Aspects of the interaction between Xanthorrhoea australis and Phytophthora cinnamomi in south-western Victoria, Australia

Diseases in natural ecosystems are often assumed to be less severe than those observed in domestic cropping systems due to the extensive biodiversity exhibited in wild vegetation communities. In Australia, it is this natural biodiversity that is now under threat from Phytophthora cinnamomi. The soilborne Oomycete causes severe decline of native vegetation communities in south-western Victoria, Australia, disrupting the ecological balance of native forest and heathland communities. While the effect of disease caused by P. cinnamomi on native vegetation communities in Victoria has been extensively investigated, little work has focused on the Anglesea healthlands in south-western Victoria. Nothing is known about the population structure of P. cinnamomi at Anglesea. This project was divided into two main components to investigate fundamental issues affecting the management of P. cinnamomi in the Anglesea heathlands. The first component examined the phenotypic characteristics of P. cinnamomi isolates sampled from the population at Anglesea, and compared these with isolates from other regions in Victoria, and also from Western Australia. The second component of the project investigated the effect of the fungicide phosphonate on the host response following infection by P. cinnamomi. Following soil sampling in the Anglesea heathlands, a collection of P, cinnamomi isolates was established. Morphological and physiological traits of each isolate were examined. All isolates were found to be of the A2 mating type. Variation was demonstrated among isolates in the following characteristics: radial growth rate on various nutrient media, sporangial production, and sporangial dimensions. Oogonial dimensions did not differ significantly between isolates. Morphological and physiological variation was rarely dependant on isolate origin. To examine the genetic diversity among isolates and to determine whether phenotypic variation observed was genetically based, Random Amplified Polymorphic DNA (RAPD) analyses were conducted. No significant variation was observed among isolates based on an analysis of molecular variance (AMQVA). The results are discussed in relation to population biology, and the effect of genetic variation on population structure and population dynamics. X australis, an arborescent monocotyledon indigenous to Australia, is highly susceptible to infection by P. cinnamomi. It forms an important component of the heathland vegetation community, providing habitat for native flora and fauna, A cell suspension culture system was developed to investigate the effect of the fungicide phosphonate on the host-pathogen interaction between X. australis and P. cinnamomi. This allowed the interaction between the host and the pathogen to be examined at a cellular level. Subsequently, histological studies using X. australis seedlings were undertaken to support the cellular study. Observations in the cell culture system correlated well with those in the plant. The anatomical structure of X australis roots was examined to assist in the interpretation of results of histopathological studies. The infection of single cells and roots of X. australis, and the effect of phosphonate on the interaction are described. Phosphonate application prior to inoculation with P. cinnamomi reduced the infection of cells in culture and of cells in planta. In particular, phosphonate was found to stimulate the production of phenolic material in roots of X australis seedlings and in cells in suspension cultures. In phosphonate-treated roots of X australis seedlings, the deposition of electron dense material, possibly lignin or cellulose, was observed following infection with P. cinnamomi. It is proposed that this is a significant consequence of the stimulation of plant defence pathways by the fungicide. Results of the study are discussed in terms of the implications of the findings on management of the Anglesea heathlands in Victoria, taking into account variation in pathogen morphology, pathogenicity and genotype. The mode of action of phosphonate in the plant is discussed in relation to plant physiology and biochemistry.

Use of phosphite as a control for Phytophthora cinnamomi in southeastern Victorian vegetation communities

One of the major aims of the research presented in this thesis was to assist managers of native vegetation communities in southeastern Australia in understanding the dynamics of P. cinnamomi with an important ecological species, Xanthorrhoea australis. It trialed the use of phosphite in large-scale field applications to establish the usefulness of this management option for the first time on Victorian flora. This thesis describes the process of disease development within mature X. Australia plants. For the first time it was shown that within X. australis plants, secondary disease symptoms are related to the percentage of stem that has been infested by the disease. It was evident that after initial invasion the pathogen moves via root xylem and throughout the plant within vascular to the stem, especially within the desmium. The research shows that the pathogen could not be isolated consistently even though it was considered to be responsible for disease symptoms. Trials of a control fungicide (Foli-R-fos 200) shows that protection occurs in many susceptible plants when 2 and 6g a.i./L phosphite is applied. Phytotoxicity occurred in native plants at Anglesea and within controlled environment trials when using ≥ 6g a.i./L. It will be shown that 2g a.i./L phosphite controls disease in sprayed plots within heathlands at Anglesea and a recently burnt coastal woodland community at Wilson’s Promontory. The proportion of healthy X. australis plants treated with phosphite was significantly higher than the proportion in control plots without phosphite. The research shows that phosphite was recovered from leaves of three species treated with Foli-R-fos 200 in the field. For the first time it has been shown that seed germination was reduced in two species when high concentrations of phosphite were applied. The first documentation of the effect that phosphite has on soil properties showed that nitrogen and oxidised organic carbon were the only parameters to alter significantly. This thesis provides answers to some important questions, answers that can now be used by managers in formulating better policies and actions at an operational level. There has been a dire need in Victoria to address many issues regarding P. cinnamomi and this thesis provides relevant and informative approaches to disease control, and a better understanding of the disease progress.

Biology and control of white blister rust of Brassicaceae vegetables

This research project was a response to the outbreak of white blister rust disease and its spread to Brassica oleracea crops in Australia. Disease management strategies based on the understanding of the Albugo - Brassica pathosystem, epidemiology, and the use of chemical control measures were developed for the Australian Brassica industry.

New governance, green planning and sustainability : Tasmania together and growing Victoria together

Bridgman and Davis(2000:91) have argued that ‘ideally government will have a well developed and widely distributed policy framework, setting out economic, social and environmental objectives’. This article compares and evaluates two such frameworks or plans, Tasmania Together and Growing Victoria Together, in terms of their potential to promote sustainability. It argues that they are very different exercises in new governance, aimed at reconnecting with community priorities and at redirecting macro-policy setting away from a preoccupation with economic priorities, respectively. Nevertheless, both plans have the capacity to ‘green’ state planning, in Tasmania in terms of more purposeful benchmarks, and in Victoria in terms of enhanced sustainability emphasis in the macro-policy setting. The article encounters tensions in its review of the plans between deliberation and planning, policy empowerment and policy progress, and policy institutionalisation and politicisation as means of achieving policy change. It finds that whilst Tasmania and Victoria are re-engaged states that are reinventing state policy, as yet they are failing to meet the governance challenges of sustainability.

Tasmania together and growing Victoria together : can state plans deliver environmental sustainability?

Sustainability has always been a contested term, environmental sustainability in particular. It presents challenges and opportunities for policy making at all levels. This paper suggests that state plans have a key role to play in the pursuit of sustainability. It argues that, in theory, sustainability requires well integrated, interactive, informed and informing, as well as institutionalised policy processes. It reviews state plans in Tasmania and Victoria to analyse their capacity for delivering sustainability. Tasmania Together and Crowing Victoria Together are very different plans, so very different conclusions are drawn here, however we find that both of them lack the explicit political and policy commitment to sustainability that is required to turn rhetoric into state planning practice.

Health system costs of diseases and injury in Australia 1993-94 : an analysis of costs, service use and mortality for major disease and injury groups

Provides a systematic analysis of the health system use and costs associated with specific disease and injury groups in Australia in 1993-94. The estimates are presented in a consistent format and are derived using a methodology that ensures the results add across disease, age and sex groups to total Australian health expenditures for 1993-94.

Comparing subjective well-being and health-related quality of life of Australian drug users in treatment in regional and rural Victoria

The aim of this study is to examine the self-reported subjective well-being and health-related quality of life (HRQOL) of alcohol and other drug users and to examine whether subjective well-being in this sample would be predicted by either HRQOL and/or severity of dependence.

Variation in Cyclaneusma minus isolates

Cyclaneusma minus is a plant pathogen that has financial impacts on the forestry industry. This study characterised the genetic variation in Australian and New Zealand isolates of Cyclaneusma minus using both molecular and morphological techniques and developed a PCR detection test for the presence of Cyclaneusma minus in tree plantations.

Interactions of Plasmodiophora brassicae with Arabidopsis thaliana

The host-pathogen interaction study between Arabidopsis thaliana and Plasmodiophora brassicae was conducted at cellular and molecular level for a better understanding of the pathogen. Gene expression studies conducted therin at the early time points during the infection process of P. brassicae discovered new information on the components of compatibility.