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The description, pathogenicity and epidemiology of Phytophthora boodjera, a new nursery pathogen of Eucalyptus from Western Australia

Simamora, A.V. (2016) The description, pathogenicity and epidemiology of Phytophthora boodjera, a new nursery pathogen of Eucalyptus from Western Australia. PhD thesis, Murdoch University.

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When this study was commenced in November 2011, a recent outbreak of damping-off diasese in a Western Australia (WA) nursery had indicated the presence of a new Phytophthora species. Despite industry standard hygiene, the disease continued across years. The impact of this new disease in the nursery caused a great concern as the plants grown there were intended for environmental plantings and hence posed the risk of introducing a new species into the natural environment. This raised many questions to be cleared: (1) was this pathogen a new species, (2) was it only a damping-off pathogen or could it infect older seedlings or trees, (3) did it have a narrow or broad host range, (4) how did it get to the nursery and survive from year to year, (5) could it persist in environmental plantings, (6) was it endemic to Western Australia? This project addressed all of these questions. A new species, Phytophthora boodjera was described. It has a relatively narrow host range and is a pathogen of Eucalyptus. P. boodjera is especially a pre and postemergence damping-off pathogen with host susceptibility decreasing with age. Older seedlings and trees have damaged root systems but did not die. Within the nursery P. boodjera survived between seedings in the debris of the used trays. Immersion in 5% Calcium hypochlorite or using dry heat at 65oC for 2 hours did not eliminate the inoculum. Tracing of infected seedlings from the nursery showed that P. boodjera can persist in the natural environment if introduced. While common in nursery and recovered from urban planting, extensive sampling in natural ecosystems has recovered very few isolates of P. boodjera. Based on this low recovery and the high susceptibility of Eucalyptus species tested I conclude that P. boodjera is not endemic to WA.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): Burgess, Treena, Hardy, Giles and Stukely, M.
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