Fusarium cumulatum Dewing, Visagie & Yilmaz, 2025

Fusarium cumulatum Dewing, Visagie & Yilmaz sp. nov.

Fig. 2 View Figure 2

Etymology.

Latin, cumulatum , meaning to accumulate or heap up, named for its abundant chlamydospore formation.

Type.

South Africa • Eastern Cape, from mixed pasture samples, May 2020, collected by A. Davis (holotype: PRU (M) 4601 , dried specimen in a metabolically inactive state); (ex-type strain: CBS 151773 View Materials = CMW 58688 View Materials = CN 104 D 3 ) .

Description.

Conidiophores borne on aerial mycelium scarce, 13–71 μm tall, unbranched, bearing terminal phialides, often reduced to single phialides; aerial phialides scarce, monophialidic, subulate to subcylindrical, proliferating percurrently, smooth- and thin-walled, 2.5–20 × 2–4 μm, with inconspicuous thickening; aerial conidia absent. Sporodochia orange, present on the surface of carnation leaves and on agar. Sporodochial conidiophores densely and irregularly branched, bearing apical whorls of 2–5 phialides; sporodochial phialides monophialidic, subulate to subcylindrical, 7–16.5 × 2–4 μm, smooth, thin-walled, with inconspicuous periclinal thickening; sporodochial conidia falcate, sometimes becoming sinuate, slender, curved dorsiventrally, tapering towards both ends, with an elongated or whip-like curved apical cell and a barely notched to prominently extended basal cell, 1–5 - septate, hyaline, smooth- and thin-walled; 1 - septate conidia 16 × 4 μm (n = 1); 2 - septate conidia 18–30 × 3–4 μm (av. 25.2 × 3.6 μm) (n = 3), 3 - septate conidia 23–42 × 2.5–4 μm (av. 25.2 × 3.5 μm) (n = 15), 4 - septate conidia 25.5–54.5 × 2.5–4 μm (av. 43.0 × 3.4 μm) (n = 14), 5 - septate conidia 38–57 × 3–4.5 μm (av. 49.1 × 3.8 μm) (n = 17). Chlamydospores abundant, globose to subglobose, subhyaline, smooth- to slightly rough-walled, terminal or intercalary, solitary or in pairs forming chains, 8–19 μm diam.

Culture characteristics.

Colonies on PDA incubated at 25 ° C in the dark with an average radial growth rate of 2–8 mm / d, reaching 44–46 mm diam at 25 ° C; surface white, flat, felty to velvety, radiate, with abundant aerial mycelium, margin irregular. Additional colony diam (after 7 d, in mm): PDA 10 ° C 13–15; PDA at 15 ° C 22–26; PDA at 20 ° C 27–32; PDA at 30 ° C 64–75; PDA at 35 ° C 0–2. Odour absent. Reverse yellowish white (2 A 2). Diffusible pigments absent. On OA in the dark, occupying an entire 90 mm Petri dish in 7 d; surface white to pale yellow, flat, felty to velvety, radiate, with abundant aerial mycelium, margin irregular, filiform. Reverse yellowish white (4 A 2). Diffusible pigments absent. On SNA with sparse aerial mycelium, sporulation moderate on the surface of the medium.

Additional materials examined.

South Africa • Eastern Cape, from mixed pasture samples, May 2020, collected by A. Davis, isolated by C. Dewing, Humansdorp area: CMW 58686 View Materials = CN 071 B 9 , CMW 58687 View Materials = CN 071 E 5 , close to Villa Fonte : CMW-IA 002138 = CMW 60936 View Materials = CN 071 G 4 .

Notes.

Fusarium cumulatum belongs to the Equiseti - clade and is closely related to F. arcuatisporum ( FIESC 7) ( Wang et al. 2019), F. brevicaudatum ( FIESC 6) ( Xia et al. 2019), F. heslopiae ( Tan and Shivas 2024) , F. longicaudatum ( Xia et al. 2019) , F. khuzestanicum and F. oryzicola ( Afzalinia et al. 2024) . No aerial phialides or conidia were observed for the closely related species ( Wang et al. 2019; Xia et al. 2019; Afzalinia et al. 2024) compared to the few scarce monophialides we recorded for F. cumulatum . Sporodochia and chlamydospores were present in F. cumulatum and its closely related species, whereas F. oryzicola lacked chlamydospore formation ( Wang et al. 2019; Xia et al. 2019; Afzalinia et al. 2024). Sporodochial conidia of F. cumulatum (1–5 - septate; 16–57 × 2.5–4 μm) are similar in length to F. arcuatisporum (5 - septate; 29–49.5 × 4–6 μm) ( Wang et al. 2019) and F. brevicaudatum (1–5 - septate; 8–64 × 3–5 μm) ( Xia et al. 2019), while generally being shorter than those observed in F. khuzestanicum (4–7 (– 9) - septate; 48.5–82 × 2.7–4.3 μm) ( Afzalinia et al. 2024), F. longicaudatum (( 3 –) 5–6 (– 7) - septate; 45–81 × 4–5 μm) ( Xia et al. 2019) and F. oryzicola (4–7 - septate; 33.5–77.9 × 3–4 μm) ( Afzalinia et al. 2024). Colony colour on PDA differs between F. cumulatum and closely related species ( Wang et al. 2019; Xia et al. 2019; Afzalinia et al. 2024) as other species show more colour across the surface and reverse compared to the white surface and yellowish white (2 A 2) reverse of F. cumulatum , whereas the colony colour of F. khuzestanicum and F. oryzicola is white to pale grey. The growth rate after 7 d on PDA for F. cumulatum (44–46 mm) is slower than that of F. arcuatisporum (48–53 mm) ( Wang et al. 2019), F. brevicaudatum (50–58 mm) ( Xia et al. 2019) and F. longicaudatum (full 90 mm plate) ( Xia et al. 2019). The growth rate for F. khuzestanicum (74–76 mm) ( Afzalinia et al. 2024) and F. oryzicola (74 mm) ( Afzalinia et al. 2024) was measured after 5 d on PDA but appears to be faster than that of F. cumulatum . No morphological data is currently available for F. heslopiae to compare with. Pairwise comparisons revealed that F. cumulatum differs from other species by at least 3, 6 and 16 bp for CaM, RPB 2 and TEF, respectively.