RUST RESISTANCE IN WINTER-WHEAT VARIETIES. - 3. 



mercial value of the durums. Carleton (8), in discussing the stem- 

 rust epidemic on wheat in 1904, observed that no wheat varieties, 

 with the exception of einkorn and some of the durums, spelts, and 

 emmers, showed marked resistance under all conditions. He stated 

 further, that during ordinary seasons when stem rust may be quite 

 prevalent the hard-kerneled Russian winter wheats are considerably 

 more resistant to rust than other varieties ordinarily grown. 



Bolley (4, 5), Biff en {2), and Nilsson-Ehle {33) were among the 

 first to conduct wheat-breeding experiments with the definite object 

 of obtaining rust-resistant varieties. No definite plan or method of 

 study, however, was described until Johnson {20) explained the 

 methods used for producing an artificial rust epidemic in Minnesota 

 and furnished a working basis for the studies which have been made 

 since in this country in breeding cereals for rust resistance. These 

 methods are further described by Freeman and Johnson {12) . They 

 state that certain varieties, such as Extra Squarehead in Sweden, 

 American Club in England, and Rerrarf and Ward's Prolific in Aus- 

 tralia, have been shown to be resistant to rust. They add, however, 

 that some of these varieties can not be said to be universally rust 

 resistant, as their behavior in different countries to different biologic 

 forms of rust is variable. 



Field experiments have verified early observations that some of the 

 durums and emmers are much more resistant than the common 

 spring-wheat varieties. Stakman {37) found this to be true in both 

 field and greenhouse experiments. Melchers and Parker {29, 31) 

 recently have called attention to the resistance of three winter-wheat 

 varieties to stem rust and leaf rust. Waldron and Clark {42) have 

 described a variety of common wheat named Kota and stated that 

 it was resistant to the strain or strains of stem rust prevalent at 

 Fargo, N. Dak., Brookmgs, S. Dak., and St. Paul, Minn., in 1918. 

 These authors state that "this resistance is decidedly greater than 

 that possessed by the common spring wheats and second only to the 

 more resistant durum wheats." Clark, Martin, and Smith {10) 

 speak of the rust behavior of varieties of durum and common wheat 

 grown during the seasons of 1914 to 1919 at several field stations in 

 the northern Great Plains. They state that none of the varieties of 

 common wheat grown is really rust resistant, but early-maturing 

 varieties have ripened before the rust has developed extensively and 

 are sometimes rust escaping. Most varieties of durum wheats are 

 more or less rust resistant, as compared with common wheats. Acme, 

 Monad, and D-5 are known to be especially rust resistant. In years 

 of heavy rust infection these varieties have produced the highest 

 yields. When grown under comparable conditions in these and 

 other experiments, the D-5 variety shows the greatest resistance of 

 all varieties to stem rust. 



