22 BULLETI^iT 1046, U. S. DEPARTMENT OF AGRICULTUEE. 



All the varieties of winter wheat used can be placed in one of two 

 classes: (1) Those which fail to show visible signs of uredinia and 

 (2) those entirely susceptible. Those of the first group are desig- 

 nated by the symbol R, and those of the second group by S. Among 

 the spring varieties there were different types of infection, these 

 being represented by the symbols R^ to R5 and by S. Following is a 

 description of the types of rust infection designated by the symbols: 



EXPLANATION OF SYMBOLS USED. 



. E.= Extremely resistant. 



Ri=iSIo uredinia produced. Occasionally very small indefinite flecks, dead areas, 

 or yellowish blotches occur. Signs of hypersensitiveness may be present. 



E,2=Very rarely the occurrence of minute uredinia (0.1 to 0.5 mm.); presence of 

 flecks, dead areas, or blotches. 



R3=Numerous minute to small uredinia (0.2 to 0.75 mm.); presence or absence of 

 yellowish "islands" surrounding uredinia, or the occurrence of numerous yellow 

 blotched areas suiTounding or adjoining uredinia. 



R4=Urediiiia numerous, variable in size and number (0.2 to 0.4 mm.); flecked or 

 blotched, yellow areas present; yellow areas adjoining uredinia. 



R5=Uredinia apparently quite normal in size and shape, but presence of yellowish 

 green areas surrounding or adjoining some uredinia indicative of slight resistance. 



S=Showing ordinary susceptibility; uredinia large, normal, Adgorous. 



The inoculations of Kanred, P1066, and P1068 both in the seed- 

 ling and in the heading stage produced consistent results, indicating 

 extreme resistance. 



The hard and soft wheat varieties did not differ strikingly in 

 susceptibility, except in the case of Kanred, P1066, and P1068. 

 The other hard red winter wheats apparently were as susceptible as 

 the soft red winter wheats, although Leach {2Jj) found a "decided 

 correlation between the hardness and softness of wheat varieties 

 and their relative susceptibility to Puccinia graminis tritici-compadi." 



A greater variation occurred among the varieties of durum spring 

 wheat. Beloturka (C. I. No. 1513) seemed to behave very much 

 like the three resistant winter-wheat varieties, in that no uredinia 

 were formed. In more recent work, however, in which the same 

 strain of rust was used, Beloturka (C. I. No. 1513) occasionally has 

 shown a few very small uredinia. Some of the durum varieties 

 showed more or less uniformly the same type of infection (R, or R^) 

 as in the case of Kubanka (C. I. No. 2094), Arnautka (C. I. No. 1493), 

 D-5 (C. I. No. 3322), and Gharnovka (C. I. No. 1443). A Poulard 

 wheat (C. I. No. 4384) manifested a high degree of resistance. 

 Among the emmers there was more or less similarity in the type of 

 infection. The type of infection fluctuated in both of these groups, 

 showing that various factors may affect the infection results. Two 

 White Spring emmers (C. I. Nos. 1524 and 4781) showed the R, and 

 R4 types of infection, while another White Spring emmer (C. I. No. 



