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

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).