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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)