Diaporthe melonis Beraha & M. J. O'Brien

Diaporthe melonis Beraha & M. J. O’Brien, Phytopath. Z. 94 (3): 205 (1979) Fig. 2 Description. Saprobic on dead unidentified branch. Sexual morph: not observed. Asexual morph: Conidiomata 148–374 × 128–338 µm high (x ̄ = 250 × 225 µm, n = 15), pycnidial, mostly scattered, immersed, slightly erumpent through the host surface, discoid or subglobose, with a solitary undivided locule. Conidiophores reduced to conidiogenous cells. Alpha conidiogenous cells 5.7–25 × 1.1–2.5 µm (x ̄ = 15.6 × 1.7 µm, n = 50), hyaline, rarely branched, mostly aseptate, densely aggregated, cylindrical, straight to slightly curved and smooth. Alpha conidia 5–7.3 × 1.9–2.7 µm (x ̄ = 6.3 × 2.3 µm, n = 40), unicellular, fusiform to ellipsoidal, apex and base rounded, hyaline, smooth, bi-guttulate. Beta conidiogenous cells 6.2–16 × 1.6–2.6 µm (x ̄ = 9.4 × 2.1 µm, n = 40), phialidic, subcylindrical, tapering towards the apex, hyaline. Beta conidia 19–27 × 1–2 µm (x ̄ = 23 × 1.5 µm, n = 40), filiform, aseptate, hyaline, smooth-walled, straight from base, and curve at apex. Gamma conidia not observed. Culture characteristics. Colonies on PDA, reaching 20 mm diam., after 3 weeks at 25 ° C, initially white, turning beige after 7–10 days, flat, felty with a thick texture at the centre and marginal area, lacking aerial mycelium; reverse, glossy grey, radiating outwardly. Material examined. Thailand, Chiang Rai Province, Muang District, on a dead unidentified dicot branch, 16 January 2023, J. Louangphan, CR 1-02 (MFLU 23–0474); living culture MFLUCC 24–0522 = MFLUCC 23–0300. Hosts. Annona squamosa (Annonaceae), Berberis aristata (Berberidaceae), Carapa guianensis (Meliaceae), Citrus grandis cv. Tomentosa (Rutaceae), Cucumis melo (Cucurbitaceae), Glottidium sp. (Fabaceae), Glycine max, G. soja (Fabaceae), unidentified branch (Dong et al. 2021 a, b; Hongsanan et al. 2023; This study). Distribution. China, Myanmar, India, Indonesia, Japan, Thailand, the United States (Dong et al. 2021 a, b; Hongsanan et al. 2023; this study). Notes. Our isolates (MFLUCC 23–0300 and MFLUCC 24–0522) clustered with D. melonis isolates (CBS 507.78, FAU 640, and ZHKUCC 20-0014) with 100 % ML / 1.00 BPP support (Fig. 1). Our isolate has a similar morphology to D. melonis but differs in having smaller conidiomata (148–374 µm vs. 100–500 µm diam.) and smaller alpha conidia (6.3 × 2.3 µm vs. 8.3 × 2.6 µm) (Beraha and O’Brien 1979). Our isolate has a beige culture compared to the brown culture of D. melonis (Beraha and O’Brien 1979). Our isolate also differs from D. melonis (D. guangdongensis ZHKUCC 20-0014) in the size of conidiomata (128–338 × 148–374 µm vs. 130–515 × 100–390 µm), alpha conidia (5–7.3 × 1.9–2.7 µm vs. 6–8 × 2–4 µm), and beta conidia (19–27 × 1–2 µm vs. 14–35 × 1–2 µm) (Dong et al. 2021 a, b). Therefore, we report our isolate as a new geographical record of D. melonis from Thailand.