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 Add this item to the list  807978 Original description
Description type:Original description 
Description:Sporangia were occasionally produced by aged cultures (> 30 days) grown in carrot agar and clarified V8 juice agar. Abundant sporangia were produced by fresh mycelial plugs submerged in 1.5% soil water extract for 10 hours. Sporangial shape varied from ovoid, ellipsoid, obpyriform and in distorted shapes. These sporangia were terminal, nonpapillate, noncaducous, ranged 30.5 to 89.7 µm length (aver. 54.3 ± 11.0 µm) and 17.5 to 40.4 µm width (aver. 30.3 ± 3.9 µm). Direct germination of sporangia was frequently observed. Nested and extended internal proliferations were common. Hyphal swellings were abundantly produced in irregular shapes. Catenulate, globose hyphal swellings were frequently produced by aged cultures. Intercalary chlamydospores were observed in aged cultures of all examined isolates. They were mostly thin-walled, rarely thick-walled, and averaged 33.5 ± 4.9 µm in diameter. Phytophthora ×stagnum is heterothallic and all isolates examined are A1. They produced no sexual structure in single cultures, while oogonia were produced in dual cultures when each P. ×stagnum isolates was paired with an A2 tester of P. cinnamomi. In the polycarbonate test, only limited numbers of gametangia were produced by four representative isolates when paired with an A2 mating type tester of P. nicotianae for more than 50 days. These gametangia had two distinct morphologies. Isolates 36H8 and 36J7 mostly produced oogonia ornamented with characteristic protuberances and averaged 33.6 ± 8.1 µm in diameter. Oogonial wall was pigmented golden with maturation. Almost all oogonia aborted. Amphigynous antheridia were commonly distorted and averaged 19.4 µm depth and 14.2 µm width. All Isolates 43F3 and 44F9 mostly produced oogonia with smooth surface and averaged 28.0 ± 5.6 µm in diameter. Oogonial wall was pigmented darkly golden-brown. Oospores were also mostly abortive. Antheridia were amphigynous, globose or distorted, and averaged 10.0 µm depth and 12.3 µm width. 
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