Aureobasidium plumeriae Senwanna, Kodchasee, J. Kumla & N. Suwannar. 2026, sp. nov.

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Aureobasidium plumeriae Senwanna, Kodchasee, J. Kumla & N. Suwannar. sp. nov. Fig. 20 Etymology. Refers to the host genus Plumeria, from which this species was isolated. Type. THAILAND • Chiang Mai Province, Mueang District, Chang Phueak, isolated from frangipani flower (Plumeria obtusa; Apocynaceae, Gentianales), Jul 2024, P. Kodchasee, C. Senwanna, J. Kumla and N. Suwannarach, holotype = CMUB 40128 (preserved in metabolically inactive state), living culture (ex-type) = SDBR-CMU 836 = GMBCC 2502 = TBRC 21788. Cultural characteristics. 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. Description. Anamorph in vitro dematiaceous hyphomycetes. Vegetative hyphae (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. Conidiogenous cells (4.8 –) 7.0–14.0 (– 18) × 3.0–5.0 μm (x ̄ = 11.9 × 3.8 μm, n = 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. Conidia (4.2 –) 5.2–8.7 (– 11.7) × 2–4.6 (– 6.0) μm (x ̄ = 7.0 × 3.9 μm, n = 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. Chlamydospores (6.5 –) 7.8–9.0 (– 10) (x ̄ = 8.5 μm, n = 25) µm wide, produced in aerial hyphae, intercalary, solitary or in branched chains, subglobose, dark brown, smooth-, thick-walled, septate, constricted near the septa. Endoconidia 3.2–5.6 (– 6.3) × 1.8–2.8 (– 3.5) μm (x ̄ = 4.4 × 2.6 μm, n = 25), obovoid to ellipsoidal, hyaline, occasionally seen in intercalary hyphal cells. Fermentation of glucose is negative. D - glucose, galactose (weak), sorbose (weak), N - acetyl glucosamine, ribose, xylose, L - arabinose, D - arabinose, L - rhamnose, sucrose, maltose, α - α - trehalose, methyl- α - D - glucoside, cellobiose, salicin, melibiose (weak), lactose (weak), raffinose, melizitose (weak), glycerol (weak), erythritol (weak), ribitol, glucitol, mannitol, galactitol, myo - inositol (weak), D - glucono- 1, 5 - lactone, D - gluconate, D - glucuronate (weak), D - galacturonic acid (weak), DL - lactate, succinate (weak), citrate (weak), ethanol, and xylitol are assimilated, but inulin, soluble starch, and methanol are not assimilated. Ammonium sulfate, ethylamine hydrochloride, L - 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 D - glucose, D - galactose, L - sorbose, N - acetyl glucosamine, D - xylose, L - arabinose, L - rhamnose, sucrose, maltose, α - α - trehalose, methyl- α - D - glucoside, cellobiose, salicin, melibiose, lactose, raffinose, melizitose, glycerol, erythritol, ribitol, D - glucitol, D - mannitol, galactitol, myo - inositol, D - glucono- 1, 5 - lactone, D - gluconate, D - glucuronate, D - galacturonic acid, DL - lactate, succinate, and citrate, while white sediment observed in D - ribose, D - arabinose, ethanol, and xylitol. Cardinal temperatures for growth. Minimum 10 ° C, optimum in the range of 25 ° C to 30 ° C. No growth at 4 ° C and 37 ° C. Additional strains examined. THAILAND • Chiang Mai Province, Mueang District, Chang Phueak, isolated from frangipani flower (Plumeria obtusa; Apocynaceae, Gentianales), Jul 2024, P. Kodchasee, C. Senwanna, J. Kumla and N. Suwannarach, living culture = SDBR-CMU 826. Habitat and distribution. Flowers of Plumeria obtusa. Known only from northern Thailand. Notes. The multilocus phylogenetic tree (Fig. 2) revealed that A. plumeriae SDBR-CMU 826 and SDBR-CMU 836 (ex-type) formed a monophyletic lineage with strong support (100 % MLBS and 0.98 BIPP). Aureobasidium plumeriae formed a sister clade to A. motuoense, A. phayaoense, A. pollinicola, and A. siamense. Sequence comparison showed that the ITS sequence of A. plumeriae showed 98.77 %, 99.66 %, 99.83 %, and 100 % similarity to those of A. motuoense, A. siamense, A. pollinicola, and A. phayaoense, respectively, whereas the LSU sequences showed 100 % similarity among all related species. In contrast, comparisons of the rpb 2, tef 1, and tub sequences revealed lower sequence similarity between A. plumeriae and its closest relatives, with 96.01 %, 92.83 %, and 97.24 % similarity to A. phayaoense; 96.33 %, 91.99 %, and 97.24 % similarity to A. pollinicola; and 96.24 %, 92.44 %, and 97.24 % similarity to A. siamense, respectively. However, differences in the rpb 2, tef 1, and tub sequence data could not be compared because sequences of A. motuoense were unavailable. Morphologically, the colony characteristics of A. plumeriae differed from those of most phylogenetically related sister taxa. In terms of growth temperature, A. plumeriae did not grow at 37 ° C, whereas A. phayaoense and A. pollinicola grew at this temperature. Aureobasidium plumeriae differs from A. phayaoense and A. siamense by the presence of endoconidia. In addition, A. plumeriae differs from A. motuoense, A. pollinicola, and A. siamense 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 A. motuoense, A. phayaoense, A. plumeriae, A. pollinicola, and A. siamense as distinct species. Based on physiological tests, A. plumeriae differs from A. phayaoense in its ability to assimilate DL - lactate and succinate (Table 1). In contrast, A. siamense differs from A. plumeriae by producing pigment when grown on D - glucono- 1, 5 - lactone. Moreover, A. pollinicola can be differentiated from A. plumeriae by differences in sediment formation characteristics (Table 1). Thus, A. plumeriae is introduced as a new species based on phylogenetic analyses, morphological and phenotypic characteristics, and growth temperature data.

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Related topics: Plant Pathogens and Fungal Diseases · Genomics and Phylogenetic Studies · Plant chemical constituents analysis