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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).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 insolita Ann & W.H. Ko 1981 (Oomycetes, Pythiales)
Distribution: Asia (Taiwan), North America (USA: OH).
Substrate: Soil, leaves.
Disease Note: Foliar necrotic lesions and twig dieback (Testa et al. 2005).
Host: Rhododendron sp. (Ericaceae). Able to infect Malus domestica (apple, Rosaceae) and Cucumis sativus (cucumber, Cucurbitaceae) fruits when inoculated (Erwin & Ribeiro 1996).
Supporting Literature:
Erwin, D.C., and Ribeiro, O.K. 1996. Phytophthora Diseases Worldwide. APS Press, St. Paul, Minnesota, 562 pages.
Kroon, L.P.N.M., Bakker, F.T., van den Bosch, G.B.M., Bonants, P.J.M., and Flier, W.G. 2004. Phylogenetic analysis of Phytophthora species based on mitochondrial and nuclear DNS sequences. Fungal Genet. Biol. 41: 766-782
Testa, A., Schilb, M., Lehman, J.S., Cristinzio, G., and Bonello, P. 2005. First report of Phytophthora insolita and P. inflata on Rhododendron in Ohio. Pl. Dis. 89: 1128
Updated on Jun 14, 2006
P. insolita is classified in group V (Stamps et al. 1990). Photomicrographs of sporangia, chlamydospores, and oogonia are shown in Figure 2 (Ann and Ko 1980). See Figure 1 for a detailed drawing, Tables 4.2 and 4.3 for tabular keys, and Appendix 4.9 for a dichotomous key (Ho 1992) in Phytophthora Diseases Worldwide (Erwin and Ribeiro 1996).
1. Sporangia
Sporangia, which measure 38 to 68 x 29 to 39 µm, are produced readily when blocks of young mycelium on V8 juice agar are transferred to water and incubated at 25oC under light. Sporangia are terminal, noncaducous, ovoid, and nonpapillate. New sporangia proliferate both externally and internally from older sporangia after zoospores have been released.
2. Chlamydospores
Thin-walled, globose chlamydospores are formed terminally and measure 22 to 48 µm in diameter. Irregularly shaped hyphal swellings of varying sizes are formed on V8 juice agar.
3. Growth Temperatures
The minimum temperature for growth is 9oC, the optimum is 32oC, and the maximum is 38oC. No growth occurs at 40oC. P. insolita is not sensitive to hymexazol (50 µg/ml) (Ann and Ko 1980).
5. Sex Organs
P. insolita is homothallic. Oospores are produced abundantly on 20% V8 juice agar neutralized with 0.2 g of calcium carbonate. Spherical oogonia (ranging in diameter from 29 to 36 µm), which form terminally, have smooth to slightly undulating walls. The oogonial stalks are variable in length and are branched sympodially from a place immediately beneath the older oogonium. Antheridia have not been seen. Thick-walled (approximately 2.4 µm) oospores (27 to 31 µm in diameter, average 30 µm) are globose and nearly fill the oogonium. Oospore formation was induced when P. insolita was paired with a P. parasitica A2 mating type on V8 juice agar but not when paired with an A1 mating type. On the basis of hormone production (Ko 1980), P. insolita was considered to belong to type 9 or 11 of group II, which forms oospores by self-induction (Ann and Ko 1980).
Nomenclature information was provided by the the Systematic Botany and Mycology Laboratory in USDA-ARS.
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