Introduction

The genus Crepidotus (Fr.) Staude was established as a “tribe” of Agaricus by Fries in 1821 and subsequently raised to the rank of genus by Staude (1857) with Crepidotus mollis (Schaeff.) Staude as the type species. It is a well-defined genus having cosmopolitan distribution with over 200 species described worldwide (Kirk et al. 2008). During our continuing study on the agaric family Crepidotaceae (Agaricales, Basidiomycota) of Kerala State, India, several noteworthy collections belonging to the genus Crepidotus were made. It appears that the genus Crepidotus is particularly rich in this region as evident from previous studies (Guzmán-Dávalos et al. 2017; Kumar et al. 2018a, b; Kumar et al. 2020).

Here, we describe five more species of Crepidotus of which three species are new to science and the other two species represents new Asian and new Indian records. Morphological, molecular, and phylogenetic details of these five species are discussed in detail in the present study.

Materials and methods

Morphological studies

Kerala State is a narrow strip of land on the south-west corner of the Indian Peninsula. Most of the forested areas of the State are parts of the Western Ghats, which is one of the biodiversity hotspots of the world. The very high biological diversity of Kerala State is primarily due to the highly diversified ecological niches and the climate which is tropical, maritime, and monsoonal. Specimens examined were collected from different natural forests and other localities of the State. The macro-morphological descriptions were based on fresh collections made from Kerala State, India. Microscopic characters were studied on dried material using hand cut sections of basidiomata stained with 1% Congo red, mounted in 3% KOH, and examined under an Olympus CX43 optical microscope (Olympus, Japan). For evaluation of the range of spore size, 20 basidiospores of each collection were measured for length and width. Basidiospore measurements include both the mean and the standard deviation, together with the range of spore quotient (Q, length/width ratio) and its mean value (Qm). Basidiospore measurements exclude the hilar appendix. Color coding follows that of Kornerup and Wanscher (1978). Microphotographs were made with a Magcam DC10 digital camera attached to the same microscope. Holotypes are deposited at Central National Herbarium (CAL), Kolkata, India. All additional materials examined are deposited at the Mycological Herbarium of Jawaharlal Nehru Tropical Botanic Garden and Research Institute, Thiruvananthapuram (TBGT).

DNA extraction, PCR amplification, and sequencing

Genomic DNA was extracted from fresh specimens following protocols of Izumitsu et al. (2012). The nuclear large subunit region (nrLSU) and the Internal Transcribed Spacer region (nrITS) of the ribosomal DNA were amplified and sequenced from the presented species. PCR reactions were performed with the primer pair ITS1 and ITS4 (White et al. 1990) for nrITS and LR0R and LR7 (Vilgalys and Hester 1990) for nrLSU. The protocols for PCR amplification and sequencing followed Kumar et al. (2018b). The newly generated sequences are deposited in GenBank.

Sequence alignment and phylogenetic analysis

The molecular phylogenetic analysis was performed using nrLSU sequences. The nrLSU sequences of the five species obtained and those retrieved from GenBank (based on BLAST similarities) were aligned using PRANK web tool (www.ebi.ac.uk/Tools/msa/prank/) with default settings. The final aligned data matrix have 73 taxa, including species of Crepidotus and related genera, viz., Simocybe, Pleuroflammula, Neopaxillus, and Inocybe (Table 1), then imported into BioEdit v7.2.6.1 (Hall 1999) for manual adjustment. Inocybe phaeoleuca Kühner and I. subpaleacea Kühner were selected as outgroup following Ge et al. (2017). Maximum likelihood (ML) analysis was performed in the web platform http://iqtree.cibiv.univie.ac.at (Trifinopoulos et al. 2016) with 1000 ultrafast bootstrap replicates. Transition model with equal frequency (TIM3e + I + G4) was selected automatically as the best fit substitution model as per BIC score in the same web platform. Bootstrap values (BS) ≥ 60% (Jeewon and Hyde 2016) were considered significant. The aligned sequence dataset has been deposited in TreeBase (http://purl.org/phylo/treebase/phylows/study/TB2:S28431). The phylogram inferred from ML analysis is displayed with MEGA 7.0.26 (Kumar et al. 2016).

Table 1 List of species, geographic origin, and GenBank accession numbers of nrLSU of sequences used in the molecular analysis. Species from the present study are indicated in bold. Sequences from type collections are indicated by “*”
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Results

Molecular phylogeny

The phylogeny inferred from ML analysis of the data matrix of nrLSU sequences is provided in Fig. 1, where 12 clades were observed. Crepidotus flavobrunneus is placed near an undescribed species of Crepidotus from Japan (AF367954) with 100% ML bootstrap in clade 1. Crepidotus tortus was placed near C. occidentalis Hesler & A.H. Sm., from the USA (AF205678) in clade 3 with 100% ML bootstrap. Crepidotus exiguus nested in clade 6 close to C. cinnabarinus F.H. Møller & Westergaard (AF205686) from the USA with 100% ML bootstrap. Sequence of C. roseus Singer from India was placed close to C. aureus E. Horak from Puerto Rico (AF205685) with 100% ML bootstrap in clade 7, while the sequence of C. alabamensis Murrill from India generated in the present study nested close to C. alabamensis from the USA (AF367960) with 98% ML bootstrap. The nrLSU sequences of C. exiguus, C. flavobrunneus, and C. tortus from India are distinct from all sequences of Crepidotus species available in GenBank, as revealed by BLAST search and phylogenetic analyses.

Fig. 1
figure 1

Maximum likelihood phylogenetic tree illustrating the placement of Crepidotus species from the present study (in bold) with related species in Crepidotaceae based on nrLSU sequences. ML bootstrap values 50% and above are shown on branches

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Crepidotus tortus A.M. Kumar & C.K. Pradeep, sp. nov. (Fig. 2).

Fig. 2
figure 2

Crepidotus tortus (CAL1740). a–c Habit in situ. d–e Basidia. f Basidiospores. g, h Cheilocystidia. i Pileipellis with pileal elements. Scale bars: a–c = 10 mm, d–i = 10 μm

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MycoBank: MB840204.

Diagnosis: Differs from Crepidotus occidentalis by its versiform contorted, flexuous branched cheilocystidia, pileipellis with distinct pileocystidia, and the different nrLSU sequence.

Typus: India. Kerala State, Thiruvananthapuram district, Palode, Plavara, 8.72° N, 77.02° E, elev. 150 m, on dead branch of rubber tree (Hevea brasiliensis) and on other dead angiosperm trees, 27 Oct. 2017, Manoj TBGT17194 (holotype CAL1740), nrITS (MK462161) nrLSU (MK462162).

Etymology: The specific epithet refers to the strangulated cheilocystidia.

Pileus 3–22 mm diam., laterally attached, convex, orbicular, flabelliform; surface chalky white when young, becoming champagne (4B4) in old ones; white woolly to appressed squamulose, nonstriate, nonhygrophanous, dry; margin incurved, undulating, entire, fringed (under stereomicroscope). Lamellae radiating from a lateral point, putty to brownish gray (4B2/5B2/5B4/6D4/7C2), up to 2 mm wide, close to subdistant with lamellulae of 2–3 lengths; edge whitish, entire. Stipe absent. Context thin, white. White mycelial mat present at the base. Odor mild, not characteristic.

Basidiospores 8–10.5 × 5.5–6.5 (6.8) μm (Lm = 9.4 ± 0.83 μm, Wm = 6.22 ± 0.40 μm); Q = (1.29)1.42–1.6 (1.78); Qm = 1.51, ellipsoid, yellowish brown in KOH, thick-walled, smooth. Basidia 22–29 × 6.5–7 μm, clavate, mostly 4-spored, occasionally with 1, 2-spored, thin-walled, hyaline. Lamella edge sterile with crowded cheilocystidia. Cheilocystidia 20–48 × 6.5–13 μm, versiform, strangulated, cylindrical, contorted, branched, flexuous, thin-walled, hyaline. Pleurocystidia absent. Hymenophoral trama subregular, hyphae 5–10 μm wide, thin-walled, hyaline. Subhymenium pseudoparenchymatous. Pileal trama composed of thin-walled, hyaline hyphae, 5.5–8 μm wide. Pileipellis a cutis, hyphae of 4–5.5 μm wide, interrupted at places with suberect to erect hyphae; terminal elements cylindric, flexuous with obtuse ends, 40–72 × 2–3 μm; pileus margin composed of tufts of slender highly flexuous coiled hyphae, rarely branched, with obtuse or bifid apices, 60–62 × 4–6.5 μm. Oleiferous hyphae abundant, yellowish. Clamp connections present.

Habit, habitat, and phenology: Scattered on dead branch of rubber tree (Hevea brasiliensis) and on other dead angiosperm trees. May, Sep.–Nov.

Additional specimens examined: India. Kerala State, Thiruvananthapuram district, Palode, Plavara, on dead branch of rubber tree (Hevea brasiliensis) and on other dead angiosperm trees, 13 Sep. 2017, Manoj TBGT17095; 19 Oct. 2017, Manoj TBGT17159; 27 Oct. 2017, Manoj TBGT17194; 03 Nov. 2017, Manoj TBGT17233; 15 May 2018, Manoj TBGT17429; 16 Aug. 2018, Manoj TBGT17639; Thiruvananthapuram district, Palode, JNTBGRI campus, 12 May 2014, Manoj TBGT15043.

Notes: Crepidotus tortus is characterized by a distinctive combination of features such as small chalky white basidiomes, 1,2,4-spored basidia, ellipsoid, smooth basidiospores, versiform strangulated, cylindrical, contorted, branched, flexuous cheilocystidia and pileipellis with distinct cylindric, flexuous pileal elements. The pileus and basidiospores of C. tortus is similar to C. occidentalis, a species originally described from the USA (Hesler and Smith 1965). However, cheilocystidia in C. occidentalis are cylindric, subventricose and the pileipellis is a repent epicutis, whereas in C. tortus, cheilocystidia are versiform, strangulated, cylindrical, contorted, flexuous, and branched, besides pileipellis an interrupted cutis with cylindric flexuous elements.

Crepidotus tortus also resembles C. podocarpi Singer, C. caspari Velen., C. albidus Ellis & Everh., C. acanthosyrinus Singer, C. autochthonus J.E. Lange, C. trichocraspedotus T. Bau & Y.P. Ge, and C. novae-zelandiae Pilát. Crepidotus podocarpi described from Argentina (Singer 1973) differs in having a slightly larger basidioma (9–33 mm), white hygrophanous pileus and smaller basidiospores (7.2–8 × 4.5–5 μm). The European C. caspari (Senn-Irlet 1995) is distinct from C. tortus by smaller, less broad (6–9.5 × 4–6 μm), marbled to faintly rugulose basidiospores, differently shaped cheilocystidia and pileipellis. Crepidotus albidus described from Bolivia and also reported from Argentina (Singer 1973) varies in having smaller, short ellipsoid to subglobose basidiospores (5–7.5 × 4.3–6 μm) and pileipellis with incrustations. Crepidotus acanthosyrinus originally described from Argentina (Singer and Digilio 1951) and also known from Brazil (Senn-Irlet and De Meijer 1998) differs by whitish to pale brown, smooth and glabrous pileus, slightly smaller basidiospores (7.5–9 × 5.0–6.5 μm), cylindrical to narrowly clavate cheilocystidia, and pileipellis an incrusted cutis. Crepidotus autochthonus differs in its smaller basidiospores (7.1–8.5 × 4.9–5.7 μm), unbranched, cylindrical, clavate cheilocystidia, gelatinized pileal trama, and terrestrial habitat (Consiglio and Setti 2008). Crepidotus trichocraspedotus, a recently described species from China (Ge and Bau 2020), is very closely related in its macro- and micromorphology to the present species, however differs in white to deep orange lamellae, slightly larger basidiospores [9.1–10.5 (–10.7) × 6.0–6.8 (–7.1) μm] and a trichodermal pileipellis with incrustations. Crepidotus novae-zelandiae originally described from New-Zealand (Pilát 1950) can be easily separated on account of its broadly ellipsoid larger basidiospores (11–12 × 8.3–8.6 μm). Smooth basidiospores and presence of clamp connections place C. tortus in subsect. Fibulatini of sect. Crepidotus (Singer 1986).

Crepidotus exiguus A.M. Kumar & C.K. Pradeep, sp. nov. (Fig. 3).

Fig. 3
figure 3

Crepidotus exiguus (CAL1758). a–b Habit. c Basidia. d Basidiospores. e–f Cheilocystidia. g Pileipellis. Scale bars: a–b = 10 mm, c–g = 10 μm

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MycoBank: MB840206.

Diagnosis: Distinct from similar species by small, thin basidiomes, ellipsoid, warty basidiospores, characteristic versiform cheilocystidia, pileipellis an undifferentiated cutis and absence of clamp connections.

Typus: India. Kerala State, Thiruvananthapuram district, Palode, JNTBGRI campus, 8.75° N, 77.02° E, elev. 150 m, on decaying log of an angiosperm tree, 23 Oct. 2017, Manoj TBGT17176 (holotype CAL1758), nrLSU: MK567974.

Etymology: The specific epithet refers to the small basidiomata.

Pileus 3–13 mm diam., convex, orbicular, flabelliform, conchate, surface white becoming yellowish white to pale orange (4A2/5A2/5A3), felted woolly with scattered white appressed squamules, dry, nonstriate, nonhygrophanous; margin incurved when young becoming straight, fringed with white hairs. Lamellae arising from a lateral rudimentary to reduced stipe, white becoming grayish orange to topaz (5B4/5C4/5C5), turning yellowish in aqueous KOH, up to 2 mm wide, close with lamellulae of 2 lengths; edge fimbriate, whitish (under stereomicroscope). Stipe rudimentary to reduced. Context thin, 1 mm, soft, golden blonde (5C4). Odor not characteristic. Taste mild. Spore print oak brown to clay (5D5/5D6).

Basidiospores 6.5–8 × 5–7 μm (Lm = 7.3 ± 0.55 μm, Wm = 5.8 ± 0.46 μm); Q = 1.17–1.3 (1.33); Qm = 1.25, mostly broadly ellipsoid, rarely ellipsoid, yellowish brown in aqueous KOH, moderately thick-walled, finely warty. Basidia 19–24 × 8–9 μm, broadly clavate to clavate, 4-spored, thin-walled, hyaline. Lamella edge sterile with crowded cheilocystidia. Cheilocystidia 48–76 × 8–14.5 μm, versiform, cylindrical, flexuous, narrowly lageniform to lageniform, often with a long flexuous narrow neck with a subcapitate apex, rarely clavate, thin-walled, hyaline. Pleurocystidia absent. Hymenophoral trama regular, hyphae 4–12 μm wide, thin-walled, hyaline. Subhymenium pseudoparenchymatous. Pileal trama hyphae 4–9.5 μm wide, thin-walled, hyaline. Pileipellis an interrupted epicutis with tufts of erect to semi-erect undifferentiated cylindrical hyphae, thin-walled, hyaline; scale cells form a thick tuft of thin cylindrical hyphae towards margin. Oleiferous hyphae present. Clamp connections absent in all tissues.

Habit, habitat, and phenology: Scattered on decaying log of an unidentified angiosperm tree. Oct. –Nov.

Additional specimens examined: India. Kerala State, Thiruvananthapuram district, Palode, JNTBGRI campus, scattered on decaying log of an angiosperm tree, 13 Oct. 2017, Manoj TBGT17156; 03 Nov. 2017, Manoj TBGT17240.

Notes: Crepidotus exiguus is characterized by small, thin basidiomes, white becoming orange white, appressed squamulose pileus, broadly ellipsoid, warty basidiospores, characteristic versiform cheilocystidia, pileipellis an interrupted epicutis and absence of clamp connections.

Crepidotus effusus Pegler, C. applanatus (Pers.) P. Kumm., C. versutus Hesler & A.H. Sm., and C. defibulatus Singer are similar in their gross morphology and in some microscopic characters. Crepidotus effusus described from Kenya (Pegler 1977) is distinct by its thin membranous basidiomata, imbricate habit, pale lamellae, slightly larger basidiospores (5.7–10 × 4.2–5.5 μm), and pileipellis an undifferentiated cutis. Crepidotus applanatus a widely distributed species (Hesler and Smith 1965; Senn-Irlet 1995; Consiglio and Setti 2008) differs by its distinct large cheilocystidia with capitate apex, smaller (4.5–7 μm) globose or subglobose punctate basidiospores, and with distinct pileocystidia. Crepidotus versutus (Hesler and Smith 1965) differs mainly by its long ellipsoid to cylindrical basidiospores (9–10.6 × 4.6–5.6 μm). Crepidotus defibulatus (Singer 1973) is similar in having a white pileus, clampless hyphae, and ornamented basidiospores but differs in its small, thin pileus (4–6 mm), smaller globose basidiospores (5.7–6.5 × 4.9–6 μm), and incrusted pileipellis hyphae.

Crepidotus exiguus is sister to C. cinnabarinus (AF205686) in our phylogenetic analyses (Fig. 1). Crepidotus cinnabarinus (Consiglio and Setti 2008) however is distinct by scarlet to cinnabar reddish pileus, subellipsoid larger basidiospores [7–9 (–10) × 5–6 μm], and fusoid ventricose cheilocystidia with reddish contents. Crepidotus thermophilus (Singer) Aime, T.J. Baroni, & O.K. Mill. originally described from the USA (as Tubaria thermophile Sing.) can easily be separated by its centrally stipitate basidiomata and hyphae with clamp connections.

Crepidotus flavobrunneus A.M. Kumar & C.K. Pradeep sp. nov. (Figs. 4, 5).

Fig. 4
figure 4

Crepidotus flavobrunneus (CAL1759). a–f Habit in situ. Scale bars: a–f = 10 mm

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Fig. 5
figure 5

Crepidotus flavobrunneus (CAL1759). a Basidia. b Basidiospores. c–e Cheilocystidia. f Pileipellis. g Pileal incrusted hyphae. Scale bars: a–g = 10 μm

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MycoBank: MB840207.

Diagnosis: Differing from Crepidotus applanatus by smaller, clavate to cylindro-clavate cheilocystidia, pileipellis a cutis lacking pileocystidia, incrusted pileal hyphae, and the different nrLSU sequence.

Typus: India. Kerala State, Thiruvananthapuram district, Palode, JNTBGRI campus, 8.75° N, 77.02° E, elev. 150 m, scattered to gregarious on dead and decaying wood, stumps, dead branches, and roots of angiosperm trees and on moist soil in evergreen forests, 23 Sep. 2015, Manoj TBGT15841 (holotype CAL1759), nrLSU: MK567981.

Etymology: The specific epithet refers to the yellowish to brownish basidiomata.

Basidiomata small to large, fleshy, soft. Pileus 3–60 mm diam., plano-convex to applanate, flabelliform, semi-orbicular, spathulate; surface white to yellowish white (4A2) when young, becoming cream to brownish orange (4A3/4B4/5B3/5C3) when mature, becoming camel brown (6D4) in very old specimens, subtomentose to tomentose, villose, velvety, more towards the base (attachment), pellucid striate up to 2/3rd from the margin to the base, strongly hygrophanous; margin straight, wavy, entire to rarely incised, pellucid striate. Lamellae radiating from a lateral point, white to orange white (4A1/4A2/4A3/4B3/5A2) in fresh young basidiomes, becoming flesh (6B3) on keeping and finally attaining camel brown (6D4) in old ones, 4 mm wide, close to crowded with lamellulae of 3–5 lengths; edge concolorous to the sides, entire. Stipe rudimentary or reduced, present in young specimens, covered with cottony white hairs. Context thin, pale to off white, 1–2 mm wide. Odor indistinct to mild, not characteristic. Spore print brown (6E4/6E5).

Basidiospores 5.6–6.4 × 5.6–6.4 μm (Lm = 5.8 ± 0.36 μm, Wm = 5.8 ± 0.36 μm); Q = 1; Qm = 1, globose, pale yellow in KOH, thick-walled, minutely punctate, or warty. Basidia 25.6–32 × 8–8.8 μm, narrowly clavate, 4-spored, thin-walled, hyaline. Lamella edge sterile with crowded cheilocystidia. Cheilocystidia (13.6) 20–36 × 8–28 μm, clavate to cylindro-clavate, thin-walled, hyaline. Pleurocystidia absent. Hymenophoral trama regular to subregular, hyphae 4–5.6 μm wide, thin-walled, hyaline. Subhymenium pseudoparenchymatous. Pileal trama composed of thin-walled hyphae, 8–10 μm wide, hyaline. Pileipellis a cutis of parallel hyph

ae, 4–5 μm wide, thin-walled, incrusted, with pale brown contents. Clamp connections present in all tissues.

Habit, habitat, and phenology: Saprotrophic, scattered to gregarious on dead and decaying wood, stumps, dead branches, and roots of unidentified angiosperm trees and on moist soil in evergreen forests. Apr.–May; Sep. –Dec.

Additional specimens examined: India. Kerala State, Thiruvananthapuram district, Palode, JNTBGRI campus, on dead and decaying wood, stumps, dead branches, and roots of unidentified angiosperm trees and on moist soil in evergreen forests, 11 May 2014, Manoj TBGT15032; 07 Oct. 2014, Manoj TBGT15369; 24 Oct. 2014, Manoj TBGT15416; 28 Apr. 2015, Manoj TBGT15575; 29 Apr. 2015, Manoj TBGT15587; 30 Apr. 2015, Manoj TBGT 15598, ibid. 15600, ibid. 15602; 01 May 2015, Manoj TBGT15611; 05 May 2015, Manoj TBGT 15615; 13 May 2015, Manoj TBGT15644; 19 Oct. 2015, Manoj TBGT15902; 19 Nov. 2015, Manoj TBGT15958; 21 Dec. 2015, Manoj TBGT16071; 26 May 2016, Manoj TBGT116193; 18 May 2017, Manoj TBGT16756; Palode, Plavara, 20 Oct. 2015, Manoj TBGT 15904; Bonacaud, 23 Sep. 2015, Manoj TBGT15838.

Notes: Crepidotus flavobrunneus belongs to subsect. Porpophorini of sect. Echinospori owing to its minutely punctate to warty globose basidiospores and presence of clamp connections. The diagnostic features of this species invite comparison with a cluster of species such as Crepidotus applanatus, C. crocophyllus (Berk.) Sacc., C. stenocystis Pouzar, C. malachioides Consiglio, Prydiuk & Setti, C. brunnescens Hesler & A.H. Sm., C. malachius Sacc., and C. ehrendorferi Hauskn. & Krisai.

Crepidotus applanatus, a widely distributed species (Hesler and Smith 1965; Singer 1973; Watling and Gregory 1989; Nordstein 1990; Senn-Irlet 1995; Krisai-Greilhuber et al. 2002), is conspicuously distinct by its large clavate, flexuous cheilocystidia with a capitate apex, pileipellis with distinct pileocystidia, and hyaline pileipellis hyphae lacking incrustation. Many workers also proposed several varieties for this species based mainly on the size of basidiospores and nature of cheilocystidia. However, all these varieties are now considered conspecific. Crepidotus malachius described from the USA (Hesler and Smith 1965) differs in having slightly larger (5–8.5 μm), globose, at times subovoid, spores; longer less broad (24–52 × 5–12 μm) ventricose, bottle shaped, ten-pin shaped cheilocystidia, and lack of incrustations in the pileipellis. Neotype and isotype studies of C. applanatus and C. malachius by Consiglio and Setti (2008) opined that it is quite difficult to separate these two species macroscopically, though there is a significant difference in basidiospore size. Bandala et al. (2008) on a detailed analysis considered C. malachius as a synonym of C. applanatus.

Crepidotus stenocystis and C. brunnescens are similar in most macro- and microscopic characters however differ among other things by their versiform cheilocystidia and pileipellis with distinct pileocystidia. Molecularly both species are having only 96% and 95% LSU sequence identity with our new species. Crepidotus malachioides can be distinguished by its strongly capitate, clavate cheilocystidia embedded in a thick brown mucus, and pileipellis a cutis with distinct pileocystidia similar to cheilocystidia. Crepidotus ehrendorferi differs by grayish orange to tinted yellow basidiomata with strigose fibrillose pileus, cylindrical, narrowly utriform flexuous branching cheilocystidia, and pileipellis a trichoderm with narrowly conical/cylindrical or mucronate elements. Crepidotus flavobrunneus is easily distinguished morphologically by its white to brownish orange tomentose pileus in contrast with the dull brown pileus of C. crocophyllus with brown to reddish brown fibrils that may aggregate in to small scales. The latter species also differs in having versiform cheilocystidia with subcapitate or branched apices and pileipellis a cutis with ascending hyphae.

Crepidotus alabamensis Murrill, N. Amer. Fl. 10(3): 150 (1917) (Figs. 6, 7).

Fig. 6
figure 6

Crepidotus alabamensis. a–b Habit in situ. Scale bars: a–b = 10 mm

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Fig. 7
figure 7

Crepidotus alabamensis. a Basidium. b Basidiospores. c–d Cheilocystidia. e Pileipellis with pileocystidia. Scale bars: a–c = 5 μm. d–e = 10 μm

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Pileus 3–20 mm diam., convex, spathuliform, flabelliform or petaloid; surface pastel yellow to maize yellow (1A4–1A7/2A2–3A5/4A2–4A6), becoming apricot yellow (5B6) in old specimens, viscid to glutinous, hygrophanous, white tomentose-fibrillose to minutely villose near base, pellucid striate almost to the base; margin straight, pellucid striate, crenate. Lamellae radiating from a lateral point, sulfur yellow to grayish orange (1A5/1A6/2A2/3A3/5A3/4B4/6B5), up to 1 mm wide, close to subdistant with lamellulae of 2–4 lengths; edge concolorous to the sides, entire. Stipe rudimentary, present only in young basidiomata, lateral, absent in mature ones. Context thin, pale (2A2), up to 1 mm wide. White pubescent hairs present near base. Odor not characteristic. Spore print golden brown (5D7).

Basidiospores 5.6–7 × 4.8–5 (5.5) μm (Lm = 6.38 ± 0.46 μm, Wm = 5.0 ± 0.20 μm); Q = 1.17–1.33; Qm = 1.27, broadly ellipsoid to ellipsoid, yellowish brown in KOH, thick-walled, smooth. Basidia 19–22 × 6.5 μm, clavate, 4-spored, thin-walled, hyaline. Lamella edge sterile with crowded cheilocystidia. Cheilocystidia tramal in origin, 17.5–40 × 5–10.5 μm, versiform, often septate, flexuous, strangulated, lageniform, ampullaceous, ventricose, often with long coiled beaks, bifurcated or with irregular excrescences, thin-walled, hyaline. Pleurocystidia absent. Hymenophoral trama regular, hyphae 2.5–4 μm wide, gelatinized, thin-walled, hyaline. Subhymenium pseudoparenchymatous. Pileal trama composed of thin-walled, gelatinized hyphae, 5.5–9.5 μm wide, hyaline. Pileipellis an ixocutis, hyphae 2.5–6.5 μm in diam., incrusted, transforming to a trichoderm towards the center. Trichodermial elements 25.5–33.5 × 3–5.5 μm, versiform, cylindric to narrowly lageniform, strangulated, curved, or with short beaks. Pileal hyphae, incrusted with light brown pigment. Oleiferous hyphae abundant, yellowish. Clamp connections absent in all tissues.

Habit, habitat, and phenology: Scattered to gregarious on dead and decaying bark and wood of unidentified angiosperm trees in evergreen forests. May–Aug.; Oct. –Nov.

Specimens examined: India. Kerala State, Thiruvananthapuram district, Palode, JNTBGRI campus, on dead and decaying bark and wood of unidentified angiosperm trees in evergreen forests, 1 May 2015, Manoj TBGT15609, ibid. Manoj TBGT15610; 20 Oct. 2015, Manoj TBGT15903; 17 Nov. 2015, Manoj TBGT15949; 17 May 2018, Manoj TBGT17454; 12 Jun. 2018, Manoj TBGT17531; 13 Jun. 2018, Manoj TBGT17532; 14 Jun. 2018, Manoj TBGT17539; 23 Jul. 2018, Manoj TBGT17595; Kollam district, Cheenikala, 23 Aug. 2016, Manoj TBGT16552.

GenBank LSU: MK459543; ITS: MK459545.

Notes: The Kerala collections agree with Crepidotus alabamensis morphologically and molecularly which is originally described from the USA (Murrill 1917; Hesler and Smith 1965). In a BLAST search in NCBI using nrLSU sequence (957 bp), the closest hit was C. alabamensis (AF367960,) with 99.37% sequence identity with zero e-value. In the ML phylogram, the Indian collection of C. alabamensis (MK459543) is placed close to C. alabamensis from the USA (AF367960) with 98% ML Bootstrap. However, slightly smaller basidiomata and presence of incrusted pileipellis hyphae are the additional/minor differences observed in the Indian collections.

Crepidotus alabamensis was so far not known from India and therefore phytogeographically significant. It belongs to sect. Crepidotus subsect. Crepidotus.

Crepidotus roseus Singer, Lilloa 13: 87 (1947) (Figs. 8, 9).

Fig. 8
figure 8

Crepidotus roseus. a–d Habit in situ. Scale bars: a–d = 10 mm

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Fig. 9
figure 9

Crepidotus roseus. a–b Basidia. c Basidiospores. d–f Cheilocystidia. g Pileipellis. Scale bars: a–g = 10 μm

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Pileus up to 12 mm diam., laterally attached, convex, orbicular to flabelliform; surface peach to pastel pink (7A4/8A4/9A4/10A3/11A4), white cottony, woolly to villose when young and sparse towards margin in mature ones, nonhygrophanous, nonstriate, dry; margin straight, variously lobed, whitish. Lamellae radiating from a lateral point, concolorous to pileus (7A4–11A4), up to 1 mm wide, close to subdistant with lamellulae of 2–4 lengths; edge concolorous to the sides or whitish. Stipe rudimentary or absent. Context thin, venetian pink (10A3). Odor not distinctive.

Basidiospores 5.5–8 × 5–7 μm, (Lm = 6.68 ± 0.87 μm, Wm = 6.12 ± 0.68 μm); Q = 1–1.14; Qm = 1.09, globose to subglobose, light brown in KOH, moderately thick-walled, coarsely verrucose. Basidia 22.5–24 (26.5) × 8–9 μm, clavate, 4-spored, thin-walled, hyaline. Lamella edge sterile with crowded cheilocystidia. Cheilocystidia versiform, 20–44 × 8–13 μm cylindro-clavate to broadly clavate, rarely with bifid apices, slightly strangulated, often with a narrow stalk, thin-walled, hyaline. Pleurocystidia absent. Hymenophoral trama regular, hyphae 2.4–3 μm wide, thin-walled. Subhymenium pseudoparenchymatous. Pileal trama composed of thin-walled, hyaline hyphae, 8–12 μm wide. Pileipellis a cutis of 4–5 μm wide hyphae, often projecting to form a turf of hyphae, thin-walled, hyaline. Oleiferous hyphae absent. Clamp connections present in all tissues.

Habit, habitat, and phenology: Scattered on dead and decaying bark of dicot trees in evergreen forest. Rarely found to cohabit with Crepidotus citrinus Petch. Sep. –Nov.

Specimens examined: India. Kerala State, Palakkad district, Dhoni, on dead and decaying bark of dicot trees in evergreen forest, 31 Oct. 2014, Manoj TBGT15512; Chittur, 10 Oct. 2014, Manoj TBGT15505; 17 Sep. 2015, Manoj TBGT15842; Thiruvananthapuram district, Palode, 15 Nov. 2014, Manoj TBGT15507; Ernakulam district, Thripunithura, 02 Sep. 2016, Manoj TBGT16584.

GenBank nrLSU: MK567977; nrITS: MK567976.

Notes: Crepidotus roseus is distinct and characterized by the small peach to pinkish basidiomes, globose to subglobose, coarsely verrucose basidiospores, versiform cheilocystidia, and presence of clamp connections. In the literature, one can find only a few species of Crepidotus having pinkish basidiomata, viz., C. roseolus Sing., C. roseoornatus Pöder & Ferrari, and C. reversus (Berk. & Broome) Sacc. Among these species, Indian collection is similar to C. roseus (Singer 1973; Hesler and Smith 1965) in most macro- and micromorphological characters. However, Singer (1973) and Hesler and Smith (1965) noted some cystidia slightly away from the edges of lamellae, which they considered pleurocystidia which is not observed in the Indian collections.

Crepidotus roseolus described from Argentina (Singer 1973) is similar in gross morphology, however differs in its smaller globose basidiospores (5–6.2 × 5.5 μm) and characteristic ventricose cheilocystidia with finger like and claviculate appendages. Crepidotus roseoornatus originally described from Italy, though similar to the present collection, may probably represent C. roseolus (Senn-Irlet 1995). Crepidotus reversus originally described from Sri Lanka (Pegler 1986) is distinct in having squamulose reddish pileus, differently shaped cheilocystidia, and pileipellis with a strongly differentiated cutis with numerous diverticulate to branching outgrowths.

In a BLAST search with nrLSU sequence (967 bp), the closest hit was C. aureus from Puerto Rico (AF205685) with 96.20% sequence identity and with 100% ML Bootstrap. Crepidotus aureus however is characterized by golden yellow to deep yellow pileus, fusoid to lageniform cheilocystidia which are incrusted with a resinous material or with distinct crystals. Crepidotus roseus was so far not reported from any Asian countries, and thus, the present Indian report is significant as it extends its distribution to the tropical Asian regions.