COMPARATIVE SUSCEPTIBILITY OF ONION VARIETIES 
AND OF SPECIES OF ALLIUM TO UROCYSTIS CEPULAE 1 
ByP. J. Anderson 
Formerly Research Professor of Botany, Massachusetts Agricultural Experiment 
Station 
INTRODUCTION 
Most pathogenic fungi show a distinct variation in their ability 
to infect different varieties of their host plant. Such a difference in 
varietal susceptibility is usually the starting point for the breeding 
or selection of resistant varieties, which is the most effectual method 
for the control of plant diseases. With respect to onion smut, how¬ 
ever, it has never been shown that there is any difference in the sus¬ 
ceptibility of the numerous varieties under cultivation; in fact, 
no very comprehensive variety tests with this objective in view 
have been conducted. Walker and Jones (. 12 ) 2 tested a few varieties, 
and Whitehead (13 y p. 449) in England tested 21 varieties of onions 
and 11 varieties of leeks ( Allium porrum ), but none showed resistance. 
Nevertheless, since there were numerous other varieties which had 
not been tested, so far as was known to the writer, it appeared worth 
while to collect seed of as many varieties as could be obtained and 
test them comparatively in the hope that some of them might show 
a degree of resistance which should warrant crossing and selection 
work. 
The genus Allium, to which the cultivated onion belongs, is a large 
genus of some 250 species which are widely distributed over the 
earth. Urocystis cepulae was first reported on Allium cepa (4, 8) 
in 1857, in eastern Massachusetts. As early as 1881 (7) it was also 
reported on A. porrum (leek), in France. Cotton (3) reported it 
as more serious on this species.than on onion in England. Clinton 
(3, p. 431) reported it as occurring on A. nevadense in the far West 
of the United States. Quite recently Zillig (14, p• 57) has also re¬ 
ported infection of A. jistulosum L., A. globosum Red., and A. odorum 
L. Thus this fungus has been found on five species of the genus 
besides A. cepa. 3 
A more thorough knowledge of the extent of its host range is de¬ 
sirable for at least three reasons: 
(1) It might give us a clue to the origin of onion smut. This 
disease seems to have been noticed for the first time on onions in 
New England about the middle of the last century. Where it came 
from and where it had passed the preceding centuries, nobody seems 
to know. There is the strong probability that it came from some 
native American susceptible Allium; yet, with the exception of 
1 Received for publication October 22, 1924; issued, September, 1925. 
2 Reference is made by number (italic) to “Literature cited,” p. 286. 
3 After this paper had been forwarded by the writer for publication, a letter was received from Doctor 
Zillig stating that he had also been able to infect A. cyaneum Reg., A . flavum L., A. huteri Sund., A. 
hymenorrhizum Ledeb., and A. obliquum L. 
Journal of Agricultural Research, Vol. XXXI, No. 3 
Washington, D. C. Aug. 1, 1925. 
Key No. Mass.-ll 
( 275 ) 
