Nov. 1, 1925 
Ophiobolus graminis and Take-All of Wheat 
815 
and 20 inches long and inoculated with the fungus. Prior to plant¬ 
ing and inoculating, the tubes containing the medium were plugged 
with cotton and sterilized at 15 pounds pressure for 40 minutes. 
After the agar solidified, disinfected Golacoin wheat seeds which 
had been previously germinated for 5 days on potato agar in Petri 
dishes were planted in the large tubes. The previous germination 
was carried out to insure seedlings that were free from fungi and 
bacteria. The seed was handled under aseptic conditions through¬ 
out the whole process previous to inoculation. Two days after 
planting the seed, a block of agar containing mycelium of a single 
strain of 0 . graminis was inserted in each tube, except the control 
tubes, which were handled similarly but not inoculated. All of the 
tubes were placed in the laboratory in such a position that they 
received equal illumination, and the plants were carefully watched 
for any inuication of disease. 
The fungus soon spread over the surface of the agar in the inocu¬ 
lated tubes, and in 4 days symptoms of the disease on the wheat 
seedlings began to appear. The characteristic dark lesions asso¬ 
ciated with take-all first started at or near the base of the roots. 
This discoloration then spread both up on the culm and farther down 
on the roots, and the leaves soon turned yellow and died. By the 
time the plants were 28 days old, all of the inoculated plants had 
died, while the uninoculated plants were still healthy and thriving. 
These latter had grown to the top of the tubes and were badly 
crumpled, due to their upward, elongation being stopped by the 
^ in the mouths of the tubes. A week later part of them 
ied, apparently due to lack of space and the drying out of the 
agar, but no disease lesions were visible. The results are given in 
Table VII. 
Table VII .—Pathogenicity of Ophiobolus graminis on Goldcoin wheat grown under 
aseptic conditions on agar contained in culture tubes 
[Inoculations were made with pure cultures of the parasite. The controls were uninoculated] 
Strain of fungus 
Number 
of tubes 
Number 
of plants 
in each 
tube 
Total number of 
plants dead in all 
the tubes 
After 
21 days 
After 
28 days 
New York.......... 
4 
3 
12 
12 
Control_ 
2 
3 
0 
0 
Oregon_ 
4 
3 
0 
12 
Control___ 
2 
3 
0 
0 
Arkansas______ 
4 
3 
0' 
12 
Control_ 
2 
3 
0 
0 
Pure cultures of Ophiobolus graminis were obtained by putting 
bits of the culms of the infected plants grown in the culture tubes on 
fresh agar in Petri dishes. Plants from uncontaminated culture 
tubes invariably gave a pure culture of the parasite. 
Delacroix (5) inoculated soil with a water suspension of ascospores 
of Ophiobolus graminis obtained from perithecia which had devel¬ 
oped on diseased plants in the field. Wheat plants grown in this 
inoculated soil developed a rather high percentage of infection and 
