Phytophthora has been rebuilt to fix security-related problems and to restore GIS tools. These tools allow users to visualize the geospatial, temporal, and environmental contexts of Phytophthora discoveries. The next phase is to update species information and add data derived from large-scale surveys. If you have suggestions and requests to make the database better, please contact Seogchan Kang (sxk55@psu.edu).
Genus wide phylogeny for Phytophthora using four mitochondrial loci (cox2, nad9, rps10 and secY; 2,373 nucleotides). Maximum likelihood branch lengths shown. Numbers on nodes represent bootstrap support values for maximum likelihood (top), maximum parsimony (middle) and Bayesian posterior probabilities as percentages (bottom). Nodes receiving significant support (>95%) in all analysis are marked with an asterisk (*). Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).
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Phytophthora constricta A. Rea, M. Stukely & T. Jung, has been isolated in Western Australia from kwongan heath-land stands since the early 1980s (Burgess et al. 2009, Rea et al. 2011), but was misidentified as P. megasperma. Phytophthora constricta has predominantly been isolated from the southern sandplains of Western Australia and thus has a different range than P. arenaria, a species isolated from kwongan vegetation predominantly from the northern sandplains.
1. Sporangia
Nonpapillate to semipapillate persistent sporangia were abundantly produced in non-sterile soil extract water (Fig. 1a-c). Sporangial proliferation was internal, usually nested or much less frequently extended (Fig. 1d-e). In all isolates most sporangiophores became constricted towards the base of the sporangium and in some cases widening again (Fig. 1b). Sporangia easily broke from the sporangiophore at the site of the constriction under slight pressure (Fig. 1c). Sporangiophores of even thickness also occurred. Sporangial apices were flat and broad. Sporangial shapes ranged from ovoid or broadly ovoid to turbinate. Sporangia averaged 59.8 ± 8.7 µm in length and 48.8 ± 7.4 µm in width, with a length:breadth ratio of 1.2 ± 0.09. Zoospores were released through wide exit pores (13.4 ± 2.7 µm). Release of a secondary zoospore from encysted zoospores (diplanetism) was regularly observed. Ellipsoid hyphal swellings were occasionally formed on sporangiophores (Fig. 1e).
2. Chlamydospores
Chlamydospores not observed.
3. Sex Organs
Phytophthora constricta is homothallic and readily produced oogonia in single culture on CA and V8A, containing oospores which matured within 14 – 21 days. Oogonia from four isolates averaged 48.0 ± 4.8 µm with isolate means ranging from 46.0 to 50.4 µm. Some oogonia had a tapering base. Elongated and slightly excentric oogonia were observed. Oospores were usually slightly aplerotic to nearly plerotic, and averaged 40.4 ± 4.3 µm diameter with isolate means ranging from 38.9 to 41.8 µm. Walls of 21-day-old oospores were moderately thick (2.9 ± 0.87 µm), often turned bronze-brown or golden-brown with maturity, and contained a clearly visible nucleus and a large ooplast at maturity (Fig. 2a-c). Oospore walls continued to thicken over the next 4 – 10 months. The oospore wall index for 14 – 21-day-old oospores was 0.36 ± 0.09 (isolate means ranging from 0.31 to 0.39), whilst for 4 – 10-month-old oospores it was 0.52 ± 0.09 (isolate means ranging from 0.49 ± 0.08 to 0.58 ± 0.04). Antheridia were exclusively paragynous (Fig. 2a-c), with some having a finger-like extension, and were attached to the oogonium either close to the oogonial stalk or at an angle of up to 90°. Antheridia averaged 16.9 ± 2.4 x 13.3 ± 2.1 µm.
4. Growth Temperatures
It grows on CA agar at 5-32.5°C with an optimum near 22.5°C (radial growth rate 6.0 ± 0.22 mm/d). No growth occurred at 32.5°C, but this temperature was not lethal.
5. Growth Characteristics in Culture
All P. constricta isolates produced colonies with petaloid morphology on V8A (Fig. 3a), CA (Fig. 3b) and PDA (Fig. 3d), and a faintly petaloid pattern on MEA (Fig. 3c).
6. Distinguishing Characteristics
A summary of decisive morphological and physiological characters discriminating P. constricta from the closely related species P. fallax and P. captiosa and P. megasperma, the species with which it has been commonly confused, can be found in Rea et al. (2011). Briefly, the closest species to P. constricta is P. megasperma, both of which belong to Waterhouse group V and share a number of morphological similarities. The major differences between P. constricta and P. megasperma are the absence of both amphigynous antheridia and external sporangial proliferation, the characteristic constriction of the sporangiophore beneath the sporangium in P. constricta and different colony morphology on CA and MEA. Phytophthora constricta is phylogenetically closest to P. fallax and P. captiosa. However, there are many morphological differences and differences in colony morphology on CA.
7. Type isolate
AUSTRALIA, Fitzgerald River National Park, isolated from soil sample collected in dying native kwongan vegetation, August 2006, M. Stukely. Holotype: MURU 454 (dried culture on V8A in the herbarium of Murdoch University, Western Australia). culture ex-type CBS 125801 and VHS 16130. rDNA ITS (HQ013225), coxI (HQ013207). MycoBank MB518793.
Causes patchy deaths of Proteaceous plant species in kwongan vegetation (Proteaceous plant species including Banksias spp., Hakea spp., Adenanthos spp. and Isopogon spp., also Pinus radiata). Control achieved by management of infested material in nurseries. Control of rare or endangered flora can be achieved through the use of phosphite.
Commonly detected by baiting of rhizosphere soil, also isolated by direct plating of damaged roots or stem cankers on PARPNH selective medium.
urgess TI, Webster JL, Ciampini JA, White DW, Hardy GESJ, Stukely MJC (2009) Re-evaluation of Phytophthora species isolated during 30 years of vegetation health surveys in Western Australia using molecular techniques. Plant Disease 93:215-223.
Dick MA, Dobbie K, Cooke DEL, Brasier CM. 2006. Phytophthora captiosa sp. nov. and P. fallax sp. nov. causing crown dieback of Eucalyptus in New Zealand. Mycological Research 110:393-404.
Rea A, Burgess TI, Hardy GES, Stukely MJC, Jung T. 2011. Two novel species of Phytophthora associated with episodic dieback of kwongan vegetation of south-west Western Australia. Plant Pathology 60:1055-1068.
This page was written by Treena Burgess, Centre for Phytophthora Science and Management, Murdoch University, Australia.
Isolate list