41 
Studies on the Inheritance of Resistance of Oat Hybrids to Loose 
and Covered Smuts 
Additional experiments were carried out with a series of oat 
hybrids: Hybrid 83, Canadian & Black Norway; Hybrid &4, Scot- 
tish Chief * Black Mesdag; Hybrid 85, Black Mesdag * Danish 
Island; and Hybrid 86, Monarch Selection & Gothland. These 
hybrids differ in the reaction of the parental varieties to definite 
as 
specialized races of loose and covered smuts. In previous years, 
data have been obtained on the behavior of second and third 
> of smut 
ar 
generation plants with a view to determining the mode 
inheritance. During the past year a large number of additional 
third generation progenies of all of these hybrids was grown, the 
results supplementing those previously obtained. 
Studies on Cultures of the Oat Smuts 
Mr. L. Gordon Utter has continued his studies on cultures of 
the loose and covered smuts of oats on artificial media in flasks 
and has carried out infection experiments with them. 
The Missouri races of loose and covered smuts of oats are 
distinct from one another on the basis of three definite charac- 
teristics: (1) type of smut produced on the oat spikelets; (2) the 
chlamydospore walls are either spiny or smooth; and (3) their 
capacity for infecting different oat varieties. In the loose smut 
the spikelets usually are entirely destroyed and replaced by black, 
dusty masses of chlamydospores which have spiny walls. The 
Gothland variety 1s completely susceptible to this smut, while 
Monarch is resistant. ies covered smut only partially destroys 
the oat spikelets, and the chlamydospores are smooth-walled. This 
smut causes complete infection ‘of Monarch, but Gothland is fully 
— 
resistant, 
On germination, the chlamydospores of both smuts produce a 
=s 
germ tube which bears four small, thin-walled spores, which can 
tured on a suitable medium. Six- 
— 
be isolated individually and cu 
teen single spore cultures of loose smut and six of covered smut 
were obtained for infection experiments. 
When single spore cultures of either smut were used to inocu- 
late the susceptible oat variety, no infection resulted. Certain 
