Colletotrichum thasutense Armand, K.D. Hyde and Jayaward., sp. nov.

Index Fungorum number: IF 900127; MycoBank number: MB 900127; Faceoffungi number: FoF 13361; Fig. 1

Etymology – Referring to the sub-district where the specimen was collected.

Holotype – MFLU 22-0206

Associated with leaf spot on Syngonium sp. Sexual morph: not observed. Asexual morph: On host: Acervuli present, setose, creamy to greyish white, subepidermal, produced solitary. Conidiophores rarely observed, hyaline, barrel shaped, 6.5–9×3–4 μm; Conidiogenous cells hyaline, cylindrical; 10.5–23 × 2.5–4 μm (x̄=16 × 3 μm, n=20). Conidia aseptate, hyaline, smooth-walled, cylindrical, straight to slightly curved, mostly rounded ends, rarely obtuse at one end, 13.5–17.5×3.5–5 μm (x̄=15.5×4.5 μm, n=20), Appressoria not observed. On PDA: Acervuli, Setae and Sclerotia absent.

Culture characteristics – Colonies on PDA white to pale yellow, reverse same color, reaching 70 mm diam. in 7 days at 28 °C. Colonies cottony, circular, slightly raised and depressed in the center, Aerial mycelia white and medium in dense.

Material examined – Thailand, Chiang Rai, Mueang, ThaSut, from Syngonium sp. (Araceae), associated with leaf spot; 16 October 2021, A. Armand, A2 (MFLU 22-0206, holotype), living ex-type living culture MFLUCC 22-0173.

GenBank numbers – OP821902 (ITS), OP831280 (act), OP831281 (chs-1),: OP831282 (gapdh), OP831283 (tub2).

Notes – Based on the phylogenetic analyses, Colletotrichum thasutense is closely related to C. xishuangbannaense (Fig. 2). Morphologically, C. thasutense differs from C. xishuangbannaense by producing longer and thicker conidia. Colletotrichum xishuangbannaense has 9–12 × 3–4 µm conidia (de Silva et al. 2021), whereas C. thasutense has 13.5–17.5×3.5–5 μm conidia. Colletotrichum thasutense can be differentiated from C. xishuangbannaense in having slightly curved conidia and obtuse at one end. However, C. xishuangbannaense produces straight conidia with rounded ends. Moreover, C. thasutense bears longer and thicker conidiogenous cells (10.5–23×2.5–4 μm) than C. xishuangbannaense (15–18×1.5–2 µm).

Figure 1 – Colletotrichum thasutense (MFLU 22–0206, holotype) a Host plant. b Host leaf with symptom. c Acervuli on the host. d setae. e–g Conidiogenous cells and conidia. h–j Conidia. Scale bars: d=10 µm, e–g=5 µm, h-j=10 µm

Figure 2 – One of two most parsimonious trees obtained with PAUP v. 4.0b10 (Swofford 2003) from a heuristic search of the combined sequence alignment of ITS, gapdh, chs-1, act and tub2 of the Colletotrichum gleosporioides species complex, rooted with C. truncatum (CBS 151.35). Bootstrap support values of MP and ML≥70% and BYPP values≥0.90 are shown at the nodes. Ex-type and reference strains are in bold. New sequence data are in red