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Description type:Original description 
Description:Phytophthora hydropathica is heterothallic. Sexual bodies in small numbers formed in hemp-seed agar beneath a polycarbonate membrane with a disc of A² P. cinnamomi in hemp-seed agar on top. Oogonia are about 43 µm in diameter, oospores 38 µm, and oospore walls about 2.2 µm thick. Antheridia are round and about 16 µm both tangential and perpendicular to the oogonia walls. Oospores are plerotic and the sexual bodies are golden in color. Sporangia are produced on lima bean agar discs very soon after they are placed in soil extract under lights, and the sporangia release zoospores relatively quickly after the sporangia are formed. Nesting and internal proliferation is very common. Sporangial shape varies from almost spherical, to ovoid, and to obpyriform. The sporangia are nonpapillate and noncaducous. The majority of sporangia tend toward being obpyriform. Their size is 43.3 - 60.0 x 33.3 - 46.7 µm (average 55.3 x 38.9 µm). The sporangia form mostly on long sporangiophores. Hyphal swellings in hemp-seed agar are irregular in shape but often are obovate in clusters or at the end of hyphae. In water minute hyphal swellings are often catenulate. Chlamydospores are terminal on short pedicels off the main hyphae and at the end of long hyphae. These thin-wall chlamydospores usually have dense protoplasm and are about 37 µm in diameter. The width of mycelium in some cultures seem relatively narrow, 3 -5 µm. Colony pattern on PDA is petaloid. All isolates grow very well at 35ºC. 
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