Browsing by Author "Swart, Lizeth"

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    Pathogens associated with diseases of Protea, Leucospermum and Leucadendron spp.
    (Stellenbosch : Stellenbosch University, 1999-12) Swart, Lizeth; Crous, P. W.; Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology.
    ENGLISH SUMMARY: The manuscript consists of six chapters that represent research on different diseases and records of new diseases of the Proteaceae world-wide. The fungal descriptions presented in this thesis are not effectively published, and will thus be formally published elsewhere in scientific journals. Chapter one is a review that gives a detailed description of the major fungal pathogens of the genera Protea, Leucospermum and Leucadendron, as reported up to 1996. The pathogens are grouped according to the diseases they cause on roots, leaves, stems and flowers, as well as the canker causing fungi. In chapter two, several new fungi occurring on leaves of Pro tea, Leucospermum, Telopea and Brabejum collected from South Africa, Australia or New Zealand are described. The following fungi are described: Cladophialophora proteae, Coniolhyrium nitidae, Coniothyrium proteae, Coniolhyrium leucospermi,Harknessia leucospermi, Septoria prolearum 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. General morphology, symptomatology and phylogenetic analysis based on random amplified polymorphic DNA (RAPD) profiles and DNA sequence of the S.8S rDNA gene and its flanking ITS 1 and ITS2 regions were used. The study provides the first evidence that several distinct Eisinoe spp. are associated with scab disease of Proteaceae. The isolates from Leucospermum, Protea and Banksia represent three distinct species. The isolates from Protea in Zimbabwe represent an additional species. The isolates from Leucadendron, Leucospermum and Serruria in South Africa and Australia, and the isolates from Leucospermum in California and Zimbabwe are representative of the same species. 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 Western Cape province. The aim of the study was to determine if Botryosphaeria proteae was an endophyte of Proteaceae, and is so, how the role of water stress would influence canker development. B. proteae was routinely isolated as an endophyte but was not regarded as a dominant taxon. Inoculation studies were done on non-stressed plants, as well as plants with a leaf water potential of -1.0 MPa (moderately stressed) and -2.0 MPa (severely stressed). From the results of the study it was concluded that Botryosphaeria proteae is primarily an endophyte and can cause leaf necrosis of Protea, and is not a serious stem canker pathogen. A new disease of cultivated Protea in southern Africa, Fusarium wilt, is described in chapter five. The disease is caused by Fusarium oxysporum. It occurs on various Protea cultivars in the North-Western province and in Zimbabwe. Disease symptoms first become visible as necrotic leaves on infected plants. Subsequently, a dark lesion develops from the roots along the stem, usually visible only on one side of the stem. The vascular tissue is discoloured, leading to branch die-back and plant death. Glasshouse trials were conducted to prove Koch's postulates on six Protea cultivars. Forty-five rooted plants of each of six cultivars were inoculated with isolates of F. oxysporum derived 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 Protea plants. 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, confirmed the Pestaloptiopsis sp. as the causal agent of the disease. A description of the fungus is given, and it is compared to other Pestalotiopsis spp. associated with Proteaceae. In conclusion, the present study has shown that several unique species of fungal pathogens 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 some of these pathogens, their host range and distribution needs to be further investigated. Furthermore, much more research needs to be done on the biology, epidemiology and control of the diseases of the Proteaceae.