Phytophthora transitoria

Name and publication

Phytophthora transitoria I. Milenković, T. Májek & T. Jung (2022)

Chen Q, Bakhshi M, Balci Y, Broders KD, Cheewangkoon R, Chen SF, Fan XL, Gramaje D, Halleen F, Horta Jung M, Jiang N, Jung T, Májek T, Marincowitz S, Milenković I, Mostert L, Nakashima C, Nurul Faziha I, Pan M, Raza M, Scanu B, Spies CFJ, Suhaizan L, Suzuki H, Tian CM, Tomšovský M, Úrbez-Torres JR, Wang W, Wingfield BD, Wingfield MJ, Yang Q, Yang X, Zare R, Zhao P, Groenewald JZ, Cai L, Crous PW, 2022. Genera of phytopathogenic fungi: GOPHY 4. Studies in Mycology. 101: 417–564.





referring to the transitional role of most primary sporangia releasing their cytoplasm into a secondary emerging sporangium which forms and releases zoospores


Type: CZECH REPUBLIC, Central Bohemian region, Obříství, isolated from rhizosphere soil of a Quercus robur (Fagaceae) seedling, Mar. 2018, I. Milenković (holotype CBS H-24578, dried culture on V8A)

Ex-type: culture CBS 147245 = CZ001

Sequences for ex-type in original manuscript:  ITS MZ753925, cox1 MZ736439, β-tubulin MZ736466, tigA MZ736493

Molecular identification

Position in ITS phylogenetic tree

Clade 3

Morphological identification

Colonies and cardinal temperatures

Colony morphology uniform and submerged on V8A and CA, uniform and felty on PDA. Minimum growth temperature <10°C, optimum 22.5°C, and maximum 30°C.

Conditions for growth and sporulation

Sporangia produced on non-sterile soil extract. Oogonia are formed readily on CA after 5 days when pair with opposite mating type.

Asexual phase

Primary sporangia were non-papillate, persistent, and predominantly sub-globose to ovoid in shape. Sporangia averaged 32.5 x 25.7 µm (overall range 20–42.5 x 15–33.3 µm). Sporangiophores unbranched. Secondary sporangia were sessile or on short stalks emerging at or near apex, non-papillate, persistent, and predominantly sub-globose to ovoid in shape. Hyphal swellings absent. Chlamydospores present.

Sexual phase

Sterile in culture.

Most typical characters

Phytophthora transitoria differs from all other know Phytophthora species by releasing zoospores almost exclusively from secondary sporangia which emerge from primary transient sporangia.

Additional specimen(s) evaluated

Czech republic, Central Bohemian region, Obříství, isolated from rhizosphere soil of nursery-grown Quercus robur seedlings, Mar. 2018, I. Milenković, CBS 147246 = CZ118; CZ119; CZ120; CZ121; CZ123

Hosts and distribution

Distribution: Czech Republic
Substrate: roots
Disease note: rhizosphere of nursery grown Quercus robur seedlings
Host: Quercus robur

Additional references and links

none available

Fact sheet author

Treena Burgess, Ph.D., Phytophthora Science and Management, Harry Butler Institute, Murdoch University