Leiothecium dictyophorum S.M.Romero & Comerio, 2025

Romero, Stella Maris, Andrade, Ernesto Rodríguez, Romero, Andrea Irene, Amarilla, Leonardo David & Comerio, Ricardo M., 2025, A new heat-resistant species of Leiothecium Samson & Mouch. (Eurotiales, Ascomycota) from soil of Argentina, Cryptogamie, Mycologie 20 (4), pp. 51-60 : 56-57

Leiothecium dictyophorum S.M.Romero & Comerio , sp. nov.

( Fig. 2 )

DIAGNOSIS. — Leiothecium dictyophorum S.M.Romero & Comerio , sp. nov.; ex affinitate L. ellipsoidei Samson & Mouch. et L. cristati Y.Marín, Stchigel & Cano , ab utroque ascosporarum ornamento reticulato-foveato sine manifestis cristis distinctum.

Leiothecium dictyophorum S.M. Romero & Comerio sp. nov.; of the affinity of L. ellipsoideum Samson & Mouch. and L. cristatum Y. Marín, Stchigel & Cano , distinct from both by the ascospores’ ornament reticulate-foveate without prominent crests.

TYPE MATERIAL. — Argentina • Catamarca,RN 60 km 1016; 29°30’4”S, 65°37’57”W; 237 m alt.; 22.VIII.2011; S.M. Romero leg.; Holotype: BAFC 53468 (dried culture); BAFCcult 4595 = FMR≈15063, culture ex type; GenBank BenA sequence PP149064 , rpb 2 sequence PP149071 .

ADDITIONAL SPECIMENS STUDIED. — Argentina • Catamarca; RN 60 km 1102; 28°55’15”S, 66°08’46”W; 338 m alt.; 5.I.2009; BAFCcult 4599 = FMR 16764 • RN 38 km 563; 28°35’5”S, 65°52’27”W; 522 m alt.; 12.I.2009; BAFCcult 4592 = FMR 15065 • RN 60 km 1016; 29°30’4”S, 65°37’57”W; 237 m alt.; 2.I.2010; BAFCcult 4608= FMR 15066 • RN 38 km 563; 28°35’5”S, 65°52’27”W; 522 m alt.; 23.VIII.2011; BAFCcult 4597 = FMR 15067 , FMR 16766 , BAFCcult 4596 = FMR 16767 .

MYCOBANK. — MB857727.

ETYMOLOGY. — Dictyon (δικτΥΟΝ, net) and phorum (ΦΟΡΟς, bearing) were combined to coin dictyophorum (adj.): net-bearing; regarding the distinctly net-like ornamentation of ascospores.

LATIN DESCRIPTION

Coloniae in agaro malto confecto, 25°C, post 7 dies, 75-79 mm diam., fuscae, albis annulis mycelialibus praeditae; pars aversa fusca. In agaro farina avenae confecto, 25°C, post 7 dies, 60-64 mm diam., fuscae, quasi continuum stratum ascomatum efficientes, mycelium aerium vix effectum.

Hyphae hyalinae, laeves, 3-11 µm diam. Cleistothecia globosa, glabra, atro-brunnea, 40-125 µm diam., inter mycelium aerium disposita vel in substratum semiimmersa; parietes cleistotheciorum persistentes, 5-8 µm lati, texturam angularem praebentes, e cellulis atro-brunneis crassitunicatis 15-25 µm diam.compositi.Asci globosi vel subglobosi,13-15 × 14-18 µm, octospori, evanescentes. Ascosporae unicelulares, ellipsoideae, hyalinae, ornamentum reticulatum-foveatum ostendentes, 5.5-7 × 7-9 µm. Chlamydosporae subglobosae vel ellipsoideae, hyalinae, plerumque terminales umbonataeque, nonnumquam intercalares, etiam endogenae, crassitunicatae, 6-18 × 5-12.5 µm diam.

ENGLISH DESCRIPTION

Colonies on MEA, 25ºC, 7 days, 75-79 mm diam., dark, with aerial white mycelium in concentric circles; reverse dark ( Fig. 2A ). At 35°C, covering the whole plate before 7 days; reverse dark due to numerous ascomata. At 15°C, 7 days, 0-8 mm diam.; at 40°C, 7 days, 21-31 mm diam. On PDA, 25°C, covering the whole plate at 7 days, dark, with scarce aerial white mycelium, reverse dark. On OA, 25°C, 7 days, 60-64 mm, dark colonies forming an almost continuous layer of ascomata, aerial mycelium scarce ( Fig. 2B ). At 35°C, spreading all over the plate before 7 days; development in subtle circles, aerial mycelium less floccose than in MEA. On CY20S, 25°C, 7 days, 83 mm diam. On MY50G, 25°C, 7 days, 42 mm diam.

Mycelium composed of hyaline, smooth-walled, hyphae, 3-11 µm wide. Cleistothecial ascomata, globose, glabrous, dark-brown 40-125 µm diam., both intermixed within the white mycelium and semi-submerged in agar ( Fig. 2C, D ); with a persistent wall, textura angularis, 5-8 µm thick, composed of dark brown thick-walled cells of 15-25 µm diam. ( Fig. 2F, G ). Asci globose to subglobose, 13-15 × 14-18 µm, eight-spored, evanescent. Ascospores one-celled, ellipsoidal, hyaline, 5.5-7 × 7-9 µm, loosely reticulated ( Fig. 2I ); SEM shows a reticulated-foveate ornamentation in mature ascospores. Chlamydospores present, subglobose to ellipsoidal, hyaline, usually terminal but sometimes intercalary, endogenously generated present as well, smooth- and thick-walled, 6-18 × 5-12.5 µm.

NOTES

Leiothecium dictyophorum S.M.Romero & Comerio , sp. nov. displayed a distinctive ascospore ornamentation which set it morphologically apart from L. ellipsoideum and L. cristatum , consisting in a reticulate-foveate-net-ascospores without prominent crests ( Fig. 2N ). Some ascospores of L. dictyophorum S.M.Romero & Comerio , sp. nov. have shown areas where the net was not completely developed, as it is shown at the central region of the ascospore illustrated in the Fig. 2M . Probably, this particular feature, present in several ascospores, reflects some unripeness degree. Leiothecium dictyophorum S.M.Romero & Comerio , sp. nov. ascospores has not exhibited prominent crests as L. ellipsoideum ( Fig. 3C, D ) and L. cristatum clearly do. The referred difference between ascospores of L. dictyophorum S.M.Romero & Comerio , sp. nov. and L. ellipsoideum is illustrated in Fig. 3 .

Figures

FIG. 2. — Leiothecium dictyophorum S.M.Romero & Comerio, sp. nov.:A, B, colony on MEA,OA,14 days, 25 at c. 1ºC; C, ascomata from aerial mycelium; D, ascomata immersed in the culture media; E, initials; F, ascoma Textura angularis wall; G-I, ascospores; J, K, chlamydospores; L, broken ascoma showing asci and ascospores (SEM); M, N, ascospores (SEM). Scale bars: E, H, J, 10 μm; F, 20 μm; I, K, L, 5 μm; M, N, 1 μm.

FIG. 3. — Ascospores (SEM): A, B, Leiothecium dictyophorum S.M.Romero & Comerio, sp. nov.: A, BAFCcult 4608; B, BAFCcult 4599; C, D, Leiothecium ellipsoideum Samson & Mouch.: C, BAFCcult 4598; D, BAFCcult 4604. Scale bars: 1 μm.