Q? 
The results of these investigations were presented as a thesis 
in partial fulfillment of the degree of Master of Arts at Columbia 
University. 
Studies on Experimentally Produced Physiologic 
Races of the Oat Smuts 
Dr. L. Gordon Utter, research assistant, continued his studies 
on the infection behavior of 40 collections of smut which origi- 
nated from the hybridization of race 1 of the loose and covered 
smuts of oats. Twenty-four of these collections showed the 
symptoms and morphology of the covered smut, while 16 re- 
sembled the loose smut. The covered smut collections were 
primarily selected on their ability to attack Gothland, which 
was resistant to race 1 of the covered smut. Monarch was re- 
sistant to most of them, although susceptible to race 1 of the 
covered smut used in crossing. Similarly, the selected loose smut 
collections infected Monarch, resistant to race 1 of the loose 
smut, more frequently than they did the usually susceptible 
Gothland. ‘Two collections of the covered smut and four of the 
loose smut behaved on Gothland and Monarch in the same man- 
ner as the original loose and covered smut parents, and thus 
appear to be the parental types which have segregated out. 
When the infection data from 1941 were combined with those 
from 1938-1940, the earlier establishment of many of these col- 
lections as physiologic races could be clearly confirmed. Thir- 
teen races of the covered smut were separated on eight varieties 
of oats, including Gothland and Monarch, Most of these oat 
varieties were resistant to race 1 of the covered smut. However, 
each variety proved to be susceptible to some of the new races 
and resistant to others. 
Similar results were obtained with nine loose smut races which 
were separated on six oat varieties. Although all the varieties 
used, except Monarch, were susceptible to race 1 of the loose 
smut, they showed susceptibility to some of the new races and 
resistance to the remainder. 
In both the loose and covered smuts, certain collections be- 
haved identically on those oat varieties which distinguished the 
races above. The evidence indicates that most of these collec- 
