Aureobasidium chiangmaiense Senwanna, Kodchasee, J. Kumla & N. Suwannar. 2026, sp. nov.
Authors: Senwanna, Chanokned, Kodchasee, Pratthana, Kathongthung, Chirayut, Samarakoon, Milan C., Khunnamwong, Pannida, Kumla, Jaturong, Suwannarach, Nakarin
Type: Taxonomic treatment
Published: 2026-08-03
Keywords: Biodiversity, Taxonomy, Fungi, Ascomycota, Dothideomycetes, Dothideales, Saccotheciaceae, Aureobasidium, Aureobasidium chiangmaiense

<p><i>Aureobasidium chiangmaiense</i> Senwanna, Kodchasee, J. Kumla & N. Suwannar. sp. nov.</p><p>Fig. 10</p><p><b>Etymology.</b></p><p>Refers to Chaing Mai Province, where the flowers containing the new fungus were collected.</p><p><b>Type.</b></p><p>THAILAND • Chiang Mai Province, Mueang District, Chang Phueak, isolated from oleander flower (<i>Nerium oleander</i>; <i>Apocynaceae</i>, <i>Gentianales</i>), Jul 2024, P. Kodchasee, C. Senwanna, J. Kumla and N. Suwannarach, <i>holotype</i> = CMUB 40129 (preserved in metabolically inactive state), living culture (ex-type) = SDBR-CMU 819 = GMBCC 2497 = TBRC 21780.</p><p><b>Cultural characteristics.</b></p><p>After 14 days of incubation at 25 ° C in the dark, colonies on PDA reaching 50–55 mm diam., surface round with slightly raised, filiform margin, velvety, white to orange gray (5 B 2), with light gray (3 D 1) at the margin; on MEA reaching 40–46 mm diam., surface flat, spreading with entire, filiform margin, velvety, grayish orange (6 B 5), with white to light gray (3 D 1) at the margin; on OA 42–47 mm diam., surface flat, woolly, spreading with filiform, entire margin, light gray (3 D 1) to brownish gray (4 E 2), with light gray (3 D 1) at the margin.</p><p><b>Description.</b></p><p><i><i>Anamorph</i> in vitro</i> dematiaceous hyphomycetes. <i>Vegetative hyphae</i> 3.0–7.0 (– 8.8) μm wide, hyaline to brown, branched, septate, smooth, thin-walled, getting darker and thicker with age, light brown to brown, constricted at the septa, guttulate. <i>Conidiogenous cells</i> 9–10.5 (– 12.5) × 4.2–7.6 μm (<i>x ̄</i> = 10.2 × 6.0 μm, <i>n</i> = 25), undifferentiated, intercalary, terminal, producing conidia percurrently from indistinct, short lateral denticles, giving rise to conidia that aggregate in a mucoid mass, or differentiated on hyphae, hyaline to light brown. <i>Conidia</i> obovoid to ellipsoidal, fusoid, or subglobose, hyaline to light brown, becoming brown with age, aseptate, occasionally with an indistinct truncated base and a hilum, smooth-walled, guttulate, (3.8 –) 5.2–7.9 (– 11.7) × (2.0 –) 2.8–5.0 (– 8.1) μm (<i>x ̄</i> = 6.7 × 3.8 μm, <i>n</i> = 160), budding occasionally observed. <i>Chlamydospores</i> (5.5 –) 7–9 (– 11.5) (<i>x ̄</i> = 8.1 μm, <i>n</i> = 25) µm wide, produced in aerial hyphae, mostly intercalary, in branched chains, globose to subglobose, light to dark brown, smooth-, thick-walled, septate, constricted near the septa. <i>Endoconidia</i> absent.</p><p>Fermentation of glucose is negative. <i>D</i> - glucose, galactose, sorbose, <i>N</i> - acetyl glucosamine, ribose (weak), xylose, <i>L</i> - arabinose, <i>D</i> - arabinose, <i>L</i> - rhamnose, sucrose, maltose, <i>α</i> - <i>α</i> - trehalose, methyl- <i>α</i> - <i>D</i> - glucoside, cellobiose, salicin (weak), melibiose (weak), lactose, raffinose (weak), melizitose, inulin (weak), glycerol, erythritol (weak), ribitol, glucitol, mannitol, galactitol, <i>myo</i> - inositol (weak), <i>D</i> - glucono- 1, 5 - lactone, <i>D</i> - gluconate, <i>D</i> - glucuronate, <i>D</i> - galacturonic acid, succinate, citrate, ethanol (weak), and xylitol (weak) are assimilated, but soluble starch, <i>DL</i> - lactate, and methanol are not assimilated. Ammonium sulfate, ethylamine hydrochloride, <i>L</i> - lysine, cadaverine, and creatine are assimilated as sole nitrogen sources. Potassium nitrate and sodium nitrite are not assimilated. After 3 weeks, light brown sediment formed in <i>D</i> - glucose, <i>D</i> - galactose, <i>N</i> - acetyl glucosamine, <i>α</i> - <i>α</i> - trehalose, cellobiose, melibiose, melizitose, and glycerol, while dark brown sediment formed in <i>D</i> - xylose, salicin, raffinose, and <i>D</i> - glucono- 1, 5 - lactone. Black sediment formed in erythritol.</p><p><b>Cardinal temperatures for growth.</b></p><p>Minimum 10 ° C, optimum in the range of 25 ° C to 30 ° C. No growth at 4 ° C and 37 ° C.</p><p><b>Additional strains examined.</b></p><p>THAILAND • Chiang Mai Province, Mueang District, Chang Phueak, isolated from Persian gentian flower (<i>Exacum affine</i>; <i>Gentianaceae</i>, <i>Gentianales</i>), Jul 2024, P. Kodchasee, C. Senwanna, J. Kumla and N. Suwannarach, living culture = SDBR-CMU 818.</p><p><b>Habitat and distribution.</b></p><p>Flowers of <i>Exacum affine</i> and <i>Nerium oleander</i>. Known only from northern Thailand.</p><p><b>Notes.</b></p><p>In the multilocus phylogenetic analyses, <i>A. chiangmaiense</i> SDBR-CMU 818 and SDBR-CMU 819 (ex-type) formed a distinct monophyletic lineage (100 % MLBS and 1.00 BIPP) that was sister to <i>A. musti</i> and <i>A. zhengzhenxiangiae</i> (Fig. 2). The <i>rpb 2</i> sequences of <i>A. chiangmaiense</i> showed 98.01 % similarity to that of <i>A. musti</i> MCA 7652, differing by 1.99 % (18 / 906 bp, including gaps), and 96.33 % similarity to that of <i>A. zhengzhenxiangiae</i> BRIP 76360 a, differing by 3.67 % (23 / 627 bp, including gaps). The sequences of <i>A. chiangmaiense</i> differed from those of <i>A. musti</i> SDBR-CMU 825 and SDBR-CMU 864 obtained in this study by 3.92 % in <i>rpb 2</i> (40 / 1,020 bp, including gaps), 9.38 % in <i>tef 1</i> (21 / 224 bp, including gaps), and 6.60 % in <i>tub</i> (27 / 409 bp, including gaps). However, <i>A. chiangmaiense</i> is distinguishable from <i>A. musti</i> based on differences in colony characteristics. Colonies of <i>A. chiangmaiense</i> are white to orange gray with a light gray margin on PDA and grayish orange with a white to light gray margin on MEA, whereas <i>A. musti</i> forms reddish to purple colonies on PDA and yellow to orange colonies on MEA (Jumbam et al. 2025; this study). Moreover, <i>A. chiangmaiense</i> did not grow at 4 ° C or 37 ° C, whereas <i>A. musti</i> was able to grow at both temperatures. The conidia of <i>A. chiangmaiense</i> are wider (2.0–8.1 µm) than those of <i>A. musti</i> (0.5–4.8 µm) (Jumbam et al. 2025; this study). Nevertheless, morphological and colony comparisons with the type strain of <i>A. zhengzhenxiangiae</i> could not be made owing to the absence of available data (Tan et al. 2026 b). Furthermore, the PHI test confirmed the genetic distinctiveness of <i>A. chiangmaiense</i>, <i>A. musti</i>, and <i>A. zhengzhenxiangiae</i> (Fig. 3). <i>Aureobasidium chiangmaiense</i> can be distinguished from <i>A. musti</i> by its ability to assimilate <i>L</i> - sorbose, <i>D</i> - arabinose, <i>L</i> - rhamnose, salicin, glycerol, erythritol, ribitol, <i>D</i> - mannitol, galactitol, <i>myo</i> - inositol, <i>D</i> - glucono- 1, 5 - lactone, <i>D</i> - gluconate, succinate, ethanol, and xylitol (Jumbam et al. 2025). In addition, <i>A. chiangmaiense</i> differs from <i>A. musti</i> in its inability to assimilate potassium nitrate and sodium nitrite and its ability to assimilate creatine, whereas <i>A. musti</i> can assimilate potassium nitrate and sodium nitrite but not creatine (Jumbam et al. 2025). Based on the combined morphological, physiological, and molecular evidence, <i>A. chiangmaiense</i> is described herein as a new species.</p>