49 
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a paper discussing the results which have been secured in this 
general field in the course of the last few years. 
I-xperiments extending over a period of vears have demonstrated 
the existence of a large number of specialized races of both loose 
and covered smuts of oats. Several new collections received from 
Mr. T. R. Stanton, Division of Cereal Crops and Diseases, Bureau 
of Plant Industry, Washington, D. C., have been tested during the 
past year. Most of these collections were made on varieties of 
the red oat group, which are commonly grown in the Southern 
States. Both species of smuts were represented by collections. 
The results obtained confirm the high degree of specialization of 
both species of smuts. A large number of varieties belonging to 
the different species and sub-species. of oats were inoculated with 
— 
the various smut collections, and very definite evidence of special- 
ization was obtained. Very few varieties or strains of oats were 
resistant to all of the collections which were used. The outstand- 
ing ones were Navarro, Victoria and Markton. 
Probably there is no end to the number of races of both loose 
and covered smuts which can be isolated from collections obtained 
from various parts of the world. These races are of both a theo- 
retical and a practical value. A very interesting problem is the 
relation between oat varieties derived from different species of 
oats and the specialized races of the smuts. One of the most 
significant practical problems has to do with the study of the in- 
heritance of smut resistance in oat hybrids. Varieties differ in 
their reaction to specialized races; it is, then, necessary to use 
races whose behavior on the parental varieties is known in order 
to determine the mode of inheritance of the smut-resistant quality. 
In the practical problem of breeding oats for a given locality, it 1s 
also necessary to consider this question of physiologic specializa- 
tion. A new strain may be developed in a region where it is 
entirely resistant to smut. When taken to another locality, how- 
ever, where different races of the parasites exist, it may prove to 
be susceptible. 
