Fusarium bubalinum J. W. Xia, L. Lombard, Sand.-Den., X. G. Zhang & Crous

Fallahi, Maryam, Armand, Alireza, Al-Otibi, Fatimah, Hyde, Kevin D. & Jayawardena, Ruvishika S., 2025, Pathogenic fungi (Sordariomycetes) associated with annual and perennial crops in Northern Thailand, MycoKeys 117, pp. 191-265 : 191-265

Fusarium bubalinum J. W. Xia, L. Lombard, Sand.-Den., X. G. Zhang & Crous , Persoonia 43: 195 (2019)

Fig. 22

Description.

Pathogenic to dragon fruit ( Hylocereus trigonus ) and causes stem rot. Sexual morph not observed. Conidiophores on aerial mycelium unbranched, sympodial, or irregularly branched, comprising terminal or lateral phialides that are frequently reduced to single phialides. Conidiogenous cells mono- or polyphialidic, subulate to subcylindrical, smooth and thin-walled, 5–25 × 1.5–3.5 μm. Aerial conidia ellipsoidal to falcate, slender, curved dorsoventrally, tap towards both ends, blunt to conical and straight to slightly curved apical cell, with a blunt to papillate basal cell, 0–7 septate, 8–28.5 × 1.3–2.8 µm (mean = 16 × 2 μm, n = 30). Microcyclic conidiogenesis often occurs. Sporodochia and chlamydospores are absent.

Culture characteristics.

Colonies on PDA reach 80 mm in diameter after 7 days of growth at 25 ° C in the dark, cottony, white to buff, floccose, and radiate with moderate aerial mycelium, filiform, and margins irregular, having sparse aerial mycelium and high sporulation on the surface of SNA medium. The reverse is a pale primrose.

Material examined.

Thailand • Chiang Rai, Mueang Chiang Rai District, Doi Hang . On stem rot in dragon fruit, February 2023, Maryam Fallahi, dried culture MF 35-5 ( MFLU 24-0249 ), living culture MFLUCC 24-0230 .

Notes.

Based on phylogenetic analysis, strain MFLUCC 24-0230 clustered in the same subclade with Fusarium bubalinum (CBS 161-25, ex-type) in Fusarium incarnatum species complex with 97 % ML, 99 % IQ bootstrap support and 0.99 BYPP (Fig. 21 ). The base pair differences between F. bubalinum strains MFLUCC 24-0230 and ex-type CBS 161-25 showed that they are identical in tef 1 and rpb 2, and sequence data of rpb 1 are not available for F. bubalinum (CBS 161-25, ex-type). Fusarium bubalinum ( MFLUCC 24-0230 ) is similar to the ex-type strain of F. bubalinum in morphology (CBS 161-25). Fusarium bubalinum was introduced as a new species in the Fusarium incarnatum-equiseti complex, and the type strain was isolated from an unknown substrate in Australia ( Xia et al. 2019). However, details regarding its host are scarce. Recently, it was reported in association with sheath rot disease of rice in Indonesia ( Pramunadipta et al. 2022). In this study, we report F. bubalinum causing stem rot in dragon fruit in northern Thailand as a new host and geographical record.

Figures

Figure 21. Phylogenetic tree of the Fusarium incarnatum species complex generated by maximum likelihood of combined tef 1, rpb 1, and rpb 2 sequence data. The ultrafast maximum likelihood (ML) and IQ bootstrap support values ≥ 50 % (BT), 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 F. concolor (NRRL 13994).

Figure 22. Fusarium bubalinum (MFLUCC 24-0230) a stem rot in dragon fruit b upper, and c reverse views of the colony after seven days of growth on PDA at 25 ° C d, e conidia f conidiophores and conidia anastomose and germination g – i conidiophores, conidiogenous cells, and aerial conidia. Scale bars: 20 μm.