A study of the taxonomy and pathogenicity of microfungi in the roots of Waikato pasture plants
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
A diverse and characteristic mycoflora was obtained from Waikato pasture plant root tissues. In general these fungi were not specific to host, site or soil type and although forming a natural ecological group were diverse in their systematic affinities. The fungi examined were dominated by hyphomycete and zygomycete genera, sterile fungi and coelomycetous pycnidial fungi. The sterile dark and hyaline sterile fungi isolated comprised almost 40% of isolates and a variety of methods were utilised to induce sporulation as well as separate this assemblage of amorphous isolates into 15 taxonomic groups on the basis of their morphological and physiological characters. Two sterile groups were induced to sporulate in culture and were identified as Thozetella tocklaiensis and a species of Phialophora. Most fungal species including the sterile fungi were tested for pathogenicity to pasture species and found to be non-pathogenic root-colonising fungi, however, a minority of fungi present in Waikato pastures were pathogenic to both grass and legume seedlings and plants. Pathogenicity of these fungi was demonstrated by a series of laboratory and pot experiments where seed emergence, plant dry weight yield and root growth were reduced, while disease symptoms and root death were increased compared to the controls and those inoculated with non-pathogenic fungi. Pot trials also demonstrated that temperature and moisture could affect the pathogenicity of pasture root pathogens. The potential importance of fungi in a pastoral agricultural ecosystem is discussed.