Mar. 22 ,1924 
Corn Rootrot Studies 
959 
with com rot diseases. These organisms are Fusarium moniliforme 
Sheldon; Gibberella saubinetii (Mont.) Sacc.; Diplodia zeae (Schw.) Lev., 
and Cephalosporium sacchari Butler. It is known that several of these 
organisms inhibit germination and appear to be active factors in the 
production of stalk and ear rots. Their importance as factors in causing 
rootrot, however, is still in dispute. It is even questioned whether soil 
reaction is not the real factor predisposing corn to the attacks of these 
so-called seedling and rootrot diseases. 
EXPERIMENTAL METHODS 
The value of an experiment such as the one herein reported depends to 
a great extent upon the care with which it is conducted and therefore the 
methods used will be described. 
The nature of the infection carried in seed com showing no external 
symptoms of disease was determined by germination. A representative 
sample was selected from each ear of com, and the fungi carried internally 
were determined by the method described by Manns and Adams (10) as 
follows: 
Fifteen or more kernels are disinfected in a test tube 150 by 20 mm. for one minute 
in a solution of 50 per cent alcohol containing 1 gm. of bichlorid of mercury in each 
liter. This solution is known as a 1 to 1,000 HgCl 2 in 50 per cent alcohol. Following 
this treatment the kernels are washed in the same tube with two successive washings 
with 20 cc. each of sterile water, and immediately 10 kernels are removed aseptically 
with sterile forceps and placed with the germ side down on 20 cc. of nutrient dextrose 
agar in a sterile culture dish. Further, 5 of the remaining kernels are each placed in a 
sterile culture dish, and with a sterile scalpel the point of the kernel, which is the 
portion that contains most of the internal infection, is cut off Ve to Vs inch from the end; 
then with a strong sterile forcep each point is placed in the mouth of a heavy-walled 
tube (it requires a strong tube and strong forceps, as crushing is not easy) 150 by 20 
mm., containing 10 cc. of [liquefied] sterile nutrient dextrose agar medium at 43° C.; 
the point is thoroughly crushed and shaken down into the medium, then well mixed 
and poured into the sterile culture dish containing the remaining part of the kernel. 
This method was used extensively by the senior author in his studies 
of flax diseases in 1904 4 and on wheat diseases in 1909 ( 12 ). 
The following method of plating soil was used: One gm. of air-dry soil 
was placed in 100 cc. of sterile water. Ten cc. of this solution were by 
means of a sterile pipette placed in 90 cc. of water, making approximately 
a 1 to 1,000 solution. Ten cc. of the 1 to 1,000 solution were placed in 
another 90 cc. of sterile water, making approximately a 1 to* 10,000 solu¬ 
tion. One cc. of each solution was put in a test tube containing 12 cc. of 
weak nutrient glucose agar, mixed thoroughly, and poured into a sterile 
Petri dish. The plates were read 7 to 10 days later. To insure a fair 
degree of accuracy, six plates of both the 1 to 1,000 solution and the 1 to- 
10,000 solution were made and the average taken when read. 
The method employed in growing the com under sterile conditions has, 
so far as could be learned, never been previously reported. The jars used 
in this work were the ordinary one-quart Mason jars, although two-quart 
jars would have permitted better growth. Each jar was filled with a rich 
garden soil and sterilized from four to six hours at 7 to 10 pounds pressure 
in a steam autoclave. Plate cultures were run on several of the jars and 
they were found to be free of all organisms. The soil used was a rich 
compost such as was being used in the greenhouse by the horticultural 
department for potting. To get disease-free seed the surface-sterilized 
4 Manns, T. F. fungi of flax sick soil and flax seed. 1904. Unpublished manuscript (Master's 
thesis) filed in Department of Botany, College of Agriculture, Fargo, N. Dak. 
