Candolleomyces rubrobrunneus P.K. Nayana & C.K. Pradeep

Nayana, P. K. & Pradeep, C. K., 2024, Morphological and phylogenetic analyses reveal two new species of Candolleomyces (Psathyrellaceae) from India, Phytotaxa 659 (3), pp. 255-267 : 262-264

Candolleomyces rubrobrunneus P.K. Nayana & C.K. Pradeep , sp. nov. ( Figs. 4 , 5 )

MycoBank: MB854241

Diagnosis:—Differs from similar species such as C. sindhudeltae , C. sultanii and C. efflorescens by small to medium reddish brown to dark brown hygrophanous pileus with pale brown velar squamules, basidiospores with a distinct germ pore, sterile lamella edge with polymorphic cheilocystidia and terrestrial habitat.

Holotype:— INDIA. Kerala State: Thiruvananthapuram District. Varkala, Sreenivasapuram , 8.43°N, 76.43°E, elev. 44 m, 13 April 2023, Nayana TBGT (M)19475! GenBank: PP741633 ( ITS); PP741636 ( LSU).

Etymology:— rubrobrunneus , refers to the reddish brown pileus.

Description:—Basidiomata small to medium sized, thin. Pileus 12–30 mm diam., conical to convex in buds, turning plano-convex, applanate to slightly uplifted with a small obtuse umbo at centre when mature; surface reddish brown to dark brown (8E4–8E6/8F5–8F7/9E4–9F5), hydrophanous, becoming orange gray (5B2) or brownish orange (5C3) with pale brown fibrillose to floccose evanescent velar squamules scattered throughout, pellucid striate, dry; margin straight, entire. Lamellae adnexed, grayish orange to brown (6C2–6E4), up to 2.5 mm, crowded with lamellulae of different lengths; edge concolourous to the sides, fimbriate. Stipe 20–50 × 1–4 mm, central, cylindrical, equal, straight or slightly curved, hollow, brittle; surface white, pruinose at the apex, minutely floccose towards base in some; base with white strigose hairs. Context concolorous to the pileus, 1 mm, soft. Odor none.

Basidiospores 7.2–8.0 × 4.0–4.8 µm (avL= 7.68 µm, avW= 4.38 µm), Q= 1.58–2.0 (Qm= 1.75), ellipsoid to elongate, brownish yellow in water, olive brown in 3% aqueous KOH, thick-walled, smooth, with a small distinct germ pore and minute hilar appendix. Basidia 13.1–15.2 × 6.3–8.1 µm, clavate, 2, 4-spored, thin-walled, hyaline. Lamella edge sterile with crowded cheilocystidia and paracystidia. Cheilocystidia abundant, 18.3–32.3 × 9.1–12.7 µm, polymorphic, utriform, broadly utriform, lageniform, broadly fusiform, ovoid, rarely bifurcate with an obtuse, capitate, subcapitate, flexuose or mucronate apex, thin- or slightly thick-walled, hyaline. Paracystidia moderately abundant, 10.3–15.3 × 6.6–9.4 µm, globose, subglobose to sphaeropedunculate, thin-walled, hyaline. Pleurocystidia absent. Hymenophoral trama regular, thin-walled, hyaline, inflated, 2.4–21.4 µm wide hyphae slightly constricted at septa. Subhymenium pseudoparenchymatous. Pileal trama composed of thin-walled, encrusted, inflated, 4.0–19.5 µm wide, hyaline to brown hyphae. Subcuticular hyphae brown in KOH. Pileipellis an epithelium, made up of clavate, ellipsoid, pyriform elements, 23–50 × 18–30 µm, thin-walled, hyaline. Veil composed of 4.5–9.2 µm wide, branched, rarely encrusted, thin- to moderately thick-walled, hyaline to golden brown hyphae. Stipitipellis a cutis composed of thin-walled, hyaline, 2.6–22.0 µm broad encrusted hyphae slightly constricted at septa. Stipe apex with caulocystidia and paracystidia. Caulocystidia abundant, crowded or scattered, 22.7–53.4 × 8.5–14.6 µm, cylindrical, utriform with an obtuse, subcapitate, rarely mucronate apex, slightly thick-walled, hyaline. Paracystidia scattered, rare, 13.6–17.6 × 8.9–11.7 µm, subglobose, clavate, thin-walled, and hyaline. Clamp connections present in all tissues.

Habit, habitat and phenology:—Solitary, scattered in groups or caespitose on soil. This species fruits in April.

Additional specimens examined:— India. Kerala State: Thiruvananthapuram District. Varkala, Sreenivasapuram : 21 April 2023, Nayana TBGT (M)19476 ; 22 April 2023, Nayana TBGT (M)19477 .

Notes:—Reddish brown to dark brown hygrophanous pileus, ellipsoid to elongate basidiospores with a distinct germ pore, polymorphic cheilocystidia, abundant cylindrical to utriform caulocystidia, and hyphal velar squamules with golden brown contents characterize C. rubrobrunneus .

Phylogenetically C. rubrobrunneus shows close relationship to C. sindhudeltae Haqnawas, Niazi & Khalid (2023: 23) , C. sultanii A. Izhar, M. Asif & Khalid (2023: 9) , C. albipes (Murrill) D. Wächt. & A. Melzer (2020: 1230) and C. efflorescens (Sacc.) D. Wächt. & A. Melzer (2020: 1233) . Candolleomyces sindhudeltae and C. sultanii are recently described species from Pakistan. Slightly larger areolate pileus (13–40 mm), annulate stipe, and smaller basidiospores (7.0–7.8 × 4.0–4.6 µm) differentiate C. sindhudeltae from C. rubrobrunneus . Candolleomyces sultanii can be distinguished by its slightly larger pileus (13–40 mm), annulate stipe and slightly smaller basidiospores (7.0–7.8 × 4.0–4.6 µm). Candolleomyces albipes described from Africa differs from C. rubrobrunneus by its pale grayish orange to pale gray, smaller (04– 10 mm) convex pileus, slightly smaller (7.0–7.8 × 4.0–4.6 µm) basidiospores, smaller (19–24 × 9.0–13.5 µm) clavate cheilocystidia and lignicolous habitat ( Desjardin & Perry 2016). Candolleomyces efflorescens , originally described from Sri Lanka, is distinguished by its smaller (05– 25 mm), convex, pinkish gray, rugose pileus, truncate basidiospores, smaller subglobose to ovoid cheilocystidia and lignicolous habitat ( Pegler 1986).

Candolleomyces asiaticus M.Asif,A. Izhar, Niazi & Khalid (2022: 180) and C. niveofloccosus P.K. Nayana & C.K.

Pradeep (2023: 475) are recently described species and closely related to C. rubrobrunneus . Candolleomyces asiaticus shares similarities in pileus size, basidiospores, cheilocystidia, and caulocystidia; however, it differs in its white pileal veil, basidiospores with an indistinct germ pore and molecularly by 23 base pairs in the ITS region. Candolleomyces niveofloccosus can be distinguished by its slightly larger pileus (20–42 mm), white pileal veil, basidiospores with an indistinct germ pore, and molecularly by 20 base pairs in the ITS region.

Figures

FIGURE 4. Candolleomyces rubrobrunneus (TBGT(M)19475, holotype). A–C. Habit in situ; D. Basidiomata with mature lamellae.Scale bars = 10 mm. Photos by: P.K. Nayana.

FIGURE 5. Candolleomyces rubrobrunneus (TBGT(M)19475, holotype). A. Basidia; B. Basidiospores; C, D. Cheilocystidia; E. Pileipellis; F. Caulocystidia. Scale bars: A, B = 10 µm C–F = 20 µm. Photos by: P.K. Nayana.