Pseudopithomyces toxicarius B.S. Weir, D. Lee, J.S. Sidhu & C.R. Voisey 2025

Caption:

Details

Name scientific

Pseudopithomyces toxicarius B.S. Weir, D. Lee, J.S. Sidhu & C.R. Voisey, Studies in Mycology 112 56 (2025)

Preferred name

Pseudopithomyces toxicarius B.S. Weir, D. Lee, J.S. Sidhu & C.R. Voisey 2025

Taxonomy reference

Weir, B.S.; Sidhu, J.S.; Brosnahan, C.L.; Lee, D.; Maclean, P.H.; Park, D.; Jauregui, R.; Johnson, R.D.; Petterson, M.E.; Williams, A.F.R.; Morse, N.R.; Sprosen, J.M.; Lim, Y.-W.; Bridgeman, B.J.; Walker, T.J.; Kumar, S.; Mace, W.J.; Prakash, S.; Liu, X.; Hume, D.E.; Couldrey, C.; Beever, R.E.; Voisey, C.R. 2025: Global diversity analysis of plant-associated Pseudopithomyces fungi reveals a new species producing the toxin associated with facial eczema in livestock: Pseudopithomyces toxicarius sp. nov. Studies in Mycology 112: 39-73.

Biostatus

Origin

Occurrence

Georegion

Schema

Biostatus source

Comment

Uncertain

Present

New Zealand

Political Region

Nomenclature

Original authors

B.S. Weir, D. Lee, J.S. Sidhu & C.R. Voisey

Authors

B.S. Weir, D. Lee, J.S. Sidhu & C.R. Voisey

Publication place

Year published

2025

Publication page

Nomenclatural code

ICN

Basionym

Pseudopithomyces toxicarius B.S. Weir, D. Lee, J.S. Sidhu & C.R. Voisey 2025

Taxonomic rank

species

Canonical form

Pseudopithomyces toxicarius

Etymology

In Latin toxicum – poison, ari – maker of/producer of; toxicarius (adj.) – the toxin producer. This species produces the toxin sporidesmin.

Classification

Kingdom

Fungi

Phylum

Ascomycota

Class

Dothideomycetes

Order

Pleosporales

Family

Didymosphaeriaceae

Genus

Pseudopithomyces

Species

toxicarius

Synonyms

Pseudopithomyces sp. nov. NZ B.S. Weir 2020

Associations

View full associations record

Association type

Associated organism

Association source

isolated from

Cynodon dactylon (L.) Pers.

ICMP (1 records from Australia.)

isolated from

Dianella nigra Colenso

ICMP (1 records from New Zealand.)

isolated from

Holcus

ICMP (1 records from New Zealand.)

isolated from

Lactuca sativa L.

ICMP (1 records from New Zealand.)

isolated from

Lolium perenne L.

ICMP (1 records from New Zealand.)

isolated from

Malus ×domestica Borkh.

ICMP (1 records from New Zealand.)

isolated from

Paspalum dilatatum Poir.

ICMP (1 records from New Zealand.)

isolated from

Poaceae

ICMP (32 records from New Zealand.)

isolated from

Ranunculus acris L.

ICMP (1 records from New Zealand.)

isolated from

Tradescantia fluminensis

ICMP (1 records from New Zealand.)

isolated from

Vitis vinifera L.

ICMP (1 records from New Zealand.)

has host

Poaceae

PDD (2 records from New Zealand.)

isolated from

Sporobolus capensis (P.Beauv.) Kunth 1833

ICMP (1 records from South Africa.)

isolated from

Holcus lanatus L.

ICMP (1 records from United Kingdom.)

isolated from

Homo sapiens L., 1758

ICMP (1 records from United States.)

Descriptions

Pseudopithomyces toxicarius B.S. Weir, D. Lee, J.S. Sidhu & C.R. Voisey 2025

Description

Colonies – Flat, some sectors can become more floccose. Alternating light grey and olivaceous grey, with dark olivaceous reverse (Fig. 11). Optimum growth temperature at 24 °C, reaching 51 mm in diameter in 6 d. Conidiophores aggregate on agar surface forming sporodochia in 2–3 wk at 25 °C. Mycelium – Hyaline or straw-coloured to brown. Hyaline mycelium is usually thin walled, with septation less common. Pigmented mycelium can be thicker walled, with frequent septation where some areas appear prominently verrucose. Conidiophore – Micronematous (looks like mycelial hyphae). Conidiogenous cells – short, cylindrical and can be flexuous, smooth-walled, faintly pigmented. Secession rhexolytic. Released conidia retain small amount of the conidiogenous cell tissue at the base. Mostly 3.7–8.6 × 2–4 µm though some conidiogenous cells are too short to measure and conidia derived from such cells tend to form a bulbous base, but those with measurable conidiogenous cells can also form this bulbous base which is observed in ICMP 24486. Conidia – Pigmented, turning from straw-coloured to dark olivaceous brown with age. Mostly barrel shaped, obovoid, oblong, ellipsoid, obpyriform, and asymmetric in shape. Some may exhibit a bulbous base. Conidia are initially non-septate and echinulate, and this echinulation becomes less visible as the cell wall becomes darker and thicker. With maturation, the conidia mostly produce 2–3 transverse septa (mostly 3), very rarely 4–5, followed by multiple longitudinal septations (2–5, mostly 2) in each of the middle segments, though longitudinal septation can rarely occur on the apex. (14.4–) 17.3–20.4 (–27.8) × (7.6–) 10–11.8 (–15.4) µm, av. 19.1 ×11 µm, n = 147 at 25 °C (Figs 6, 12).

Notes

This species is strongly supported as different from Pse. chartarum and other Pseudopithomyces species through individual gene and genome analyses, and the production of the toxin sporidesmin. The conidia under controlled conditions were slightly smaller (with overlapping ranges) than Pse. palmicola and Pse. chartarum (Fig. 6), but in general conidial morphology (shape, colour, and septation) was indistinguishable from Pse. chartarum and Pse. palmicola (Fig. 12). Searches of literature and global culture collections revealed no earlier description under another name. The type isolate ICMP 24442 was isolated from a dairy farm in 2022 with animals showing signs of FE, this was selected as the type over the original 1958 ‘strain C’ isolate (ICMP 7074) (Percival & Thornton 1958) due to the possibility of changes or attenuation occurring during six decades of storage.

Typification

New Zealand, Bay of Plenty, Whakatāne, 37.9511°S 176.7924°E, on dead Poaceae leaf blade, 23 Mar. 2022, M. Gow, Ag031 (holotype PDD 120424, ex-holotype culture ICMP 24442 = CBS 153580 = IMI 507425). GenBank: OR691816 (ITS); SRR27202368 (genome).

Distribution

The origin of Pse. toxicarius is unknown, although it has caused problematic disease in New Zealand livestock for more than 100 years (di Menna et al. 2009). It is predominantly found on exotic pasture grasses rather than native plants, suggesting an origin outside of New Zealand. We also record this species from Australia, France, South Africa, United Kingdom, United States, and Uruguay (Table S1). Additional host range countries inferred from GenBank sequence homology are, Belgium (OW987887), Canada (KT965035), Colombia (EU272493), Costa Rica (KX499297), and the Netherlands (MH860299).