Spiromyces sinensis H. Y. Wang & Y. F. Han sp. nov.

Fig. 4

Etymology.

Referring to China where the species was isolated.

Type.

China • Guizhou Province, Tongren City, tea garden (28°2'7"N, 108°59'58"E), rhizosphere soil of tea plant, April 2025, Haiyan Wang, ex-type culture GZUIFR 25.271, dried holotype GZAC 25.271.

Description.

Rhizosphere fungi associated with the tea plant. The fungus sporulated on PDA within 14 days of incubation at 25 ° C. Hyphae hyaline, septate, 1.0–3.5 μm diam. Sporophores absent or erect, arising directly tips of hyphae. Sporocladia reduced to enlarged cells from the apex of hyphae, producing a membraneous remnant of the pedicel after spores falling off at maturity. Spores globose, abundant, rough-walled, hyaline, with pyramidal on the surface, 3.0–4.5 μm (av. 3.82 μm, n = 30), arising mostly directly from hyphae or a few from tips of hyphae enlarged cells, falling off at maturity. Zygospores unknown. Chlamydospores ovoid, abundant, thick-walled, 6.5–19.0 × 4.0–15.0 μm (av. 11.49 × 6.93 μm, n = 10).

Culture characteristics.

Colony on PDA, after 14 days of incubation at 25 ° C, reaching up to 20–25 mm diam., dense, villiform, margins entire, mycelia creamy white to gray, exudates and diffusible pigments absent, reverse, creamy white to gray, margin entire. Colony on MEA, reaching up to 10–15 mm diam., thick, fluffy, flocculence, margins entire, mycelia white, exudates and diffusible pigments absent, reverse, margins entire, white. Colony on OA, reaching up to 10–15 mm diam., thin, fluffy, flocculence, margin partial, mycelia gray, exudates and diffusible pigments absent, reverse, gray, margin partial.

Additional specimens examined.

China • Guizhou Province, Tongren City, Tea Garden (28°2'7"N, 108°59'58"E), rhizosphere soil of tea plant, April 2025, living cultures GZUIFR 25.272; ibid., GZUIFR 25.273.

Notes.

BLASTn analysis with the ITS, LSU, and SSU sequences of Spiromyces sinensis showed similarities to S. minutus of 95.92 % with 28 gaps, 89.26 % with 3 gaps, and 97.49 % with 6 gaps, respectively. Phylogenetically, the three strains (GZUIFR 25.271, GZUIFR 25.272, and GZUIFR 25.273) can apparently be distinguished from S. minutus, S. aspiralis, and Mycoëmilia scoparia in Spiromycetaceae (Spiromycetales) and clustered in a single clade with a high support value (100 % MLBS and 1.00 BYPP; Fig. 1). In the morphological characteristics, the three strains of S. sinensis have globose spores with pyramidal projections on the surface, arising directly from hyphae or enlarged cells, and ovoid chlamydospores, without zygospores. Spiromyces sinensis differed from S. minutus by producing ovoid and spinose mitospores, with globose zygospores, and without chlamydospores (Benjamin 1963; O’Donnell et al. 1998). Spiromyces sinensis differed from S. aspiralis in its presence of subglobose and warted mitospores, and absence of chlamydospores and zygospores (O’Donnell et al. 1998). Spiromyces sinensis can be distinguished from Mycoëmilia scoparia by its fusiform spores, spherical zygospores, and absence of chlamydospores (Kurihara et al. 2004). Therefore, S. sinensis is introduced as a new species.