Septonema fasciculare (Corda) S. Hughes

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 : 14

Septonema fasciculare (Corda) S. Hughes

( Figs 5 , 6 )

In Canadian Journal of Botany 36: 803 (1958).

MATERIAL EXAMINED. — Belgium. Haasrode, Meerdaalwoud, on the outer side of bark of Pinus sylvestris L., 16. V.1966, coll. G. L. Hennebert, isol. G. L. Hennebert ( MUCL [ MUCL 8886], deposited as Septonema secedens ).

Canada. Quebec province, Gatineau Parkway, near Pink Lake, on bark of Coniferae, X.1959, coll. W. B. Kendrick, det. W. B. Kendrick ( IMI [ IMI 84944a]). — Septonema secedens Corda , Great Britain, Surrey County, Ashtead Common, on bark of Betula sp. , 12. I.1947, coll. S. J. Hughes, det. S. J. Hughes ( IMI [ IMI 9939]); ibid., Oxshott, on periderm of Betula sp. , 7.III.1948 ( IMI [ IMI 25538a]).

DESCRIPTION

Colonies on natural substrate effuse, hairy or cottony, black. Mycelium partly superficial, partly immersed composed of branched, septate, smooth, brown hyphae, 1.5-2 µm wide. Conidiophores macronematous, monomenatous, erect, simple, straight or flexuous, sometimes bent at a 90° angle or rarely bifurcating, cylindrical, septate, smooth, brown, sometimes paler distally and constricted at the septa delimiting terminal or subterminal cells, up to 480 µm long, 3-4 µm wide, 5-9 µm wide at the base. Conidiogenous cells monoblastic or polyblastic, integrated, terminal or intercalary, occasionally intercalary-pleurogenous, determinate, cylindrical, subcylindrical or somewhat clavate at the tip, pale brown, brown or grayish brown, 0-1(-4) septate, sometimes constricted at the basal delimiting septa, 17-28 × 3-5(-6) µm, with 1-2 truncate or subdenticulate, neither thickened nor darkened apical conidiogenous loci giving rise to ramoconidia. Ramoconidia cylindrical to narrowly clavate, sometimes fusoid-ellipsoid, 0-1(-3)-septate, thick-walled, smooth, pale brown to brown or dark grayish brown, in chains of up to 3, 15-21(-25) × 3-5 µm, with 1-2 truncate or subdenticulate apical conidiogenous loci; conidia cylindrical, sometimes slightly attenuated in their central part, pale grayish brown to grayish brown, 1-4-septate, mostly 3, rarely up to 7 septa, thin-walled, smooth, with rounded ends, (11-)13-22(-30) × 4-5 µm, in simple or rarely branched acropetal chains of up to 9 conidia.

Colonies on MEA restricted, very slow growing, reaching 4-5 mm diam. after 1 month at room temperature (22-25° C), circular, black, velvety, convex, raised 1-2 mm, sometimes with a slight amount of dark gray aerial mycelium in the center, margin entire, reverse black, sporulation not observed after four months.

NOTES

The strain MUCL 8886 did not sporulate on any of the culture media used including nutrient poor water agar with sterile wooden toothpicks. Morphological examination of the herbarium specimen source of this strain showed that it is conspecific with S. fasciculare and not with S. secedens . The specimen closely matches previous descriptions of S. fasciculare ( Ellis 1976; Holubovà-Jechovà 1978) in forming black, hairy to cottony colonies on bark of Pinus species, particularly P. sylvestris , and having simple conidiophores up to 880 µm long, cylindrical, grayish brown to brown, mostly 3- but also 1-, 2- or 4-septate conidia with rounded ends, 14-20 µm long, consistently 4-5 µm wide and produced in branched, acropetal chains ( Fig. 6 B-J). Further evidence of conspecificity was found by comparing MUCL 8886 with specimen IMI 84944a belonging to S. fasciculare . Septonema secedens , on the other hand, differs from S. fasciculare by forming olivaceous brown to dark brown, velvety colonies on natural substrate, shorter, branched conidiophores up to 200 µm long and pale brown to brown, wider conidia 5-7 µm wide, with truncate ends ( Fig. 6 K-N). A comparison between MUCL 8886 and two specimens of S. secedens deposited in IMI (9939 and 25538a) confirmed that they belong to different taxa. Dried cultures found inside the herbarium packet of MUCL 8886 and grown on MA (Malt Agar) or MEA according to their labels were sterile as well.

Figures

FIG. 5. — Septonema fasciculare (Corda) S. Hughes (MUCL 8886, herbarium specimen): A, conidiophores, ramoconidia and conidia in chains; B, conidia. Scale bar: 20 μm.

FIG. 6. — Septonema fasciculare (Corda) S. Hughes (MUCL 8886) in culture (MEA): A, colonies after 1 month. Herbarium specimen; B, colonies on natural substrate; C, D, conidiophores, conidiogenous cells and conidia; E, F, conidia. Ibid. (IMI 84944a); G, colonies on natural substrate; H, J, conidia; I, conidiophores, conidiogenous cells and conidia. Septonema secedens (IMI 9939); K, colonies on natural substrate. L, M, conidia. Ibid. (IMI 25538a); N, conidiophore, branches and conidia. Scale bars: B, G, 200 μm; K, 500 μm; C-F, H-J, L-M, 10 μm; N, 20 μm.