Diaporthe fistulosi Fallahi, Jayawar. & K. D. Hyde, 2025

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

Diaporthe fistulosi Fallahi, Jayawar. & K. D. Hyde sp. nov.

Fig. 13

Etymology.

‘ fistulosi ’ refers to the host plant species from which the fungus was isolated.

Description.

Pathogenic to spring onion ( Allium fistulosum ) and causes basal rot and wilting symptoms on infected plants. Sexual morph not observed. Pycnidia immersed with black neck, slightly elongated. Conidiophores densely aggregated, unbranched, hyaline, subcylindrical, straight to sinuous, 6.5–17.5 × 1.5–2.5 μm (mean = 13 × 1.5 μm, n = 10). The conidiogenous cells phialidic, terminal, slightly tapering towards the apex. Paraphyses elongate above the conidiophores, hyaline, smooth, cylindrical, septate, unbranched, 10–20 × 2–2.5 μm (mean = 15 × 2.3 μm, n = 15). Beta conidia filiform, curved at one tip, hyaline, aseptate, rounded at tips, 15–25 × 1–1.4 μm (23 × 1 μm, n = 40). Alpha and gamma conidia are absent.

Culture characteristics.

Colonies on PDA reach 65–70 mm in diameter after 7 days of growth at 25 ° C in the dark, covered with plenteous greyish-white villous aerial mycelium after 7 days. The reverse is slightly reddish-yellow in the center, with black fruiting bodies with age.

Material examined.

Thailand • Chiang Rai Province, Mueang Chiang Rai District, Doi Hang , spring onion ( Allium fistulosum ), February 2023, Maryam Fallahi, dried culture MF 112-3 ( MFLU 24-0261 , holotype), ex-holotype culture, MFLUCC 24-0244 .

Notes.

Based on phylogenetic analysis of ITS, tef 1, tub 2, cal, and his 3 sequence data, the strain MFLUCC 24-0244 formed a distinct branch within the subclade containing Diaporthe pterocarpicola ( MFLUCC 10-0580 a [ex-type] and MFLUCC 10-0580 b) in the Diaporthe arecae species complex, supported by 100 % ML bootstrap and 1.0 BYPP (Fig. 12 ). It is introduced here as a new species, Diaporthe fistulosi . The base pair differences between D. fistulosi strains MFLUCC 24-0244 (ex-holotype) and MFLUCC 10-0580 a were 0.97 % (5 / 513 bp) in ITS, 0.31 % (1 / 315 bp) in tef 1, 0.25 % (1 / 391 bp) in tub 2, and 1.4 % (3 / 212 bp) in cal. The sequence data of his 3 is not available for D. pterocarpicola ( MFLUCC 10-0580 a). Unlike the holotype of D. pterocarpicola ( MFLU 12-0129 ), which produced alpha conidia and did not produce beta conidia ( Udayanga et al. 2012), D. fistulosi ( MFLUCC 24-0244 ) only produced beta conidia. A pairwise homoplasy index (PHI) test indicated no significant recombination (Φw = 1.0) between D. fistulosi ( MFLUCC 24-0244 ) and its closely related taxa (Fig. 14 ).

Figures

Figure 12. Phylogenetic tree of the Diaporthe arecae species complex generated by maximum likelihood of combined ITS, tef 1, tub 2, cal, and his 3 sequence data. The ultrafast maximum likelihood (ML) bootstrap support values ≥ 50 % (BT) and Bayesian posterior probabilities ≥ 0.90 (BYPP) are shown, respectively, near the nodes. The ex-type strains are marked with an asterisk. The tree is rooted in two strains of Diaporthe xunwuensis (CFCC 53086, CFCC 53085).

Figure 13. Diaporthe fistulosi (MFLUCC 24-0244, holotype) a wilting symptom in spring onion b front, and c back view of the colony on PDA after 10 days d front and e back view of the colony on PDA after 60 days f conidiomata g, h section view of conidiomata, conidiogenous cells, and paraphyses i – k beta conidia. Scale bars: 20 μm.

Figure 14. Pairwise homoplasy index (PHI) test of Diaporthe fistulosi (MFLUCC 24-0244, holotype) and closely related species using both LogDet transformation and splits decomposition. PHI test results (Φw) < 0.05 indicate significant recombination among the species (Φw = 1).