JOCBMAL OP AOMIDRAl RESEARCH 
Vol. XXVII Washington, D. C., February 16, 1924 No. 7 
EXPERIMENTS WITH FLAG SMUT OF WHEAT AND THE 
CAUSAL FUNGUS, UROCYSTIS TRITICI KCKE . 1 
Marion A. Griffiths 2 
Assistant Pathologist, Office of Cereal Investigations, Bureau of Plant Industry, United 
States Department of Agriculture 
INTRODUCTION 
Urocystis tritici Kcke., the causative organism of flag smut of wheat, 
though long known to be common in Australia and certain Asiatic coun¬ 
tries, was not observed in the United States until May, 1919, when it 
was discovered by Dr. J. G. Dickson in a wheat field near Granite City, 
Ill. Because of its reported destructiveness to the wheat crops in other 
parts of the world, especially Australia, experiments in varietal resist¬ 
ance of wheats were begun in the fall of that year at Granite City. This 
line of investigation was considered the most expedient at that time 
because it was known that infestation of soil rather than of seed was the 
most important factor in the annual occurrence of the disease in Aus¬ 
tralia. From previous experiments in that country, it had been shown 
that seed treatment was ineffective in controlling flag smut in infested 
fields because of infection by viable spores in the soil. Thus, by select¬ 
ing and sowing varieties which do not become infected in the field, even 
with artificial inoculation, the disease could be controlled. The results 
of these and later field experiments relating to varietal resistance and 
seed treatments have been published recently by Tisdale, Dungan, and 
Leighty (J5). 3 
The data here presented are based on greenhouse experiments begun 
in the autumn of 1919 at Arlington Experiment Farm, Rosslyn, Va. 
In the first year only preliminary experiments were attempted, such as 
the testing of 25 varieties of wheat for susceptibility to flag smut and 
making a detailed study of the diseased plants. In the autumn of 1920 
the number of varieties was increased, and as the work progressed and 
numerous problems presented themselves it was decided to study some 
of the physiologic aspects of the disease during the following years. 
The varietal resistance studies, therefore, cover a period of three years, 
while the other data are based mainly on a year’s investigation conducted 
at Washington, D. C., and Rosslyn, Va., and a second year’s study con¬ 
ducted cooperatively with the Missouri Botanical Garden, St. Louis, Mo. 
1 Received for publication Nov. 33, 1933. 
* The writer is indebted to Dr. G. M. Reed, formerly pathologist in charge of cereal smut investigations, 
under whose direction the varietal resistance experiments were begun; to Dr. W. H. Tisdale, who suc¬ 
ceeded Doctor Reed in 1930 and whose aid has been invaluable in the greater part of these investigations; 
and to Dr. B. M. Duggar, of the Missouri Botanical Garden, St. Louis, Mo., who gave helpful advice concern¬ 
ing the 1922-33 experiments reported in this paper. 
Most of the seed used in these experiments was obtained from the agronomic division of the Office of 
Cereal Investigations, Bureau of Plant Industry, U. S. Department of Agriculture, though that of one or 
two varieties was obtained from each of the State agricultural experiment stations at Knoxville, Tenn., 
Urbana, Ill., Manhattan, Kans., Davis, Calif., and Pullman, Wash. 
* Reference is made by number (italic) to "Literature cited”, p. 448-449. 
Journal of Agricultural Resaerch, Vol. XXVII, No. 7 
Washington, D. C. Feb. 16,1924 
Key No. G -3 66 
74026—24-1 
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