Characterisation of both Hoodia gordonii and the associating wilt causing pathogen Fusarium oxysporum
| dc.contributor.advisor | Van Biljon, A. | |
| dc.contributor.advisor | Minnaar-Ontong, A. | |
| dc.contributor.advisor | Swart, W. J. | |
| dc.contributor.author | Philippou, Onoufrios Agathoclis | |
| dc.date.accessioned | 2015-11-10T12:50:55Z | |
| dc.date.available | 2015-11-10T12:50:55Z | |
| dc.date.copyright | 2014-01 | |
| dc.date.issued | 2014-01 | |
| dc.date.submitted | 2014-01 | |
| dc.description.abstract | English: Hoodia gordonii has been used by the San people for centuries as an appetite suppressant while they were on long hunting trips. These succulents are globally known as an important component in diet supplements and products which assist in weight-loss. Together with other plants these contribute towards a multimillion US dollar market, as many pharmaceutical and nutritional companies have made significant financial investments in the research and development for people who suffer from weight problems and obesity. In South Africa, H. gordonii is classified as being endangered, because so many pharmaceutical companies cashed-in on the dietary characteristics of these succulents. The plant is found in the South Western parts of Southern Africa mainly in the Karoo, Kalahari and Namib deserts. Plants were also grown in cultivated nurseries under favourable conditions for commercial use. However, diseases have dramatically hampered production in nurseries with almost total loss of crop. Although not many diseases have been documented on this plant, Fusarium wilt, a devastating fungal disease of H. gordonii, caused by F. oxysporum had been identified. This disease is not only responsible for economic losses, but also contaminates the soils with spores, which remain dormant until the next season as inoculum. This study concentrated on the morphological characterisation and molecular identification of the Fusarium wilt causing pathogen present in four areas (Kakamas, Klein Pella, Pofadder and Prieska) as well as the morphological evaluation of the host. Fusarium oxysporum was identified as the causal agent of Fusarium wilt on H.gordonii plants. The AFLP analysis and DNA sequences resulted in two distinct groups. Those that clustered in the AFLP cluster B were also grouped in a TEF cluster B, however some isolates from AFLP cluster A also grouped together with the TEF cluster B. The low genetic variation revealed by the AFLP analysis indicated that differences amongst the pathogen isolates occur, but the DNA sequences confirmed that these isolates share a common ancestor. DNA sequencing analysis was used to place 44 South African F. oxysporum isolates into the phylogenetic groups as described by O’Donnell and associates. South African F. oxysporum isolates clustered into two groups. The observed genetic variation amongst individual isolates was lower than the genetic variation between out-group isolates. Two clusters were identified; within each cluster isolates had a relatively high frequency of clones. These clones confirm that these pathogen isolates share similar allele frequencies. Results from sequencing data showed that the isolates fall within the FOSC, however there was no isolates identified that show 100% similarities when compared with all three genes sequences with recorded genetic sequences of F. oxysporum isolates in other parts of the world. Therefore, based on the current taxonomic system, of host specificity the fungus only infects H. gordonii, so the study has proved that a possible new formae specialis has been identified. New preventative measures must be applied to the host when planting in nurseries. Knowledge gained from analyses of the genetic fingerprinting, DNA sequencing of these isolates and the mporphological evaluation of the host might assist with the development of effective control strategies, i.e. resistance breeding against Fusarium wilt. This will provide an incentive to potential farmers to plant H. gordonii, thus improving production of this succulent for pharmaceutical companies and nurseries in South Africa. | en_ZA |
| dc.description.abstract | Afrikaans: Hoodia gordonii is al vir eeue deur die San as eetlus-demper op hul lang jagtogte gebruik. Hierdie vetplant is wêreldwyd bekend as ‘n belangrike komponent in dieet- aanvullings en produkte wat met gewigsverlies help. Saam met ander plante dra dit by tot ‘n multimiljoen Amerikaanse dollar mark, deurdat baie farmaseutiese en voedingsmaatskappye betekenisvolle finansiële beleggings in navorsing en ontwikkeling maak, vir oorgewig- en mense wie aan vetsug ly. In Suid-Afrika word H. gordonii as ‘n bedreigde spesie geklassifiseer, omdat so baie farmaseutiese maatskappye probeer muntslaan uit die waardevolle voedingseienskap van hierdie vetplant. Die plant word in die Suidwestelike gedeelte van Suid-Afrika gevind hoofsaaklik in die Karoo, Kalahari en Namib-woestyn. Plante was ook onder gunstige toestande vir kommersiële gebruik, in kwekerye aangeplant. Siektes het die produksie so drasties belemmer dat aanplantings omtrent uitgewis is, alhoewel nie baie siektes vir die gewas aangeteken is nie. Fusarium verwelksiekte is ‘n vernietigende swamsiekte wat deur F. oxysporum veroorsaak word en op H. gordonii geïdentifiseer is. Hierdie siekte is nie net verantwoordelik vir ekonomiese verliese nie, maar besoedel die grond met spore wat in ‘n dormante toestand agterbly en die volgende groeiseisoen as innokulum dien. In hierdie studie is klem op die morfologiese karakterisering en molekulêre identifikasie van die fungus verantwoordelik vir Fusarium verwelksiekte uit vier gebiede (Kakamas, Klein Pella, Pofadder en Prieska) asook die morfologiese evaluasie van die gasheerplant, gelê. Fusarium oxysporum was geïdentifiseer as die patogeen wat wat hoofsaaklik vir Fusarium verwelksiekte op H. gordonii verantwoordelik is. Resultate van die AFLP (geamplifiseerde fragment lengte polimorfisme) analises en DNS volgorde bepalings toon dat die patogeen isolate in twee definitiewe groepe verdeel. Die groepe wat in die AFLP kluster B gegroepeer het is ook in die TEF kluster B aangetref, alhoewel sommige isolate van die AFLP kluster A ook saam in die TEF kluster B voorgekom het. Die lae genetiese variasie wat deur die AFLP analysis aangetoon word, dui daarop dat verskille tussen die isolate wel voorkom, maar ook dat die isolate ‘n gemeenskaplike voorouer deel. Volgorde bepalings-analises is gebruik om 44 Suid-Afrikaanse F. oxysporum isolate in philogenetise groepe, soos beskryf deur O’Donnell en medewerkers, te verdeel. Suid-Afrikaanse isolate groepeer in twee filogenetiese groepe. Die waargenome genetiese variasie binne individuele isolate was laer as die genetiese variasie tussen buite-groepe isolate. Twee groepe is geïdentifiseer en binne elke groep was daar ‘n relatiewe hoë frekwensie van klone. Die klone bevestig weer dat hierdie isolate ooreenstemmende alleel frekwensies deel. Resultate van die DNS volgorde bepalings data dui aan dat die isolate binne die FOSC groepeer. Alhoewel daar 100% ooreenstemming tussen isolate in die drie geen- volgordes voorgekom het, het dit goed vergelyk met aangetekende DNS volgordes van F. oxysporum isolate uit ander dele van die wêreld. Gebasseer op die huidige taksonomiese sisteem van die spesifike gasheerplant is gevind dat die swam net H. gordonii affekteer, dus het die studie heel moontlik ‘n nuwe formae specialis geïdentifiseer. Nuwe voorsorgmaatreëls moet op die gasheerplant toegepas word wanneer daar in ‘n kwekery geplant word. Die inligting/kennis wat deur die genetiese- analises, DNS volgordebepaling van die isolate en morfologiese evaluasie van die gasheerplant ingewin is mag help met die ontwikkeling van beheer-strategieë vir weerstandsteling teen Fusarium verwelksiekte. Dit sal aan potensiële boere die voordeel gee om die verbeterde H. gordonii aan te plant en sodoende produksie verhoog vir die farmaseutiese mark en vir kwekerye in Suid-Afrika. | af |
| dc.description.sponsorship | National Research Foundation (NRF) | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11660/1587 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Thesis (Ph.D. (Plant Pathology))--University of the Free State, 2014 | en_ZA |
| dc.subject | Hoodia | en_ZA |
| dc.subject | Hoodia -- Diseases and pests | en_ZA |
| dc.subject | Fungal diseases of plants | en_ZA |
| dc.subject | Medicinal plants | en_ZA |
| dc.subject | Ascomycetes | en_ZA |
| dc.subject | Fusarium diseases of plants | en_ZA |
| dc.subject | Appetite depressants | en_ZA |
| dc.subject | Morphological characterization | en_ZA |
| dc.subject | P57 components | en_ZA |
| dc.subject | Genetic variation | en_ZA |
| dc.subject | Soil-borne pathogene | en_ZA |
| dc.subject | DNA fingerprinting | en_ZA |
| dc.subject | Pathogenisity | en_ZA |
| dc.subject | Fusarium wilt | en_ZA |
| dc.title | Characterisation of both Hoodia gordonii and the associating wilt causing pathogen Fusarium oxysporum | en_ZA |
| dc.type | Thesis | en_ZA |