecology, in an effort to develop effective methods of disease control. The population dynamics of R. solani have received considerable attention in regard to plant infection and disease development. However, few studies have focused on the saprophytic population dynamics of this organism that has been described as a saprophyte in which parasitism is largely incidental to saprophytism. The objectives of the present study were to investigate the effects of abiotic and biotic factors, principally incubation temperature and the presence of the fungal antagonist Trichoderma viride, on the temporal and spatio-temporal dynamics of saprophytic populations of two isolates of R. solani under controlled environment conditions. The saprophytic population dynamics of R. solani were investigated using a combination of fungal quantification techniques and inoculum placement studies. After investigation of the Enzyme Linked Immunosorbent Assay, ELISA, as a tool for quantification of R. solani, in comparison with ATP and chitin assays, ELISA was selected as the most appropriate assay for an investigation of population dynamics. Inoculum placement studies were used to evaluate the effects of T. viride on the growth and ability of R. solani to colonise a substrate from varying distances. The progress of the parasitic phase of R. solani is determined by, among other factors, initial inoculum density, propagule size and isolate. This study has shown that saprophytic populations of R. solani exhibit cycles of fungal activity that are affected by interactions between temperature with initial inoculum components and isolate. These factors determine the magnitude, duration and timing of cycles of saprophytic activity, as measured by ELISA. In no instance was the antagonist, T. viride, able to eliminate R. solani within a microcosm. Placement studies, in which propagules of T. viride were placed at varying distances from propagules of R. solani, concluded that the controlling effects of T. viride were localised and limited due to the slow growth of the fungus from its initial substrate in comparison with the growth of R. solani.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available