Aureobasidium plumeriae 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 plumeriae

<p><i>Aureobasidium plumeriae</i> Senwanna, Kodchasee, J. Kumla & N. Suwannar. sp. nov.</p><p>Fig. 20</p><p><b>Etymology.</b></p><p>Refers to the host genus <i>Plumeria</i>, from which this species was isolated.</p><p><b>Type.</b></p><p>THAILAND • Chiang Mai Province, Mueang District, Chang Phueak, isolated from frangipani flower (<i>Plumeria obtusa</i>; <i>Apocynaceae</i>, <i>Gentianales</i>), Jul 2024, P. Kodchasee, C. Senwanna, J. Kumla and N. Suwannarach, <i>holotype</i> = CMUB 40128 (preserved in metabolically inactive state), living culture (ex-type) = SDBR-CMU 836 = GMBCC 2502 = TBRC 21788.</p><p><b>Cultural characteristics.</b></p><p>After 14 days of incubation at 25 ° C in the dark, colonies on PDA reaching 58–64 mm diam., surface flat, spreading with entire margin, velvety, concentric, yellowish white (2 A 2), olive gray (1 D 2), with white to olive gray (1 D 2) at the margin; on MEA reaching 55–60 mm diam., surface flat, spreading with filiform margin, velvety, yellowish white (2 A 2) or pale yellow (2 A 3) at center, gradient from dark to light olive (2 F 6), with yellowish gray (4 B 2) to dull yellow (3 B 3) at the margin; on OA 65–70 mm diam., surface flat, spreading with entire margin, velvety, yellowish white (2 A 2), with light gray (2 C 1) at the margin.</p><p><b>Description.</b></p><p><i><i>Anamorph</i> in vitro</i> dematiaceous hyphomycetes. <i>Vegetative hyphae</i> (2.2 –) 3.3–8.0 (– 10) μm wide, hyaline, becoming light brown to brown melanized with age, branched, septate, smooth, thin-walled, getting thicker, constricted at the septa with age, anastomosis observed. <i>Conidiogenous cells</i> (4.8 –) 7.0–14.0 (– 18) × 3.0–5.0 μm (<i>x ̄</i> = 11.9 × 3.8 μm, <i>n</i> = 25), undifferentiated, intercalary, terminal, producing conidia percurrently from short lateral denticles, giving rise to conidia that aggregate in a mucoid mass, or differentiated on hyphae, hyaline to dark brown. <i>Conidia</i> (4.2 –) 5.2–8.7 (– 11.7) × 2–4.6 (– 6.0) μm (<i>x ̄</i> = 7.0 × 3.9 μm, <i>n</i> = 200), oval, ellipsoidal to obovoid, or globose to subglobose, hyaline, becoming light brown to brown with age, aseptate, occasionally with an indistinct truncated base and a hilum, guttulate, smooth-walled. <i>Chlamydospores</i> (6.5 –) 7.8–9.0 (– 10) (<i>x ̄</i> = 8.5 μm, <i>n</i> = 25) µm wide, produced in aerial hyphae, intercalary, solitary or in branched chains, subglobose, dark brown, smooth-, thick-walled, septate, constricted near the septa. <i>Endoconidia</i> 3.2–5.6 (– 6.3) × 1.8–2.8 (– 3.5) μm (<i>x ̄</i> = 4.4 × 2.6 μm, <i>n</i> = 25), obovoid to ellipsoidal, hyaline, occasionally seen in intercalary hyphal cells.</p><p>Fermentation of glucose is negative. <i>D</i> - glucose, galactose (weak), sorbose (weak), <i>N</i> - acetyl glucosamine, ribose, 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, melibiose (weak), lactose (weak), raffinose, melizitose (weak), glycerol (weak), 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 (weak), <i>D</i> - galacturonic acid (weak), <i>DL</i> - lactate, succinate (weak), citrate (weak), ethanol, and xylitol are assimilated, but inulin, soluble starch, 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, black sediment formed in <i>D</i> - glucose, <i>D</i> - galactose, <i>L</i> - sorbose, <i>N</i> - acetyl glucosamine, <i>D</i> - xylose, <i>L</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, melibiose, lactose, raffinose, melizitose, glycerol, erythritol, ribitol, <i>D</i> - glucitol, <i>D</i> - mannitol, galactitol, <i>myo</i> - inositol, <i>D</i> - glucono- 1, 5 - lactone, <i>D</i> - gluconate, <i>D</i> - glucuronate, <i>D</i> - galacturonic acid, <i>DL</i> - lactate, succinate, and citrate, while white sediment observed in <i>D</i> - ribose, <i>D</i> - arabinose, ethanol, and xylitol.</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 frangipani flower (<i>Plumeria obtusa</i>; <i>Apocynaceae</i>, <i>Gentianales</i>), Jul 2024, P. Kodchasee, C. Senwanna, J. Kumla and N. Suwannarach, living culture = SDBR-CMU 826.</p><p><b>Habitat and distribution.</b></p><p>Flowers of <i>Plumeria obtusa</i>. Known only from northern Thailand.</p><p><b>Notes.</b></p><p>The multilocus phylogenetic tree (Fig. 2) revealed that <i>A. plumeriae</i> SDBR-CMU 826 and SDBR-CMU 836 (ex-type) formed a monophyletic lineage with strong support (100 % MLBS and 0.98 BIPP). <i>Aureobasidium plumeriae</i> formed a sister clade to <i>A. motuoense</i>, <i>A. phayaoense</i>, <i>A. pollinicola</i>, and <i>A. siamense</i>. Sequence comparison showed that the ITS sequence of <i>A. plumeriae</i> showed 98.77 %, 99.66 %, 99.83 %, and 100 % similarity to those of <i>A. motuoense</i>, <i>A. siamense</i>, <i>A. pollinicola</i>, and <i>A. phayaoense</i>, respectively, whereas the LSU sequences showed 100 % similarity among all related species. In contrast, comparisons of the <i>rpb 2</i>, <i>tef 1</i>, and <i>tub</i> sequences revealed lower sequence similarity between <i>A. plumeriae</i> and its closest relatives, with 96.01 %, 92.83 %, and 97.24 % similarity to <i>A. phayaoense</i>; 96.33 %, 91.99 %, and 97.24 % similarity to <i>A. pollinicola</i>; and 96.24 %, 92.44 %, and 97.24 % similarity to <i>A. siamense</i>, respectively. However, differences in the <i>rpb 2</i>, <i>tef 1</i>, and <i>tub</i> sequence data could not be compared because sequences of <i>A. motuoense</i> were unavailable. Morphologically, the colony characteristics of <i>A. plumeriae</i> differed from those of most phylogenetically related sister taxa. In terms of growth temperature, <i>A. plumeriae</i> did not grow at 37 ° C, whereas <i>A. phayaoense</i> and <i>A. pollinicola</i> grew at this temperature. <i>Aureobasidium plumeriae</i> differs from <i>A. phayaoense</i> and <i>A. siamense</i> by the presence of endoconidia. In addition, <i>A. plumeriae</i> differs from <i>A. motuoense</i>, <i>A. pollinicola</i>, and <i>A. siamense</i> in having smaller conidia [(4.2 –) 5.2–8.7 (– 11.7) × 2.0–4.6 (– 6.0) μm vs. (6.5 –) 10.0–17.0 × 3.9–6.5 (– 7.4) μm vs. (3.2 –) 6.0–9.4 (– 14.5) × (2.1 –) 3.3–5.5 (– 6.6) μm vs. (5.1 –) 7.4–11.0 (– 16.2) × (2.1 –) 3.6–5.9 (– 8.2) μm] (Wu et al. 2023; this study). Furthermore, the PHI test indicated no significant recombination among these taxa (Fig. 3), supporting the recognition of <i>A. motuoense</i>, <i>A. phayaoense</i>, <i>A. plumeriae</i>, <i>A. pollinicola</i>, and <i>A. siamense</i> as distinct species. Based on physiological tests, <i>A. plumeriae</i> differs from <i>A. phayaoense</i> in its ability to assimilate <i>DL</i> - lactate and succinate (Table 1). In contrast, <i>A. siamense</i> differs from <i>A. plumeriae</i> by producing pigment when grown on <i>D</i> - glucono- 1, 5 - lactone. Moreover, <i>A. pollinicola</i> can be differentiated from <i>A. plumeriae</i> by differences in sediment formation characteristics (Table 1). Thus, <i>A. plumeriae</i> is introduced as a new species based on phylogenetic analyses, morphological and phenotypic characteristics, and growth temperature data.</p>