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The biochemical effect of phosphite on the virulence of Phytophthora cinnamomi

Stasikowski, P.M., McComb, J.A., Hardy, G.E.St.J. and O'Brien, P.A. (2008) The biochemical effect of phosphite on the virulence of Phytophthora cinnamomi. In: ICPP 2008 9th International Congress of Plant Pathology, 24 - 29 August, Torino, Italy,.


Phytophthora cinnamomi is a broad-host-range necrotrophic oomycete pathogen responsible for the destruction of native florain many parts of Australia. Disease symptoms and pathogen spread can be contained by treatment with phosphite as a foliar spray, trunk injection or soil drench. It has been proposed that phosphite, an analogue of phosphate, exerts its fungistatic effect either by direct inhibition of pathogen growth at the point of ingress, or indirectly by stimulating host-plant defence responses. However the biochemical processes that underlie and mediate these effects are not known. We have developed a Lupinus angustifolius – P. cinnamomi hydroponic bioassay to assess the action of various specific biochemical inhibitors on the pathways expected to be involved in pathogenesis. The direct application of 3mM phosphite to cultures of P. cinnamomi alone is sufficient to completely inhibit the development of disease symptoms on 5 day-old lupins without affecting pathogen viability. Pathogen virulence is also significantly altered by the guanine nucleotide exchange inhibitor, brefeldrin A; the serine/threonine phosphatase inhibitor, okadaic acid; and the phospholipase D inhibitor, butan-1-ol. Results are presented within the context of the effect of phosphate on the signal transduction pathways involved in pathogenesis.

Item Type: Conference Item
Murdoch Affiliation(s): Centre for Phytophthora Science and Management
School of Biological Sciences and Biotechnology
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