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Studies on the etiology of a bacterial wilt disease of the water weed Myriophyllum Aquaticum
Thesis (MScAgric.) -- University of Stellenbosch, 1994.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2012
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| _version_ | 1867613816620056576 |
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| access_status_str | Open Access |
| author | Fouche, Wilma |
| author2 | Lennox, C. L. |
| author_browse | Fouche, Wilma Lennox, C. L. |
| author_facet | Lennox, C. L. Fouche, Wilma |
| author_sort | Fouche, Wilma |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MScAgric.) -- University of Stellenbosch, 1994. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/58556 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:42:09.814Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/58556 Studies on the etiology of a bacterial wilt disease of the water weed Myriophyllum Aquaticum Fouche, Wilma Lennox, C. L. Dicks, L. M. T. Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology. Aquatic weeds -- Diseases and pests Bacterial diseases of plants Wilt diseases Myriophyllum Dissertations -- Plant pathology Thesis (MScAgric.) -- University of Stellenbosch, 1994. The water weed Myriophyllum aquaticum is native to South America and now occurs worldwide. It was introduced before 1919 for use as an ornamental in fish tanks and lilly ponds and has since spread to all the provinces of South Africa. This weed threatens recreational activities, aquatic ecosystems and irrigation schemes. Mechanical and chemical control of this water weed is expensive and ineffective and there are no chemicals registered for its control in South Africa. Successful biological control of this weed has also not yet been obtained anywhere in the world.In this study a bacterial wilt disease observed on M. aquaticum plants near Bronkhorstspruit in the North West Province has been studied as a potential biological control agent. A yellow-pigmented, slimy, Gram negative bacterium was isolated from the wilted leaves and stems. Subsequently 19 isolates of the bacterium were isolated from different geographical areas in three of the provinces. The predominant symptom of infection is wiling of the leaves without prior yellowing. Wilting usually starts near the top of the aerial shoots and sometimes leaves on only one side of the plant are affected. By studying the morphological and physiological characteristics and determining the moles percent guanine-plus-cytosine content of the 19 isolates, the bacterium was identified as Xanthomonas campestris.Scanning electron, transmission electron and light microscope studies confirmed that X. campestris spreads and proliferates in the xylem vessels. The highest number of bacteria were consistently isolated from the top aerial parts. Initially, after inoculation the bacterial population in and on the plant surface declined sharply and from 48 h later the population increased to reaching a plateau after 4-5 days. Extrusion of bacteria occurred through the hydathodes and stomata.The most effective methods of inoculating M. aquaticum plants with X. campestris were spraying of the aerial shoots and soaking wounded roots in a bacterial suspension. It was shown that hydathodes occur on the leaf tips which are believed to be an important site of entry for X. campestris. Aphids were unable to transmit the disease from infected to healthy plants. Little variation in virulence occurred between the 19 isolates. The optimum temperature for disease development was 25-30°C and symptoms developed readily when inoculum was applied at concentrations of \(10^{7}\)-\(10^{9}\) cfu/ml. Spraying plants on a farm dam early in the morning when guttation droplets were still present resulted in wilting of all the aerial shoots after four weeks. New shoots, however, grew from the submerged stems even after repeated inoculations. The bacterium has limited potential as a bioherbicide on its own, but might be useful in an integrated control program. Masters 2012-08-27T11:39:02Z 2012-08-27T11:39:02Z 1994 Thesis http://hdl.handle.net/10019.1/58556 en Stellenbosch University 88 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Aquatic weeds -- Diseases and pests Bacterial diseases of plants Wilt diseases Myriophyllum Dissertations -- Plant pathology Fouche, Wilma Studies on the etiology of a bacterial wilt disease of the water weed Myriophyllum Aquaticum |
| title | Studies on the etiology of a bacterial wilt disease of the water weed Myriophyllum Aquaticum |
| title_full | Studies on the etiology of a bacterial wilt disease of the water weed Myriophyllum Aquaticum |
| title_fullStr | Studies on the etiology of a bacterial wilt disease of the water weed Myriophyllum Aquaticum |
| title_full_unstemmed | Studies on the etiology of a bacterial wilt disease of the water weed Myriophyllum Aquaticum |
| title_short | Studies on the etiology of a bacterial wilt disease of the water weed Myriophyllum Aquaticum |
| title_sort | studies on the etiology of a bacterial wilt disease of the water weed myriophyllum aquaticum |
| topic | Aquatic weeds -- Diseases and pests Bacterial diseases of plants Wilt diseases Myriophyllum Dissertations -- Plant pathology |
| url | http://hdl.handle.net/10019.1/58556 |
| work_keys_str_mv | AT fouchewilma studiesontheetiologyofabacterialwiltdiseaseofthewaterweedmyriophyllumaquaticum |