title: Phytophthora aquimorbida sp. nov. and Phytophthora taxon 'aquatilis' recovered from irrigation reservoirs and a stream in Virginia, USA.
abstract: Two distinct subgroups (L2 and A(-2)) were recovered from irrigation reservoirs and a stream in Virginia, USA. After molecular, morphological and physiological examinations, the L2 subgroup was named Phytophthora aquimorbida and the A(-2) designated as Phytophthora taxon 'aquatilis'. Both taxa are homothallic. P. aquimorbida is characterized by its noncaducous and nonpapillate sporangia, catenulate and radiating hyphal swellings and thick-walled plerotic oospores formed in globose oogonia mostly in the absence of an antheridium. P. taxon 'aquatilis' produces plerotic oospores in globose oogonia mostly with a paragynous antheridium. It has semi-papillate, caducous sporangia with variable pedicels, but it does not have hyphal swelling. Analyses of ITS, CO1, β-tubulin and NADH1 sequences revealed that P. aquimorbida is closely related to P. hydropathica, P. irrigata and P. parsiana, and P. taxon 'aquatilis' is related to P. multivesiculata. The optimum temperature for culture growth is 30 and 20 C for P. aquimorbida and P. taxon 'aquatilis' respectively. Both taxa were pathogenic to rhododendron plants and caused root discoloration, pale leaves, wilting, tip necrosis and dieback. Their plant biosecurity risk also is discussed.
authors.affiliation: Virginia Polytechnic Institute and State University, Hampton Roads Agricultural Research and Extension Center, Virginia Beach, VA 23455, USA. chhong2@vt.edu
authors.forename: Chuanxue
authors.initials: C
authors.lastname: Hong
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Richardson
authors.forename: Wei
authors.initials: W
authors.lastname: Hao
authors.forename: Sita R
authors.initials: SR
authors.lastname: Ghimire
authors.forename: Ping
authors.initials: P
authors.lastname: Kong
authors.forename: Gary W
authors.initials: GW
authors.lastname: Moorman
authors.forename: John D
authors.initials: JD
authors.lastname: Lea-Cox
authors.forename: David S
authors.initials: DS
authors.lastname: Ross
mesh_terms: D004271:DNA, Fungal / Q000235:genetics; D010802:Phylogeny; D010838:Phytophthora / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000648:ultrastructure; D010935:Plant Diseases / Q000382:microbiology*; D029793:Rhododendron / Q000382:microbiology*; D045483:Rivers / Q000382:microbiology*; D014768:Virginia; D014871:Water Microbiology
chemical_list: D004271:DNA, Fungal