Lifecycle, Biology and Diversity of Puccinia Boroniae in Western Australia

The rust fungi (Uredinales, Basidiomycota) are an expansive and diverse group of fungal species, consisting of approximately 7000 different species in over 160 different genera. Fungi of the genus Puccinia represent a large proportion of these rust fungi, many species of which are well known for their role in causing massive yield and subsequent economic losses in agricultural crops worldwide. Puccinia boroniae is one such rust fungus and is a significant pathogen of several species of Boronia (Rutaceae), a native Australian wildflower grown commercially in Western Australia as a cutflower. Complete control of the rust pathogen is rarely achieved using chemical fungicides. Improving the level of disease control is vital for the long-term sustainability and future growth of the Boronia industry, and requires an understanding of the pathogen. The objectives of this thesis were to investigate aspects of the epidemiology, the biology and the diversity of P. boroniae in Western Australia, providing a broad understanding of the pathogen, which in turn could be employed to improve disease control. The lifecycle of P. boroniae was conclusively shown to be microcyclic by artificial inoculation of Boronia heterophylla with basidiospores released from germinating teliospores suspended over the host plant. Telia developed on the leaves within 21 days, with no intermediate rust spore stages (pycnial, uredial or aecial) observed. Rarely, low numbers of pycnia of P. boroniae were observed on field specimens collected from leaves of B. megastigma cultivated at one commercial floriculture plantation. This was the first record of pycnia of P. boroniae; however, as pycnia were not observed on other host species or plantations, or formed during controlled inoculation trials, their functional role in the lifecycle is currently unresolved. Telia were subepidermal, erumpent and pulvinate, amphigenous on leaves, stems and parts of developing flower buds, and generally persistent year round. Intracellular