82 



data have not been analyzed to determine whether the three factors 

 are identical. The third generation progenies inoculated with race 

 12 of the loose smut gave results differing greatly from those ob- 

 tained with race 1 of the loose smut, and also with the two races 

 of covered smut. Relatively few resistant progenies were ob- 

 served, most of them containing infected plants, and a large num- 

 ber being very susceptible. 



Physiologic Races of the Oat Smuts 



During the past year a large number oi tests with specialized 

 races of both loose and covered smuts were made on newly devel- 

 oped smut-resistant varieties. Mr. T. R. Stanton, Senior Agrono- 

 mist, Division of Cereal Crops and Diseases, Bureau of Plant 

 Industry, Washington, D. C, and his associates have been active 

 in (he development of varieties of oats for various sections oi the 

 United States. Most of these possess the desirable quality of 

 smut resistance, insofar as they have been tested. Since we have 

 a very complete collection of definite races of both loose and 

 covered smuts, an important part of the general program of breed- 

 ing new resistant types was to determine whether the selections are 

 resistant to all known races of smut. 



Studies on Experimentally Produced Physiologic Races 



of the On I Smuts 



Infection studies have been continued by Dr. L. Gordon I 'tier 

 with 40 collections of smut which resulted from the hybridization 

 of races 1 of the loose and covered smuts of oats. Certain ot 

 these collections resembled the covered smut, while others were 

 similar to the loose smut. Most of the covered smut collections 

 were characterized by their high infection of Gothland, an oat: 

 variety normally resistant to race 1 of the covered smut, although 

 it is very susceptible to race 1 oi the loose smut. Further, most 

 of the loose smut collections sttidied attacked Monarch, a variety 

 usually resistant to race 1 of the loose smut, being susceptible, 

 however, to race 1 ot the covered smut. In the previous report, 8 

 distinct new races of covered smut and 7 of the loose smut were 

 differentiated by their behavior on several oat varieties. Adcli- 



