Introduction to Fungi, Third Edition

GLOMALES
219
Fig 7.45 Furia americana from blowfly.
(a) Branched conidiophore. (b) Single
conidiophore and conidium. Note that the
wall of the conidium is bitunicate. (c) Conidia
after discharge. (d) Conidium germinating by
means of a germ tube. (e) Primary conidia
germinating to produce secondary conidia.
(f) Spherical resting bodies from dead fly.
Sivasithamparam, 1990). Sporocarps may form
part of the diet of some mammals and chlamydospores
can be dispersed by soil animals, including
invertebrates and some rodents as well as
larger hoofed mammals. Chlamydospores can
survive in their faeces and are also dispersed in
wind-borne soil dust (Allen, 1991; Allen et al.,
1997; Linderman, 1997).
The spores of Glomales can be extracted from
soil by wet sieving and decanting from soil
slurries using a series of sieves in the
2000 60 mm size range (Gerdemann & Nicolson,
1963). After surface sterilization, single chlamydospores
placed near the roots of susceptible host
plants such as Trifolium and Sorghum germinate,
produce hyphae which make contact with the
root surface and form appressoria before infecting
the root (Hepper, 1984; Menge, 1984). In this
way, dual cultures have been established and can
be maintained by the addition of freshly
extracted spores or infected root pieces to pots
containing a suitable host plant. Viable spores
derived from dual cultures maintained on potted
plants are available from the International
Collection of Vesicular Arbuscular Mycorrhizal
Fungi (Morton et al., 1993). Spores have also been
produced under aseptic conditions in association
with hairy root cultures (Mugnier & Mosse, 1987;
Bécard & Fortin, 1988). Limited extension of germ
tubes takes place after germination in vitro, but
sustained growth in the absence of living root
tissues does not occur, so the fungi causing this