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

Fig. 7

Etymology.

Refers to the host genus Bougainvillea, from which this species was isolated.

Type.

THAILAND • Phayao Province, Mueang District, isolated from bougainvillea (Bougainvillea hybrid; Nyctaginaceae, Caryophyllales), Aug 2024, P. Kodchasee, C. Senwanna, J. Kumla and N. Suwannarach, holotype = CMUB 40141 (preserved in metabolically inactive state), living culture (ex-type) = SDBR-CMU 858 = GMBCC 2509.

Cultural characteristics.

After 14 days of incubation at 25 ° C in the dark, colonies on PDA reaching 56–60 mm diam., surface flat, spreading, round with radiating, irregular margin, velvety, grayish brown (6 E 3), with grayish yellow (4 B 6) at the margin; on MEA reaching 35–44 mm diam., surface flat, spreading, round with radiating, lobate margin, velvety, brownish gray (4 E 2), grayish brown (6 E 3), and black at the margin; on OA 62–67 mm diam., surface flat, spreading with filiform, entire margin, velvety, slimy, pale orange (6 A 3), with yellowish brown (5 E 8), light brown (6 D 4) at the margin.

Description.

Anamorph in vitro dematiaceous hyphomycetes. Vegetative hyphae 3.0–11.0 (– 19.0) μm, hyaline to brown, branched, septate, smooth, thin-walled, becoming light to dark brown with age, constricted at the septa, thick-walled. Conidiogenous cells 5.0–15.0 (– 17.0) × 3.5–8.8 μm (x ̄ = 12.2 × 5.1 μm, n = 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, occasionally elongated, solitary, becoming brown with age. Conidia (3.8 –) 6.0–11.5 (– 13.5) × (2.5 –) 3.5–7.0 (– 9.4) μm (x ̄ = 8.7 × 4.7 μm, n = 180), obovoid to ellipsoidal, elongated, or globose to subglobose, hyaline becoming light to dark brown with age, aseptate, occasionally with an indistinct truncated base and a hilum, smooth-walled, guttulate, budding occasionally observed. Chlamydospores (8.2 –) 10.1–16.0 (– 20.0) μm wide (x ̄ = 13.3 μm, n = 30), produced in aerial hyphae, mostly intercalary, solitary or in branched chains, globose to subglobose, pigmented, light to dark brown, smooth-, thick-walled, septate, 1–2 cells, constricted near the septa. Endoconidia absent.

Fermentation of glucose is negative. D - glucose, galactose, sorbose, N - acetyl glucosamine, ribose, xylose, L - arabinose, D - arabinose, L - rhamnose, sucrose (weak), maltose, α - α - trehalose, methyl- α - D - glucoside, cellobiose, salicin, melibiose, lactose, raffinose, melizitose, glycerol, erythritol, ribitol, glucitol, mannitol, galactitol, myo - inositol, D - glucono- 1, 5 - lactone, D - gluconate, D - glucuronate, D - galacturonic acid (weak), DL - lactate (weak), succinate, 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, light brown sediment formed in D - glucose, raffinose, and D - galacturonic acid, while dark brown sediment formed in N - acetylglucosamine, D - xylose, L - rhamnose, maltose, α - α - trehalose, methyl- α - D - glucoside, cellobiose, salicin, melibiose, lactose, myo - inositol, D - glucono- 1, 5 - lactone, citrate, and xylitol. Black sediment formed in D - galactose, L - sorbose, D - arabinose, glycerol, erythritol, D - mannitol, and D - gluconate.

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 • Phayao Province, Mueang District, isolated from bougainvillea (Bougainvillea hybrid; Nyctaginaceae, Caryophyllales), Aug 2024, P. Kodchasee, C. Senwanna, J. Kumla and N. Suwannarach, living culture = SDBR-CMU 859.

Habitat and distribution.

Flowers of Bougainvillea hybrid. Known only from northern Thailand.

Notes.

Phylogenetic analyses showed that A. bougainvilleae strains SDBR-CMU 858 (ex-type) and SDBR-CMU 859 formed a distinct monophyletic lineage that was sister to A. catharanthi, with 77 % MLBS and 0.96 BIPP support (Fig. 2). The rpb 2, tef 1, and tub sequences of A. bougainvilleae differed from those of A. catharanthi by 4.96 % (47 / 948 bp, including gaps), 9.29 % (25 / 269 bp, including gaps), and 2.93 % (12 / 409 bp, including gaps), respectively. Morphologically, colonies of A. bougainvilleae on PDA, MEA, and OA were grayish brown with a grayish-yellow margin, brownish gray with a grayish-brown to black margin, and pale orange with a light brown margin, respectively. In contrast, colonies of A. catharanthi were olive brown with grayish-yellow margins on PDA, grayish yellow mixed with olive brown and with grayish-yellow margins on MEA, and light gray with dark gray margins on OA. Although the conidial size ranges of A. bougainvilleae and A. catharanthi overlapped, the conidia of A. bougainvilleae became brown at maturity, whereas those of A. catharanthi remained hyaline. Aureobasidium bougainvilleae can be distinguished from A. catharanthi by its ability to assimilate D - xylose, D - arabinose, L - rhamnose, maltose, α, α - trehalose, cellobiose, melibiose, lactose, raffinose, ribitol, D - mannitol, myo - inositol, D - glucuronate, succinate, and ethanol, with sediment formation observed during growth on these carbon sources (Table 1). Thus, A. bougainvilleae is described here as a new species based on phylogenetic analysis and morphological characteristics.