Pathogenicity and mycotoxin production of the Fusarium graminearum species complex in South African grains
| dc.contributor.advisor | Viljoen, Altus | en_ZA |
| dc.contributor.advisor | Rose, Lindy J. | en_ZA |
| dc.contributor.author | Beukes, Cornelia Elizabeth | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology. | en_ZA |
| dc.date.accessioned | 2015-12-14T07:42:09Z | |
| dc.date.available | 2018-01-31T03:00:16Z | |
| dc.date.issued | 2015-12 | |
| dc.description | Thesis (MScAgric)--Stellenbosch University, 2015. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Fusarium graminearum is one of the most ubiquitous Fusarium species complexes causing diseases of various grain crops worldwide. The most common grain diseases associated with the F. graminearum species complex (FGSC) include Gibberella ear rot (GER) of maize, Fusarium head blight (FHB) of small-grain cereals such as wheat and Grain Mould (GM) of sorghum. High infection rates lead to reduced seed germination, seedling blight and low kernel weight, and drastically reduced profits. Infection, furthermore, poses a health threat, as the FGSC produces toxic secondary metabolites known as mycotoxins, of which zearalenone (ZEA) and the type-B trichothecenes (TCT-B), deoxynivalenol (DON) and nivalenol (NIV), are the most common. Increasing efforts to manage the occurrence of harmful Fusarium spp. and their mycotoxins, both in commercial and subsistence farming systems, should be made. Host- pathogen relations, such as host-preference and -specificity, are important concepts when developing disease control strategies, as it affects the application of crop rotation systems, and could lead to novel approaches to achieve improved resistance in commercial cultivars. Precise measurements of fungal colonisation and mycotoxin contamination in host crops are fundamental requirements when studying diseases caused by species of the FGSC. Differences in the measured values should be consequential to the fungi screened, and not the quantification technique used. High variability in measurements of the same sample, indicating low precision, will result in unreliable results. The reproducibility and repeatability of quantitative real-time PCR (qPCR) and liquid chromatography mass spectrometry (LC- MS/MS) assays were, therefore, demonstrated for colonisation and mycotoxin deposition by FGSC species in maize, wheat and sorghum grain. The in-house validated mycotoxin analysis technique was successfully used to evaluate maize, wheat and sorghum grain grown under greenhouse conditions, following artificial inoculation with isolates of the FGSC. The validated qPCR assay was further applied to quantify fungal colonisation in the inoculated maize grain. To study host-preference by FGSC species, the pathogenicity, colonisation and mycotoxin production of five FGSC members known to occur in South African grains were tested by inoculation of maize, wheat and sorghum grain under field conditions. Higher colonisation and TCT-B production was observed by isolates of F. boothii in maize, and F. graminearum isolates in wheat. However, a selective advantage of F. boothii to cause disease on maize could not be established. Fusarium graminearum was the most aggressive FGSC species on wheat. Climatic conditions are proposed as an influential factor, as wheat was planted during the cooler winter months in this study, and F. graminearum prevalence correlates with cooler regions in global survey studies. Host preference could, therefore, neither be confirmed nor refuted and isolate-specific, rather than species-specific characteristics are proposed as an additional variable in assessing fungal colonisation and mycotoxin production in grain. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Fusarium graminearum is een van die mees alomteenwoordige Fusarium spesie komplekse wat siektes van verskillende graangewasse wêreldwyd veroorsaak. Die mees algemene graan verwante siektes wat met die F. graminearum spesie kompleks (FGSK) geassosieer word sluit in: Gibberella kopvrot van mielies, Fusarium aarskroei van kleingrane soos koring, en Graan skimmel van sorghum. Hoë infeksiekoerse lei tot verminderde saadontkieming, saailing roes en lae graan gewig, wat drastiese verliese in winste tot gevolg kan hê. Infeksie hou verder ook 'n gevaar in vir die gesondheid van mense en diere, aangesien die FGSK giftige sekondêre metaboliete produseer wat bekend staan as mikotoksiene. Zearalenone (ZEA) en die tipe-B trichothecenes (TCT-B), veral deoxynivalenol (DON) en nivalenol (NIV), is die mees algemeen. Toenemende pogings om die voorkoms van skadelike Fusarium spp. en hulle mikotoksiene te bestuur, beide in kommersiële en bestaansboerdery stelsels, moet gemaak word. Gasheer-patogeen verhoudings, soos gasheer-voorkeur en -spesifisiteit, is belangrike konsepte wanneer siekte beheer strategieë ontwikkel word, aangesien dit 'n invloed op die toepassing van wisselboustelsels kan hê. Betroubare metings van swam kolonisasie en mikotoksien besmetting in gasheer gewasse is fundamentele vereistes wanneer verskille in siekte-veroorsakende aktiwiteite van swamme, soos die FGSK, bestudeer word. Verskille in gemete waardes moet die gevolg wees van verskille tussen die swamme, en nie die kwantifisering tegniek wat gebruik word nie. Hoë veranderlikheid in metings van dieselfde monster, sal lei tot onbetroubare resultate. Die tussen-monster en tussen-analise herhaalbaarheid van kwantitatiewe polimerase ketting reaksie (kPKR) en vloeichromatografie tandem massaspektrometrie (VC-MS/MS) tegnieke was dus bewys vir kolonisasie en mikotoksien afsetting deur FGSK spesies in mielies, koring en sorghum graan. Die ge-optimiseerde mikotoksien analise tegniek is suksesvol gebruik om mielies, koring en sorghum graan te evalueer na kunsmatige inenting met isolate van die FGSK. Die kPKR analise tegniek is verder toegepas om swam kolonisasie te kwantifiseer in die inokuleerde mielie graan. Om gasheer-voorkeur deur FGSK spesies te bestudeer, is die patogenisiteit, kolonisasie en mikotoksien produksie van vyf FGSK lede, bekend om voor te kom in Suid-Afrikaanse grane, getoets deur inokulasie van mielies, koring en sorghum graan onder veldtoestande. Hoër kolonisasie en TCT-B produksie is waargeneem deur isolate van F. boothii in mielies, en F. graminearum isolate in koring. Alhoewel, 'n selektiewe voordeel van F. boothii om siekte te veroorsaak op mielies nie kon vasgestel word nie. Fusarium graminearum was die mees aggressiewe FGSK spesies op koring. Klimaatstoestande word voorgestel as 'n invloedryke faktor, aangesien koring geplant is tydens die koeler wintermaande in hierdie studie, en F. graminearum voorkoms stem ooreen met koeler streke in wêreldwye opname studies. Gasheer voorkeur kan dus nie bevestig of weerlê word nie en isolaat spesifieke, eerder as spesie-spesifieke kenmerke, word voorgestel as 'n bykomende veranderlike in die bepaling van die swam kolonisasie en mikotoksien produksie in graan. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.embargo.terms | 2018-01-31 | |
| dc.format.extent | ix, 138 pages : illustrations (some color) | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/97754 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject.lcsh | Fusarium graminearum -- Pathogenesis | en_ZA |
| dc.subject.lcsh | Fusarium diseases of plants -- South Africa | en_ZA |
| dc.subject.lcsh | Mycotoxins -- Physiological effect | en_ZA |
| dc.subject.lcsh | Plants -- Effect of mycotoxins on | en_ZA |
| dc.subject.lcsh | Grain -- Diseases and pests -- South Africa | en_ZA |
| dc.subject.lcsh | Wheat fusarium culmorum head blight | en_ZA |
| dc.subject.lcsh | Maize -- Disease and pest resistance -- Genetic aspects | en_ZA |
| dc.subject.lcsh | Sorghum -- Diseases and pests | en_ZA |
| dc.subject.name | UCTD | en_ZA |
| dc.title | Pathogenicity and mycotoxin production of the Fusarium graminearum species complex in South African grains | en_ZA |
| dc.type | Thesis | en_ZA |