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dc.contributor.advisorSwart, W. J.
dc.contributor.advisorMcLaren, N. W.
dc.contributor.authorTesfaendrias, Michael Tecle
dc.date.accessioned2017-11-01T05:51:29Z
dc.date.available2017-11-01T05:51:29Z
dc.date.issued2006-05
dc.identifier.urihttp://hdl.handle.net/11660/7371
dc.description.abstractEnglish: The major sorghum grain mould fungi in South Africa were determined by assaying five sorghum cultivars from three localities in 2002 and eight localities in 2003. The predominant fungal isolates from all the cultivars and localities were Alternaria, Curvularia, Fusarium and Phoma spp. The relative frequency of grain mould fungal isolates differed with locality. Grain mould fungi were least frequently encountered at Bethlehem followed by Heilbron. The incidence of grain mould fungi negatively affects the milling and malting quality of sorghum grains. The effect of fungal isolates on various grain quality parameters was examined by inoculating sorghum panicles under glasshouse conditions. All inoculated fungi reduced seed germination with C. lunata showing the highest reduction, followed by a mixed population of fungi. F. proliferatum, A. alternata, F. graminearum, P. sorghina and a fungal mixture were important pathogens in terms of reducing the 1000 kernel mass. F. thapsinum, F. proliferatum and the mixed fungal population followed by P. sorghina, C. lunata and A. alternata resulted in higher levels of grain discolouration in glasshouse studies. Various levels of mycotoxin were produced in grains inoculated in the glasshouse and sorghum grains from experimental plots. The role of weather on the grain mould fungal incidence was determined by planting five cultivars on different planting dates at three localities. Fungal frequency varied across localities and flowering dates. In all cultivars, highest grain mould incidence was recorded at Potchefstroom. A. alternata was the most dominant fungus at all localities and at all flowering dates. An increase in moisture and temperature was positively correlated with fungal invasion. Results indicated significant correlations between grain mould incidence and certain grain quality parameters, such as the milling and malting quality. Wetness duration significantly affected grain mould development and subsequent grain quality under controlled conditions. Increased wetness duration resulted in an increase in grain infection by the respective grain mould fungi. Sorghum grain infection and subsequent grain quality deterioration as affected by insect damage was assessed in experimental plots at Bethlehem, Cedara and Potchefstroom. Insects were collected from sorghum heads and grain mould fungi were isolated from all specimens collected. A. alternata were most frequently isolated from specimens collected from Cedara while the incidence of Fusarium spp. were highest in insect samples from Bethlehem. Insecticides significantly increased 100 kernel mass compared with unsprayed grains. Mycotoxin production of grains from the insecticide treated and untreated plots were assessed and some of them produced significant levels of mycotoxins, but the effect was not consistent. Puncture marks created by insect damage were positively correlated with the incidence of Fusarium spp. It was evident that insects are involved either in transporting the fungal propagules or damaging the sorghum kernels resulting in higher fungal incidence, which consequently reduced the quality of the grains. Mycotoxins in samples from different stages of malting were assayed. The highest concentration of aflatoxin was found in samples from the steeping stage. Different concentration levels zearalenone and fumonisin were also isolated from the malting samples. Mycotoxin contamination of commercial sorghum products and other cereal products were assayed. Higher concentrations of aflatoxin were found in sorghum products followed by maize samples while aflatoxin was only recorded in two of six wheat samples. No fumonisin was found in all the samples tested. NaOCl in water used for steeping resulted in reduced isolation frequency of grain mould fungi with significant improvement in the percentage germination and root length. It was concluded that grain mould fungi are potential mycotoxin producers in sorghum products and may reduce its quality. The results of the current study confirmed the involvement of various fungi in the disease complex known as grain mould and elucidate their possible role in both qualitative and quantitative losses in sorghum. The results also demonstrated the role of favourable weather conditions and insects in the development of grain mould and the effect that the pathogens have on quality and quantity of sorghum grain. The involvement of insects in the development of grain mould warrants further attention. It is hoped that the findings of this study may serve as motivation for the development of a holistic strategy to manage grain moulds and to maintain the quality of sorghum product.en_ZA
dc.description.abstractAfrikaans: Die vernaamste fungi wat met skimmel van graansorghum geassosieer word, is deur middel van ‘n opname van vyf cultivars by drie lokaliteite in 2002, en agt lokaliteite in 2003 vasgestel. Die mees algemene isolate afkomstig vanaf alle cultivars en lokaliteite het behoort aan die genera Alternaria, Curvularia, Fusarium en Phoma. Die relatiewe frekwensie van graanskimmel-isolate het tussen lokaliteite verskil. Die minste graanskimmel-isolate was vanaf graanmonsters uit Bethlehem geïsoleer, gevolg deur Helibron met die tweede meeste. Die voorkoms van graanskimmel het ‘n negatiewe invloed op die maal- en moutkwaliteit van graansorghum gehad. Die effek van swamisolate op verskeie kwaliteits parameters van graan was ondersoek deur die inokulasie van sorghumare onder glashuistoestande. Alle geïnokuleerde swamme het saadontkieming verminder. C. lunata het die grootste verlaging veroorsaak, gevolg deur ‘n gemengde swampopulasie. F. proliferatum, A. alternata, F. graminearum, P. sorghina en die gemengde swampopulasie was belangrike patogene in terme van hulle invloed op die verlaging van 1000 pit massa. F. thapsinum, F. proliferatum en ‘n gemengde swampopulasie, gevolg deur P. sorghina, C. lunata en A. alternata het hoë vlakke van graanverkleuring in glashuis-studies veroorsaak. Verskeie vlakke van mikotoksiene was in grane wat in die glashuis geïnokuleer was, asook in die wat vanaf veldproewe afkomstig was, waargeneem. Die rol van weerfaktore op die voorkoms van graanskimmel is deur die aanplanting van vyf cultivars op verskillende plantdatums by drie lokaliteite bepaal. Swam-frekwensie het oor lokaliteite en met blomdatums gevarieer. Die hoogste voorkoms van graanskimmel is in alle cultivars uit Potchefstroom waargeneem. A. alternata was die mees algemene swamsoort by alle lokaliteite en met alle blomdatums. ‘n Toename in vog en temperatuur is positief gekorreleer met swamkolonisasie van graan. Resultate het beduidende korrelasies tussen graanskimmelvoorkoms en sekere graankwaliteitsparameters soos maal- en moutkwaliteit, getoon. Die benatingstydperk van are onder beheerde toestande het die ontwikkeling van graanskimmel en graankwaliteit beduidend beïnvloed. ‘n Toename in die benattingstydperk het ‘n toename in graaninfeksie deur die onderskeie graanskimmelfungi meegebring. Graansorghum-infeksie en die daaropvolgende afname in graankwaliteit soos deur insekskade beïnvloed, was in eksperimentele persele by Bethlehem, Cedara en Potchefstroom, ondersoek. Insekte was vanaf are versamel en graanskimmelfungi was vanaf alle insekmonsters geïsoleer. A. alternata was die mees algemene swamsoort afkomstig van insekte wat in Cedara versamel is, terwyl Fusarium spp. die hoogste voorkoms getoon het op insekte wat in Bethlehem versamel is. Insekdoders het ‘n beduidende positiewe invloed op 100 pit massa getoon in vergelyking met onbehandelde grane. Mikotoksienproduksie was op grane wat met insekdoder behandel is, asook op onbehandelde grane, bepaal. Sekere behandelings het beduidende vlakke mikotoksiene getoon maar die voorkoms daarvan was nie konsekwent nie. Penetrasiepunte wat deur insekte veroorsaak is, is positief gekorreleer met die voorkoms van Fusarium spp. Dit was duidelik dat insekte óf in die vervoer van swampropagules betrokke is, óf dat hulle skade aan grane veroorsaak wat swamkolonisasie vergemaklik en sodoende graankwaliteit verlaag. Mikotoksiene in graanmonsters in verskillende stadia van vermouting is gemeet en die hoogste konsentrasie aflatoksien was in monsters vanuit die “steeping” stadium waargeneem. Verskillende vlakke van zearalenone and fumonisin was ook uit moutmonsters waargeneem. Moontlike mikotoksien kontaminasie van kommersiële sorghumprodukte en ander graanprodukte was bepaal. Hoër konsentrasies aflatoksien is in sorghumprodukte as in mielie-produkte waargeneem, terwyl dit slegs in twee uit ses koringmonsters waargeneem is. Geen fumonisin was in enige van die monsters waargeneem nie. Die toevoeging van NaOCl tot die water wat vir “steeping” gebruik is, het ‘n verlaagde voorkoms van graanskimmelfungi meegebring, met ‘n gepaardgaande en beduidende verbetering in ontkiemingspersentasie en wortel-lengte. Die algemene afleiding was dat graanskimmelfungi potensieële mikotoksienproduseerders in sorghumprodukte is wat kwaliteit kan verminder. Die resultate van die huidige studie het die betrokkendheid van verskeie fungi in die siektekompleks bekend as graanskimmel bevestig. Die studie het ook fungi se moontlike rol in beide kwalitatiewe en kwantitatiewe verliese in sorghum verduidelik. Die resultate het ook die rol van gunstige weerfaktore en insekte in die ontwikkeling van graanskimmel en die effek daarvan op kwaliteit en kwantiteit demonstreer. Die betrokkendheid van insekte in die ontwikkeling van graanskimmel verdien dus verdere aandag. Daar word gehoop dat die bevindings uit hierdie studie as motivering sal dien vir die ontwikkeling van ‘n holistiese strategie om graanskimmels te bestuur tot die voordeel van geassosieerde produkte.af
dc.description.sponsorshipInternational Sorghum and Millet collaborative Research Support Program (INTSORMIL)en_ZA
dc.description.sponsorshipSorghum Trusten_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectSorghum -- Diseases and pests -- South Africaen_ZA
dc.subjectMolds (Fungi)en_ZA
dc.subjectGrain -- Qualityen_ZA
dc.subjectThesis (Ph.D. (Plant Sciences (Centre for Plant Health Management))--University of the Free State, 2006en_ZA
dc.titleGrain mould of sorghum with specific reference to grain quality in South Africaen_ZA
dc.typeThesisen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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