Mar. i 7f 1923 Influence of Soil Temperature on Seedling-Blight 853 
none at 36°. The preponderance of platings gave what was apparently 
Trichoderma, Penicillium, Rhizopus, and Aspergillus in the order 
named. These organisms generally invaded the endosperm and devel¬ 
oped from there into the seedling. 
At other soil temperatures, 12 0 to 28° C., Gibberellasaubinetii was univer¬ 
sally reisolated, generally in pure culture even in unsterilized soil, if the 
seedlings were plated before they were badly decomposed. At soil 
temperatures of 20° to 28° perithecia were often formed in gregarious 
masses on the first-leaf sheath of the blighted seedlings near the surface 
of the soil. 
Infection takes place and the blight progresses, then, at or above 
12 0 C., but it is rather evident that, for very severe development of the 
blight, a soil temperature above 16 0 and below 28° is necessary. Since 
the attack of the organism is chiefly on the young seedling, the range of 
temperature during the “nursing period” is undoubtedly the important 
factor in determining the severity of this stage of the disease. 
INFLUENCE OF SOIL TEMPERATURE ON THE DEVELOPMENT OF SEEDLING- 
BLIGHT IN TURKEY WHEAT 
The seven different series of Turkey wheat were handled as previously 
described for Marquis wheat experiments, except that all of the winter 
wheat was grown in the fall or early winter. All the series were in¬ 
oculated with the more dilute conidial suspension, containing 65,000 
conidia per cubic centimeter of solution. Data similar to those obtained 
for Marquis wheat were obtained in all cases. The average results of the 
seven experiments are given in Table VI and shown graphically in 
Figure 6. 
Tabi<E VI .—Influence of soil temperature on the development of seedling-blight in Turkey 
wheat 
[Average of seven experiments.] 
Average 
Average 
Control. 
Inoculated with Gibberella saubinetii. 
soil 
number of 
days to 
Average 
Average 
Average 
Average 
Average 
temper¬ 
ature. 
percentage 
percentage 
percentage 
percentage 
percentage 
emerge. 
of germi¬ 
of healthy 
of germi¬ 
of healthy 
of blighted 
nation. 
plants. 
nation. 
plants. 
plants. 
# C. 
8 
18 
98.0 
97.O 
96. 0 
96. O 
12 
12 
89.4 
89.4 
73-1 
67. I 
6. 0 
16 
8 
95 -S 
95 * 5 
60. 1 
47-3 
12. 8 
20 
6 
9 *-S 
93 ° 
61. 7 
44 - 7 
17. 0 
24 
5 
82. s 
82. 5 
67.6 
49*3 
18.3 
28 
4 
80. 4 
77-7 
56. 1 
35 -o 
21. 1 
31 
6 
62. 5 
62. 5 
59-2 
57 - 1 
2. 1 
35 
10 
48. 0 
43 - 7 
25 -9 
25-9 
0 
The response of winter wheat to the blight was similar, in almost 
all cases, with that described for spring wheat in the previous pages. 
The only differences noticeable were that blighting was more severe at 
20 0 in the Marquis series and was less extensive in the winter wheat 
seedlings at a soil temperature of 12 0 C. The average percentage of 
blighted seedlings in the winter wheat was less at all temperatures, but 
27975—23 - 2 
