Phytophthora aleatoria

Name and publication

Phytophthora aleatoria P.M. Scott, R. L McDougal & P.M. Taylor (2019)

Scott P, Taylor P, Gardner J, Puértolas A, Panda P, Addison S, Hood I, Burgess T, Horner I, Williams N, and McDougal R. 2019. Phytophthora aleatoria sp. nov., associated with root and collar damage on Pinus radiata from nurseries and plantations. Australasian Plant Pathology, 48 (4): 313–321.





from Spanish “aleatorio”, meaning random, fortuitous, casual, accidental, referring to the sporadic variable disease expression


Type: NEW ZEALAND (AOTEAROA), Nelson, isolate from a two-year-old Pinus radiata seedling. Collected by Rod Baigent, NZFS 4037 (live culture and dried culture on V8A medium, New Zealand Forest Research Mycological Herbarium, Rotorua, New Zealand).

Ex-type: living culture preserved in a metabolically inactive state as NZFS 4037 (New Zealand Forestry Service Culture Collection)

Sequences of ex-type in manuscript: ITS MK282209, β-tubulin MK294172, cox1 MK294177

Molecular identification

Position in ITS phylogenetic tree

Clade 1a

Genome sequence

Phytophthora aleatoria strain ex-type NZFS4037. Accession genome NZFS4037v1 reference, BioProject, PRJNA687640, University of Exeter (2021)

Morphological identification

Colonies and cardinal temperatures

Slow growing species and uniform without a pattern on V8A, MEA, and PDA. Minimum growth temperature 4°C, optimum 20°C, and maximum 25°C.

Conditions for growth and sporulation

Sporangia are produced in water cultures (non-sterile pond water) and not observed in solid media. Oogonia common in single culture.

Asexual phase

Sporangia were papillate, mostly persistent (some caducous sporangia were observed), and predominantly ovoid in shape with no proliferation. Sporangia averaged 31.7 x 23.3 µm (overall range 16.6–55.3 x 12.6–39.2 µm).Sporangiophores simple. Hyphal swellings present. Chlamydospores absent.

Sexual phase

Homothallic. Oogonia had smooth walls and size ranged from 24–45.6 µm; Oospores aplerotic, globose, size ranged 20.8–39.1 µm, often aborting before the formation of the oospore wall. Antheridia both amphigynous and paragynous.

Most typical characters

Phytophthora aleatoria is a sister species to P. catorum and P. hedraiandra in clade 1a, and morphological features overlap. The most distinguishing features are the slower growth rate and optimum and maximum temperature for growth.

Additional specimen(s) evaluated

New Zealand, Nelson, from a two-year-old Pinus radiata seedling. 2014, Rod Baigent, NZFS 4037; 1999, NZFS 351; Hawkes Bay, 2000, NZFS 451; Bay of Plenty, 2008, NZFS 3022; 2011, NZFS 4037

Hosts and distribution

Distribution: New Zealand
Substrate: stems, roots
Disease note: resin bleeding, cankers, discoloured foliage, and sometimes mortality in small seedlings
Host: Pinus radiata

Additional references and links

none available

Fact sheet author

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