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Survival of different life stages of phytophthora cinnamomi (RANDS) in soil and plant roots under mine site conditions

Gyeltshen, Jamba (2018) Survival of different life stages of phytophthora cinnamomi (RANDS) in soil and plant roots under mine site conditions. PhD thesis, Murdoch University.

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Phytophthora cinnamomi (Rands) is a soil and water-borne plant pathogen associated with a devastating dieback disease in the jarrah (Eucalyptus marginata) forest in Western Australia. As extensive open-cut bauxite mining occurs in the jarrah forest, it is difficult to prevent or minimize the spread of the pathogen. Despite years of research, we do not fully understood the survival strategies of P. cinnamomi. This study investigated how long P. cinnamomi survives under adverse mine site conditions that periodically are extremely hot and dry with surface temperatures reaching 60 ºC. The study looked at the life span of oospores, chlamydospores and encysted zoospores under conditions reflecting the mine sites.

The findings indicate that oospores of P. cinnamomi survive in the soil for less than one year, irrespective of soil moisture conditions. Chlamydospores survive for less than 12 weeks under similar conditions. The effect of exogenous treatments on survival was variable and observed only under moist soil conditions. Encysted zoospores under submerged conditions (similar to those in drainage sumps) did not survive beyond one week. At matric potentials between -1 kPa and -6 MPa there was a clear decline in oospore viability, and at -6 MPa, oospore viability was reduced to 66% after 60 days.

The possible role of non-susceptible or tolerant host plants growing on the stockpiles contributing to survival was investigated. Meta-barcoding and high throughput sequencing detected P. cinnamomi on 16 of the 20 plant species being screened. Unexpectedly, the technique revealed the putative presence of 24 other Phytophthora species, thereby raising more questions on the role of these plants in the Phytophthora disease cycle. Based on the findings, this study recommends that the stockpiles be maintained in situ for at least 2-3 years and be prevented from any plant growth to minimize the risk of spreading the pathogen.

Publication Type: Thesis (PhD)
Murdoch Affiliation: School of Veterinary and Life Sciences
Supervisor: Hardy, Giles, Burgess, Treena and Dunstan, Bill
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