Bactrodesmium atrum M. B. Ellis, Mycol. Pap.

Sánchez, Romina M. & Bianchinotti, M. Virginia, 2023, New records of mitosporic ascomycetes on Nothofagaceae from Patagonia, Argentina, Boletin de la Sociedad Argentina de Botanica 58 (4), pp. 491-503 : 493-495

2. Bactrodesmium atrum M. B. Ellis, Mycol. Pap. 72: 9. 1959. Fig. 1 G-J.

Conidiomata sporodochial, scattered, punctiform or irregular, bright black, superficial, sometimes effuse colonies. Mycelium immersed, branched, hyaline to pale brown, formed by cylindrical cells, thin-walled, smooth, 6-21 × 4-5 µm (M = 13.9 × 4.8). Conidiophores cylindrical, unbranched, pale brown, ca. 7-10 × 2 µm. Conidiogenous cells cylindrical, widening towards the apex, monoblastic, integrated, determinate, terminal, smooth, pale brown, ca. 3-7 × 6 µm. Conidial secession rhexolytic. Conidia solitary, obovoid, 2-6 septate, mostly smooth, sometimes punctate, apical cells black, basally pale brown to subhyaline, 32-68 × 20-38 µm (M = 49 × 28.4; n = 52).

Distribution and habitat. Growing on bark of Lophozonia obliqua in Nothofagaceae forest in Argentina ; on rotten branches of unidentified tree from China ( Zhao et al., 2009), on bark of deciduous trees of England including Betula sp. and Fagus sylvatica L. ( Ellis, 1959); on F. crenata Blume in Japan ( Matsushima, 1975); on stems of Phragmites australis (Cav.) Steud. , in a brackish tidal marsh of the river Scheldt in the Netherlands ( Van Ryckegem & Verbeken, 2005); on Agathis australis (D. Don) Lindl. , Beilschmiedia tarairi Kirk , Corynocarpus laevigatus J.R. Forst. & G. Forst. , Elaeocarpus dentatus (J.R. Forst. & G. Forst.) Vahl , Laurelia novae-zelandiae A. Cunn. , Leptospermum scoparium J.R. Forst. & G. Forst. , Rhopalostylis sapida H. Wendl. & Drude and Rhopalostylis sp. from New Zealand ( Hughes, 1978); on unidentified dead wood from Spain ( Silvera-Simón et al., 2009); on Elaeis guineensis Jacq. in Tanzania ( Pirozynski, 1972).

Comments. The material is fully consistent in all its features with the originally described growing on Fagus sylvatica and Betula sp. in England ( Ellis, 1959). It only differs in having thicker hyphae than that (1.5-4 µm wide). Three species have been earlier found growing on Nothofagaceae hosts. One of them, B. biformatum (Hönh.) S. Hughes found on corticated branches of Nothofagus sp. in New Zealand, differs from B. atrum in the paler and smaller (18-40 × 7-9.4 µm), ellipsoidal to clavate, 3 to 9 septate conidia ( Hughes, 1983). The second one is B. traversoanum (Peyronel) M.B. Ellis which differs from B. atrum in the length of the conidiophores (up to 35 µm) and in the shape (clavate to ellipsoidal) of the smaller conidia (20-37 × 8-12 µm) ( Ellis, 1959). The third one, B. nothofagi J.A. Cooper , has paler and smaller conidia (47-55 × 18-25 μm) with more septa (5-8) (Cooper, 2005).

Material examined. ARGENTINA. Neuquén: Parque Nacional Lanín, ascent path to the Cascada Chachín waterfall (40° 8′ 25.29 ″S, 71° 40′ 3.84″ W), 757 m alt., 15-V-2007, on bark of Lophozonia obliqua, Bianchinotti & Sánchez 591 ( BBB) .

Figures

Fig. 1. Avettaea salvadorae. A: Pycnidial conidioma on substrate. B: Vertical section of a pycnidial conidioma. C: Conidiogenous cell. D: Conidiogenous cell with two annelidic percurrences. E: Conidium before liberation from conidiogenous cell. F: Conidia. Bactrodesmium atrum. G: Sporodochial conidioma on substrate. H: Conidium detached from conidiogenous cell and view of the conidiophore. I: Conidium 6 septate, septa visible by constrictions. J: Conidium with ornamented wall. Abbreviations: cg: conidiogenous cell; sh: sheath; sp: septa. Scale bars= A, G: 100 µm; B: 40 µm; C-D: 2 µm; E: 5 µm; F: 10 µm; H-J: 20 µm.