Phytophthora pseudotsugae, a new species causing root rot of Douglas-fir

摘要

Phytophthora pseudotsugaen. sp. was isolated from rotted roots of Douglas-fir growing in forest tree nurseries in Oregon and Washington. It is distinguished by large oogonia and oospores, mostly paragynous antheridia, and predominantly spherical or ovoid, persistent sporangia borne primarily on simple and unbranched sporangiophores. Sporangia are formed occasionally in liquid culture, rarely in solid media.Phytophthora pseudotsugaeis distinguished most readily fromP. cactorumby its unbranched sporangiophores and persistent sporangia. It also differs in growth on defined media, electrophoretic protein patterns, and pathogenicity. Comparison is also made withP. iranica, the other species in group 1 of Waterhouse.