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Biological control of Pythium wilt and root rot in hydroponically grown lettuce
Dissertation (MSc (Plant Pathology))--University of Pretoria, 2008.
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University of Pretoria
2013
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| _version_ | 1867613622164783104 |
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| access_status_str | Open Access |
| author2 | Labuschagne, Nico |
| author_browse | Labuschagne, Nico |
| author_facet | Labuschagne, Nico |
| collection | Thesis |
| dc_rights_str_mv | © University of Pretoria 2005E233/ |
| description | Dissertation (MSc (Plant Pathology))--University of Pretoria, 2008. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/22883 |
| institution | University of Pretoria (South Africa) |
| last_indexed | 2026-06-10T12:39:04.068Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2013 |
| publishDateRange | 2013 |
| publishDateSort | 2013 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/22883 Biological control of Pythium wilt and root rot in hydroponically grown lettuce Labuschagne, Nico upetd@up.ac.za Korsten, Lise Boshoff, Jane Pythium Wilt Root rot Lettuce Hydroponics UCTD Dissertation (MSc (Plant Pathology))--University of Pretoria, 2008. A number of techniques were used to obtain a variety of bacterial and fungal species antagonistic to Pythium - F group in hydroponic systems. Isolations were made from roots of ‘escape’ lettuce plants in a commercial hydroponic gravel system as well as Pythium mycelium exposed to the hydroponic solution. Seventy four bacterial and eighteen fungal isolates were obtained and were screened for in vitro activity against Pythium by means of the dual culture method. Twenty-two bacterial isolates rendered between 10.8 and 48 % inhibition and ten fungal isolates rendered between 24.3 and 54 % inhibition of Pythium mycelial growth. Potential biocontrol agents were screened in a static aquaculture system on butterhead lettuce seedlings in the greenhouse prior to evaluation in a re-circulating gravel bed hydroponic system in the greenhouse and field, for both growth promoting and biocontrol ability. Significant increases of between 689 % and 922 % in total fresh yield were obtained from plants preventatively treated with isolates JH49, JH41, JH83, JM6R and JM16W. The eight best performing isolates were further evaluated for biocontrol activity against Pythium as well as growth promotion on butter head lettuce in a re-circulating gravel bed hydroponic system in the greenhouse. Significant increases of 1.5 % - 63.5 % and 0.9 % - 38.8 % in total fresh yield were obtained from plants evaluated for growth promotion and Pythium control, respectively. Based on their performance five of the eight isolates were selected for evaluation in a re-circulating gravel bed hydroponic field system. Treatment with Pseudomonas fluorescens and Bacillus subtilis significantly increased fresh leaf weight of lettuce plants in comparison with the untreated control indicating effective suppression of Pythium. Of the isolates that were previously evaluated against Pythium wilt and root rot of lettuce in a hydroponic system (Chapters 2 and 3), 6 bacteria and 2 fungi were most effective. The following possible modes of action of these isolates, were investigated, namely competition, production of inhibitory substances and induced resistance. The root colonizating ability of the isolates was also assessed. Competition between the isolates and the pathogen were confirmed by testing for siderophore and hydrolytic enzyme production. Five of the isolates produced siderophores much faster than the rest, demonstrating that these isolates were able to take-up iron from the media at a faster rate, thus indicating a significant competitive ability. Antibiotic production by the isolates was confirmed in vitro by means of the dual culture technique. Of the eight isolates screened, only one isolate showed in vitro inhibition of the pathogen. This result was confirmed by a TLC assay, where fluorescent bands were formed by the same isolate, indicating the presence of phenolic compounds. These compounds were separated by HPLC. Analysis of total soluble and cell wall phenolic levels in Pythium infected and non-infected plants treated and untreated with the biocontrol isolates did not render conclusive results. Three of the eight isolates were able to colonize 100% of the lettuce roots. Microbiology and Plant Pathology unrestricted 2013-09-06T13:52:07Z 2007-02-27 2013-09-06T13:52:07Z 2006-05-02 2008-02-27 2007-02-27 Dissertation a 2005E233/ag http://hdl.handle.net/2263/22883 http://upetd.up.ac.za/thesis/available/etd-02272007-163651/ © University of Pretoria 2005E233/ application/pdf University of Pretoria |
| spellingShingle | Pythium Wilt Root rot Lettuce Hydroponics UCTD Biological control of Pythium wilt and root rot in hydroponically grown lettuce |
| title | Biological control of Pythium wilt and root rot in hydroponically grown lettuce |
| title_full | Biological control of Pythium wilt and root rot in hydroponically grown lettuce |
| title_fullStr | Biological control of Pythium wilt and root rot in hydroponically grown lettuce |
| title_full_unstemmed | Biological control of Pythium wilt and root rot in hydroponically grown lettuce |
| title_short | Biological control of Pythium wilt and root rot in hydroponically grown lettuce |
| title_sort | biological control of pythium wilt and root rot in hydroponically grown lettuce |
| topic | Pythium Wilt Root rot Lettuce Hydroponics UCTD |
| url | http://hdl.handle.net/2263/22883 http://upetd.up.ac.za/thesis/available/etd-02272007-163651/ |