Biology Reference
In-Depth Information
Smuts
Smuts, of the fungus order Ustilaginales, are
named for their sooty black spore masses. Like
the rusts, they belong to the Basidiomycetes and
are all plant parasites, of most economic impor-
tance on cereals and grasses, but they differ from
rusts in having a less complicated life history and
in being able to live part of their lives saprophyt-
ically in rich organic matter or in culture media.
There are two spore forms. The teliospore,
usually called a chlamydospore, is formed by
the rounding up of a hyphal cell. In addition to a
thin inner endospore wall, it has a thick outer
exospore wall, usually dark, smooth or ornamen-
tal. Teliospores are formed singly or united into
balls. They can be distributed long distances by
wind, and spores of some species remain viable
for years. Some have to ripen several months
before they can germinate.
Occasionally the teliospore puts out a germ
tube that penetrates host tissue directly. More
often it produces a promycelium that gives rise
to sporidia, which can bud to more sporidia.
Classically true smuts have been divided into
two families on the type of sporidial formation:
Ustilaginaceae, with sporidia produced on the
sides of a four-celled promycelium, and
Tilletiaceae, with sporidia produced at the end
of a one-or two-celled promycelium. Fischer,
however, points out that there are so many vari-
ations that it is preferable to include all species in
a single family, Ustilaginaceae, and to differenti-
ate the species on the basis of morphological
characters and the host family. This is logical,
but we include here the families as they are
given in most textbooks and also the false
smuts, Graphiolaceae (Ustilaginales), which
have an uncertain taxonomic position.
There are three types of infection with smuts,
with control measures modified according to
type. The mycelium always penetrates
the
young host
tissue directly;
it does not enter
through stomata.
1. Infection of seedlings as the seed germinates,
from spores adhering to the outside of the
seed or present in soil; controlled by dusting
seed and planting in noninfested soil.
2. Seedling infection by mycelium within the
seed as a result of ovary infection from spores
germinating on the stigma; controlled by
treating seed with hot water.
3. Infection of any actively growing meriste-
matic tissue (roots, shoot, tassels, or young
ears) by spores transported by wind
from decaying plant material; controlled,
partially, by spraying or dusting susceptible
plants.
Burrillia
Tilletiaceae. Sori in various host parts, often in
leaves, rather permanently embedded. Spore
balls with a central sterile mass surrounded by
fertile teliospores but no sterile cortex (surface
layer). Teliospore hyaline to yellowish, rather
firmly united. On water plants.
Burrillia decipiens
Leaf Smut
of floating heart
(
Nymphoides
).
