Phytophthora austrocedrae Gresl. & E.M. Hansen (2007) was isolated from necrotic lesions of stem and roots of Austrocedrus chilensis (Cupressaceae). It is homothallic with semi-papillate sporangia, oogonia with amphigynous antheridia, and very slow growth. It is the cause of “mal del ciprés”, a lethal disease of Austrocedrus in Argentina. Austrocedrus chilensis (ciprés de la cordillera) is endemic to southern Argentina and Chile. It is the most widely distributed tree species of the few conifers inhabiting the slopes of the Andes Mountains in Patagonia.
Etymology: ‘austrocedrae’ refers to Austrocedrus, the tree that is attacked by this pathogen.
Sporangia are borne terminally on mostly unbranched sporangiophores. Sporangiophores frequently have hyphal swellings. Sporangia are ovoid, limoniform or ellipsoid and semi-papillate. They average 50 x 36 μm (range 22-83 μm x 15-58 μm) with the length/breadth ratio about 1.4, and frequently have distorted shapes. Sporangia with hyphal projections and lateral attachment to the sporangiophore are frequently observed in all isolates. Sporangia are not observed in solid media.
Oogonia form in single-strain culture after about 20 days. Oogonia are globose or nearly so, averaging 39 μm diameter (range 22-56 μm), with hyaline to light brown, smooth walls. Oospores are globose, 31 μm diameter, hyaline, with smooth walls. Antheridiaare amphigynous and one-celled. Hyphal swellings usually form in liquid and solid media but are more abundant in the former. Swellings are globose to subglobose and catenulated, sometimes with distorted shapes.