Treena Burgess

Two economically, environmentally and culturally important Australian native tree species, Araucaria cunninghamii (hoop pine) and A. bidwilli (bunya pine) are rapidly declining in the Bunya Mountains national park. Some of the affected bunya pines are estimated to be more than 600 years old. Symptoms include yellowing of the crown and rapid dieback, which is consistent with infection by Phytophthora, a fungal-like oomycete. Aerial surveys have shown that symptomatic trees of both species are spread throughout the national park. Phytophthora multivora, a pathogen associated with dieback of Eucalyptus gomphocephala and Pinus radiata in Western Australia, was isolated from the rhizosphere of symptomatic bunya pines. Phytophthora multivora has also been associated together with P. cinnamomi in the dieback of wollemi pine (Wollemia nobilis) in New South Wales, and kauri pine (Agathis australis) in New Zealand. Both pathogens have wide host ranges that include agriculturally and environmentally important plant species. DNA meta-barcoding analysis of the soil detected both pathogens at high numbers. Pathogenicity testing of the organisms is currently being conducted on bunya and hoop pine to confirm aggressiveness. Additional surveys and testing need to be conducted to confirm how wide spread the problem is, and to implement control measures to prevent future damage to the national park and surrounding softwood plantations. From initial observations of the symptoms, spread patterns and environmental history of the affected trees, P. multivora is the most likely causal agent of the dieback.

The Cape Town Hypothesis Test is the third phase of the pilot study for Cape Citizen Science (http://citsci.co.za/), a project to engage non-scientists as pathogen hunters. This phase was initiated because urban environments provide opportunities for the early detection of Phytophthora invasions. The hypothesis is that the Phytophthora species in the urban areas of Cape Town are different to those in the less disturbed Table Mountain National Park. Citizens were invited to contribute to the hypothesis test by submitting samples from their backyard as well as a few targeted areas in the urban areas. This is the first citizen-driven microbiology based hypothesis test in South Africa. Cape Citizen Science has already demonstrated the efficacy of engaging non-scientists in microbiological research, but the primary aim of this phase of the project was to demonstrate that citizens can contribute to testing hypotheses. In addition, by empowering citizens as biodiversity “protectors”, this phase will test the potential to mobilize the public to detect new invasions early.

The Botryosphaeriaceae is an important and diverse family of latent fungal pathogens of woody plants. Because some species appear to have a worldwide distribution, they are increasingly being used as model organisms to understand patterns in the global movement of latent pathogens. The aim of this study was to consider the diversity of Botryosphaeriaceae on 14 native Proteaceae species across South Africa and Australia, as well as on South African plants grown in Portugal. Ten species of the Botryosphaeriaceae were identified from 200 isolates using sequence data of the ITS rDNA, TEF-1α and β-tubulin loci. Surprisingly, Neofusicoccum parvum was found only from Portugal materials, despite its global distribution and common occurrence in Australia and South Africa on the other hosts. Neofusicoccum protearum and N. australe were the only shared species in Australia, South Africa and Portugal, while Diplodia allocellula was found in Australia and South Africa. The other six species were obtained from a single country and include D. mutila, D. alatafructa and N. macroclavatum in Australia, and D. pseudoseriata, N. viticlavatum and N. cryptoaustrale in South Africa. The results of this study show that the Botryosphaeriaceae diversity on the Proteaceae is geographically distinct, but there is also evidence for specialist species, such as N. protearum, that have been transported globally with plant material.

Cape Citizen Science (http://citsci.co.za) is a plant disease awareness initiative in South Africa. The pilot study was designed to reveal the diversity and distribution of Phytophthora species in the Cape Floral Kingdom. The project has engaged many non-scientists as pathogen hunters and samples have been submitted from several plant producers, botanical gardens, nature reserves, and national parks. Citizen engagement activities have revealed the presence of multiple species of Phytophthora previously undocumented in South Africa and they have facilitated the discovery of at least one novel species. The most recent phase of the project invited citizens to participate in The Cape Town Hypothesis Test, a study designed to promote the early detection of Phytophthora species introductions in urban areas of Cape Town. This pilot study has pioneered the application of several methods of public engagement in plant disease research. Citizens have submitted samples from their home gardens, invited researchers to collect samples on private property, participated in hikes for science and training workshops and they have reported dying plants online. The project has also revealed an abundance of opportunities to involve non-scientists in important microbiological research. Based on our experiences, we recommend establishing similar initiatives to Cape Citizen Science in other parts of the world.

Mediterranean biomes represent five biodiversity hotspots worldwide and cover just 2% of the Earth's land area; however, they support 20% of the Earth's known plant diversity. The Jarrah forest of South West, Western Australia, represents one of these valuable biomes. Documented climate change in Western Australia shows 35 years of consistently less rainfall and higher temperatures, with an extreme drought event in 2011 resulting in mortality of 1.7% or 19,000 ha of Northern Jarrah forest. To assess drought impact on vegetation of the Northern Jarrah forest, sites were chosen with a steep gradient from areas of canopy collapse to healthy forest. This provided an opportunity to assess the forest vegetation across an ecotone using space for time substitution. Our objectives were: 1) to determine factors affecting drought /heatwave induced vegetation mortality and 2) to assess differences in species response to this event. Results from this study show mortality of species occurs in zones on sites of drought induced canopy collapse in the Northern Jarrah Forest. Midstorey mortality is determined by soil depth. Results, indicate a complex interaction between plants with differing root functional traits and soil depth, determines the collapse response in an extreme drought event. There is an ongoing shift in the species composition and structure of the forest in and around areas of drought induced canopy collapse. We anticipate the use of presence /absence of midstorey, as a proxy for soil depth, and stand composition to predict areas of forest likely to collapse in the future.

Marri (Corymbia calophylla) is an iconic and keystone forest tree in Western Australia. A canker disease caused by the fungus Quambalaria coyrecup has devastated many marri stands. Disease incidence is higher in remnant stands that border cleared land such as road edges and farmland where there is greater anthropogenic disturbance, such as fertiliser, pesticide and herbicide use, and the introduction of plant pathogens. The progression of the decline strongly suggests a breakdown in the ability of the trees to maintain nutrient balance and we hypothesize that mycorrhizal fungi play a role in this process. The aim of this project was to examine the mycorrhizal species associated with marri and how these communities differ between intact and anthropogenically disturbed forest sites and whether pesticide use, changes in soil nutrition and/or soilborne pathogens are responsible for changes in communities of mycorrhizal fungi and hence canker disease incidence and severity. Seventeen sites were surveyed. Each site consisted of a disturbance gradient. Soil was collected from each transect and tested for nutrient composition, mycorrhizal composition and pathogens. Preliminary results demonstrate differences in soil nutrition between the disturbed transect and all intact forest transects. In addition, there are differences among the communities of fungi between the disturbed and intact forest transects. Disturbed transects show a higher proportion of pathogenic fungi particularly Phytophthora species, than in intact forest transects. Currently, the presence of pesticides and herbicides across the transects are being examined to determine their role in marri decline.

The incidence and severity of cankers caused by Quambalaria coyrecup in marri (Corymbia calophylla) have increased significantly in south-western Australia since the early 1990s. Marri is an iconic overstorey forest tree across a number of forest ecosystems. It is a major food source, habitat tree, and refugium for numerous fauna, including the endangered Carnaby’s cockatoo (Calyptorhynchus latirostris), as well as a “staple species” for apiarists. Consequently, the impact of the pathogen on marri is causing widespread concern across the community for many reasons. The authors have developed an application that works across mobile platforms (e.g., IPhone and Android) that is being used by interested members of the public, local government agencies, foresters, and scientists to capture location (GPS), incidence, and severity of cankers on trees, and upload photographs and other site information to a central server. The “Marri App” also informs users on what a canker looks like at different stages of development. Importantly, it also provides information on how to establish and monitor trials including fungicide and other treatment trials that will be statistically robust and informative for scientific purposes. The importance and power of the “Marri App” for information dissemination, community engagement, and citizen science will be discussed.