Mycologia (2007) 99, 639-643

Paul W. Reeser, Everett M. Hansen and Wendy Sutton (2007)
Phytophthora siskiyouensis, a new species from soil, water, myrtlewood (Umbellularia californica) and tanoak (Lithocarpus densiflorus) in southwestern Oregon
Mycologia 99 (5), 639-643
Abstract: An unknown Phytophthora species was recovered in southwestern Oregon from rhododendron and tanoak leaf baits used for monitoring streams and soils for the presence of Phytophthora ramorum, from a blighted shoot of myrtlewood and from tanoak bark cankers. Isolates of this species yielded ITS-DNA sequences that differed substantially from other Phytophthora sequences in GenBank. Morphological features also differed from available descriptions of known Phytophthora species. Based on the combination of unique morphology and unique ITS sequences a new species is proposed. The new species, Phytophthora siskiyouensis, is homothallic with globose to subglobose oogonia, which may be terminal, sessile or laterally intercalary. Antheridia are capitate and mostly paragynous but sometimes amphigynous. Oospores are mostly aplerotic. Sporangia are variable but commonly ovoid to reniform, with apical, subapical or lateral semipapillae (occasionally more than one). Sporangia are terminal, subterminal or occasionally intercalary on unbranched sporangiophores, with basal, subbasal or lateral attachment. Sporangia are weakly deciduous, with variable length pedicels. This combination of characters clearly separates Phytophthora siskiyouensis from other known Phytophthora species.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Everett M. Hansen

Research topic(s) for pests/diseases/weeds:
identification/taxonomy

---

Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Phytophthora siskiyouensis	Tanoak (Notholithocarpus)	U.S.A. (NW)