Rossbeevera griseobrunnea Iqbal Hosen & T.H.Li

Hosen, Md. Iqbal, Zhong, Xiang-Jing, Gates, Genevieve, Orihara, Takamichi & Li, Tai-Hui, 2019, Type studies of Rossbeeverabispora, and a new species of Rossbeevera from south China, MycoKeys 51, pp. 15-28 : 20-22

Rossbeevera griseobrunnea Iqbal Hosen & T.H.Li sp. nov. Figs 4, 5, 6c, d

Diagnosis.

Basidiomata hypogeous, small; pileus grayish white to grayish brown, surface bluing slightly when injured; hymenophore dull white to very pale blue in some portion when injured, finally rusty brown to dark brown at maturity; stipe absent; basidiospores 17-20 × (8 –)9– 12 μm, fusoid, ornamented with 4-longitudinal ridges (star-shaped in cross section), brown to dark brown; pileipellis a subcutis, with terminal elements short cylindro-clavate.

Typification.

CHINA. Guangdong Province, Boluo County, Xiangtoushan National Nature Reserve, 19 November 2015, Tai-Hui Li, Ting Li, Hao Huang & Jun-Ping Zhou (GDGM 45913, holotype).

Etymology.

The epithet name ‘griseobrunnea’ (Lat.) refers to the grayish brown pileus.

Description.

Basidiomata hypogeous, 15-35 mm broad, 12-25 mm high, small, globose to subglobose, napiform, sometimes deformed or reniform, fleshy when fresh, firm when dry. Pileus very thin, surface glabrous to slightly velvety, shiny, grayish white to grayish brown, whitish at the lower portion, turning to pale blue when touched or injured. Hymenophore off-white, white to dull white when young, becoming pale blue to bluish in some parts/patches then rusty brown to dark brown when exposed to air for 3-5 minutes, often greenish brown around insect damage, firm, composed of minute, irregular locules, becoming partially collapsed with many small empty chambers when dried. Stipe absent. Stipe base present but reduced, white, dull white to grayish white, somewhat dendroid or as a small basal pad or rhizomorph. Odor and taste not recorded.

Basidiospores [50/2/2] 17-20(−21) × (8 –)9–12(– 13) μm [mean = 18.5 × 10.5 μm, Q = (1.52 –)1.63–1.91(– 2.1), Qm = 1.81 ± 0.18] fusoid, ornamented with 4-longitudinal ridges (star-shaped in cross section) (up to 2.5 μm high), inamyloid, non-dextrinoid, brown to dark brown in KOH and H2O, thick-walled up to 2 μm thick, hilar appendages 1.5-3 μm long. Basidia 15-27 × 5-9 μm, narrowly clavate to cylindro- clavate, hyaline to pale yellow, usually 2-spored, occasionally 1-spored; basidioles 18-25 × 8-10 μm, clavate to short clavate. Hymenial cystidia absent. Hymenium developed when immature but collapsed at maturity, hyaline to pale yellowish; subhymenium not developed. Hymenophoral trama 60-130 μm wide, subgelatinous, composed of hyaline, cylindrical, loosely interwoven to parallel, frequently branched, thin-walled, cylindrical hyphae 2-5 μm wide. Pileipellis a subcutis with terminal elements 15-20 × 7-9 μm, short clavate to cylindro-clavate, yellowish brown to brownish pigmented, smooth, thin-walled. Clamp connections absent in all tissues.

Additional specimen examined.

CHINA, Guangdong Province, Boluo County, Xiangtoushan National Nature Reserve, 19 November 2015, Tai-Hui Li, Ting Li, Hao Huang & Jun-Ping Zhou (GDGM 45266).

Habit and habitat.

Solitary or in small groups beneath or on the ground, hypogeous or partially epigeous in a subtropical evergreen broad-leaved forest, putatively associated with Castanopsis fissa , C. chinensis , C. fabri and Schima superba .

Known distribution.

Currently known only from south China (Guangdong Province, Xiangtoushan National Nature Reserve).

Comments.

The voucher specimen (GDGM 45266) was cited as Rossbeevera sp. by Hosen et al. (2018), while studying boletes from the Xiangtoushan National Nature Reserve, Guangdong Province, China. After morphological and molecular comparisons with other known species of Rossbeevera the voucher specimen (GDGM 45266) is described here as R. griseobrunnea . It is characterized by its dull white, grayish white to grayish brown basidiomata, with hymenophore that discolors very slowly in some portions (pale blue in some patches becoming rusty brown to dark brown) after being cut or injured, fusoid ornamented basidiospores with mostly 4-longitudinal ridges and subcutis elements (short clavate terminal cells) in the pileus.