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Etiology and alternative control of potato rhizoctoniasis in South Africa
Dissertation (MSc (Plant Pathology))--University of Pretoria, 2005.
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University of Pretoria
2013
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| _version_ | 1867613675208048640 |
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| access_status_str | Open Access |
| author2 | Wehner, F.C. |
| author_browse | Wehner, F.C. |
| author_facet | Wehner, F.C. |
| collection | Thesis |
| dc_rights_str_mv | © 2005, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MSc (Plant Pathology))--University of Pretoria, 2005. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/23933 |
| institution | University of Pretoria (South Africa) |
| last_indexed | 2026-06-10T12:39:54.964Z |
| 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:2263/23933 Etiology and alternative control of potato rhizoctoniasis in South Africa Wehner, F.C. mariette.truter@up.ac.za Truter, Mariëtte Alternative control Rhizoctonia solani Stem canker Potato Organic amendments Heat treatment Fungicides Disinfectants Black scurf Biofumigation Anastomosis groups Antagonists UCTD Dissertation (MSc (Plant Pathology))--University of Pretoria, 2005. Rhizoctoniasis of potato occurs in all regions of the world where the crop is grown. The disease is caused by various anastomosis groups (AGs) of the fungus Rhizoctonia solani, of which AG-3 is the most common. Very little information is available on the AGs involved in potato rhizoctoniasis in South Africa. This study elucidated the etiology of the disease in the country and also provided guidelines regarding alternative control strategies. The vast majority (99.3 %) of R. solani isolates from symptomatic potato tubers collected at seven of the 14 potato production regions in South Africa belonged to AG-3, and 0.7 % to AG-5. Of the isolates from infected stems and roots, 82.1 % were AG-3, 12.8 % AG-4, and 5.1 % AG-5. Isolations from soil yielded 67.7 % AG-3, 22.0 % AG-4, 5.5 % AG-5, and 2.4 % of each of AG-7 and AG-8. In vitro screening indicated that AG-3 isolates were the most virulent. The progeny of seed tubers naturally infected with R. solani was rendered free of infection by dipping the tubers in hot water at 55 C for 8 minutes, 60 ºC for 6 minutes, or 65 ºC for 4 minutes. However, treatments more severe than 55 ºC for 8 minutes progressively increased tuber mortality. OA5 DP, an organic tin complex, proved to be the most effective of 20 disinfectants for killing sclerotia of the pathogen on seed tubers and rendering the progeny free of infection, but exhibited acute phytotoxicity towards the tubers. Significant control without any phytotoxicity was achieved with the didecyl ammonium chloride compound, Sporekill. Tolclofos-methyl was the only fungicide that provided total control of potato rhizoctoniasis, whereas seed tuber treatment with fludioxonil, kresoxim-methyl and metam-sodium significantly reduced disease in the progeny. Incorporation of of the biocontrol formulation TrykocideTM (Trichoderma harzianum) into soils artificially infested with R. solani AG-3 eradicated the pathogen. Significant reductions in pathogen populations were also evident in soils amended with azoxystrobin, kresoxim-methyl, MaxifloTM Azospirillum brasilense), AvogreenTM (Bacillus subtilis), cattle, chicken and sheep manure, citrus and mango waste compost, composted kraal manure, and shoot tissues of Brassica napus, B. oleracea var. capitata, Raphanus sativus, Sinapsis alba and Tagetes minuta. TrykocideTM provided total control of stem canker in artificially infested soil, whereas kresoxim-methyl, azoxystrobin, sheep manure, B. napus and B. oleracea var. capitata shoot tissue, mango waste compost, and the systemic resistance-inducing compound, acibenzolar-s-methyl, reduced the disease significantly. Microbiology and Plant Pathology unrestricted 2013-09-06T16:11:57Z 2005-05-26 2013-09-06T16:11:57Z 2005-04-14 2005 2005-04-12 Dissertation Truter, M 2005, Etiology and alternative control of potato rhizoctoniasis in South Africa, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://hdl.handle.net/2263/23933 > http://hdl.handle.net/2263/23933 http://upetd.up.ac.za/thesis/available/etd-04122005-112047/ © 2005, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | Alternative control Rhizoctonia solani Stem canker Potato Organic amendments Heat treatment Fungicides Disinfectants Black scurf Biofumigation Anastomosis groups Antagonists UCTD Etiology and alternative control of potato rhizoctoniasis in South Africa |
| title | Etiology and alternative control of potato rhizoctoniasis in South Africa |
| title_full | Etiology and alternative control of potato rhizoctoniasis in South Africa |
| title_fullStr | Etiology and alternative control of potato rhizoctoniasis in South Africa |
| title_full_unstemmed | Etiology and alternative control of potato rhizoctoniasis in South Africa |
| title_short | Etiology and alternative control of potato rhizoctoniasis in South Africa |
| title_sort | etiology and alternative control of potato rhizoctoniasis in south africa |
| topic | Alternative control Rhizoctonia solani Stem canker Potato Organic amendments Heat treatment Fungicides Disinfectants Black scurf Biofumigation Anastomosis groups Antagonists UCTD |
| url | http://hdl.handle.net/2263/23933 http://upetd.up.ac.za/thesis/available/etd-04122005-112047/ |