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Biological control of Phytophthora cinnamomi: The potential of Western Australian native legumes to protect susceptible plant species

D'Souza, Nola Kim (2001) Biological control of Phytophthora cinnamomi: The potential of Western Australian native legumes to protect susceptible plant species. Honours thesis, Murdoch University.


ABSTRACT The plant pathogen Phytophthora cinnamomi is having a major negative impact on the biodiversity of native ecosystems in the south west of Western Australia. Acacia pu/chella has previously been shown to suppress P. cinnamomi in the jarrah forest of Western Australia and protect susceptible species from infection. This has management implications for the control of P. cinnamomi in rehabilitated bauxite pits infested with the pathogen and severely diseased forest areas. The objective of this thesis was to determine if other Western Australian native legume species have the potential to biologically control P. cinnamomi.

In a rehabilitated bauxite pit trial, five Acacia species were planted with Banksia grandis, to determine their ability to protect this highly susceptible species against P. cinnamomi infection. A. pulchella protected B. grandis from infection for over a year. This protection was not the result of a decrease in soil moisture or soil temperature, as was previously suggested. A. urophylla, A. extensa, A. latericola and A. drummondii did not protect B. grandis in this trial. The trial was replicated in the glasshouse under conditions conducive to the pathogen. The infection of B. grandis by P. cinnamomi was delayed for up to 7 weeks by all of these Acacia species; however, none of them protected B. grandis from eventual mortality.

In a glasshouse soil inoculation trial, native legumes other than A. pulchella were able to reduce the soil inoculum potential of P. cinnamomi. Based on these findings, the species with the greatest potential for biological control of P. cinnamomi along with A. pulchella were A. extensa, A. stenoptera and A. a/ata. 11 By assessing the roots of soil inoculated native legumes from the glasshouse trial, P. cinnamomi was found to asymptomatically infect fine lateral roots of some species and sporulate from them. These species can potentially harbour the pathogen and allow for an inoculum increase when environmental conditions are favourable. A. urophylla and Viminaria juncea were the species with the least potential for biological control of P. cinnamomi due to this finding.

A possible management tool for bauxite pits in infested areas and in severely diseased forest areas is the ability to influence the density and composition of species used for rehabilitation, by manipulating the seed mix ratio. The implications of this study would be to increase seed in a seed mix of those legume species with the potential for biological control and decrease seed of those species that can harbour the pathogen. However, before rehabilitation management practices are adjusted, further investigation is required to understand how P. cinnamomi suppression occurs and whether it is transferable to a natural environment. The actions of P. cinnamomi suppression by legume species and future research directions are discussed.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Biological and Environmental Sciences
Notes: A digital copy of this thesis is not available. Your library can request a copy from Murdoch University Library via Document Delivery. A fee applies to this service.
Supervisor(s): Hardy, Giles, Shearer, Bryan and Colquhoun, Ian
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