Introduction to Fungi, Third Edition

504 BASIDIOMYCOTA
Auricularia auricula-judae, a parasite of elder
(Sambucus nigra), develops successive blastic
conidia from conidiophores on germinating
basidiospores (Fig. 21.6c) or from monokaryotic
hyphae. At discharge, each basidiospore is
unicellular, but three transverse septa divide
the basidiospore before germination and each of
the resulting cells may form a short conidiophore
which swells and curves at the tip to form
a horseshoe-shaped (lunate) conidium, followed
by further similar conidia.
Sistotrema hamatum (anamorph Ingoldiella
hamata) is a subtropical aquatic basidiomycete
with large, septate, branched conidia (Fig. 25.17;
Nawawi & Webster, 1982). They consist of a main
axis over 400 mm long with two to three tapering
laterals. The tips of the branches are recurved.
Conidia are formed on dikaryotic and on
monokaryotic mycelia. Dikaryotic conidia are
distinguished by the presence of clamp
connections at the septa (Figs. 25.17a,b) which
are absent from the otherwise similar monokaryotic
conidia (Fig. 25.17c). Other species
with aquatic branched conidia are recognizable
as basidiomycetes either by the presence of
clamp connections or dolipore septa within
their conidia and mycelia (Nawawi, 1985;
Webster, 1992).
Fig18.15 Spiniger state of Heterobasidion annosum.
Conidiophores and conidia.Conidial development is blastic.
adopted by many basidiomycetous yeasts is an
example of blastic development (see p. 659).
Heterobasidion annosum, a tree-pathogenic
polypore, forms clusters of dry blastoconidia
synchronously on the swollen tips of upright,
club-shaped conidiophores (Fig. 18.15). Following
detachment of the conidia, the surface of the
swollen tip of the conidiophore bears spiny
denticles. These conidiophores resemble the
Oedocephalum type of conidia found in certain
ascomycetes (see Fig. 14.4), but the anamorph
name Spiniger has been given to them (Stalpers,
1974).
18.8.3 Chlamydospores
The term chlamydospore is used here in a wide
sense following the definition by Kirk et al. (2001)
as ‘an asexual one-celled spore (primarily for
perennation, not dissemination) originating
endogenously and singly within part of a preexisting
cell, by the contraction of the protoplast
and possessing an inner secondary and often
thickened hyaline or brown wall, usually impregnated
with hydrophobic material.’ A common
example of a basidiomycete forming chlamydospores
is Laetiporus sulphureus, a yellowish-orange
bracket fungus parasitic on a range of tree hosts
such as oak, willow and yew. In culture they are
mostly formed terminally on aerial branched
conidiophores which develop from a mycelium
lacking clamp connections (Fig. 18.16a). In the
mycelium within the substrate, intercalary chlamydospores
are also formed. Adjacent to the