Agriculture Reference
In-Depth Information
Fungal classification
Fungi are classified into four groups (Figure 4.15):
X
Zygomycota
(mitosporic fungi) have simple
asexual and sexual spore forms. Damping off,
downy mildew and potato blight belong to
this group (see p. 253).
X
Ascomycota
have chitin cell walls, and
show, throughout the group, a wide variety
of asexual spore forms. The sexual spores
are consistently formed within small sacs
(asci), numbers of which may themselves
be embedded within fl ask-shaped structures
(perithecia), just visible to the naked eye. Rose
black spot (see p. 257), apple canker, powdery
mildew and Dutch elm disease belong to this
group.
X
Basidiomycota
have chitin cell walls, and
may produce, within one fungal species (e.g.
cereal rust), as many as fi ve different spore
forms involving more than one plant host. The
fungi within this group bear sexual spores
(basidiospores) from a microscopic club-
shaped structure (basidium). Carnation rust,
honey fungus and silver leaf diseases belong
to this group (see p. 261).
X
Deuteromycota
are an artifi cially derived
fourth grouping which is included in the
classifi cation of fungi. It includes species of
fungi that only very rarely produce a sexual
spore stage. As with plants, the sexual
structures of fungi form the most reliable basis
for classifi cation. But, here, the main basis for
naming is the asexual spore and mycelium
structure. Grey mould (
Botrytis
) (see p. 258),
Fusarium
patch of turf and
Rhizoctonia
rot are
placed within this group.
(b)
(a)
(c)
(d)
Figure 4.15
Classifi cation of fungi: (a) damping-off disease - a zygomycota; (b) a courgette with powdery
mildew - an ascomycota; (c) pear rust - a basidiomycota; (d) Fusarium wilt - a deuteromycota
