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Effect of temperature and disinfectants on pathogenic enterobacteriaceae in potatoes in South Africa
Dissertation (MSc (Agriculture))--University of Pretoria, 2014.
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| Format: | Thesis |
| Language: | English |
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2026
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| _version_ | 1867613522770264064 |
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| access_status_str | Open Access |
| author2 | Van der Waals, Jacqueline Elise |
| author_browse | Van der Waals, Jacqueline Elise |
| author_facet | Van der Waals, Jacqueline Elise |
| collection | Thesis |
| description | Dissertation (MSc (Agriculture))--University of Pretoria, 2014. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/110060 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:37:29.594Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/110060 Effect of temperature and disinfectants on pathogenic enterobacteriaceae in potatoes in South Africa Van der Waals, Jacqueline Elise susan.duraan@gmail.com Coutinho, Teresa A. Du Raan, Susan Pectobacterium Optimal temperature Dickeya Temperature range Pectinolytic bacteria Dissertation (MSc (Agriculture))--University of Pretoria, 2014. Blackleg and soft rot are some of the most important diseases in potato production and responsible for major losses annually worldwide. Blackleg and soft are the result of various species of gram-negative pectinolytic bacterial pathogens from the genera Pectobacterium and Dickeya. As seed borne diseases, symptom development and degree of losses are determined mainly by bacterial titre present in seed tubers and prevailing environmental conditions. Due to limited chemical aids available for control of these pathogens, management relies mostly on sanitation and the implementation of cultural practises. Pectobacterium carotovorum subsp. brasiliense (Pcb) is the most important species in South Africa responsible for blackleg and soft rot and was thus the main focus of this study. Four Pcb isolates from different regions in South Africa were transformed with the pPROBE-AT-gfp plasmid. Evaluation of growth, pathogenicity and plasmid stability indicated that the transformed Pcb isolates could represent wild type Pcb isolates in trials. The addition of the green fluorescent protein and ampicillin resistance gene to the bacteria made identification of the target organism, Pcb, easier and more accurate compared to when using wild type isolates. This biotechnological technique is a valuable tool that can be used in future aetiological and epidemiological studies. iv Developments in taxonomy over the last few years have classified the potato pectinolytic bacterial pathogens, previously known as Erwinia spp., into several species and subspecies of Pectobacterium spp. and Dickeya spp.. Additionally, continuous identification of new species that are responsible for blackleg and soft rot on potato, expands the gap in our basic knowledge of how these various species act in and interact with environmental parameters such as temperature. This study identified cardinal temperatures of six different species and subspecies responsible for blackleg and soft rot on potatoes. These species include Pectobacterium atrosepticum (Pat), Pectobacterium carotovorum subsp. carotovorum (Pcc), Pectobacterium carotovorum subsp. brasiliense (Pcb), Pectobacterium wasabiae (Pwa), Dickeya dadantii (Dda) and Dickeya solani (Dso). Results from this study agree with literature with Dickeya spp. being able to grow at higher temperatures compared to Pectobacterium spp.. Pectobacterium carotovorum subspecies, Pcb and Pcc, showed similar optimal temperatures (31oC to 34oC) and temperature ranges (20oC to 40oC). Pectobacterium atrosepticum and Pwa appears to be more temperature sensitive species, only being able to grow up to maximum temperatures of 31oC and 34oC and optimal temperatures of 26oC to 27oC and 30oC, respectively. Dickeya dadantii grew at cardinal temperatures similar to Pcb and Pcc. Dickeya solani, a species not yet reported in South Africa, grew at a significantly higher optimal temperature (35oC) and could grow up to 42oC. The South African climate provides an ideal niche for Dso, making this species a major threat to the potato industry especially since it has been found that this species is also more virulent in warmer climates. Another objective of this study was to investigate efficacy of disinfectants to aid in management of blackleg and soft rot. The chemical disinfectants included chlorine, phenolic, quaternary ammonium compounds (QACs), copper, and surfactant based products. Chlorine based products showed the most promising results for managing Pcb responsible for soft rot of potatoes. Comparing control between genera, Pectobacterium and Dickeya, results revealed Dda to be less susceptible to QACs compared to Pcb. Furthermore, a European Pcb isolate was found to be less susceptible to QACs compared to a South African Pcb isolate. Results obtained from this study highlight the vulnerability of the South African potato industry in the event of introduction of new species or isolates resistant to chemicals. This emphasizes the need to enforce high quality quarantine practices in order to protect a very important industry in South Africa. Plant Production and Soil Science MSc (Agriculture) 2026-05-15T17:26:12Z 2026-05-15T17:26:12Z 15/05/12 2014 Dissertation http://hdl.handle.net/2263/110060 en application/pdf |
| spellingShingle | Pectobacterium Optimal temperature Dickeya Temperature range Pectinolytic bacteria Effect of temperature and disinfectants on pathogenic enterobacteriaceae in potatoes in South Africa |
| title | Effect of temperature and disinfectants on pathogenic enterobacteriaceae in potatoes in South Africa |
| title_full | Effect of temperature and disinfectants on pathogenic enterobacteriaceae in potatoes in South Africa |
| title_fullStr | Effect of temperature and disinfectants on pathogenic enterobacteriaceae in potatoes in South Africa |
| title_full_unstemmed | Effect of temperature and disinfectants on pathogenic enterobacteriaceae in potatoes in South Africa |
| title_short | Effect of temperature and disinfectants on pathogenic enterobacteriaceae in potatoes in South Africa |
| title_sort | effect of temperature and disinfectants on pathogenic enterobacteriaceae in potatoes in south africa |
| topic | Pectobacterium Optimal temperature Dickeya Temperature range Pectinolytic bacteria |
| url | http://hdl.handle.net/2263/110060 |