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100 CHAPTER 5

in Fig. 5.18. The proconidia become conidia when
septa develop to separate them, starting at the base
of the chain. At this stage the spores of Neurospora
develop their characteristic pink color. Each conidium
of Neurosporacontains several nuclei because it has
developed by the budding of a multinucleate hyphal
(conidiophore) tip. However, in some other types of
blastic development the conidia are characteristically
uninucleate. For example, in Penicillium, Aspergillus, and

Trichodermathe conidiophore produces flask-shaped
phialides (Fig. 2.33) each of which is uninucleate. The
phialide extrudes a spore from its tip, and during this
process the nucleus divides so that one daughter
nucleus enters the developing spore while the other
nucleus remains in the phialide to repeat this process.
Essentially the same pattern occurs in Fusariumspecies
(Fig. 9.5) which produce a succession of spores from the
phialides. But in this case the single nucleus that enters

Fig. 5.18Some examples of conidial development. (a) Single conidia of Thermomyces lanuginosus, produced at the
ends of short hyphal branches. (b) Branched chains of conidia of Monilinia (the asexual stage of Sclerotinia fructigena)
produced by a repeating budding-like process before the spores separate by the development of septa. (c) Penicillium
expansumconidiophores with phialides that produce chains of spores. (d) Coremia of Ophiostoma ulmi; the conidio-
phores are aggregated to form stalk-like structures that produce masses of spores at their tips (but most of the spores
have been dislodged during preparation of this specimen).


(a) (b)

(c) (d)
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