Metacapnodium stanhughesii Berbee & Aliabadi sp. nov.

Fig. 15

Typification.

Canada • British Columbia Province, Vancouver, The University of British Columbia, 2075–2099 Main Mall, 49.26504°N, 123.25290°W, on bark of Taxus sp., 2 July 2021, F. Aliabadi & L. Le Renard (holotype: UBC F 35817).

Etymology.

Named in honor of mycologist Stanley J. Hughes.

GenBank accession numbers.

ITS, OR 532926; LSU, PP 140681; ef 1 - α, OR 820949.

Description.

Subicula dark brown to black, velutinous, thin, up to 2–4 mm thick, covering the bark of a trunk of Taxus sp. and intermingled with other sooty molds. Mycelium of moniliform hyphae, hyphae brown to dark brown, constricted at septa, surfaces finely verrucose throughout, cell wall thickness of 0.5–1 μm. Hyphae curved, straight, occasionally anastomosing, narrowing towards their tips. Cells usually broader than long, subglobose to doliiform, 13–21 × 10–16 μm, narrowing to 5–7 μm at hyphal tips.

Sexual form unknown.

Asexual forms. Capnobotrys – Differentiated conidiophores not observed. Conidiogenous cells in botryose clusters laterally or terminally on hyphal tips or at ends of short, 1–2 celled lateral branches, spherical, subspherical, ellipsoid, 3–10 × 3–9 μm, light brown to dark brown, bearing denticulate scars where successive conidia budded out, then seceded. Conidia brown to dark brown, smooth walled, initially subglobose, then ellipsoid or ovoid, occasionally cornute or allantoid, with a single median or supramedial septum, not or only slightly constricted at septa. Conidia (10) – 12.7 – (15) + / – 1.3 × (6) – 7.7 – (9) + / – 0.9 µm, N = 30, Q = 1.7. Proximal cells longer and wider than distal cells; proximal cell 7.0 + / - 0.9 × 7.7 + / - 0.8 µm; distal cell 5.7 + / - 0.9 × 7.0 + / - 0.7 µm. Proximal cell: distal cell length ratio, 1.3, width ratio 1.2. Proximal cells sometimes with inconspicuous oblique scar resulting from secession from diagonal attachment to a conidiogenous cell; apex of distal cells shows wall thinning, light in color, which sometimes protrudes slightly.

Capnophialophora – Phialides scanty, occasionally at hyphal tips, with a verruculose, brown, subspherical venter, 4–5 × 5 μm, bearing a funnel-shaped, pale brown collarette 2–3 μm long, with a narrow constriction at its base, 2.5–3 μm wide at its opening. No phialidic conidia observed.

Capnosporium – Branched, erect hyphae bear individual conidia at or near their tip cells. Capnosporium conidia ellipsoid, obclavate, mainly straight, occasionally curved, 2–6 septate, sessile, 19–21 × 8–10 μm (2 – septate), 27–34 × 8–12 μm (3 – septate), 33–42 (– 47) × 11–12 μm (4 – septate) μm.

Host and distribution.

Known only from a single collection on Taxus sp. in shaded, landscaped area next to Chemistry Building on University of British Columbia campus. The subiculum, first noticed by Ludovic Le Renard, changed little over five years.

Notes.

Among the described Metacapnodium species, M. moniliforme is similar to M. stanhughesii in morphology. Phylogenetically, M. stanhughesii cannot be included in M. moniliforme because the ITS tree and the concatenated region tree show M. stanhughesii as branching outside of a clade consisting of M. neesii and M. moniliforme. Metacapnodium guava is also similar to M. stanhughesii in that it shares capnophialophora, capnobotrys, and capnosporium forms (Hughes, 1981). While the dimensions of conidia in M. stanhughesii fall between those of M. moniliforme and M. guava, M. stanhughesii (Fig. 15 E) and M. moniliforme (Fig. 10 I) exhibit cornute conidia with a slight point at one end, which were not seen in M. guava (Hughes, 1981). Cornute and allantoid conidial morphology arise in Capnobotrys lechlerianus (Hughes and Seifert 2012), but the hyphal walls of Capnobotrys lechlerianus are smooth rather than verrucose as in M. stanhughesii and M. moniliforme. Hughes and Seifert (2012) used the absence of capnophialophora and capnosporium forms, and the smaller dimensions of conidia to distinguish Capnobotrys lechlerianus from the capnobotrys form of M. moniliforme (Hughes and Seifert 2012).