Introduction to Fungi, Third Edition

HYPOCREALES
339
mushroom mycelium. Some are lichenicolous.
The ability to parasitize other fungi has been
employed for the biological control of fungal
pathogens of plants, using species of Trichoderma,
Gliocladium and Clonostachys (see below).
Several antifungal compounds, e.g. gliotoxin
or viridin, are produced as secondary metabolites
by anamorphs of Hypocrea spp. (Trichoderma and
Gliocladium; see below). Other pharmacologically
important secondary metabolites synthesized
by anamorphic Hypocreales include the antibacterial
antibiotic cephalosporin from Acremonium
spp. The gibberellins are growth hormones
ubiquitous in all higher plants, but they were
first detected as a secondary metabolite
produced by Gibberella fujikuroi (anamorph
Fusarium moniliforme). This species causes the
‘foolish seedling disease’ in rice, in which
seedlings show excessive stem elongation and
eventually keel over due to the production of
gibberellic acid by the infecting fungus
(Tudzynski, 1997). Mycotoxins poisonous to
farm animals and humans are produced by
some species of Fusarium (see below) and other
species have been reported as human pathogens.
The edible fungus food ‘Quorn’ is
Table12.2. Some teleomorph anamorph
connections in the Hypocreales.
Teleomorph genus
Nectria sensu lato
Bionectria
Calonectria
Gibberella
Hypocrea
Sphaerostilbella
Hypomyces
Apiocrea
Melanopsamma
Anamorph genus
Tubercularia, Fusarium,
Cylindrocarpon,
Verticillium, Heliscus,
Flagellospora
Clonostachys
Cylindrocladium
Fusarium
Trichoderma,Gliocladium,
Acremonium-like
Gliocladium
Mycogone,Cladobotryum
Sepedonium
Stachybotrys
manufactured by large-scale fermentation of
F. venenatum (previously identified as F. graminearum)
(Trinci, 1991; Moore & Chiu, 2001).
Cellulase production by Trichoderma reesei is
exploited commercially.
General accounts of the Hypocreales have
been given by Rogerson (1970) with keys to
genera, and by Rossman (1996). The taxonomic
treatment, i.e. the division into orders and
families, varies between different authors, some
placing Claviceps and its allies as a family
(Clavicipitaceae) of the Hypocreales, whilst
others, e.g. M. Barr (2001), placed them in a
separate order (Clavicipitales), a disposition
followed in this book. However, all are agreed
that the two groups are closely related, a view
based on morphological and molecular evidence
(Spatafora & Blackwell, 1993). Samuels and
Blackwell (2001) included four families in the
Hypocreales, i.e. Hypocreaceae, Nectriaceae,
Bionectriaceae and Niessliaceae, but we shall
consider representatives only of the first two.
12.4.1 Hypocrea (Hypocreaceae)
Species of Hypocrea, of which about 100 are
known, usually fruit on decaying wood or
occasionally on herbaceous plant material, forming
brightly coloured fleshy perithecial stromata,
with perithecia embedded in the outer
layers. The thin-walled asci contain 8 two-celled
ascospores, and in many species the spores
separate into 2 part-spores before ascus
discharge, so that 16 part-ascospores are released
(Fig. 12.15c). The ascospores may be colourless
(hyaline) or green in colour. Hypocrea pulvinata
forms bright yellow stromata on the underside
of dead overwintered basidiocarps of Piptoporus
betulinus, the birch polypore. It is possible that
this fungus grows parasitically on the basidiocarp.
The ascospores are often visible as white
tendrils issuing from the ostioles of the perithecia
(Plate 5c). In culture, conidia are formed in
sticky masses at the tip of single phialides
(Fig. 12.15b; Rifai & Webster, 1966). Conidia of
this type are described as Acremonium-like.
Some species of Hypocrea have conidia of the
Trichoderma type, in which whorls of phialides
give rise to separate, sticky green or white