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dc.contributor.advisorWingfield, M. J.
dc.contributor.advisorCoutinho, T. A.
dc.contributor.advisorWingfield, B. D.
dc.contributor.authorSlippers, Bernard
dc.date.accessioned2017-04-24T09:43:37Z
dc.date.available2017-04-24T09:43:37Z
dc.date.issued1998-12
dc.identifier.urihttp://hdl.handle.net/11660/6137
dc.description.abstractEnglish: In Chapter 1 of this thesis, the literature pertaining to the symbiosis between Sirex noctilio and Amy/ostereum areo/atum in the Southern Hemisphere, is reviewed. It is evident from this review that S. noctilio and A. areo/atum have become established throughout the pine growing regions of the Southern Hemisphere, despite measures to prevent its introduction. Unlike its relative unimportance as a pathogen in the Northern Hemisphere, this fungal-insect complex has resulted in great losses to softwood industries during a number of severe outbreaks in the Southern Hemisphere. The use of biological control agents in combination with preventative silvicultural practices, has been shown to be very effective in controlling Sirex in Australasia. It is, however, also evident from this review that despite the rather large collection of knowledge concerning the wasp and its control, information regarding the population structure and phylogenetic relationships of the fungal symbiont of Sirex, is scarce. The recent introduction of S. noctilio into South Africa and its confinement to a rather small area in this country provided the opportunity to study the population of its fungal symbiont in detail. Results from Chapter 2 suggest that the fungus has a very narrow genetic base in South Africa and that the introduction of Sirex into this country was limited. The genetic base of A. areolatum in Brazil and Uruguay is similarly uniform. Of even greater interest is the fact that South Africa and Brazil share a common vegetative compatibility group and, thus, a common origin of A. areo/atum and S. noctilio. Moreover, field isolates from the Southern Hemisphere appear to be closely related, which indicates that Sirex might have spread among countries of the Southern Hemisphere and were not necessarily new introductions from the Northern Hemisphere. Isolates of the fungus associated with the biocontrol nematode, De/adenus siricidicola, are, however, distinct from isolates from other Southern Hemisphere populations of the fungus. This could negatively influence the efficacy of the nematode as biocontrol agent in countries to which the nematode has been distributed. Boidin and Lanquetin (1984) report triangular mating incompatibility between isolates from the different Amy/ostereum spp. Results of Chapter 3 support their conclusions by clearly showing that A. areolatum is more distantly related to A. chailletii, A. laevigatum and A. ferreum, than these three species are to each other. The relationship between the latter three species is, however, more clearly defined in Chapter 3 where it is shown that A. ferreum and A. laevigatum are most closely related to each other. One isolate collected from Sirex areolatus, and, therefore, expected to be A. chailletii, was most closely related to A. laevigatum and A. ferreum. Neither of the latter species has, however, been implicated in associations with woodwasps. Furthermore, the data from this study show that Amylostereum spp. group with neither Stereum nor Peniophora, as has been previously hypothesised, but rather with Echinodontium tinctorium. This grouping was included in a larger clade that included species of Russula, Heterobasidion, Lentinellus and Auriscalpium. Analysis of DNA sequence data derived from the nuc-IGS-rDNA in Chapter 4 supported the phylogenetic relationships of the Amylostereum spp. inferred in Chapter 3. Similarly, the isolate obtained from S. areolatus, did not group with any of the four species of Amylostereum and might represent a new species or a distinct group in of one of the current species. Isolates of A. areolatum associated with both S. noctilio and S. juvencus contained four heterogenic sequences in the DNA region analysed. These heterogenic sequences were contained in each isolate of the fungus in one of five combinations. Neither the heterogenic sequences included in the fungal isolates, nor the different combinations of these sequences, separated the populations of A. areolatum associated with different wasp species. Despite the heterogenic nature of this DNA region in some isolates, RFLP analysis was used effectively to distinguish between the different species of Amylostereum. The work presented in this thesis represents the first molecular. view of the phylogeny of the genus Amylostereum, as well as that of some of the Amylostereum spp. associated with woodwasp species. It is clear from Chapter 5 that these findings now provide a powerful tool to give a clearer picture of the taxonomy and evolution of these fungi, as well the ecology of their symbiosis with woodwasps. The study of the genetic structure of the fungal populations associated with woodwasps also gives new insight into the geographical origin and history of both the insects and their associated fungi.en_ZA
dc.description.abstractAfrikaans: In Hoofstuk 1 word 'n oorsig gegee van die literatuur aangaande die simbiose tussen Amylostereum areolatum en Sirex noctilio. Uit hierdie oorsig blyk dit dat S. noctilio en A. areolatum deeglik gevestig is in dié areas van die suidelike halfrond met kommersiële denneplantasies, ten spyte van pogings om dit te verhoed. In die noordelike halfrond het hierdie wesp/swamkompleks min ekonomiese invloed, maar in die suidelike halfrond was dit verantwoordelik vir groot finansiële verliese vir dennehout-industrieë. 'n Kombinasie van biologiese beheermaatreëls en voorkomende beheer deur deeglike bosboupraktyke is egter effektief in die bekamping van Sirex in Australasië. Verder is dit duidelik uit die oorsig dat, ten spyte van die groot databasis oor die wespe en sy beheer, min inligting beskikbaar is oor die populasiestruktuur en filogenetiese verwantskappe van die simbiont van Sirex. Die onlangse aankoms van S. noctilio. in Suid Afrika en die redelik beperkte verspreiding van die pes in die land, bied 'n geleenthied om die populasiestuktuur van die swam-simbiont deeglik te bestudeer. Die resultate in hoofstuk 2 toon aan dat die genetiese basis van A. areofatum in Suid Afrika baie klein is en dat S. noctilio die land dus in 'n beperkte getal binnegekom het. Net so het die swam ook 'n klein genetiese basis in Brasilië en Uruguay. Van meer belang is dat die isolate van die swam van Suid Afrika and Suid Amerika een vegetatiewe verenigbare groep vorm en dus 'n oorsprong van beide A. areolatum en S. noctilio het. Verder blyk die isolate van die suidelike halfrond naby verwant te wees aan mekaar Dit beteken dat die beweging van Sirex na nuwe areas in die suidelike halfrond moontlik tussen die lande van die halfrond is en nie noodwendig nuwe aankomelinge van die noordelike halfrond nie. Isolate van die swam, afkomstig van kulture van die nematode (Deladenus siricidicola) wat gebruik word in biologiese beheer, was egter geneties baie verskillend van die isolate van ander suidelike halfrond lande. Dit kan die effektiwiteit van die nematode as biologiese beheeragent beïnvloed, sowel as die populasies van die swam in lande waar die nematode bekend gestel is. Die resultate in hoofstuk 3 toon duidelik dat A. areolatum minder verwant is aan A. chailletii, A. laevigatum en A. ferreum, as wat die laasgenoemde drie spesies aan mekaar is. Van hierdie laaste drie spesies is A. laevigatum en A. ferreum die naaste verwant. Die verwagting was dat een isolaat wat afkomstig is van S. areolatus saam met ander isolate van A. chailletii sou groepeer. Dit het egter saam met A. laevigatum en A. ferreum gegroepeer, alhoewel nie een van die laasgenoemde spesies al ooit in simbiose met wespes gevind is nie. Verder het die studie getoon dat Amylostereum spesies die naaste verwant is aan Echinodontium tinctorium van al die spesies wat by die analise ingesluit is, en nie aan Peniophora of Stereum, soos wat vroeër voorgestel is nie. Hierdie groepering was ingesluit in 'n groter groepering wat ook spesies van Russuia, Heterobasidion, Lentinellus and Auriscalpium ingesluit het. Basisopeenvoling analise van die nukluêre intergeen spasiëring van die ribosomale DNS kompleks (nuk-IGS-rDNS) in hoofstuk 4, ondersteun die bevindings in hoofstuk 3 aangaande die filogenetiese verwantskappe van die Amylostereum spesies. Die isolaat afkomstig van S. areolatus het apart van die bestaande Amylostereum spesies gegroepeer en verteenwoordig moontlik 'n nuwe spesie of 'n afsonderlike groep binne een van die spesies. Vier heterogeniese DNS basisopeenvolgings is geidentifiseer vir die nuk-IGS-rDNS gebied in isolate van A. areolatum afkomstig van beide S. noctilio en S. juvencus. Hierdie heterogeniese opeenvolgings het in een van vyf kombinasies voorgekom in elke isolaat. Nie die heterogeniese opeenvolgings, of die verskillende kombinasies daarvan kon egter die populasies van die swam skei volgens hul assosiasie met die verskillende wesp spesies nie. Desnieteenstaande hierdie variasie, kon die verskillende Amylostereum spesies suksesvolonderskei word met beperkingsfragment lengte-polimorfisme (RFLP) analise van die DNS gebied. Die resultate van hierdie tesis verteenwoordig die eerste molekulêre analise van die genus Amylostereum, sowel as die filogenie en taksonomie van sekere Amylostereum spesies geassosieer met wespes. Uit hoofstuk 5 is dit duidelik dat hierdie ontwikkelinge nou 'n kragtige tegniek bied wat 'n duideliker beeld kan gee aangaande die taksonomie en evolusie van hierdie swamme, asook die ekologie van hul simbiose met wespes. Verder gee die bestudering van die genetiese stuktuur van die swampopulasies, geassosieer met wespes, nuwe insig oor die geografiese oorsprong en geskiedenis van beide die swam en die insek.af
dc.description.sponsorshipFoundation for Research Development (FRD)en_ZA
dc.description.sponsorshipDepartment of Microbiology and Biochemistry, University of the Orange Free Stateen_ZA
dc.description.sponsorshipTPCPen_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectInsect-plant relationships -- South Africaen_ZA
dc.subjectWood-decaying fungi -- South Africaen_ZA
dc.subjectPine -- Diseases and pests -- South Africaen_ZA
dc.subjectSiricidaeen_ZA
dc.subjectBasidiomycetesen_ZA
dc.subjectDissertation (M.Sc. (Microbiology and Biochemistry))--University of the Free State, 1998en_ZA
dc.titleThe Amylostereum symbiont of Sirex noctilio in South Africaen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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