Fusarium castaneophilum M. W. Zhang & C. M. Tian, 2025

Fusarium castaneophilum M. W. Zhang & C. M. Tian sp. nov.

Fig. 4 View Figure 4

Type.

China • BeiJing, Huairou District Castanea Technology Test and Promotion Station (40°25'37.21"N, 116°32'42.83"E), on branch of Castanea mollissima , 9 Oct 2022, Y. Ren, holotype BJFC-HR 08 , ex-type living culture CFCC 70814 GoogleMaps .

Etymology.

Named after the host genus from which it was isolated, Castanea .

Description.

Conidiophores in aerial mycelia, 12–49 μm tall, simple or loosely irregularly branched, bearing terminal or intercalary polyphialides, smooth- and thin-walled, 5.9–35.8 × 1.9–4.3 (av. ± sd. 14.2 ± 6.5 × 2.7 ± 0.5 μm), periclinal thickening inconspicuous or absent; aerial conidia hyaline, smooth- and thin-walled, of two types: (a) microconidia ellipsoidal, obovoid to subclavate, 0–1 - septate: 4.5–12 × 2–3.6 μm (av. ± sd. 7.2 ± 1.5 × 2.7 ± 0.3 μm); (b) macroconidia clavate to falcate, straight or dorsiventrally curved, with a blunt to slightly papillate apical cell and a blunt to barely notched or foot-like basal cell, smooth- and thin-walled, 1–3 - septate; 1 - septate conidia: 14.7–48.6 × 2.3–7.5 μm (av. ± sd. 28.9 ± 8.1 × 4.8 ± 1.3 μm); 2 - septate conidia: 24.6–70.4 × 2.2–7.1 μm (av. ± sd. 39.9 ± 8.9 × 5.1 ± 0.9 μm); 3 - septate conidia: 26.6–90.4 × 2.2–7.3 μm (av. ± sd. 56.3 ± 14.1 × 5 ± 1.2 μm). Chlamydospores formed in pairs or forming chains, intercalary, globose to subglobose, 7.3–9.5 µm diam, thick-walled, smooth. Sporodochia not observed.

Culture characteristics.

Colonies on PDA growing in the dark reaching 7.8–8.0 cm diam after 7 days at 25 ° C, optimal 25–30 ° C (after 7 days), raised, aerial mycelia dense, colony margin filamentous, surface vinaceous purple in the center, pale luteous at the margin; reverse dark purple in the center, pure yellow at the margin. Colonies on OA growing in the dark reaching 6.8–7 cm diam after 7 days at 25 ° C, raised, aerial mycelia dense, colony margin entire, surface white; reverse orange in the center, luteous at the margin. Colonies on SNA grown in the dark reaching 6.4–6.6 cm diam after 7 days at 25 ° C, flat, aerial mycelia scant, colony margin entire, white; reverse white. Pigment and odor absent.

Notes.

The isolates of F. castaneophilum were phylogenetically closely related to F. elaeagni (ex-type, LC 13627) isolated from Elaeagnus pungens in China (Fig. 2 View Figure 2 ). There were 24 nucleotide position differences between the two species (7 / 658 in tef 1, 1 / 591 in CaM, 9 / 891 in rpb 1, 3 / 879 in rpb 2, 4 / 490 in tub 2). The PHI analysis showed that there was no significant recombination between F. castaneophilum isolates and its related species (Φw = 0.7005) (Fig. 3 A View Figure 3 ). Morphologically, F. elaeagni did not produce any pigment, and the aerial mycelium on PDA was raised, aerial mycelia dense, sporodochia were grayish-orange, and abundantly formed on carnation leaves. However, F. castaneophilum produces a purple pigment, and the mycelium on PDA is sparser than the former, no obvious protruding colonies. Microscopically, F. castaneophilum has chlamydospores and its aerial phialides are longer than F. elaeagni , microconidia are slightly larger than F. elaeagni . Thus, F. castaneophilum is recognized as a novel species in FFSC.