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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).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 melonis Katsura 1976 (Oomycetes, Pythiales)
= Phytophthora sinensis Y.N. Yu & W.Y. Zhuang 1982 Note: Synonymy supported by molecular analysis (Cooke 2000).
Notes: Ho & Jong (1986) considered Phytophthora melonis a synonym of Phytophthora drechsleri but this was not supported by molecular analysis (Cooke et al. 2000).
Distribution: Asia.
Substrate: Stems, vines, fruits, leaves.
Disease Note: Late blight or foot rot.
Host: Cucumis sativus (cucumber, Cucurbitaceae). Also reported from Citrullus lanatus (Cucurbitaceae) and Pistacia vera (Anacardiaceae).
Supporting Literature:
Cooke, D.E.L., Drenth, A., Duncan, J.M., Wagels, G., and Brasier, C.M. 2000. A molecular phylogeny of Phytophthora and related Oomycetes. Fungal Genet. Biol. 30: 17-32
Erwin, D.C., and Ribeiro, O.K. 1996. Phytophthora Diseases Worldwide. APS Press, St. Paul, Minnesota, 562 pages.
Ho, H.H. 1986. Phytophthora melonis and P. sinensis synonymous with P. drechsleri. Mycologia 78: 907-912
Ho, H.H., and Jong, S.C. 1986. A comparison between Phytophthora cryptogea and P. drechsleri. Mycotaxon 27: 289-319
Updated on Jun 06, 2006
P. sinensis is classified in group VI (Stamps et al. 1990). The morphology of P. sinensis is similar to that of P. drechsleri (Chapter 23, Figure 23.1). See Tables 4.2 and 4.3 in Phytophthora Diseases Worldwide (Erwin and Ribeiro 1996) for tabular keys. The following is summarized from Yu and Zhuang (1982).
1. Sporangia
Sporangia are induced by incubation of mycelial blocks of agar media (not specified) in Petri?s solution (see Appendix 3.34 in Chapter 3 in Phytophthora Diseases Worldwide (Erwin and Ribeiro 1996). Sporangia are ovoid to elongate, persistent, and nonpapillate and proliferate from the empty sporangia.
Sporangia measure 24 to 80 20 to 40 µm, average 51.7 13.1 31.1 5.5 µm. The length-breadth ratio is approximately 1.7 (range 1.2 to 2.2). The exit pore is 9 to 18 µm in width. Sporangia form on undifferentiated, simple or branched sporangiophores.
2. Hyphal Swellings
Hyphal swellings are globose to subglobose and 10 to 30 µm in diameter.
3. Chlamydospores
Chlamydospores were not observed by Yu and Zhuang (1982) or by Ho (1986b).
4. Sex Organs
According to Yu and Zhuang (1982), P. sinensis isolates were homothallic; however, Ho (1986b) stated that they acted as heterothallic isolates because oospores were formed when paired with A1 or A2 isolates of P. melonis, P. drechsleri, or P. cinnamomi. Yu and Zhuang (1982) reported that oogonia produced on oatmeal agar were spherical or subspherical, tapering at the base, with a smooth wall. Sizes ranged from 19 to 31 µm in diameter, average 27.4 2.8 µm. Antheridia are amphigynous, single, hyaline, and subglobose, short cylindrical, or variable in shape. Antheridia are mostly one-celled, but occasionally a two-cell antheridium is seen. Antheridia measure 7 to 37 9 to 25 µm, average 19.3 18.5 µm. Oospores are spherical to subspherical and plerotic in the oogonium. Oospores measure 16.5 to 28.0 µm in diameter, average 23.9 2.8 µm. Ho et al. (1984b) reexamined the type culture of P. sinensis but stated that oogonia were abortive.
5. Growth Temperatures
The minimum temperature for growth is 9oC, optimum 29 to 32oC, and maximum 36.5oC.
6. Distinguishing Characteristics
Yu and Zhuang (1982) noted the similarity of P. sinensis to P. melonis and P. drechsleri. They distinguish P. sinensis from P. melonis on the following evidence: Katsura?s (1968) report that P. sinensis produces nonpapillate sporangia versus semipapillate for P. melonis; proliferation of sporangia (up to 17 times); larger antheridia averaging 19.3 18.5 µm versus 15 20 µm for P. melonis; production of an occasional two-celled antheridium by P. sinensis; and absence of chlamydospores in P. sinensis. Ho (1986b) reexamined the type culture of P. sinensis, authentic cultures of cucumber isolates of P. melonis from Japan, and a P. drechsleri isolate from Iran (Ershad and Mostowfipoor 1969). He found that all isolates were predominantly heterothallic but formed a few oospores in single culture, proliferation of nonpapillate sporangia occurred, antheridia were occasionally two celled, and that chlamydospores were not formed by any culture when mycelial disks of V8 agar were incubated in sterile distilled water at 15oC for 5 weeks. Ho (1986b) concluded that P. sinensis should be included in P. drechsleri.
We conclude that there is little rationale for maintaining P. sinensis as a species. The mtDNA RFLP and isozyme pattern data of Mills et al. (1991), however, indicate that several biotypes within the P. drechsleri-P. cryptogea complex differ markedly from the P. melonis, P. sinensis, P. drechsleri group from melons. Until a more definitive evaluation and redescription of P. sinensis or P. melonis are made, the cucumber isolates should be classified as P. drechsleri.
Nomenclature information was provided by the the Systematic Botany and Mycology Laboratory in USDA-ARS.
Isolate list