Sept. 15, 1924 
Infection of Barley by Ustilago nuda 
265 
Uspulun and Germisan (organic mer¬ 
cury compounds) have been found to 
control the loose-smut of barley (20,22 ). 
These results were surprising in view 
of the claims and apparent proof of floral 
infection of barley by Ustilago nuda. 
At the same time, it led to the belief 
that it might be possible that previous 
investigators were misled, in some way, 
regarding infection of barley by the 
loose-smut fungus. Of course, it 
seemed entirely possible that floral 
infection might take place and the 
fungus mycelium remain in the super¬ 
ficial cells of the kernel where it could be 
destroyed by disinfectants which pene¬ 
trate the seed coat. 
Tisdale (19) found that by inoculat¬ 
ing dehulled 3 barley kernels with spores 
of the covered smut fungus Ustilago 
hordei, high percentages of infection 
could be obtained, while often little 
The occurrence of 25 per cent of 
loose-smut in plants from inoculated- 
dehulled seed appeared to be signifi¬ 
cant. This led to plans for further 
experiments in which both floral and 
seedling infection . could be studied. 
Six varieties of barley were used in 
these studies. Floral inoculations were 
made in the spring of 1923 on barleys 
growing in the greenhouse. Each 
flower was carefully inoculated by open¬ 
ing the glumes with forceps and dust¬ 
ing the floral parts with fresh spores of 
Ustilago nuda from Tennessee Winter 
barley growing in the greenhouse. 
Flowers and seeds were inoculated in 
different stages and treated in different 
ways, as follows: 
1. —Inoculated when anthers were 
green; no pollen shed. 
2. —Inoculated when anthers were 
shedding pollen. 
♦ 
Table I .—Infection of barley seedlings by Ustilago nuda in the greenhouse in 
1922-23 
Variety 
Treatment 
Number of plants 
Percent¬ 
age of 
smut 
Total 
1 
! Smutted 
1 
'Tennessee Winter 
Hulled-uninoculated._ 
25 
0 
0 
Do 
Hulled-inoculated... 
20 
1 
5.00 
Do 
Dehulled-uninoculated.. 
22 
1 
4. 55 
Do 
Dehulled-inoculated__ 
20 
5 
25.00 
Natan n Wase 
Hulled-uninoculated____ 
21 
0 
0 
Do . .. .... 
Hulled-i noculated. 
20 
0 
0 
Do 
Dehulled uninoculated.. 
24 
0 
0 
Do 
Dehulled-inoculated___ 
19 
0 
0 
or no infection could be secured by 
inoculating the hulled seed. In the 
fall of 1922, while conducting the 
experiments on covered smut, the 
senior writer inoculated some dehulled 
seed of Tennessee Winter and Nakano 
Wase barleys with spores of U. nuda 
and sowed it on a bench in the green¬ 
house at Arlington Experiment Farm, 
Rosslyn, Va. Dehulled-uninoculated, 
hulled-inoculated, and hulled-uninocu- 
lated seed of both varieties also was 
sown. The seed for this and subse¬ 
quent experiments was dehulled by 
carefully removing the glumes with a 
sharp-pointed knife or scalpel. The 
basal end was first broken and the 
glumes stripped off. Nakano Wase 
remained smut-free in all experiments. 
The dehulled-inoculated seed of Ten¬ 
nessee Winter produced 25 per cent of 
loose-smut, or 5 plants in a total of 20, 
while only 1 plant in 22 from the de¬ 
hulled-uninoculated and 1 in 20 from 
the hulled-inoculated seed produced 
loose-smut. (Table I.) 
3. —Inoculated when pollen was re¬ 
cently shed, stigma plumose, and show¬ 
ing no signs of withering. 
4. —Inoculation at tip of kernel when 
in the milk stage. The glumes were 
pulled back slightly, spores placed on 
the kernel, and the glumes replaced. 
5. —Mature seed dehulled and sown 
without inoculation. 
6. —Mature seed dehulled and inocu¬ 
lated by shaking thoroughly in an en¬ 
velope with spores until almost black. 
7. —Mature hulled seed sown without 
inoculation. 
8. —Mature hulled seed inoculated. 
Spore material used for inoculating 
the mature seed was collected from 
Tennessee Winter barley grown on 
Arlington Experiment Farm in 1923. 
The seed inoculated by the various 
methods given above was sown on a 
bench in the greenhouse on November 
4, 1923. The seeds were sown about 
1 inch deep and 2 inches apart in rows 
7 inches apart. The results of these 
experiments are given in Table II. 
3Hulled=hulls not removed, and dehulled hulls removed 
