Aureobasidiaceae K. M. Thambugala & K. D. Hyde, fam. nov., Index Fungorum number: IF 550732.
Parasitic or saprobic on twigs, wood and leaves or human skin. Sexual state: Ascomata black, subglobose, immersed to erumpent, uniloculate, sometimes ostiolate. Peridium composed of several layers of brown to dark brown cells of textura angularis. Hamathecium lacking pseudoparaphyses. Asci 8-spored, bitunicate, saccate to broadly clavate with a short bifurcate pedicel or apedicellate, apex broadly rounded with a distinct ocular chamber. Ascospores biseriate to triseriate, partially overlapping, hyaline, 3 to many septate or aseptate, muriform to phragmosporous, obovoid or elliptic with broad to narrow rounded ends. Asexual state: Coelomycetous or hyphomycetous. Hyphomycetous asexual state: Stromata present or absent, visible in substomatal cavity, hyaline or lightly pigmented, dark brown with globose to broadly ellipsoidal, round or elongated pseudo-parenchymatous cells when present. Colonies spreading, smooth, often covered with slimy masses of conidia, usually with sparse aerial mycelium; light brown, yellow, pink or black. Hyphae with cells commonly wider than long, hyaline, frequently soon becoming brown and thick-walled sometimes thin, smooth, transversely septate. Conidiogenous cells on hyaline hyphae, lateral, terminal or intercalary, cylindrical, clavate or globose, integrated, terminal, with holoblastic, polyblastic conidiogenesis, with numerous synchronously produced conidia. Conidia blastic, hyaline to dark brown, smooth, aseptate, straight, ellipsoidal to spherical, reniform to sickle-shaped, oblong to cylindrical, sometimes cylindrical with obtuse ends and occasionally with a slightly truncate base. Secondary conidia common; endoconidia often present. Coelomycetous asexual state: Conidiomata dark brown, pycnidial or acervular, separate or aggregated, scattered, immersed or superficial, globose, unilocular, thin-walled; walls 2−3 layers thick, composed of lightly pigmented to brown, thick-walled cells of textura angularis, with or without an ostiole. Conidiophores reduced to conidiogenous cells or hyaline, irregularly branched at the base and above, 1 to 3-septate, smooth when present. Conidiogenous cells enteroblastic, phialidic, discrete, determinate or ampulliform, hyaline to pale brown, smooth, subglobose, obpyriform or obovoid, collarette and channel minute, with apical periclinal thickening, guttulate, formed from the inner cell of the pycnidial wall, slightly tapered toward the apex. Conidia holoblastic, aseptate, falcate, fusiform, ellipsoidal to obovoid, eguttulate or irregularly guttulate, smooth, at first thin-walled, hyaline or pale brown, later pale brown with thicker walls, smooth-walled or verruculose.
Type: Aureobasidium Viala & G. Boyer
Notes: The Aureobasidiaceae clade comprises Aureobasidium, Kabatiella, Pseudoseptoria, Saccothecium and Selenophoma species and Columnosphaeria fagi, for which we propose a new family, Aureobasidiaceae. The CBS 584.75 ex-neotype strain of Aureobasidium pullulans clustered here. Aureobasidiaceae separates from Dothideaceae with 65/80 % bootstrap support. Morphologically, Aureobasidiaceae can be distinguished from Dothideaceae usually by having only immersed to erumpent, uniloculate ascostromata and aseptate to many-septate, hyaline ascospores. The recently introduced Sydowia eucalypti also clustered within Aureobasidiaceae and we propose a new genus, Pseudosydowia for Sydowia eucalypti. The asexual states of Aureobasidiaceae Aureobasidium, Kabatiella, Pseudoseptoria and Selenophoma species cluster here, while Columnosphaeria, Pseudosydowia and Saccothecium nested as sexual genera. Columnosphaeria fagi, Pseudosydowia eucalypti and Saccothecium sepincola are the only sexual species cluster in the Aureobasidiaceae clade. The sexual species Discosphaerina (Columnosphaeria) fagi is closely related with Aureobasidium pullulans (Schoch et al. 2006; Zalar at al 2008). Our phylogenetic tree also shows the close relationship of these two species which form a single clade. We accept three sexual genera and four asexual genera in Aureobasidiaceae.
Key to sexual genera of Aureobasidiaceae
1. Ascospores septate, obovoid to ellipsoid…………………………………………………………………………. 2
1. Ascospores aseptate, ellipsoidal-fusiform, or fusiform……………………………… Columnosphaeria
2. Asci broadly ellipsoid to clavate, straight to slightly curved, subsessile, ascospores bi- to multiseriate, overlapping, hyaline, (1–)3(–4)-septate at maturity, constricted at the median septum, obovoid to ellipsoid with obtuse ends, tapering towards both ends, but more prominently towards the lower end………………. Pseudosydowia
2. Asci saccate to broad-clavate with a short bifurcate pedicel or apedicellate, ascospores biseriate to triseriate, partially overlapping, hyaline, 3 to many septate, muriform to phragmosporous, obovoid or elliptic with broad to narrowly rounded ends…………………………………………………………………………………………….. Saccothecium
Key to asexual genera of Aureobasidiaceae
1. Coelomycetous asexual states………………………………………………………………………………………… 2
1. Hyphomycetous asexual states………………………………………………………………………………………. 3
2. Conidia falcate, fusiform, ellipsoidal to obovoid, aseptate, eguttulate or irregularly guttulate, smooth, at first thin-walled, hyaline or pale brown, later pale brown with thicker walls and verruculose………………………………………………………………………….. Selenophoma
2. Conidia fusiform, lunate or irregular, curved, aseptate, colourless, smooth-walled with or without an excentric basal appendage, continuous with conidium body, plectronoid to podiform, or with a blunt or spathulate distal end………………………………………………………………………………………………. Pseudoseptoria
3. Conidia blastic, produced simultaneously in dense groups, hyaline to dark brown, smooth, aseptate, straight, ellipsoidal to spherical, reniform to sickle-shaped…………………………………………… Aureobasidium
3. Conidia clustered on swollen apex, borne on tiny sterigmata, aseptate, hyaline, oblong to cylindrical…………………………………………………………… Kabatiella