RUST EESISTAFCE IN WINTER-WHEAT VARIETIES. 27 



crop as a result of the production of Kanred wheat would be $21,000,- 

 000. A statement of the agronomic value of this variety will be 

 found in Circular 194 of the United States Department of Agriculture. 

 Although the problem of breeding wheat for resistance to stem rust 

 has been greatly complicated by recent discoveries of a number of 

 distinct biologic strains of rust which are present in the several grain- 

 growing regions, Kanred wheat in the future probably will prove of 

 great value as a parental variety in crosses, for it certainly contains 

 factors for resistance to some strains of leaf rust and stem rust. 

 There is good evidence that these factors are transmitted in wheat 

 hybrids in the same general way as the factors for other characters. 

 Kanred wheat is being used by the Tennessee Agricultural Experi- 

 ment Station as the rust-resistant parent in a series of crosses with 

 adapted varieties of soft red winter wheat, in the hope of producing 

 varieties of soft red winter wheat resistant to leaf rust and otherwise 

 equal to the best varieties now being grown, which are often severely 

 damaged by leaf rust. Kanred also has been used at the Kansas 

 and Minnesota Agricultural Experiment Stations as a parent in a 

 large number of crosses. It is too early to make any predictions as 

 to the value of any of these hybrids, although several of them appear 



promising. 



SUMMARY. 



(1) Field experiments to determine the resistance to black stem rust 

 (Puccinia graminis tritici) of about 100 varieties and strains of winter 

 wheat, many of them pure-line selections, and of a few varieties of 

 spring wheat, were conducted in a rust nurser}^ at Manhattan, Kans., 

 in 1915, 1916, and 1917. Greenhouse experiments were conducted 

 during the winter of 1916-17, using the same varieties. Special 

 methods were developed for producing rust epidemics under the pre- 

 vailing climatic conditions of Kansas. 



(2) In the rust nursery severe epidemics were produced each 

 season, and the percentage of rust infection probably represented 

 the maximum rust attack which the varieties would encounter under 

 field conditions. 



(3) All the winter-wheat varieties grown were found to be suscep- 

 tible to stem rust except Kanred and two very similar pure-line 

 selections, P1066 and P1068. These three varieties were found to be 

 resistant. Another pure-line strain, Kansas No. 2390, gave evidence 

 of being partially resistant. 



(4) Plumpness of kernels usually is reduced by severe rust attack. 

 The three resistant varieties produced grain of good quality in 1916 

 and 1917, when other varieties grown under the same conditions 

 but much more severely rusted produced very badly shrunken 

 kernels. 



