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Doctor Tracey Steinrucken

Candidature

Tracey SteinruckenGraduated PhD 2017

Thesis Title

Investigating the cause of dieback in the invasive plant, Parkinsonia aculeata

Research Project

Parkinsonia aculeata is a weed of national significance in Australia. It negatively impacts biodiversity, water access and pasture availability across Western Australia, the Northern Territory and Queensland. This thorny tree forms dense monocultures, usually along water courses, and is spread primarily through flooding. A phenomenon called dieback has been observed in some parkinsonia populations, often reducing population size dramatically. Due to the size and remoteness of these populations, the use of dieback as biocontrol agent for parkinsonia would have many potential benefits. However the first step is to identify the cause of dieback in order to assess its suitability for biocontrol.

For most of my PhD I've been based in Brisbane with CSIRO Health and Biosecurity, with my main field sites in Charters Towers in central QLD. My research answers a number of questions in regards to the cause of dieback in parkinsonia, using molecular and microbial techniques. With terminal restriction fragment length polymorphism (TRFLP) and Illumina sequencing, I characterized the fungal, bacterial and archaeal endophyte communities of healthy and dieback-affected parkinsonia, showing a significant correlation with dieback occurrence for all three communities. I also isolated and tested putative fungal pathogens in a glasshouse pathogenicity trial with the aim of causing dieback-like symptoms in parkinsonia, and I surveyed Phytophthora species associated with parkinsonia in WA and QLD. Extensive sampling of invasive parkinsonia across northern Australia, and native parkinsonia populations in Arizona and the USA allowed for comparison of endophyte communities between the native and invasive range. This was while I was on a nine-month Fulbright scholarship at the University of California Berkeley. I showed that fungal and bacterial communities differ significantly between the native and invasive range, and also between closely related species from the same region in Arizona.

Research Project Supervisors

A/Professor Jeff Powell, Dr Rieks van Klinken and Dr Andrew Bissett

Publications

Raghavendra AKH, Bissett AB, Thrall PH, Morin L, Steinrucken TV, Galea VJ, Goulter KC, van Klinken RD, (2017) 'Characterisation of above-ground endophytic and soil fungal communities associated with dieback-affected and healthy plants in five exotic invasive species', Fungal Ecology, vol.26, pp 114-124

Steinrucken TV, Aghighi S, Hardy GES, Bissett A, Powell JR, van Klinken RD, (2017) 'First report of oomycetes associated with the invasive tree Parkinsonia aculeata (Family: Fabaceae)', Australasian Plant Pathology, vol.46, no.4, pp 313-321

Steinrucken TV, Raghavendra AKH, Powell JR, Bissett A, Van Klinken RD, (2017) 'Triggering dieback in an invasive plant: endophyte diversity and pathogenicity', Australasian Plant Pathology, vol.46, no.2, pp 157-170

Steinrucken TV, Bissett A, Powell JR, Raghavendra AKH, van Klinken RD, (2016) 'Endophyte community composition is associated with dieback occurrence in an invasive tree', Plant and Soil, vol.405, no.s 1-2, pp 311-323