Pezicula chiangraiensis Ekanayaka & K.D. Hyde, sp. nov.                    

Index Fungorum Number: IF551789

Diagnosis: Differs from other Pezicula species by possessing ascospores with a gelatinous sheath.

Type: Thailand, Chiang Rai Province, Kun Korn waterfall, 21 January 2015, A.H. Ekanayaka (Holotype, MFLU 15-3566; ex-type culture, MFLUCC 15-0170)

Etymology: With reference to the province where the holotype was collected.

Sexual morph: Saprobic on dead stems. Apothecia 800–870 × 230–280 µm (x = 826 × 253 µm, n = 10), arising singly or in small groups, sessile, slightly erumpent from the substrate, subsphaerical, urceolate, bright yellow when fresh, brownish yellow when dried. Disc convex. Receptacle yellow to light brown when fresh. Ectal excipulum variably thick, composed of large thin-walled yellow cells in a textura angularis. Medullary excipulum thin, not clearly distinguishable, composed of vertically arranged rows of yellow cells in a textura prismatica. Hymenium hyaline. Paraphyses 1.8–2.1 µm diam. (x = 2.0 µm, n = 20), numerous, filiform, obtuse, septate, branched, slightly enlarged at the apex. Asci 90–120 × 15–25 µm (x = 108 × 19 µm, n = 30), 8-spored, unitunicate, cylindric-clavate, short pedicellate, arising from croziers with conical and non-amyloid apices. Ascospores 18–22 × 8–10 µm (x = 20 × 9 µm, n = 40), partially biseriate, lower spores uniseriate, hyaline to grey, fusoid, gelatinous sheath present; immature spores non-septate and filled with guttules; mature spores 3-septate, aguttulate, and smooth-walled.

Asexual morph: Conidiomata sporodochium-like, produced in 7-day-old cultures, gregarious, dark brown. Conidiophores 11–12 × 5–6 (x = 11.5 × 5.8 µm, n = 20), branched near the base, septate, smooth-walled, composed various size cells. Conidiogenous cells holoblastic, cylindrical, smooth, hyaline. Conidia 23–29 × 11–12 µm (x = 25.2 × 11.2 µm, n = 20), cylindrical, straight, smooth with rounded apex and slightly truncate base, multi-guttulate or filled with granular cytoplasm, hyaline and aseptate when immature, pale brown and 1–3-transversely septate at maturity.

Culture characteristics: Ascospores germinating on MEA within 24 h. Colonies on MEA plates at 25–27 °C reaching 2 cm diameter within 1 week, circular, flat or effuse, with diffuse edge, medium honey-brown, grey aerial mycelium surrounded by pink mycelia, mycelium composed of 2–3 µm wide, septate, branched, smooth, hyaline hyphae, reverse dark brown to black.

GenBank Accession Numbers: ITS: KU310621, LSU: KU310622, RPB2: KU310623

Notes—Pezicula cinnamomea is morphologically similar to P. chiangraiensis in having apothecia, paraphyses, asci, and ascospores of a similar size and shape, but differs by its pale luteous to cinnamon or red-brown apothecia, its transversely and longitudinally septate spores without gelatinous sheaths, its faster growth rate, and absence of diffusing pigment in culture (Ooki et al. 2003, Verkley 1999). Pezicula aesculea Kirschst. differs from P. chiangraiensis by its larger apothecia, asci, and ascospores; P. amoena Tul. & C. Tul. by its dark brown, thick-walled ascospores; P. heterochroma Verkley, P. frangulae (Pers.) Fuckel, P. rubi (Lib.) Niessl, P. puberula (E.J. Durand) Verkley, P. crataegicola (E.J. Durand) J.W. Groves, P. myrtillina (P. Karst.) P. Karst., and P. grovesii Wehm. by their short, stout stalked apothecia; P. linda Korf and P. sepium (Desm.) Dennis by their asci with an amyloid ring; P. tasmanica W.Y. Zhuang & Korf by its positive reaction with Meltzer reagent after pretreating with KOH; P. hamamelidis J.W. Groves & Seaver by its broader apothecial base that is entirely hidden under the bark of its host substrate; and P. melastomatis Rehm by its smaller asci and ascospores (Verkley 1999). The asexual morphs of most Pezicula species produce both macro and microconidia (Verkley 1999), but microconidia were not observed in P. chiangraiensis.

Plate 1. Pezicula chiangraiensis (holotype, MFLU 15-3566).  a. Substrate; b. Ascomata on wood; c. Ascoma; d. Cross section of ascoma; e. Vertical section of ascomal margin; f. Septate paraphyses; g–j. Short pedicellate asci; k. Germinated ascospore; l. Apex of mature ascus; m. Ascospore with gelatinous sheath; n–q. Fusoid ascospores. Scale bars: b = 500 µm; c, e = 100 µm; d = 300 µm; f, k = 50 µm; g–j = 40 µm; l, m = 20 µm; n–q = 10 µm.

Plate 2. Pezicula chiangraiensis (MFLUCC 15-0170), asexual morph in culture: a. 7-day-old MEA colony from above; b. 7-day-old MEA colony from below; c. Conidiomata; d. Conidioma; e. Septate and branched hyphae; f. Fragment of small sporodochium-like conidioma; g, h. Different stages of conidiogenesis; i–l. Conidia at different stages. Scale bars: e = 50 µm; f, j–l = 20 µm; g, h = 30 µm; i = 10 µm.