Pathogens associated with diseases of Protea, Leucospermum and Leucadendron spp.

[摘要] ENGLISH SUMMARY: The manuscript consists of six chapters that represent research on different diseases andrecords of new diseases of the Proteaceae world-wide. The fungal descriptions presentedin this thesis are not effectively published, and will thus be formally published elsewherein scientific journals. Chapter one is a review that gives a detailed description of themajor fungal pathogens of the genera Protea, Leucospermum and Leucadendron, asreported up to 1996. The pathogens are grouped according to the diseases they cause onroots, leaves, stems and flowers, as well as the canker causing fungi.In chapter two, several new fungi occurring on leaves of Pro tea, Leucospermum, Telopeaand Brabejum collected from South Africa, Australia or New Zealand are described. Thefollowing fungi are described: Cladophialophora proteae, Coniolhyrium nitidae,Coniothyrium proteae, Coniolhyrium leucospermi,Harknessia leucospermi, Septoriaprolearum and Mycosphaerella telopeae spp. nov. Furthermore, two Phylloslicla spp.,telopeae and owaniana are also redecribed.The taxonomy of the Eisinoe spp. associated with scab disease of Proteaceae in Australia,California, South Africa and Zimbabwe is elucidated in chapter three. Generalmorphology, symptomatology and phylogenetic analysis based on random amplifiedpolymorphic DNA (RAPD) profiles and DNA sequence of the S.8S rDNA gene and itsflanking ITS 1 and ITS2 regions were used. The study provides the first evidence thatseveral distinct Eisinoe spp. are associated with scab disease of Proteaceae. The isolatesfrom Leucospermum, Protea and Banksia represent three distinct species. The isolatesfrom Protea in Zimbabwe represent an additional species. The isolates fromLeucadendron, Leucospermum and Serruria in South Africa and Australia, and theisolates from Leucospermum in California and Zimbabwe are representative of the samespecies. In chapter four, fungal endophytes occurring in leaves and stems of a species of Protea,Leucospermum and Leucadendron were investigated in three localities in the WesternCape province. The aim of the study was to determine if Botryosphaeria proteae was anendophyte of Proteaceae, and is so, how the role of water stress would influence cankerdevelopment. B. proteae was routinely isolated as an endophyte but was not regarded asa dominant taxon. Inoculation studies were done on non-stressed plants, as well as plantswith a leaf water potential of -1.0 MPa (moderately stressed) and -2.0 MPa (severelystressed). From the results of the study it was concluded that Botryosphaeria proteae isprimarily an endophyte and can cause leaf necrosis of Protea, and is not a serious stemcanker pathogen.A new disease of cultivated Protea in southern Africa, Fusarium wilt, is described inchapter five. The disease is caused by Fusarium oxysporum. It occurs on various Proteacultivars in the North-Western province and in Zimbabwe. Disease symptoms firstbecome visible as necrotic leaves on infected plants. Subsequently, a dark lesiondevelops from the roots along the stem, usually visible only on one side of the stem. Thevascular tissue is discoloured, leading to branch die-back and plant death. Glasshousetrials were conducted to prove Koch's postulates on six Protea cultivars. Forty-fiverooted plants of each of six cultivars were inoculated with isolates of F. oxysporumderived from the same cultivar. Disease symptoms similar to those occurring in the field,developed 6 weeks after inoculation. This is the first record of Fusarium wilt on Proteaplants.In chapter six, Pestalotiopsis leaf spot disease of Proteaceae in Zimbabwe is described.Pestaloptiopsis Steyart causes necrotic leaf spots in Leucospermum R. Br. and Protea L.species in Zimbabwe. Inoculation studies conducted to prove pathogenicity, confirmedthe Pestaloptiopsis sp. as the causal agent of the disease. A description of the fungus isgiven, and it is compared to other Pestalotiopsis spp. associated with Proteaceae.In conclusion, the present study has shown that several unique species of fungalpathogens are associated with the Proteaceae. Several of these have proven to be new to science, and are described in this thesis. It is clear, however, that the taxonomy of someof these pathogens, their host range and distribution needs to be further investigated.Furthermore, much more research needs to be done on the biology, epidemiology andcontrol of the diseases of the Proteaceae.

[发布机构] Stellenbosch University