2 BULLETIN 1046, U. S. DEPAETMENT OF AGEICULTUEE. 



Climatic conditions at Manhattan, Kans., are generally unfavor- 

 able for the development and spread of the stem rust of wheat; the 

 development of a suitable technique for the production of severe epi- 

 demics in the rust nursery was therefore an essential part of these 

 investigations. 



Special attention was given to those varieties which are most 

 promising agronomically. 



If a variety of hard red winter wheat could be found which was 

 resistant to stem rust and suitable for Kansas conditions, breeding 

 for rust resistance would be much simpler than if it becomes neces- 

 sary to cross with varieties of the durum or emmer groups. 



Hayes, Parker, and Kurtzweil (i5)* recently have found that " there 

 is an indication of linkage of durum or emmer characters and rust 

 resistance, since the production of rust-resistant durums or emmers in 

 the F2 and F3 generations is comparatively easy and the production 

 of resistant common wheats much more difficult." Moreover, the 

 only known rust-resistant varieties of the emmer or durum groups 

 are spring forms, a fact which complicates the task of obtaining a 

 rust-resistant winter wheat from such a cross. Winter hardiness, 

 high yield, and good milling quality also are essential for the success 

 of any variety of wheat in Kansas, which increased the complexity 

 and difficulty of the problem. To obtain accurate information as 

 to the resistance of existing varieties of winter wheat was, therefore, 

 the first important step. 



REVIEW OF THE LITERATURE. 



Differences in the resistance of wheat varieties to rust were known 

 to exist as early as 1841, when Henslow {16) observed that some 

 wheats were injured less by rust than others. La Cour {23) and Little 

 {26) made similar observations. BoUey (S) noted that hardy and 

 stiff-stemmed varieties with smooth, fibrous leaves seem to resist 

 rust for a longer time. Anderson {1) observed that hard, flinty 

 wheats are more resistant than others, believing that this might be 

 due to a larger proportion of silica in the plant. Cobb and Farrer 

 {35) and Farrer {35) found that wheat varieties resist leaf rusts and 

 stem rusts in different degrees. Hitchcock and Carleton {16) state 

 that hard varieties of wheat suffer least from rust in Kansas and 

 early varieties are likely to mature before being seriously injured. 

 Henning {IJf) and Eriksson and Henning {11) found that certain wheat 

 varieties resisted different kinds of cereal rusts. 



It has long been known that some of the emmers ( Triticum dicoc- 

 cum) and certain varieties of du,rum wheat {Triticum durum) show 

 marked resistance to stem rust. Carleton and Chamberlain {9) and 

 Carleton {8) called attention to this in connection with the com- 



*The serial numbers (Italic) in parentheses refer to "Literature cited" at the end of this bulletin. 



