Septonema lohmanii G. Delgado & Koukol, 2019

Delgado, Gregorio, Koukol, Ondřej, Miller, Andrew N. & Piepenbring, Meike, 2019, Septonema lohmanii G. Delgado & O. Koukol, sp. nov., a new species in Mytilinidiales (Dothideomycetes) and the phylogenetic position of S. fasciculare (Corda) S. Hughes, Cryptogamie, Mycologie 20 (2), pp. 3-21 : 9-14

Septonema lohmanii G. Delgado & Koukol , sp. nov.

( Figs 2 , 3 )

ETYMOLOGY. — Named in honor of Dr Marion Lee Lohman (1903-), American mycologist who pioneered the study of hysteriaceous and mytilinidiaceous fungi in culture and whose strains remain today a reference source of molecular data.

MATERIAL EXAMINED. — United States. Arizona, Coconino County, Forest Lakes Estates, Apache-Sitgreaves National Forest , around Willow Springs Lake , 34°18’45.7”N, 110°52’46.1”W, on rotting stump of Pinus ponderosa P. Lawson & C. Lawson , 21.IX.2014, coll. G. Delgado (holo-, BPI [ BPI 910175 ]; iso-, ILLS [ ILLS 82053 ]; ex-holotype culture, CBS [ CBS 141174 ]; ex-holotype sequences, CBS [ ITS-LSU LS998797 , EF 1-α LS998800 ]).

Czech Republic. Northern Bohemia, Doubice, Tokáň , 50°53’14”N, 14°25’11.4”E, on rotten bark of P. strobus L., 15.X.2015, coll. O. Koukol (para-, PRC [ PRC 4117 ]; ex-paratype culture, CCF [ CCF 6124 ]; ex-paratype sequences, CCF [ ITS-LSU LS998796 , EF 1-α LS998799 ]).

MYCOBANK MB 829281

Colonies on natural substrate more or less orbicular, densely floccose, dark brown or dark reddish brown, often confluent and forming irregular patches, sometimes effuse and hairy, with powdery spores easily dispersed when touched. Mycelium mostly superficial consisting of branched, septate, strongly verruculose, echinulate, verrucose or strongly verrucose, subhyaline to pale brown ascending hyphae, sometimes anastomosing, 2-4 µm wide, and septate, smooth or sparingly verrucose, thick-walled, brown to dark brown, interwoven creeping hyphae, often constricted at the septa and forming angular or irregularly swollen cells, 5-9 µm wide, warts when prominent more or less rounded, 2-3.5 µm wide. Conidiophores macronematous or semimacronematous, mononematous, arising terminally or laterally from the hyphae, solitary, erect or somewhat repent, flexuous or sinuous, rarely straight, cylindrical or subcylindrical, mostly branched, septate, sometimes constricted at some septa and readily breaking along the constrictions, verruculose, verrucose to strongly verrucose, sometimes locally smooth or thick-walled, yellowish brown to brown or reddish brown to dark brown, up to 515 µm long, 3-7(-9) µm wide, width and ornamentation may vary along the length of the conidiophore, warts when prominent similar to those on hyphae, occasionally with brown blobs of mucilage 6-11 µm diam.; branches cylindrical or subcylindrical, straight or flexuous, verruculose or verrucose, similarly ornamented as the near conidiophore, up to 205 µm long, 4-6 µm wide, basal cells often attenuated at the junction with the conidiophore to a truncate end and easily breaking off, 2-4 µm wide; young hyphae, conidiophores and branches extend by forming subhyaline to pale yellow or pale brown, finely verruculose or sparingly verruculose elongations tapering to an acute, smooth apex 1.5-2µm wide. Conidiogenous cells monoblastic or polyblastic, integrated, terminal or intercalary on conidiophores and branches, determinate, cylindrical or subcylindrical, rounded at the apex or slightly attenuated to a truncate end, 5-15(-18) × 4.5-7 µm, with 1-2 inconspicuous conidiogenous loci. Conidia acrogenous or acropleurogenous, cylindrical, subcylindrical or narrowly ellipsoidal, straight or somewhat flexuous, (1-) 2-11(-13)-septate, slightly constricted at some septa, smooth, verruculose, verrucose or strongly verrucose, sometimes ornamentation not uniform, yellowish brown or brown to reddish brown, formed in simple or branched, short acropetal chains of 2-3(-4) conidia at conidiophores or branches, each conidium with 0-3 apical or lateral inconspicuous or subdenticulate hila or 0-2 per individual conidial cell, sometimes small isthmi seen between conidia, 12-57(-63) × 4-6(-8) µm, apex rounded or somewhat truncate, base truncate. Teleomorph unknown.

Colonies on MEA moderately slow growing, reaching 16-21 mm diam. after 21 days at 25°C, velvety, dark brown, umbonate, raised 1-3 mm at the center, sulcate, sometimes zonate with 1-2 concentric rings of growth, margin slightly undulate, whitish to pale brown, reverse blackish brown, sporulation late and abundant after 2 months. Colonies on PDA similar to MEA, moderately slow growing, reaching 16-17 mm diam. after 21 days at 25°C, velvety, more umbonate than on MEA, raised up to 4 mm and dark brown at the center, outer zone brown, less sulcate, margin slightly undulate, whitish to paler brown, reverse black, sporulation lacking. Mycelium immersed and superficial, aerial hyphae similar to those on natural substrate but width and ornamentation often not uniform and may gradually vary along the length of the hyphae, anastomosing, often with prominent, brown to dark brown warts, 2-5 µm wide and pale brown or with brown blobs of mucilage, 3-4 µm thick, some cells inflated, thick-walled, brown, functioning as conidiogenous cells, 5-9 µm wide. Conidiophores similar to those on natural substrate, often strongly verrucose and distinctly warted, width and ornamentation may also vary along the length of the conidiophores, basal cell sometimes slightly narrower and then conidiophores gradually widening distally, up to 268 µm long, (3-) 4-8 µm wide; branches up to 142 µm long, 3-7.5 µm wide. Conidia similar to those on natural substrate, cylindrical, subcylindrical or narrowly clavate, with 2-13 transverse septa, 0-1 longitudinal septa and very rarely with 1 oblique septum, slightly constricted at some septa or around the central portion, in short, simple or branched acropetal chains of 2-4 (-5) conidia, each one with 0-4 apical or lateral hila or 0-2 per single conidial cell, 14-58(-63) × (5-) 6-10(-11) µm.

NOTES

Among species of Mytilinidion forming septonema-like anamorphs, S. lohmanii G. Delgado & O. Koukol , sp. nov. is morphologically close to anamorphic M. rhenanum in having coarsely ornamented semi-macronematous conidiophores, conidia and hyphae, and producing short, simple or branched acropetal chains of 2-3 conidia on natural substrate or 2-4 conidia on PDA or MEA ( Lohman 1939; Bisby & Hughes 1952). Conidia of both species are also similar in width being 6-8 µm wide in the lectotype specimen of M. rhenanum from Finland where the anamorph is also present mixed with hysterothecia, and they both occur on bark and wood of Pinus spp. However, colonies of anamorphic M. rhenanum on natural substrate are dull black and conidiophores are shorter being up to 60 µm long. Conidia are different in shape and shorter, fusiform to oblong and 15-35 µm long, with less number of septa and 2-7 per conidium. Our fungus is also comparable to anamorphic Oedohysterium insidens in its strongly verrucose conidiophores and conidial walls ( Hughes 1952b; Ellis 1976). However, conidial chains in O. insidens mature basipetally instead of acropetally with the older conidia located at the distal end of longer, simple chains of up to 15 conidia. Conidia of O. insidens are oblong or ellipsoidal in shape, wider being 8-18 µm wide with less 3-5(-9) transverse septa and may develop later 1-3 longitudinal septa. Conidiophores are shorter than those of S. lohmanii G. Delgado & O. Koukol , sp. nov., up to 50 µm long, and they arise in a palisade from a conspicuous, pulvinate and erumpent stroma.

Both specimens of S. lohmanii G. Delgado & O. Koukol , sp. nov. studied here were morphologically similar on natural substrate but minor variations in color, conidiophore length, branching and ornamentation were detected between them. Conidiophores and conidia of the Arizona specimen BPI 910175 were more reddish brown in color whereas the Czech material PRC 4117 was more yellowish brown. The Arizona fungus had shorter conidiophores, up to 268 µm long, than the Czech specimen with up to 515 µm long. Conidiophores were more uniformly ornamented, more consistent in width and less branched in the Arizona specimen. Segments of conidiophores and branches of the Czech fungus, on the other hand, were unevenly wide, some cells thick-walled, darker in color, smooth or sparingly verrucose, 8-9 µm wide, and abruptly constricted a few times along the length of the same conidiophore reaching 3-3.5 µm in width.

Figures

FIG. 2. — Septonema lohmanii G. Delgado & O. Koukol, sp. nov. (BPI 910175, holotype): A, conidiophores, branches and conidia; B, acute apices of young co- nidiophores and branches. Scale bars: 20 μm.

FIG. 3. — Septonema lohmanii G.Delgado& O.Koukol,sp.nov.(BPI910175,holotype= CBS 141174).On natural substrate:A, conidiophores,branches and conidia.In culture (MEA);B, colonyafter 21 days;C, D, conidiophores,branches and conidia;E, hyphal segment showing warts.Ibid.(PRC 4117,paratype);F, colony on natural substrate; G, conidiophores, branches and conidia; H, conidia. Scale bars: A, 20 μm; C-E, G-H, 10 μm; F, 200 µm.