Introduction to Fungi, Third Edition

360 HYMENOASCOMYCETES: PYRENOMYCETES
Fig12.32 Alkaloids produced by Neotyphodium endophytes in grasses. (a) Ergovaline, an ergopeptide similar to ergotamine
(see Fig.12.28). (b) Lolitrem B, an alkaloid derived from geranylgeranylpyrophosphate and tryptophan.This substance is neurotoxic
to grazing animals, causing ryegrass staggers. (c) Loline, an insecticidal pyrrolizidine alkaloid derived from ornithine and
S-adenosylmethionine. (d) Peramine, an insecticidal pyrrolopyrazine-type alkaloid.
Other evidence comes from the distribution
of alkaloids in species of Epichloe and
Neotyphodium. Epichloe festucae is the only sexual
species known to synthesize representatives of
three classes of alkaloids, namely ergovaline,
lolitrem B and lolines (Fig. 12.32). Neotyphodium
lolii produces the same three alkaloids and it
seems reasonable to assume that E. festucae
was the ancestor that contributed the genes for
synthesis of these three alkaloids (Clay & Schardl,
2002).
12.5.4 Cordyceps and its anamorphs
There are about 400 500 species of Cordyceps
(Kobayasi, 1982; Liu et al., 2002) with an epicentre
of species diversity in northeastern Asia and
Japan. There are 29 species in the United States
and Canada, and 18 species in Europe (Humber,
2000). Most species are necrotrophic parasites
of insect adults, larvae or pupae, but several
species grow on the ascocarps of Elaphomyces
(Mains, 1957). There is a wide range of insect
hosts including moths, ants, beetles, and cicadas.
Spiders are also attacked. Within the dead body
of an infected insect a mass of mycelium or a
sclerotium develops, and from this a perithecial
stroma grows out. The perithecial stroma is
usually fleshy and brightly coloured. It may
bear perithecia over its entire surface or they
may be restricted to an upper or lateral portion
so that there is a stalk region lacking perithecia.
The perithecia are embedded in stromatal tissue
and tightly packed together. They are elongate,
with protruding ostioles. They contain numerous
narrowly cylindrical asci, each with a conspicuous
swollen cap pierced by a narrow canal.
There are 4 8 long cylindrical ascospores which
are typically divided by transverse septa into
cylindrical or fusoid part-spores which may
number 16, 32, 64 or 128 (Hywel-Jones, 2002).
The ascospores escape singly through the narrow
pore at the tip of the ascus and usually, but not
invariably, break up into constituent part-spores
outside the ascus.
There is an exceptionally wide range of
conidial forms including the anamorph genera
Paecilomyces, Hirsutella, Hymenostilbe, Beauveria,
Metarhizium and Tolypocladium (Hodge, 2003;
Stensrud et al., 2005). Some of these are
shown in Fig. 12.35. Evidence for the connection
between anamorphs and their Cordyceps teleomorphs
has been obtained in various ways,
e.g. by the development of anamorphs in cultures
derived from ascospores or from hyphal
bodies within a parasitized insect, by the development
of perithecial stromata on insect larvae