CBR6AL CROPS 4 DISEASES, 
JOURNAL OF AOTLim RESEARCH 
Vol. XXXI Washington, D. C., November 1 , 1925 No. 9 
STUDIES ON OPHIOBOLUS GRAMINIS SACC. AND THE 
TAKE-ALL DISEASE OF WHEAT 1 
By Ray J. Davis 2 
Formerly Field Assistant , Office of Cereal Investigations, Bureau of Plant Industry , 
United States Department of Agriculture 
INTRODUCTION 
This paper deals with laboratory, greenhouse, and limited outdoor 
studies on the take-all disease of wheat and the causal fungus. Since 
this disease does not occur in the region where these studies were made, 
it was not practicable to make extensive field studies. 
MATERIALS AND TECHNIQUE 
ORGANISM 
Three single-spore strains of Ophiobolus graminis Sacc., isolated 
from diseased plants growing in widely different regions, were supplied 
the wrijber by H. H. McKinney, of the United States Department of 
Agriculture, and these have been used throughout the investigations. 
One of these strains came originally from R. S. Kirby, of Cornell 
University, who isolated it from a wheat plant affected by take-all 
in New i ork State. This strain is referred to throughout this paper 
as the “New York strain.” The other two strains were isolated by 
Hurley Fellows, of the United States Department of Agriculture, from 
take-all diseased wheat plants growing near Hillsboro, Oreg., and 
Fayetteville, Ark., respectively, and are referred to throughout the 
paper as the “Oregon strain” and the “Arkansas strain.” 
MEDIA 
Preliminary experimentation dealing with the growth and sporula- 
tion of the organism on different media led to the adoption of the 
following three media for the greater part of the work: (1) potato- 
dextrose agar, (2) string-bean agar, and (3) cooked kernels of barley 
and oats (equal portions). 
In the physiological experiments potato-dextrose agar was used as 
the principal substratum. Nutrient broth and Czapek’s full nutrient 
solution also were employed in the studies on the growth of the 
fungus in relation to hydrogen-ion concentration. 
Potato-dextrose agar was prepared, according to the usual labora¬ 
tory method, as follows: Two hundred grams of peeled potatoes were 
cut into small pieces, placed in 1,000 c. c. distilled water, and steamed 
1 Received for publication Feb. 2,1925; issued January, 1925. These studies were carried on coopera¬ 
tively by the Office of Cereal Investigations, U. S. Department of Agriculture, and the Wisconsin Agri¬ 
cultural Experiment Station, Madison, Wis. ^ _ ,, 
2 The writer wishes to express his appreciation to L. R. Jones, James G. Dickson, and H. H. McKinney 
for their many valuable suggestions during the progress of these studies, and to Mr. McKinney and A. G. 
Johnson for assistance in revising the manuscript. 
Journal of Agricultural Research, 
Washington, D. C. 
74333—26t-1 ( 801 ) 
Vol XXXI, No. 9 
Nov. 1, 1925 
Key No. G-511 
i 
.-n&AL INVESTIGATIONS. 
