8 3 8 
Journal of Agricultural Research 
Vol. XXIII, No. II 
only at soil temperatures above i6°. These observations and experi¬ 
ments tend to confirm Wollenweber’s (34) generalization that the root- 
invading Fusariums are warm-soil organisms. 
The Fusarium seedling-blight of wheat and other cereals (Gibberella 
saubinetii) has proved to be well adapted to a critical study of the rela¬ 
tion of environment to parasitism, as th£ same parasite is able to attack 
a number of different host plants, especially wheat and other small 
grains and com. The field observations on winter wheat, mentioned 
previously, indicate that soil temperature and soil moisture are im¬ 
portant factors, in the development of the disease. As a result of the 
suggestions from these field observations and the apparent importance 
of the diseases on both wheat and com, investigations were undertaken 
to determine the relation of soil temperature and soil moisture to the 
development of seedling-blight of wheat and com caused by G. saubinetii. 
The responses of the two hosts, wheat and com, were so markedly differ¬ 
ent that the studies are being continued with the view of determining 
the physiological and chemical responses which determine host suscepti¬ 
bility. Although the results here presented are not complete, it is be¬ 
lieved that they will serve to show the relation of temperature and 
moisture to the development of the blights caused by this one organism. 
SEEDLING-BLIGHT OF WHEAT 
The seedling-blight of wheat was not connected with the headblight 
or scab described by Smith (29), Weed (33 ), Chester (8), Arthur (j), 
and Hickman (16), until Selby and Manns (27) described the diseased 
seedlings obtained by sowing scabbed kernels. The seedling-blight has 
been mentioned since, and its close association with unfavorable weather 
conditions has been suggested by Bolley (6, 7), Schaffnit (23 ), Akerman 
(i), Atanasoff (4), and others. This disease is prevalent in the winter- 
wheat areas of the Mississippi Valley. The losses from this stage of the 
disease vary greatly from year to year, depending upon climatic condi¬ 
tions. 
The symptoms of the seedling-blight caused by Gibberella saubinetii 
vary, depending upon the portion of the seedling attacked and the 
environing conditions during the development of the blight. In case of 
severe attacks many of the germinating seedlings may be killed before 
theyemerge, which results in reduced stand. When the attacks are less 
severe the seedlings emerge and are weakened or killed, according to 
the severity of the attack. Such seedlings, when carefully removed 
from the soil before disintegration, show all gradations of attack (PI. 1 
and 2). In many cases the developing embryo is invaded and killed 
before either roots or plumules elongate (PI. 3, B). The embryo as well 
as the invaded portions of the kernel become reddish brown, to carmine 
red as the soil-moisture condition varies from dry to wet. The fungus 
growth tends to accumulate over the surface of the infected tissues, 
causing the soil to cling tightly to the diseased parts. 
In other instances, the plumule is blighted when less than 1 cm. long, 
the root development continuing, however, for some time afterwards 
(PI. 1, 6, and 3). Often the roots develop to a length of 5 to 10 cm. 
before they are invaded by the fungus. The invasion usually occurs by 
the parasite growing from the invaded endosperm into the proximal 
portions of the roots, after which the entire root is invaded and rotted. 
Other seedlings do not succumb to the attack until the first-leaf or often the 
