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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).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 aquimorbida C.X. Hong was recovered from irrigation runoff reservoirs in Virginia. Phylogenetically it is closely related to the clade 9 species P. irrigata, P. hydropathica and P. parsiana.
1. Sporangia
Monosporic cultures of P. aquimorbida produced abundant sexual structures and some hyphal swellings in both CV8 and carrot agar, but sporangia were produced only in sterile soil water extract. Sporangia are noncaducous, nonpapillate (but appeared “semi-papillate” at maturity, right before releasing zoospores) and predominantly ovoid to ellipsoidal with an average length to width ratio of 1.3:1.4 but their sizes differed by isolate. Sporangia of isolate 40E3 were 27.6–58.8(41.0) μm long and 21.3– 44.8(32.7) μm wide, while 44G9 sporangia were 39.0–68.0(54.2) μm long and 26.4–47.5(37.9) μm wide. Most sporangia grow on unbranched sporangiophores. Some have nested or extended proliferation. Catenulate and radiating hyphal swellings occur in some isolates; they were common in isolates 40A6 and 40E3 but less so in 40F9 and 44G9.
2. Chlamydospores
3. Sex Organs
Phytophthora aquimorbida is homothallic, producing terminal, intercalary or lateral oogonia with a plerotic oospore. Many oogonia were intercalary and lateral and some had a tapered base. Oogonia from all isolates were globose with a smooth surface and varied in size among the isolates (P < 0.0001). Oogonia of isolate 40A6 were 23.9–40.1(33.2) μm diameter; those of 44G9 were 30.8–48.5(40.7) μm. Plerotic oospores were formed and averaged 29.1–36.4 μm diam. Antheridia are seldom present and if so are amphigynous. Oospore wall indexes varied among isolates, 45–66%, with average of 52%.
4. Growth Temperatures
The optimum temperature for culture growth is 30° C with a minimum of 5° C and maximum of 40° C.
5. Growth Characteristics in Culture
6. Distinguishing Characteristics
P. aquimorbida is characterized by its noncaducous and nonpapillate sporangia, catenulate and radiating hyphal swellings and thick-walled plerotic oospores formed in globose oogonia mostly in the absence of an antheridium. Phytophthora aquimorbida can be distinguished easily from P. hydropathica, P. irrigata and P. parsiana by its homothallism, intercalary and lateral oogonia. It also can be distinguished from closely related homothallic species by morphology and cardinal temperatures. Specifically, both P. gallica and P. macrochlamydospora are sterile. Neither of these species grew at 35 C at which P. aquimorbida grew well. Both P. polonica and P. insolita have optimal and maximal growth temperatures close to those of P. aquimorbida, but unlike P. aquimorbida, P. polonica does not produce sporangia in soil water extract and P. insolita does not produce antheridia. Temperature growth response of P. aquamorbida is similar to P. irrigata and P. hydropathoica.
Phytophthora aquimorbida is pathogenic on rhododendron plants and caused root discoloration, pale leaves, wilting, tip necrosis and dieback.
Hong, C., Richardson, P. A., Hao, W., Sita R. Ghimire, S. R., Moorman, G. W., Lea-Cox, J. D., Ross, D. S. and Kong, P. 2012. Phytophthora aquimorbida sp. nov. and Phytophthora taxon ‘aquatilis’ recovered from irrigation reservoirs and a stream in Virginia, USA. Mycologia 104(5):1097-1108
This species page was adapted from Hong et al. (2012).
Isolate list