STINKING SMUT OF WHEAT 
: Although the loose smut is the more common on wheat in eastern 
United States, the stinking smut is frequently serious. In the great wheat- 
fields of the west it is the common and destructive wheat smut. The 
losses from the stinking smut may be very Jarge, not only from the reduc- 
tion in yield but also from the lowering of the market-value of grain with 
which the smutted kernels become mixed. The life-history of the causal 
fungus is very different from that inducing the loose smut of wheat. 
SYMPTOMS 
Heads of wheat affected with the stinking smut are readily distinguished 
from the healthy heads as soon as they emerge from the leaf-sheath. 
Read Barrus, Phytopath. 6:21-28; study fig. 2; and the diseased and 
healthy specimens collected in different stages of development. 
NOTE — 
1. The difference in size and color of the heads. 
2. On dissecting flowers, the differences exhibited by ovaries 
and stamens; size, color, form and odor. 
Confirm, so far as available material will permit, the observations 
of Barrus. Make a series of DRAWINGS to show the comparative morphol- 
ogy of diseased and healthy heads and flowers, from flowering-time to 
matunity. : 
ETIOLOGY 
This disease is caused by Tilletia Tritici (Bjerkander) Winter, or by 
Tulletia foetens (Berkley and Curtis) Trelease. (=T. laevis Kahn). This 
is a case in which two distinctly different species of fungi cause the same 
type of disease, in fact the two species may occur together in the same 
ovary. It is the latter form, 7. foetens, which is most commonly found 
in eastern United States and will be the one here considered. These are 
species of the Ustilaginales, family Tilletiaceae. 
Life-history. This pathogene exhibits only the primary cvcles in its 
life-history. Since the chlamydospores usually become attached to 
the healthy grains during harvesting or threshing and so are almost con- 
tinuously associated with the living host, this smut-fungus like most others 
may be said to have normally no saprogenic phase. Infection from spores 
in the soil appears to be rare for this species. The sown wheat in the 
Pacific Coast regions is said to become inoculated by wind-borne spores of 
T. .Tritict. 
Pathogenesis. Inoculation, as indicated above, occurs at thresh- 
ing-time, when spores from the crushed smutted kernels become attached 
to the healthy grains. Crush one of the diseased grains between thumb 
and finger. NOTE:— 
3. The greasy character of the spore-mass. This evidently 
helps to attach the spores to the seed-coat. 
Mount a bit of the spore-mass in a drop of water. Cover and examine. 
OBSERVE :— 
4. The numerous, more or less globose, smooth brown spores, 
—the chlamydospores. DRAW. 
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