Highlights of the Didymellaceae - Studies in Mycology

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Phoma And relAted pleoSporAleAn generA
Fig. 5. Phoma dimorpha (CBS 346.82). A–C. Fourteen-day-old colonies on OA (A), MEA (B) and CHA (C). D. Pycnidia on stem of Urtica dioica. E. Pycnidia. F. Pycnidial wall.
G–H. Conidia in vitro (G) and in vivo (H). Scale bars: D–E = 100 μm; F = 20 μm; G–H = 10 μm.
Phoma viburnicola Oudem., Contr. Flora Mycol. d. Pays-
Bas 17: 247. 1901.
Specimens examined: The Netherlands, Wageningen, Aboretum, from Viburnum
cassioides, 1969, G.H. Boerema, CBS H-16605, culture CBS 523.73 = PD 69/800;
from Chamaecyparis lawsoniana, 1981, G.H. Boerema, CBS 371.91 = PD 81/413;
Baarn, from a leaf of Ilex aquifolium, 1993, J. de Gruyter, CBS 500.91 = PD 83/222.
Group J:
This small group (BPP = 1.00, RBS = 96 %) comprises only two
species. Because of the production of dictyochlamydospores, Phoma
boeremae was suggested to belong to the section Peyronellaea
(Group K, Aveskamp et al. 2009a), to which the present group is
closely related. No such structures were, however, observed in its
sister species, Ph. dimorpha sp. nov. This species is known from a
single strain, which sporulates poorly and may be degenerated.
Phoma boeremae Gruyter, Persoonia 18 (1): 91. 2002.
Specimen examined: Australia, Victoria, Burnley Gardens, from seed of Medicago
littoralis cv. Harbinger, Febr. 1982, M. Mebalds, neotype L 996.294.536, ex-neotype
culture CBS 109942 = PD 84/402.
Phoma dimorpha Aveskamp, Gruyter & Verkley, sp. nov.
MycoBank MB515595. Fig. 5.
Conidia dimorpha, in vitro cylindrica, glabra, hyalina, continua, 8–9.5(–10.5) ×
(2–)2.5–3(–3.5) μm, (5–)6–8(–10) guttulis minutis apolaribus praedita, in vivo
eguttulata, (8–)9–12(–12.5) × (4.5–)5–5.5(–6.5) μm.
Etymology: The epithet refers to the two different conidial types that
are observed.
Pycnidia produced only scarcely in vitro, in clusters of ca.
4–10 elements, globose, glabrous, non-papillate, produced on
the agar surface, relatively small, measuring (65–)85–170(–
190) μm diam. Ostioles single, non-pappillate. Pycnidial wall
pseudoparenchymatous, composed of isodiametric cells, 4–7
layers, 14–20 μm thick. Conidiogenous cells phialidic, hyaline,
simple, smooth, flask-shaped, ca. 5.5–7 × 4.5–6.5 μm. Conidia
cylindrical, thin-walled, smooth, hyaline, aseptate 8– 9.5(–10.5) ×
(2–)2.5–3(–3.5) μm, with (5–)6–8(–10) minute apolar guttules. In
vivo eguttulate and somewhat broader, measuring (8–)9–12(–12.5)
× (4.5–)5–5.5(–6.5) μm. Conidial exudates not observed.
Culture characteristics: Colonies on OA 45–50 mm diam after 7 d,
margin regular. Immersed mycelium olivaceous-black, in some sectors
covered by a low mat of floccose white to grey aerial mycelium, towards
colony margin the aerial mycelium is gradually becoming more felted
and white; reverse olivaceous buff to dark mouse-grey. Colonies on
MEA 50–55 mm diam after 7 d, margin regular. Immersed mycelium
hyaline, amber or iron-grey. Only sparsely small white tufts of whitish
aerial mycelium are produced in older cultures; reverse concolourous.
Colonies on CHA 55–60 mm diam after 7 d, margin regular. Immersed
mycelium hyaline, honey to isabelline or dark mouse-grey. Aerial
mycelium more proliferent near colony margin initially white, later
developing to iron-grey with olivaceous-grey tinges; reverse black,
but hyaline near colony centre. Application of NaOH did not have any
effect. In older cultures white dendritic crystals are formed both in the
aerial mycelium and in immersed in the agar.
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