June 15, 1921 
Varietal Susceptibility of Beans to Rust 
395 
characters of a number of varieties was made. The data on seed char¬ 
acters have been drawn largely from Jarvis (6), supplemented by obser¬ 
vations when necessary. The details of this study are shown in Table 
V. Only two classes with respect to susceptibility are provided, the 
rust-enduring, rust-proof, and rust-free varieties all being classed as 
resistant. Although it is probably impossible to draw conclusions that 
would not be subject to exceptions, nevertheless the following general 
statements can be made for the 51 varieties included in the study. 
With respect to color, all solid red or red mottled beans are rust- 
resistant. With respect to shape, all marrow beans are rust-resistant. 
White beans seem to be more susceptible as a group than black or brown 
beans, and pea beans more so than medium or kidney. 
variability of varieties 
It is of interest to note to what extent the individual plants of a 
variety differ in behavior to rust infection. Although the number of 
plants of a variety under observation in the experiments is not large 
enough to justify more than tentative conclusions, sufficient additional 
evidence from field trials is available to indicate that the stability or 
variability of a variety as indicated below is approximately correct. 
The majority of varieties studied were stable with respect to rust infec¬ 
tion, all individuals responding in the same way. The standard used, 
Tennessee Green Pod, is especially reliable in this respect. Of the 340 
plants inoculated in the experiments all developed sori, and not a single 
fleck was observed. The stable varieties are grouped as follows, accord¬ 
ing to the character of the response to inoculation. 
Table V .—Correlation between seed characters and susceptibility to rust 1 
1 The denominator shows the total number of varieties, the numerator the number that are rust-resistant. 
