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dc.contributor.advisorHerselman, Liezel
dc.contributor.advisorKriel, Wilmarie
dc.contributor.advisorLeslie, John F.
dc.contributor.authorMinnaar-Ontong, Adré
dc.date.accessioned2016-01-13T08:29:00Z
dc.date.available2016-01-13T08:29:00Z
dc.date.copyright2011-05
dc.date.issued2011-05
dc.date.submitted2011-05
dc.identifier.urihttp://hdl.handle.net/11660/2170
dc.description.abstractEnglish: Wheat, after maize, is globally the most widely cultivated cereal crop and the staple diet of most people around the world. In South Africa, wheat, as the second most important grain crop, is produced in all nine provinces under either irrigation or dryland conditions. Diseases, however, restrain wheat production due to yield and grain quality reduction. Fusarium head blight (FHB) is a globally devastating fungal disease of wheat, primarily caused by F. graminearum. This disease is not only responsible for economic losses due to yield and quality reduction, but also contaminates the grain with trichothecene mycotoxins. This study concentrated on the genetic structure of the FHB causing populations present in seven South African wheat-growing areas under centre-pivot irrigation (Prieska, Barkly West, Orania, Douglas, Greytown, Cradock and Potchefstroom). Fusarium graminearum was identified as the dominating causal agent of FHB in South Africa and the tricothecene genotype of these isolates indicated a higher frequency of DON rather than NIV producers. DON producers have been described as more pathogenic to plants than NIV producers. This might explain the high DON frequency as well as the displacement of other Fusarium species in the less temperate regions of the South African wheat-growing areas with F. graminearum. AFLP analysis was used to place 793 South African F. graminearum isolates into the phylogenetic groups as described by O’Donnell and associates. South African F. graminearum isolates clustered with the lineage 7 reference isolates, although previous reports indicated the presence of lineages 3 and 5 in South Africa. Even though the currently studied population was dominated by lineage 7 isolates, significant genetic variation was detected. The observed genetic variation within individual populations was higher than the genetic variation between populations. The genotypic variation was consistent with outbreeding occurring under field conditions in South Africa. Although the Prieska population tended to be isolated, with a relatively high frequency of clones, the low genetic variation between all seven field populations suggested a larger randomly mating FHB population for South Africa due to similar allele frequencies. These results are consistent with previous reports on the genetic structure of FHB populations in other parts of the world. Knowledge gained from analyses of the genetic structure of this population might assist with the development of effective control strategies, i.e. resistance breeding against FHB, using resistance sources from other lineage 7 regions. This will provide an incentive to farmers to plant wheat, thus improving wheat production in South Africa.en_ZA
dc.description.abstractAfrikaans: Koring, naas mielies, is die mees verboude graangewas asook stapelvoedsel wêreldwyd. Koring, as tweede belangrikste graangewas, word in al nege Suid- Afrikaanse provinsies, hetsy onder besproeiing of droëlandtoestande, verbou. Koringproduksie word egter nadelig deur die teenwoordigheid van koringsiektes, wat opbrengs en graankwaliteit beïnvloed, geraak. Fusarium aarskroei is wêreldwyd as ‘n vernietigende swamsiekte bekend, wat hoofsaaklik deur F. graminearum veroorsaak word. Hierdie koringsiekte is nie net vir ekonomiese verlies as gevolg van verlies van opbrengs en graankwaliteit verantwoordelik nie, maar kontamineer die graan met trichothecene mikotoksiene. In hierdie studie is klem op die genetiese struktuur van die fungus populasies verantwoordelik vir aarskroei in sewe Suid-Afrikaanse koringverbouingsgebiede onder besproeiing (Prieska, Barkley Wes, Orania, Douglas, Greytown, Cradock en Potchefstroom) gelê. Fusarium graminearum is as die patogeen wat hoofsaaklik vir aarskroei in Suid-Afrika verantwoordelik is, geïdentifiseer. Mikotoksien toetse van die F. graminearum isolate het daarop gedui dat ‘n hoër frekwensie isolate ‘n neiging tot DON produksie eerder as NIV produksie toon. Vorige studies het getoon dat individue met die DON genotipe patogenies meer aggressief is as individue met die NIV genotipe. Dit kan dalk die hoë DON frekwensie in die Suid- Afrikaanse aarskroeipopulasie asook die verplasing van ander Fusarium spesies met F. graminearum, veral in die koeler Suid-Afrikaanse koringverbouingsgebiede, verklaar. AFLP (geamplifiseerde fragment lengte polimorfisme) analises is vir die plasing van 793 Suid-Afrikaanse F. graminearum isolate in die filogenetiese groepe, soos beskryf deur O’Donnell en kollegas, gebruik. Die Suid-Afrikaanse F. graminearum isolate het saam met die filogenetiese spesie 7 verwysings isolate gegroepeer, alhoewel vorige studies slegs die teenwoordigheid van filogenetiese spesies 3 en 5 in Suid-Afrika aangetoon het. Betekenisvolle genetiese variasie is in die huidige populasie waargeneem, alhoewel filogenetiese spesie 7 isolate die populasie gedomineer het. Die waargenome genetiese variasie binne individuele populasies was hoër as variasie tussen populasies. Die waargenome genotipiese variasie was ooreenstemmend met verbastering onder natuurlike veldtoestande in Suid-Afrika. Alhoewel ‘n groot aantal klone in die Prieska populasie waargeneem is en díe populasie geïsoleerd voorgekom het, het die lae genetiese variasie tussen die sewe individuele populasies aangedui dat die Suid- Afrikaanse aarskroei F. graminearum isolate weens van die ooreenstemmende alleel frekwensies deel van ‘n groter willekeurige inteelpopulasie vorm. Hierdie resultate stem met die evaluasie van die genetiese struktuur van aarskroeipopulasies in ander dele van die wêreld ooreen. Inligting ingewin rakende die genetiese struktuur van die Suid- Afrikaanse aarskroeipopulasie kan moontlik gebruik word om effektiewe beheermaatreëls teen aarkroei te ontwikkel. Vir weerstand teen aarskroei kan byvoorbeeld weerstandsbronne uit ander filogenetiese spesie 7 gebiede gebruik word. Hierdie moontlike verbetering asook ontwikkeling van bestaande (fungisiede) en nuwe (weerstandsteling) beheermaatreëls teen aarskroei sal dit dan vir Suid-Afrikaanse koringboere die moeite werd maak om meer koring te plant en sodoende koringproduksie in Suid-Afrika verbeter.af
dc.description.sponsorshipNational Research Foundation (NRF)en_ZA
dc.description.sponsorshipGrow Our Own Timber Programme (GOOT)en_ZA
dc.description.sponsorshipUniversity of the Free State (UFS)en_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectThesis (Ph.D. (Plant Breeding/Plant Pathology))--University of the Free State, 2011en_ZA
dc.subjectWheat -- Diseases and pests -- South Africaen_ZA
dc.subjectWheat fusarium culmorum head blight -- South Africa -- Geneticsen_ZA
dc.subjectWheat scaben_ZA
dc.subjectMycotoxinsen_ZA
dc.subjectIrrigationen_ZA
dc.subjectGenetic variationen_ZA
dc.subjectFusarium graminearumen_ZA
dc.subjectDeoxinivalenol (DON)en_ZA
dc.subjectAmplified fragment length polymorphism (AFLP)en_ZA
dc.subjectWheat fusarium culmorum head blight -- South Africaen_ZA
dc.titlePopulation dynamics of fusarium head blight causing species in South Africaen_ZA
dc.typeThesisen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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