Crepidotus ulmicola T. Bau & Y.P. Ge, 2022

Zhang, Peng, Ge, Yupeng & Bau, Tolgor, 2022, Two new species of Crepidotus (Crepidotaceae) from China, Phytotaxa 552 (1), pp. 22-34 : 28-30

Crepidotus ulmicola T. Bau & Y.P. Ge sp. nov. Figs. 3c, 3d , 5 , 6

MycoBank MB837627

Diagnosis:—Pileus minute, white, tomentose,with a very small stipe visible when mature,lamellae distant, basidiospores broadly ellipsoid to ellipsoid, weakly rugulose, cheilocystidia lageniform, whip-like to slightly flexuous, pileipellis a trichoderm.

Etymology:—The epithet refers to its habitat on and colonization of species of Ulmus .

Type:— CHINA. Inner Mongolia Autonomous Region: Tumuji National Nature Reserve , Jalaid Banner , Hinggan League , elev. 137 m, 46°27′ N, 123°01′ E, 26 July 2015, Tolgor Bau & Yupeng Ge, HMJAU37011 (Holotype!), GenBank no. KX456184 (ITS) .

Description:— Pileus (2–) 3–5 mm, in young stage angulate to round flabelliform, more or less spheroidal, white (1A1), distinctly radial-silky, becoming flabelliform, semicircular to subcircular, convex, whitish to light orangeyellow (5A2–5B2), tomentose, margin slightly inflexed, occasionally darker to honey yellow (4C6–4D6) or maize yellow (4A5–4B4), not hygrophanous, without striate edge when mature, attached laterally to dorsally. Lamellae 1–2 mm long, 0.5 mm broad, distant, L = 4–7, l = 2–4, white (1A1) when young, later light yellow (1A4) to yellow (3A5– 3B6), becoming rust brown when mature, subventricose to arcuate, adnexed to decurrent. Stipe 0.5–1.0 × 0.2–0.5 mm, light yellow (1A4–1A5), mostly curved, visible when mature (under stereomicroscope). Context white (1A1), very thin. Odor and taste nondistinctive. Spore print light brown (5D7).

Basidiospores (6.9–)7.5–8.7 × (4.9–)5.6–6.7 μm, Q = 1.20–1.46, broadly ellipsoid to ellipsoid, slightly inequilateral in side view, yellow to light brown, almost smooth under immersion oil, weakly rugulose or vermiculate under SEM. Basidia 27–31.8 × (4.1–)6.3–10.8 μm, clavate, (2–)4-spored, thin-walled, hyaline, clamped. Pleurocystidia absent. Cheilocystidia 29–42(–53) × (3–)5–8(–10) μm, lageniform, whip-like to slightly flexuous, occasionally clavate, not septate at apex, thicker in the lower portion, hyaline, thin-walled, clamped. Pileipellis a trichoderm, composed of loosely interwoven hyphae. Clamp connections present in all tissues.

Habitat:—Scattered on fissures in the bark of Ulmus trees.

Known distribution:— China.

Additional material examined:— CHINA. Jilin Province: Taohaotai Town, Qian Gorlos Mongol Autonomous County, Songyuan City , 162 m, 44°92′ N, 124°73′ E, 1 August 2015, Tolgor Bau & Yupeng Ge, HMJAU37017 !.

Notes: According to the classification proposed by Consiglio and Setti (2008), C. ulmicola should be assigned to series Dochmiopus Consiglio & Setti, section Dochmiopus, Crepidotus subgen. Dochmiopus . The tiny white basidiomes, tomentose pileus, and weakly rugulose basidiospores are the most distinctive features for distinguishing C. ulmicola from other Crepidotus species. Only a few Crepidotus species produce a basidiome similar in size to that of C. ulmicola , whose pileus is less than 10 mm in diameter. Hesler & Smith (1965) assigned most species with a pileus not exceeding 10 mm in diameter to Crepidotus subgen. Sphaerula Hesler & A.H. Sm. sect. Sphaerula Hesler & A.H. Sm. or subsect. Colorantes Hesler & A.H. Sm.; however, all such species are distinct from C. ulmicola on account of the honey-yellow to brownish or pale tawny pileus. In subsect. Colorantes, C. albidus Ellis & Everhart (1894: 322) and C. amarus Murrill (1943: 430) have the greatest morphological resemblance to C. ulmicola , but they differ in basidiospore size. Krisai-Greilhuber et al. (2002) described C. albidus as possessing 5.9–6.9 × 4.7–5.6 μm basidiospores and occasionally clamps. The basidiospores of C. albidus are distinctly shorter than those of C. ulmicola . Crepidotus amarus differs from C. ulmicola in possessing clavate to cylindrical cheilocystidia, which are lageniform in C. ulmicola ( Hesler & Smith 1965) .

In our BLASTn search, the closest match to the ITS sequence ( KX456184 ) of C. ulmicola was C. occidentalis ( OK376745 ), with 95% sequence similarity, which is consistent with the results of the phylogenetic analysis. Crepidotus occidentalis is similar to C. ulmicola in basidiospore size but differs in possessing clavate cheilocystidia and a much larger pileus ( Hesler & Smith 1965).

Figures

FIGURE 3. Scanning electron micrographs of basidiospores. a–b. Crepidotus herbaceus (from holotype!). c–d. Crepidotus ulmicola (from holotype!). Photographs by Yupeng Ge.

FIGURE 5. Basidiomata of Crepidotus ulmicola. Bars = 5 mm (a–b), 1 mm (c–d). Photographs by Tolgor Bau (a) and Yupeng Ge (b–d).

FIGURE 6. Crepidotus ulmicola (HMJAU37011, holotype!). a. Basidiomes b. Basidiospores c. Basidia d. Pileipellis e. Cheilocystidia. Bars = 1 mm (a), 5 μm (b), 10 μm (c–e). Illustration by Yupeng Ge.