Introduction to Fungi, Third Edition

CLAVICIPITALES
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artificially infected with conidia, or by molecular
comparison of gene sequences (Liu et al., 2002).
Teleomorphic states may be rare and some of
the fungi listed above are far better known as
anamorphs than as teleomorphs. This is especially
true of Beauveria bassiana and Metarhizium
anisopliae, both of which are widely distributed
in soil, probably growing as saprotrophs.
They have been used in the biological control of
insect pests.
Cordyceps
Cordyceps militaris forms club-shaped orange- or
red-coloured stromata (Plate 5g) which project
above the ground in autumn from buried lepidopteran
larvae and pupae (Winterstein, 2001).
Species from several genera of Lepidoptera and
some Hymenoptera are susceptible. If ascospore
segments or conidia come into contact with the
integument of a pupa, germination occurs and is
followed by penetration of the cuticle, aided by
the secretion of chitinolytic enzymes. Soon after
penetration, cylindrical hyphal bodies appear
in the haemocoel. The hyphal bodies increase in
number by budding, and become distributed
within the insect’s body. Death of the insect is
probably associated with the secretion of the
toxin cordycepin (3’-deoxyadenosine) which also
accumulates in the perithecial stroma (Yu et al.,
2001; Kim et al., 2002). After death some 5 days
after infection, mycelial growth takes place and
the body of the dead insect becomes transformed
into a sclerotium. Under suitable conditions
one or more perithecial stromata develop
above ground, some 45 60 days post infection.
Perithecial stromata can also form in pure
culture on rice grain supplemented with haemoglobin
or casein (Basith & Madelin, 1968). In pure
cultures derived from single ascospores, a phialidic
conidial state called Paecilomyces militaris
is formed (Fig 12.33c).
It is not known whether C. militaris is homoor
heterothallic. Perithecial development has
been studied in C. militaris by Varitchak (1931).
Coiled septate ascogonia arise in the peripheral
layers of the perithecial stroma. The segments
of the ascogonium become multinucleate and
give rise to ascogenous hyphae from which asci
develop in a single cluster at the base of the
Fig12.33 Cordyceps militaris. (a) Two perithecial stromata
attached to pupae. (b) Ascus and multiseptate ascospores.
Note the ascus cap. (c) Conidiophores and conidia.
perithecium. The perithecial wall is derived
from hyphae which develop from the stalk of
the ascogonium or from surrounding hyphae.
Paraphysis-like hyphae grow inwards from the
perithecial wall, but at maturity these hyphae
dissolve and disappear.
Cordyceps sinensis (Fig. 12.34) is highly prized in
traditional Chinese medicine (Pegler et al., 1994).
It grows on the larvae of hepialid moths at
3600 5000 m in mountainous areas in southern