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

Fig. 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 .

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). 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). 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.