Phaeoisaria guiyangensis W. M. Zhang & L. Lu, 2025

Phaeoisaria guiyangensis W. M. Zhang & L. Lu sp. nov.

Fig. 3 View Figure 3

Etymology.

The specific epithet “ guiyangensis ” refers to the type locality, Guiyang City, Guizhou Province.

Holotype.

GZAAS 25-0658

Description.

Saprobic on submerged decaying wood in a freshwater habitat. Asexual morph: Colonies effuse, solitary, dark brown to black, hairy, covered by white conidial. Mycelium partly immersed, partly superficial, composed of septate, branched, brown hyphae. Synnemata 349–801 × 11–30.5 μm ( x ̄ = 549.5 × 19.5 μm, n = 20), solitary or gathered, erect, rigid, subulate, tapering towards the apex, pale brown to black, paler towards the apex, composed of compact appressed conidiophores. Conidiophores macronematous, synnematous, septate, cylindrical, branched, straight or slightly flexuous, pale brown to black, smooth-walled. Conidiogenous cells 8–18.5 × 2–2.7 μm ( x ̄ = 13.5 × 2.4 μm, n = 20), integrated, terminal and intercalary, polyblastic, fertile portion bent outwards, smooth-walled, with multiple small, hyaline, cylindrical denticulate conidiogenous loci clustered in the apical part. Conidia 6–7 × 2.1–2.8 μm ( x ̄ = 6.6 × 2.4 μm, n = 30), solitary, obovoid to subcylindrical, smooth, rounded apical and obtuse basal, hyaline, aseptate, straight or slightly flexuous, guttulate. Sexual morph: Undetermined.

Culture characteristics.

Conidia germinate on PDA within 9 hours, producing germ tubes from the conidial body. Colonies on PDA are irregular with a raised surface and undulating margin, reaching 2.9 cm in diameter after 35 days at room temperature (approximately 25 ° C), and are grey to dark brown on both the surface and reverse sides.

Material examined.

China • Guizhou Province, Guiyang City, Baiyun District, Changpo Ling National Forest Park , on rotting wood in a freshwater habitat, 15 March 2025, Wang-Ming Zhang, WW 60 ( GZAAS 25-0658 , holotype), ex-type GZCC 25-0626 ; Ibid., WW 60.1 ( GZAAS 25-0659 , isotype), ex-isotype GZCC 25-0627 .

Notes.

Phaeoisaria guiyangensis ( GZAAS 25-0658 ) is morphologically similar to P. sedimenticola (HKAS 131978) in having solitary or gathered, erect, rigid, subulate synnemata; macronematous, synnematous, septate conidiophores; terminal and intercalary, polyblastic conidiogenous cells; and solitary, obovoid to subcylindrical, hyaline, aseptate conidia ( Wang et al. 2024 a). However, Phaeoisaria guiyangensis can be distinguished from P. sedimenticola by its shorter conidiogenous cells (8–18.5 μm vs. up to 31 μm) and shorter conidia (6–7 μm vs. up to 10.2 μm) ( Wang et al. 2024 a). According to the phylogenetic analysis (Fig. 1 View Figure 1 ), our new isolates formed a distinct lineage within the clade, which comprises Phaeoisaria fasciculata ( CBS 127885 and DAOM 230055), P. loranthacearum (BYCDW 24, BYCDW 25, and CBS 140009), and P. sparsa ( FMR 11939), indicating that GZCC 25-0626 and GZCC 25-0627 represent a distinct species. In addition, Phaeoisaria guiyangensis ( GZAAS 25-0658 ) can be distinguished from P. fasciculata ( PRM 933855) and P. loranthacearum ( CBS 140009) by the presence of distinct synnemata, which are absent in both comparison species ( Crous et al. 2015; Réblová et al. 2016). Furthermore, Phaeoisaria guiyangensis ( GZAAS 25-0658 ) differs from P. loranthacearum ( CBS 140009) and P. sparsa ( FMR 11939) by its shorter conidia (6–7 μm vs. 7–8 μm and 10–15.5 μm, respectively) ( Sutton 1973; Crous et al. 2015). Therefore, we propose Phaeoisaria guiyangensis ( GZCC 25-0626 and GZCC 25-0627 ) as a novel species based on molecular and morphological evidence.