Thermoascus endophyticus T.M. Silva, C.S. Oliveira & J.D.P. Bezerra, sp. nov.

Index Fungorum number: IF 846409; Mycobank number: MB 846409; Facesoffungi number: FoF 13376; Fig. 1

Etymology – The epithet “endophyticus” refers to the fungus’s lifestyle, which was found to occur endophytically in Brosimum gaudichaudii.

Holotype – UFG 34289.

Cleistothecial ascomata, globose to subglobose, light brown to brown, abundantly present with colony age (178‒)418(‒465)×(108‒)372(‒465) µm. Asci globose to subglobose, 8-spored, 13.5‒16.5 ×11‒13.5 µm. Ascospores ellipsoids, ornamented, light brown to brown with age (5.5‒)8×(4‒)5.5 µm. Conidiophores straight to flexuous, septate, branched, hyaline, smooth-walled, abundantly present at the initial colony growth stage (40.5‒)108‒148(‒216)×(4‒)5.5 µm. Phialides ampulliform with a cylindrical basal portion and tapering to a thin neck, hyaline, smooth-walled, in groups of two to three (occasionally one) on short metulae, single phialides are occasionally born directly on the hyphae (13.5‒)16‒19(‒21.5)×(3‒)5.5 µm. Conidia cylindrical, occasionally subglobose, aseptate, hyaline to light brown with age, smooth walled, produced in chains (5.5‒)8‒11×3(‒5.5) µm. Chlamydospores not observed.

Culture characteristics – Colonies on PDA, MEA and DG18 growing fast and attaining a diameter of 90 mm at 25 °C after 1 week in the dark and growing up to 70 mm on CZ. On PDA, colonies are plane, floccose, whitish, yellowish to orange and orange with age, exudate yellowish; reverse yellowish to orange. On MEA, colonies are plane, slightly cottonose, whitish, salmon to orange with age, concentric circles, exudate salmon to orange; reverse brownish to orange. On DG18, colonies are slightly cottonose, whitish to light orange with age, exudate not observed; reverse white and yellowish to orange. On CZ, colonies are plane, floccose, yellowish to orange, exudate not observed; reverse light brown to orange. At 36 °C after 1 week in the dark, colonies on PDA, MEA and DG18 growing fast and
attaining a diameter of 90 mm and morphologically similar as described at 25 °C.

Habitat and distribution – The new species occur endophytically in branches of Brosimum gaudichaudii Trécul (Moraceae) and is currently only found in Brazil’s Cerrado biome.

Material examined – Brazil, Goiás state, Goiânia municipally, Escola de Agronomia of the Universidade Federal de Goiás, 16º 35′ 58.5″ S, 49º 16′ 45.8″ W, isolated as an endophyte from branches of Brosimum gaudichaudii (Moraceae), 20 October 2020, T. M. Silva & J.D.P. Bezerra (UFG 34289, holotype), ex-type living culture, FCCUFG 19 = URM 8565, ibid., FCCUFG 20 and FCCUFG 21.

GenBank numbers – FCCUFG 19 = URM 8565: ITS= OP325230, CAL= OP351562, TUB2= OP351559, RPB2=OP351565; FCCUFG 20: ITS=OP325231, CAL=OP351563, TUB2=OP351560, RPB2=OP351566; FCCUFG 21: ITS=OP325232, CAL=OP351564, TUB2=OP351561, RPB2=OP351567.

Notes – The new species is phylogenetically placed in a well-supported clade (ML-BS=100% and BYPP=1), having Thermoascus aegyptiacus and Thermoascus crustaceus as related species (Fig. 2). Morphologically, T. endophyticus differs from T. aegyptiacus by the size of cleistothecia (250‒550 µm), asci (14‒18×11‒15 µm) and ascospores (6.0‒8.5 × 4.0‒5.5 µm) in the teleomorph; and in the anamorph by the size of conidiophores (50‒300×5‒7 µm), phialides (12‒30×3‒6 µm) and conidia (4.5‒11×3‒4 µm) (Salar and Aneja 2007). The new species also differs from T. crustaceus by the size of orange cleistothecia (300‒900 µm diameter), asci (16‒20 × 13‒15 µm) and ascospores (6.5‒8×5‒6.5 µm) in the teleomorph; in the anamorph by the size of conidiophores (up to 1000 µm long, 7‒12 µm wide at the base and 4‒5 µm at the apex), phialides (15‒30 µm long) and conidia (6‒10×3‒6 µm, Stolk 1965).

Figure 1 – Thermoascus endophyticus (UFG 34289, holotype). a Colonies (verse and reverse) on MEA, PDA, DG18 and CZ at 25 °C after 1 week in the dark and PDA after 30 days. b Cleistothecial ascomata and ascospores. c‒e Asci and ascospores. f‒j Conidiophores and conidia. k Conidia. Scale bars: b=50 µm, c‒k=10 µm

Figure 2 – Phylogram generated from maximum likelihood analysis based on combined ITS, TUB2, CAL and RPB2 sequence data representing Thermoascus in Thermoascaceae, Eurotiales. Eleven strains are included in the combined analyses which comprised 2815 characters (610 characters for ITS, 533 characters for TUB2, 625 characters for CAL and 1047 characters for RPB2) after alignment. Paecilomyces niveus (CBS 100.11) and Paecilomyces variotii (CBS 102.74) in Thermoascaceae (Eurotiales) were used as the outgroup taxa. The best scoring RAxML tree with a final likelihood value of -9050.155654 is presented. The matrix had 699 distinct alignment patterns, with 20.42% of undetermined characters or gaps. Estimated base frequencies were as follows: A=0.212703, C=0.286868, G=0.279343, T=0.221086; substitution rates: AC=0.719132, AG=1.931043, AT=0.828377, CG=0.434883, CT=3.720518, GT=1.000000; gamma distribution shape parameter α=0.268628. Bootstrap support values for ML equal to or greater than 70% and Bayesian posterior probabilities (BYPP) equal to or greater than 0.95 are given near nodes. Ex-type strains are in bold and newly generated sequences (Thermoascus endophyticus) are in blue