In 2016 and 2017, surveys of Phytophthora
diversity were performed in 25 natural and semi-natural forest stands and 16 rivers in temperate and subtropical montane and tropical lowland regions of Vietnam. Using baiting assays from soil samples and rivers and direct isolations from naturally fallen leaves, 13 described species, five informally designated taxa and 21 previously unknown taxa of Phytophthora
were isolated from 58 of the 91 soil samples (63.7%) taken from the rhizosphere of 52 of the 64 woody plant species sampled (81.3%) in 20 forest stands (83.7%), and from all rivers: P. capensis
, P. citricola
VII, VIII, IX, X and XI, P.
sp. botryosa-like 2, P.
sp. meadii-like 1 and 2, P.
sp. tropicalis-like 2 and P.
sp. multivesiculata-like 1 from Phytophthora
major phylogenetic Clade 2; P. castaneae
and P. heveae
from Clade 5; P. chlamydospora
, P. gregata
sp. bitahaiensis-like and P.
sp. sylvatica-like 1, 2 and 3 from Clade 6; P. cinnamomi (Pc)
, P. parvispora
, P. attenuata
sp. attenuata-like 1, 2 and 3 and P.
from Clade 7; P. drechsleri
, P. pseudocryptogea
, P. ramorum (Pr)
sp. kelmania from Clade 8, P. macrochlamydospora
sp. ×insolita-like, P.
sp. ×kunnunara-like, P.
sp. ×virginiana-like s.l. and three new taxa, P.
sp. quininea-like, P.
sp. ×Grenada 3-like and P.
sp. ×Peru 4-like, from Clade 9; and P.
sp. gallica-like 1 and 2 from Clade 10. The A1 and A2 mating types of both Pc
co-occurred. The A2 mating type of Pc
was associated with severe dieback of montane forests in northern Vietnam. Most other Phytophthora
species, including Pr
, were not associated with obvious disease symptoms. It is concluded that (1) Vietnam is within the center of origin of most Phytophthora
taxa found including Pc
, and (2) Phytophthora
clades 2, 5, 6, 7, 8, 9, and 10 are native to Indochina.