JOURHAL OF ACEIOILTIAI KESEARd 
Vol. XXIX Washington, D. C., September 15, 1924 No. 6 
INFECTION OF BARLEY BY USTILAGO NUDA THROUGH 
SEED INOCULATION 1 
By W. H. Tisdale, Pathologist, and V. F. Tapke, Associate Pathologist, Office of 
Cereal Investigations, Bureau of Plant Industry, United States Department of 
- Agriculture 
INTRODUCTION 
Floral infection of barley (Hordeum 
sativum L.) by Ustilago nuda (Jens.) 
Kell, and Sw., as well as floral infection 
of wheat (Triticum vulgare Vill.) by 
Ustilago tritici (Pers.) Jens., has been 
considered an established fact for many 
years. There was considerable con¬ 
fusion regarding the infection of cereals 
by smut fungi before the different spe¬ 
cies of these fungi were identified and 
described. Since these differences were 
found steady progress has been made in 
the discovery of the morphological and 
physiological differences of the smut 
fungi, of their host relationships, and of 
the control of the smuts caused by them. 
Since the discovery of floral infec¬ 
tion (16 ) 2 the hot-water seed treatment 
has been considered the only means of 
controlling the loose smuts of wheat 
and barley. Recently, however, for¬ 
maldehyde and some of the organic 
mercury compounds have been found to 
control the loose-smut of barley in cer¬ 
tain varieties ( 18,20,21 , and 22 ). This 
led to the belief that there remained im¬ 
portant facts to be learned regarding the 
infection of barley by Usitlago nuda. 
In the autumn of 1922 the senior 
writer planned to study the possibility 
of seedling infection by this fungus. 
The results of the first experiment were 
so striking that a number of experi¬ 
ments, in which nine varieties of barley 
were used, was conducted during the 
past season, 1923-24. The results of 
these studies were even more striking 
than those of the previous year. 
This paper gives a brief review of the 
literature dealing with floral infection 
of wheat and barley by their respective 
loose-smut fungi, presents the data of 
the writers’ recent studies showing that 
previous investigators have been con¬ 
fused regarding the infection of barley 
by Ustilago nuda, at least to a certain 
extent, and that the fungus infects the 
seedlings, at least of certain varieties of 
barley, and causes severe injury to the 
seedlings when heavily infected. 
HISTORY OF FLORAL INFECTION 
Hoffman (10), in 1866, long before 
the discovery of the difference in the 
fungi causing the smuts of barley, men¬ 
tioned the possibility of floral infection. 
He was studying barley smut princi¬ 
pally but did some work with the smuts 
of wheat and oats. 
In 1888, Jensen (12), after several 
years of study of infection of barley 
and oats by smut (Ustilago segetum), 
made the following statement: 
Since we have seen that spores adhering to the 
exterior of the grain do not to any appreciable 
extent cause the infection of the crop, it follows 
that this must take place by means of those spores 
which succeed in entering the space between the 
“cosh” or husk and the kernel. 
He then suggested two possibilities for 
infection; one being floral infection by 
direct germination of the spores imme¬ 
diately after they enter the flowers, and 
the other being the infection of the 
seedlings by spores which remained 
quiescent between the husk and the 
kernel until the seed was sown and 
then germinated. He says that his 
experiments of 1887 point to the latter. 
He found that by removing the hulls 
(glumes) of barley and oats and inocu¬ 
lating the seed, higher percentages of 
infection could be obtained. 
After a large part of these experi¬ 
ments was concluded Jensen found 
that there were two smuts of barley and 
described them as Ustilago segetum, 
variety hordei nuda, “the naked smut,” 
and Ustilago segetum, variety hordei 
tecta, “the covered smut.” Previous to 
this, he had assumed that the two were 
identical, V. segetum DC. After this 
discovery he says: 
In the experiment quoted above with barley smut 
the variety tecia only was used for infecting the 
bare kernels. 
At about the same time, 1888, Bre- 
feld (1) failed to obtain infection of 
barley by inoculating the seed and 
young seedlings with germinated and 
ungerminated spores. He then ob¬ 
tained smutty barley heads from Japan 
and found that the spores from these 
1 Received for publication. Aug. 26, 1924. Issued January, 1925. 
2 Reference is made by number (italic) to “Literature cited,” p. 283-284. 
Journal of Agricultural Research, 
Washington, D. C. 
99183—25t-1 
Vol. XXIX, No. 
Sept. 15, 1924 
Key No. G-430 
(263) 
