STUDIES OF THE LIFE HISTORY 



OF USTILAGO A VENAE (PERS.) JENSEN 



AND OF FSTILAGO LEVIS (FELL. & SWING.) MAGN. 1 



George Raymond Gage 



Although seed treatment for the control of the two smuts of oats 

 caused by Ustilago avenae (Pers.) Jensen and U. If vis (Fell. & Swing.) 

 Magn. has been developed to such a point that it is generally regarded 

 as fairly successful, it seems that the ultimate and most economical 

 control of these smuts should lie in the selection or the breeding of re- 

 sistant varieties. That this is the opinion of most cereal pathologists is 

 evidenced bv the marked activitv alomr this line in recent years, as 

 shown bv tile work of Zavitz (1909, 1914, 1915), Heald (1919), Staple- 

 don (1920), Reed and others (1920, 1924, and 1925), Zade (1922), Ar- 

 land (1924), Roesch (1926), and many others. Successful procedure 

 toward such an end necessitates not only a thorough knowledge of the 

 physiology and anatomy of the suscept, but also a rather detailed and 

 exact understanding of the life histories of the pathogenes. If one is to 

 test varieties for susceptibility or resistance, he must, above all, under- 

 stand and be able to manipulate those factors which condition infection. 



Because of the many conflicting ideas of various investigators, and 

 especially because of the recent pronouncements on blossom infection 

 made by Zade and his students, it has seemed advisable to reinvestigate 

 the life histories of the pathogenes causing the smut diseases of oats. It 

 is very evident that the life histories of these pathogenes — Ustilago 

 an nae, the rough-spored species causing the so-called "loose smut," and 

 U. levis, the smooth-spored species causing the so-called ' ' covered smut ' ' 

 — are not adequately understood. 



It is not the intention of the writer to bring together into an historical 

 account the development of the present-day ideas on the life histories of 

 these two pathogenes. It will be noticed at once by one who delves into 

 the history of the subject that the writings of the earlier investigators 

 are very confusing and indefinite. All of the loose smuts of cereals were 

 at first considered to be caused by one and the same pathogene, com- 

 monly called Ustilago carbo or U. segetum. It was not until 1888 that 



'Also Dresented to the Facultv of the Graduate School of Cornell University, Auyust, 

 1926, as'a major thesis in partial fulfillment of the requirements for the degree of doctor 

 of philosophy. 



Author's acknowledgment. The investigations discussed in this paper were under- 

 taken at the suggestion of Professor H. H. Whetzel, under whose direction and kindly 

 criticism they were conducted and completed ; for all of which, the writer wishes to 

 express his most sincere appreciation. 



