Chaetomium globosum Kunze

Juxu, Rong, Phukhamsakda, Chayanard & Boonmee, Saranyaphat, 2024, Identification of a new species and three new records of Chaetomiaceae associated with commercial herbal teas in northern Thailand, Phytotaxa 653 (2), pp. 134-154 : 146

Chaetomium globosum Kunze , in Kunze & Schmidt, Mykologische Hefte (Leipzig) 1: 16 (1817) ( Fig. 6 ), new host record

Index Fungorum number: IF172545, Facesofungi number: FoF04560

Culture characteristics:—Colonies growing on PDA, reaching 4 cm diam., in 1 week at 25 °C in the dark condition, slightly fluffy, circular, radially striate with entire to undulate edge, initially white, becoming dark grey within 2–3 weeks, with white hyphal filaments at the center, covered by black ascomatal structure, yellow pigmented in medium. Mycelium superficial, hyaline, brown to dark brown, branched, septate, smooth-walled. Ascomata produced in culture within 3 weeks.

Sexual morph on PDA culture: Ascomata (96–)105–186 µm diam., superficial, uniloculate, solitary, subglobose, dark brown to black, covered by long and flexuous hairs, ostiole. Peridium composed of dark brown cells of textura angularis, membranaceous, thin-walled, paraphyses not seen. Terminal-lateral hairs 2–3 µm wide, elongate, flexuous, with or without branched, septate, dark brown at base, light brown towards the apex, verrucose-walled. Asci thin-walled and quickly evanescent, unable to be observed. Ascospores 9–10 × 7.5–8 µm (x = 9.5 × 8 µm, n = 10), globose to subglobose, ellipsoidal broad fusiform, symmetrical to asymmetrical ends, olivaceous brown to brown, with 1 or 2 apical germ pores, guttulate, externally smooth, roughened on the inner surface. Asexual morph: Undetermined.

Material examined:— THAILAND, Chiang Rai Province, Mae Fah Luang District, Doi Mae Salong market, stevia leaf tea ( Stevia rebaudiana , Asteraceae ), 22 February 2023, Saranyaphat Boonmee, HBT5 (MFLU 24–0084, dried culture, new host record), living cultures (MFLUCC 24–0067); ibid., mulberry leaf tea ( Morus alba , Moraceae ), 22 February 2023, Saranyaphat Boonmee, HBT25B (MFLU 24–0085, dried culture, new host record), living culture MFLUCC 24–0068; Thailand, Chiang Mai Province, Muang, Warorot Market, chrysanthemum flower tea ( Chrysanthemum morifolium or Ch. indicum , Asteraceae ), 2 March 2023, Saranyaphat Boonmee, HBT50 (MFLU 24–0086, dried culture, new host record), living cultures (MFLUCC 24–0069).

Notes:— Chaetomium globosum ( Kunze & Schmidt 1817) is the type species of Chaetomium , and it represents a diverse species, encompassing several complex groups, which has been described frequently by worldwide mycologists ( von Arx 1984, Ames 1963, Mazzucchetti 1965, Asgari & Zare 2011, Doveri 2013, Wang et al. 2016a, b). Wang et al. (2016b) revised Ch. globosum strains and designated the neotype of Ch. globosum (CBS 160.62), based on the collecting site of the type specimen. Wang et al. (2016b) confirmed the monophyly of Ch. globosum through the phylogenetic analysis and restricted the genus Chaetomium to the Ch. globosum species complex. Chaetomium globosum is characterised by producing globose to ovate ascomata and covered by ascomatal hairs, evanescent asci, and limoniform and bilaterally-flattened shaped, with or without apical germ pore ascospores ( von Arx 1984, Wang et al. 2016b). Chaetomium globosum is a common species and can be found in the air, dried agricultural products, indoor environment, and also endophytic from aquatic and terrestrial environments ( Wang et al. 2016a, b, Kamat et al. 2020).

Chaetomium globosum is also known as one of the causal agents of human onychomycosis ( Aspiroz et al. 2007, Latha et al. 2010, Hwang et al. 2012), and is a widespread pathogen causing leaf spot on diverse host plants ( Guo et al. 2016, Hassan et al. 2022). On the other hand, Ch. globosum was used as a biological control agent for plant diseases and to manage some pathogenic fungi in Thailand ( Ungprasit et al. 2021). Phylogenetic analysis of a combined ITS, TUB2 and RPB2 sequence dataset places our three isolates with the ex-type strain, Ch. globosum (CBS 160.62) clade with 84% ML, 1.00 PP statistical support ( Fig. 5 ). These three isolates share morphological characters of ascomata, ascomatal hairs, and ascospores identical to Ch. globosum ( Fig. 6 ). Therefore, we report three isolates (MFLUCC 24–0067, MFLUCC 24–0068 and MFLUCC 24–0069) as a new record of Ch. globosum associated with commercial herbal teas from northern Thailand.

Figures

FIGURE 5. Phylogram generated from RAxML analysis based on combined ITS, RPB2 and TUB2 sequence data of Chaetomium taxa. Xanthiomyces spinosus isolates CBS 789.71 and CBS 796.83 are selected as the outgroup taxa. Bootstrap support values for ML values equal to or>70% and PP values equal to or>0.95 are shown as ML/PP above the nodes. Newly generated sequences in this study are in blue. Type strains are indicated in bold.

FIGURE 6. Chaetomium globosum (MFLUCC 24–0067, new host record). a, b Stevia leaf tea and isolation. c Culture colony on PDA after one month from surface view. d Side view of ascomata covered by elongate flexuous hairs and white in reflected light. e Squash mouth of the ascoma in water. f Close-up of ascomatal hairs. g–i Ascospores. Scale bars: d = 200 µm, e = 100 µm, f–i = 10 µm.