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Studies of breeding relationships are integrated with the nomenclature of Agrocybe praecox. Type studies of potential synonyms are presented. Nomenclatorial and type studies indicate that Agrocybe molesta has been confused with A. praecox sensu lato. New field and microscopic characteristics are introduced which differentiate between A. molesta and the A. praecox group. A. molesta is redescribed to reduce confusion and a neotype is designated for this taxon. Four sibling species of Agrocybe praecox are identified and neotypes designated for A. praecox and A. gibberosa. A new species, Agrocybe montanus is described. / M.S.

Thesis (MSc)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: It is known that many hyphomycetous fungi are dispersed by wind, water and insects. However, very little is known about how these fungi may differ from each other regarding their ability to be disseminated by different environmental vectors. Consequently, to obtain an indication of the primary means of spore dispersal employed by representatives of the genera Acremonium, Aspergillus and Penicillium, isolated from soil and indoor environments, we monitored spore liberation of cultures representing these genera in an airflow cell. The experimental data obtained, of plate counts conducted of the air at the outlet of the airflow cell, were subjected to an appropriate analysis of variance (ANOVA), using SAS statistical software. Intraspecific differences occurred regarding aerial spore release. Under humid conditions, however, Penicillium species were more successful in releasing their spores than Aspergillus and the Acremonium strain. Under desiccated conditions the Aspergillus took longer to release their spores than representatives of Acremonium and Penicillium. The taxa that were investigated did not differ from each other regarding the release of spores in physiological salt solution (PSS). Although not proven, indications are that water may act as an important dispersion agent for these fungi, because washing of cultures with PSS resulted in all cases in an immediate massive release of colony forming units. Subsequently, using standard plate count techniques, conidial adhesion of the fungi mentioned above to synthetic membranes, leaf cuttings and insect exoskeletons differing in hydrophobicity and electrostatic charge were investigated. We found that the different genera showed different adhesion profiles for the series of test surfaces, indicating differences in physico-chemical characteristics of the fungal spore surfaces. In general, the Penicillium strains showed a greater ability to adhere to the test surfaces, than the aspergilli, while the representative of Acremonium showed the least adherence. No significant difference in the percentage spore adhesion was found between hydrophobic and hydrophilic materials. Furthermore, evidence was uncovered supporting the contention that, under dry conditions, electrostatic surface charges play a role in the adherence of fungal spores to surfaces, because adherence was positively correlated (Correlation coefficient = 0.70898, p = 0.001) to positive electrostatic charges on the lamellar surfaces. In the next part of the study, standard plate count methods were used to determine the relative adhesion of the above mentioned hyphomycetous fungi, as well as a polyphyletic group of yeasts, to the test surfaces submerged in 10 mM sodium phosphate buffer (pH 7.0). As was found with the experiments with the dry surfaces, both intraspecific and intergenus differences were uncovered. Overall, the fungi adhered better to hydrophilic surfaces than to hydrophobic surfaces. This indicated that the fungal surfaces were covered with relatively hydrophilic compounds such as carbohydrates. Subsequently, it was demonstrated that all the fungi adhered to plasma membrane glycoprotein coated polystyrene and the presence of fungal carbohydrates on the surfaces of the fungal propagules was confirmed using epi-fluorescence microscopy. Differences in the strategy of the fungal genera to release their airborne spores, as well as differences in their adhesion profiles for the series of test materials, may be indicative of a unique environmental niche for each genus. In future, this phenomenon should be investigated further. / AFRIKAANSE OPSOMMING: Hifomisete fungi is daarvoor bekend om te versprei deur middel van wind, water, en insek vektore. Maar nietemin, daar is bykans geen kennis m.b.t. hoe hierdie fungi van mekaar verskil t.o.v. hul vermoë om versprei te word deur omgewings vektore nie. Gevolglik was spoorvrystelling van kulture, verteenwoordigend van die genera Acremonium, Aspergillus en Penicillium gemoniteer om ‘n aanduiding te kry van primêre wyse van spoorverspreiding waardeur verteenwoordigers van die onderskeie genera ingespan word. Eksperimentele data ingewin, vanaf plaat tellings wat uitgevoer was op lug afkomstig vanuit die uitlaat-klep van die lugvloei kapsule, was onderwerp aan ‘n toepaslike analise van afwyking (ANOVA), deur gebruik te maak van ‘n SAS statistiese pakket. Intraspesie verskille is waargeneem t.o.v. lug spoorvrystelling. Desnieteenstaande was Penicillium meer suksesvol onder vogtige kondisies t.o.v. spoorvrystelling in vergelyking met Aspergillus en die Acremonium stam. Onder droë kondisies het verteenwoordigers van Aspergillus langer geneem om hul spore vry te stel as verteenwoordigers van onderskeidelik, Penicillium en Acremonium. Geen verskille was waargeneem m.b.t. spoorvrystelling in fisiologiese soutoplossing (FSO) tussen die verskillende filogenetiese stamme nie. Alhoewel dit nie bewys is nie, wil dit voorkom asof water as belangrike verspreidingsagent van die betrokke fungi dien, aangesien die spoel van kulture met FSO tot ‘n oombliklike enorme vrystelling van kolonie-vormende eenhede gelei het. Gevolglik, deur gebruik te maak van standaard plaattellings tegnieke, was spoor aanhegting van bogenoemde fungi aan sintetiese membrane, blaar snitte en insek eksoskelette wat verskil in terme van hidrofobisiteit en elektriese lading, ondersoek. Daar was gevind dat die aanhegtingsprofiele m.b.t. hierdie reeks toetsoppervlaktes van die verskillende genera verskil, wat op sigself ‘n aanduiding was van verskille in fisieschemiese eienskappe van die swamspoor oppervlaktes. Penicillium stamme het ‘n hoër aanhegtings vermoë aan die toetsoppervlaktes getoon as die aspergilli, terwyl die verteenwoordiger van Acremonium die laagste aanhegting getoon het. Geen betekenisvolle verskille i.t.v. persentasie spoor aanhegting was gevind tussen hidrofobiese en hidrofiliese oppervlakte nie. Daarbenewens was die argument dat spoorvrystelling onder droë kondisies beïnvloed word deur elektrostatiese oppervlak ladings, bevestig deur ons bevindinge, want aanhegting het positief gekoreleer (Korrelasie koëffisient = 0.70898, p = 0.001) met positiewe ladings op die oppervlaktes. ‘n Standaard plaattellingstegniek was aangewend in die volgende fasset van die studie om die relatiewe aanhegting van bogenoemde hifomisete fungi, sowel as ‘n polifilitiese groep giste aan die toetsoppervlaktes, gedompel in 10 mM natrium fosfaat buffer (pH 7.0) vas te stel. Intraspesie en intragenus verskille was weereens waargeneem, net soos in die geval van die eksperimente met die droë oppervlakte. In die algemeen het die swamme baie beter geheg aan hidrofiliese oppervlaktes in vergelyking met hidrofobiese oppervlakte. Dit was ‘n aanduiding dat die swamspoor oppervlaktes bedek was met relatiewe hidrofiliese verbindings bv. koolhidrate. Verder was daar bewys dat alle swamme ingesluit in hierdie studie die vermoë het om plasmamembraan glikoproteïn bedekte polistireen te bind, en gevolglik was die teenwoordigheid van van koolhidrate op die swamspore bevestig m.b.v epi-fluoresensie mikroskopie. Verskille in die strategie van swamme om spore in die lug vry te stel, sowel as verskille in die aanhegtingsprofiele vir ‘n reeks toetsmateriale, mag net ‘n aanduiding wees van ‘n unieke omgewings nis vir elke genus wat in hierdie studie ondersoek is. Hierdie verskynsel moet dus in die nabye toekoms nagevors word.

Thesis (MScAgric)--Stellenbosch University, 1998. / ENGLISH ABSTRACT: Eyespot is an important disease of spring wheat (Triticum aestivum L.). Four species of Ramulispora are associated with this disease, of which Tapesia yallundae and T. acuformis. are common. This thesis investigates the broader subjects of genetic variability, reproductive dynamics and fungicide resistance in Tapesia yallundae. Each of the chapters treats specific but related topics. T. yallundae, which is the only species thus far reported from South Africa, has been associated with yield losses of up to 50%. To enable the implementation of more accurate and effective control measures, understanding the dynamics of reproduction and the genetics of the pathogen is of utmost importance. Of the many plant disease control measures such as cultural practices, sanitation, biological control, etc., fungicide application is the most commonly resorted to measure in eyespot control. This thesis investigates the broader subjects of genetic variability, reproductive dynamics and fungicide resistance of Tapesia yallzll7dae. Fungicide application, however, is not without problems. The pathogen can build up resistance to fungicides. The most commonly used fungicides in eyespot control include the benzimidazole carbendazim, triazoles such as flusilazole, tebuconazole, propiconazole, bromuconazole, flutriafol, fenbuconazole, triademinol, and the imidazole, prochloraz. Cases of resistance to the groups listed above have been reported. Frequent monitoring for resistance is thus crucial to prevent wastage of fungicide and unnecessary impregnantation of the environment with potentially ineffective chemicals. In chapter 2 of this thesis 300 isolates of T. yallundae from 15 fields were evaluated for resistance against carbendazim, flusilazole, tebuconazole, propiconazole, bromuconazole, flutriafol and fenbuconazole. These results indicated that to some triazoles, such as fenbuconazole, a high level of resistance was already present in field populations. In a sexually reproducing fungus such as T. yallundae, knowledge pertaining to its ability to pass resistance factors to offspring is equally important. Mating studies were, therefore, also conducted with parental strains that showed signs of triazole resistance. Three generations were subsequently tested for resistance to five triazoles, namely flusilazole, tebuconazole, propiconazole, bromuconazole and flutriafol. Results of this study showed variable sensitivity in progeny, which indicated quantitative inheritance of resistance to triazoles. Although the sexual stage has not yet been observed in the field in South Africa, this knowledge lays the foundation for the long-term understanding of the population dynamics of the fungus. The ability of a heterothallic ascomycete population to reproduce sexually is dependent on the availability of its two mating types, MATI-I and MATI-2, their distribution, and female fertility amongst other factors. In the UK. the teleomorph is commonly observed in the field, which is in contrast to the situation in South Africa, where it has only been induced in the laboratory. A comparative study between the South African and the UK. populations was therefore undertaken. Isolates representative of the two populations were mated with tester strains as both sperm recipients and as sperm donors. This allowed the percentage of hermaphrodites to be determined. No difference in terms of female fertility was observed between the South African and the UK. populations, with both populations showing low effective population numbers. These data suggested, therefore, that the teleomorph would also occur more frequently in South Africa if the climate was more indusive to its development. The overall results of this study indicated that eyes pot could still be controlled by means of fungicide application in South Africa. Although a shift in sensitivity was observed towards fenbuconazole and flusilazole, no resistance was detected towards carbendazim. The latter might be due to the absen<.:eof the sexual stage in the field, coupled by the monocyclic nature of the pathogen and sensible fungicide regimes. The absence of T. acujormis makes the disease situation less complicated in terms of fungicide application and management. Continuous surveys will have to be conducted, however, to monitor this situation in future. / AFRIKAANSE OPSOMMING: Hierdie studie ondersoek die genetiese variasie, reproduksie dinamika en fungisied weerstand in Tapesia yallundae. Elke hoofstuk handel oor spesifieke maar verwante onderwerpe. Oogvlek is 'n belangrike siekte van lentekoring (Triticum aestivum L.). Vier spesies van Ramulispora word geassosieer met die siekte, waarvan Tapesia yallundae en T. acuformis mees algemeen voorkom. T. yallundae, wat tans die enigste spesie is wat in Suid-Afrika aangeteken is, het al verliese van tot 50% veroorsaak. Om meer akkurate en effektiewe beheermaatreels te implementeer, is dit noodsaaklik om die oorlewingsdinamika van die patogeen te verstaan. Van al die siektebeheermaatreels soos kulturele praktyke, sanitasie, biologiese beheer ens., bly fungisiedbehandeling die mees algemene maatreel vir die beheer van oogvlek. Fungisiedtoediening het egter ook verskeie probleme. Die patogeen kan weerstand opbou teen die fungisied. Die mees algemene fungisiedes wat vir oogvlekbeheer aangewend word sluit onder meer die benzimidasool karbendazim in, triasole soos flusilasool, tebukonasool, propikonasool, bromukonasool, flutriafol, fenbukonasool, triadimenol, en die imidasool, prochloraz. Weerstand is egter reeds teen hierdie middels bekend. Gedurige monitering vir weerstand is dus krities om die vermorsing van fungisied en besoedeling van die omgewing met oneffektiewe middels te beperk. In hoofstuk 2 van hierdie manuskrip word 300 isolate van T. yallundae van 15 lande geevalueer vir weerstand teenoor karbendazim, flusilasool, tebukonasool, propikonasool, bromukonasool, flutriafol en fenbukonasool. Resultate dui daarop dat teen sommige van hierdie triasole, soos bv. fenbukonasool, daar reeds 'n hoe vlak van weerstand teenwoordig was in veldpopulasies. In 'n seksueel reproduserende fungus soos T. yalluJ1dae, is dit noodsaaklik om te bepaal wat sy vermoe is om weerstandbiedenheid aan die nageslag oor te dra. Om die rede is paringstudies ook op ouers wat tekens van weerstand teenoor triasole getoon het uitgevoer. Drie generasies was gevolglik getoets vir weerstand teenoor vyf triasole, naamlik flusilasool, tebuconasool, propikonasool, brumukonasool en flutriafol. Resultate van die studie het 'n variasie in sensitiwiteit van die nageslag getoon, wat op 'n kwantitatiewe oorerwing van weerstand teen £riasole dui. Alhoewel die teleomorf nog nie in lande in Suid-Afrika opgemerk is nie, Ie hierdie kennis die fondament vir die langtermyn vertolking van die populasie dinamika van hierdie fungus. Die vermoe van 'n heterotalliese askomiseet populasie om seksueel voort te plant is afhanklik van die beskikbaarheid van sy twee paringstipes, MATI-I en MATl-2, hul verpreiding, vroulike vrugbaarheid en ander faktore. Alhoewel die teleomorf algemeen in lande in die Verenigde Koninkryk opgemerk word, is dit in kontras met die situasie in Suid-Afrika, waar hierdie stadium nog slegs in die laboratorium gelnduseer kon word. 'n Studie is dus onderneem om die Suid-Afrikaanse en V.K. populasies met mekaar te vergelyk. Isolate van die twee populasies is dus gepaar met paringsisolate as beide sperm ontvangers en sperm donors. Hierdie prosedure het dit moontlik gemaak om die persentasie hermafrodiete te bepaal. Geen verskille in vroulike fertiliteit is tussen die Suid-Afrikaanse en V.K. populasies bespeur nie, en beide populasies het ook 'n lae effektiewe populasie getal getoon. Hierdie data het dus voorgestel dat die teleomorf ook meer algemeen in Suid-Afrika sou voorkom as die klimaat meer geskik was vir teleomorf vormmg. Die resultate van hierdie studie het tot die slotsom gelei dat oogvlek steeds deur fungisiedbehandeling in Suid-Afrika beheer kan word. Alhoewel daar 'n merkbare verskuiwing in sensitiwiteit teenoor fenbukonasool en flusilasool was, was geen weerstand teenoor karbendazim waargeneem nie. Laasgenoemde kan dalk toegeskryf word aan die afwesigheid van die teleomorf in die veld, gekombineer met die monosikliese natuur van die patogeen en gebruik van alternerende fungisiedes. Die afwesigheid van T. acuformis maak die plaaslike siektetoestand minder gekompliseerd in terme van fungisied aanwending en bestuur. Voortdurende opnames sal egter uitgevoer moet word om hierdie situasie ook in die toekoms te monitor.