Evaluation of foliar fungicides for the control of mycotoxigenic fungi associated with Fusarium head blight of wheat in South Africa
| dc.contributor.advisor | Rose, Lindy J. | en_ZA |
| dc.contributor.advisor | Viljoen, Altus | en_ZA |
| dc.contributor.advisor | Van Coller, Gert J. | en_ZA |
| dc.contributor.author | Jacobs, Carlynn Melissa | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology. | en_ZA |
| dc.date.accessioned | 2021-05-24T13:21:09Z | |
| dc.date.available | 2022-08-31T03:00:09Z | |
| dc.date.issued | 2021-03 | |
| dc.description | Thesis (MScAgric)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Wheat (Triticum aestivum L.) is considered one of the most important cereal grains constrained by the fungal genus Fusarium, globally as well as in South Africa. Fusarium species are the causal organisms of Fusarium head blight (FHB), an economically important disease that results in significant yield and grain quality losses. These plant pathogens are also known to produce secondary metabolites called mycotoxins that further reduce grain quality, but also induce foodborne intoxication in humans and animals when contaminated grain is ingested. Trichothecene type B mycotoxins, especially deoxynivalenol (DON), is important in South Africa as it is predominantly associated with commercially produced wheat. Management practices to reduce FHB and mycotoxin accumulation depends on factors like agronomical practices, resistant cultivars, and the use of fungicides. To date, there are no fungicides registered for the control of FHB in South Africa, yet fungicides are extensively used in wheat production. Therefore, this study aimed to determine the potential of foliar fungicides, currently used in South Africa’s wheat production, to reduce FHB and mycotoxin accumulation. Fungicides evaluated in this study included Folicur (tebuconazole), Prosaro (prothioconazole + tebuconazole) and Abacus (pyraclostrobin + epoxiconazole). Initially the effect of these fungicides was tested in vitro at different concentrations while three agar-based assays were used to assess the sensitivity of Fusarium and Alternaria pathogens. Following this optimisation, the fungicide sensitivity of three Fusarium species was determined on a population of 25 isolates per species. The sensitivity of isolates, based on the effective concentration (EC50 and EC90) values, differed significantly (P<0.05) for each species and fungicide tested. Fusarium graminearum was the least sensitive to prothioconazole + tebuconazole with EC50 and EC90 values ranging from 0.51 ppm to 2.35 ppm while F. pseudograminearum was the least sensitive to both tebuconazole [EC50:0.96 ppm and EC90: 3.07 ppm] and pyraclostrobin + epoxiconazole [EC50:1.82 ppm and EC90:51.3 ppm]. Overall, prothioconazole + tebuconazole showed the best efficacy in reducing fungal growth of FHB pathogens. Significant differences of fungicides on mycotoxin production were also obtained. A significant cultivar x fungicide interaction was determined for all FHB disease parameters measured in the greenhouse trial while a significant fungicide x cultivar x treatment interaction was determined for the field trial. Generally, the application of fungicides significantly decreased FHB incidence, decreased the percentage Fusarium-damaged kernels and increased the thousand kernel weight of most wheat cultivars evaluated. The results of the study provide support for the use of commercial foliar fungicides that can additively contribute to the management of FHB and mycotoxin contamination. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Koring (Triticum aestivum L.) word as een van die belangrikste grane beskou wat deur die swamgenus, Fusarium, wêreldwyd, asook in Suid-Afrika, beperk word. Fusarium spesies is die veroorsakende organismes van Fusarium aarskroei (FHB), ‘n ekonomies-belangrike siekte wat tot betekenisvolle verliese in opbrengs en graankwaliteit lei. Hierdie plantpatogene is ook daarvoor bekend dat hulle sekondêre metaboliete, genaamd mikotoksiene, produseer wat verder die kwaliteit van die graan verlaag, maar ook voedselgedraagde vergiftiging in mense en diere induseer wanneer gekontamineerde graan ingeneem word. Trichothecene tipe B mikotoksien en veral deoxynivalenol (DON), is belangrik in Suid-Afrika aangesien dit hoofsaaklik met kommersieel-geproduseerde koring geassosieer word. Bestuurspraktyke om FHB en mikotoksien-akkumulasie te verminder, hang van faktore soos landboupraktyke, weerstandbiedende kultivars, en die gebruik van swamdoders af. Tot op datum is daar geen swamdoders vir die beheer van FHB in Suid-Afrika geregistreer nie, tog word swamdoders wyd in koringproduksie gebruik. Hierdie studie het dus ten doel gehad om die potensiaal van blaarswamdoders, wat tans in Suid-Afrikaanse koringproduksie gebruik word, om FHB en mikotoksien-akkumulasie te verminder, te bepaal. Swamdoders wat in hierdie studie geëvalueer is, sluit in Folicur (tebukonasool), Prosaro (protiokonasool + tebukonasool) en Abacus (piraklostrobien + epoksikonasool). Aanvanklik is die effek van hierdie swamdoders in vitro by verskillende konsentrasies getoets, terwyl drie agar- gebaseerde toetse gebruik is om die sensitiwiteit van Fusarium en Alternaria patogene vas te stel. Volgende op hierdie optimalisering, is die swamdoder sensitiwiteit van drie Fusarium spesies op ‘n populasie van 25 isolate per spesie vasgestel. Die sensitiwiteit van isolate, gebaseer op die effektiewe konsentrasie (EC50 en EC90) waardes, het betekenisvol (P<0.05) vir elke spesie en swamdoder wat getoets is, verskil. Fusarium graminearum was die minste sensitief vir protiokonasool + tebukonasool met EC50 en EC90 waardes wat vanaf 0.51 dpm en 2.35 dpm gevarieer het, terwyl F. pseudograminearum die minste sensitief vir beide tebukonasool [EC50:0.96 dpm en EC90: 3.07 dpm] en piraklostrobien + epoksikonasool [EC50:1.82 dpm en EC90:51.3 dpm] was. Oor die algemeen het protiokonasool + tebukonasool die hoogste effektiwiteit in die vermindering van swamgroei van FHB patogene getoon. Betekenisvolle effek van swamdoders op mikotoksienproduksie is ook verkry. ‘n Betekenisvolle kultivar x swamdoder interaksie is vasgestel vir alle FHB siekte parameters wat in die glashuisproef gemeet is, terwyl ‘n betekenisvolle swamdoder x kultivar x behandeling interaksie vir die veldproef vasgestel is. Oor die algemeen het die toedien van swamdoders FHB voorkoms betekenisvol verminder, die persentasie Fusarium-beskadigde korrels verminder, en die duisend korrel gewig van meeste koringkultivars wat geëvalueer is, verhoog. Die resultate van hierdie studie ondersteundie gebruik van kommersiële blaarswamdoders wat bykomend tot die bestuur van FHB en mikotoksienkontaminasie kan bydra. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.embargo.terms | 2022-08-30 | |
| dc.format.extent | ix, 117 pages : illustrations (some color) | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/110501 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject.lcsh | Wheat (Triticum aestivum L.) -- South Africa | en_ZA |
| dc.subject.lcsh | Wheat fusarium culmorum head blight | en_ZA |
| dc.subject.lcsh | Fusarium diseases of plants -- Control | en_ZA |
| dc.subject.lcsh | Mycotoxins | en_ZA |
| dc.subject.lcsh | Fusarium head blight -- Pathogenesis | en_ZA |
| dc.subject.lcsh | Grain -- Losses | en_ZA |
| dc.subject.lcsh | Wheat -- Quality -- South Africa | en_ZA |
| dc.subject.name | UCTD | en_ZA |
| dc.title | Evaluation of foliar fungicides for the control of mycotoxigenic fungi associated with Fusarium head blight of wheat in South Africa | en_ZA |
| dc.type | Thesis | en_ZA |