MISCELLANEOUS STUDIES ON THE 
CROWN RUST OF OATS i 
G. R. HOERNER 
(Received for publication March 7, 192 1) 
During a somewhat extensive study of the infection capabilities of 
crown rust of oats, Fuccinia coronata Cda. (i), the following data were 
collected. 
I 
McAlpine (2) ventures the opinion that crown rust of oats was probably 
introduced into Australia by means of seed. He does not state whether 
he thinks the rust was carried within or upon the seed in the form of my- 
celium or of urediniospores. 
As far as surface-borne urediniospores are concerned, it seems question- 
able whether under ordinary conditions urediniospores would remain viable 
upon the seed surface long enough to be transported to any great distance 
and still be able, after relatively long periods of time and probably under 
adverse environment, to infect the developing seedlings. In an attempt to 
throw some light upon this question the following experiment was devised : 
Twenty oat seeds of a variety knowm to be susceptible to crown rust 
(Victory, Minn. 514) were moistened in water and heavily smeared with 
fresh viable urediniospores. Five seeds were then planted about one half 
inch deep in each of four four-inch pots of a uniform soil mixture. These 
pots were placed in a ventilated cage in order to protect the developing 
seedlings from chance infection from air-borne spores. 
After the seedlings had been allowed to grow for ten days, a sufficient 
period to show evidence of infection, it was found that none of the twenty 
seedlings became infected. The temperature within the cage was previously 
determined to be an optimum one, since artificial inoculations of seedling 
leaves of the same variety in the same environment resulted in normal 
infection, and moisture was present in sufficient amounts to cause guttation 
from the seedling leaves. 
These results, though the experimental work was not extensive, would 
seem to indicate that in the case of Puccinia coronata Cda., urediniospores 
borne upon the surface of the seed do not commonly offer a favorable means 
of spreading the rust to the seedling plants developed from these seeds. 
1 Investigations carried on while the author was a graduate student at the University 
of Minnesota, 1916-1918. 
