Fusarium nirenbergiae
Fusarium nirenbergiae L. Lombard & Crous, Persoonia 41: 29 (2018)
Index Fungorum number: IF 826845 Facesoffungi number:
Pathogenic to spring onion (Allium fistulosum) and causes yellowing, curling, and wilting of leaves, often accompanied by basal rot and reddish-brown discoloration of the roots and bulb plate. Sexual morph not observed. Conidiophores on aerial mycelium unbranched or slightly branched, comprise terminal or intercalary monophialides, often reduced to single phialides. Aerial phialides, subulate to subcylindrical, smooth, thin-walled, 9–23 × 1.5–2.5 µm, with unnoticeable or absent periclinal thickening. Aerial conidia formed in small false heads on the tips of the phialides, 0–1-septate 0-septate conidia: 5–9 × 2–4 μm (mean = 8 × 3 μm, n = 20), 1-septate conidia: 9–14 × 2–4 μm (mean = 12 × 3 μm, n = 20). Macroconidia falcate, curved dorsoventrally, with apical cell blunt to papillate, curved, basal cell blunt to foot-like, hyaline, smooth, and thin-walled, 3–5-septate: 3-septate conidia: 31–41 × 3.5–4 μm (mean = 35 × 4 μm, n = 20), 4-septate conidia: 35–45 × 3–5 μm (mean = 38 × 4 μm, n = 20), 5-septate conidia: 42–55 × 3–4 μm (mean = 50 × 4 μm, n = 20). Sporodochia and chlamydospores were not observed.
Culture characteristics: Colonies on PDA reach 65 mm in diameter after 7 days of growth at 25 °C in the dark, white to pale vinaceous, with abundant aerial mycelium and filiform margins. Reverse is pale vinaceous.
Material examined: Thailand, Chiang Rai Province, Mueang Chiang Rai District, Doi Hang, on spring onion (Allium fistulosum), February 2023, Maryam Fallahi, dried culture MF112-2 (MFLU 24-0251), living culture MFLUCC 24-0248.
Notes: In the phylogenetic tree generated for Fusarium oxysporum species complex, strain MFLUCC 24-0248 clustered with the ex-type strain of Fusarium nirenbergiae (CBS 840 88) with 68% ML, 73% IQ bootstrap support, and 0.99 BYPP (Fig. 25). The base pair differences between F. nirenbergiae strains MFLUCC 24-0248 and CBS 840 88 revealed a 0.16% (1/612 bp) difference in tef1 and a 0.57% (5/876 bp) difference in rpb2. The sequence data of rpb1 is not available for F. nirenbergiae (CBS 840 88). Fusarium nirenbergiae (MFLUCC 24-0248) did not produce sporodochia or chlamydospores; however, the ex-type strain of F. nirenbergiae did produce both structures. (Lombard et al. 2019). Phylogenetically, F. nirenbergiae is closely related to F. curvatum; however, they are distinguished based on morphology and molecular analysis (Lombard et al. 2019). Fusarium nirenbergiae is globally recognized as a causative agent of wilting on various hosts (Lombard et al. 2019; Aiello et al. 2021). To the best of our knowledge, this study represents the first report of Fusarium wilt on spring onion caused by F. nirenbergiae.
Figure 1. Phylogenetic tree of the Fusarium oxysporum species complex generated by maximum likelihood of combined tef1, rpb1, and rpb2 sequence data. The ultrafast maximum likelihood (ML) and IQ bootstrap support values ≥ 50% as well as Bayesian posterior probabilities ≥ 0.95 (BYPP) are shown, respectively, near the nodes. The ex-type strains are marked with an asterisk. The tree is rooted in Fusarium proliferatum (CBS 480 96).
Figure 2. Fusarium nirenbergiae (MFLUCC 24-0248) a spring onion wilting b front and c back views of the colony after seven days of growth on PDA at 25 °C d, e aerial conidiophores, conidiogenous cells, and conidia. Scale bars: 10 μm.
- Fallahi M, Armand A, AI-Otibi F, Hyde KD. Pathogenic fungi (Sordariomycetes) associated with annual and perennial crops in Northern Thailand. MycoKeys 117, 191–265.
https://doi.org/10.3897/mycokeys.117.137112
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