July 15,1925 
Bean Varietal Tests for Disease Resistance 
111 
In case of anthracnose it will be noted that the writers have fol¬ 
lowed very closely the definitions adopted by Barrus (I, p. 59S) as a 
result of his extensive studies of this disease. The terms express the 
general effect of the disease on the plant, which takes into considera¬ 
tion both the number and size of the lesions, although, as Leach ( 8) 
has recently pointed out, size of lesion is doubtless the more impor¬ 
tant index of resistance. 
In Table II there are listed all the varieties and selections of 
Phaseolus vulgaris which have been tested and, in successive columns, 
their reaction to the different diseases as expressed by the summary 
terms defined in Table I. 
In examining the detailed records positive evidence was necessarily 
given most weight. Negative evidence, or signs of resistance, was 
considered significant only after comparison with controls and the 
behavior of the variety in the greenhouse and in other plots in differ¬ 
ent years. Unfortunately many of the varieties have not been tested 
long enough or under the necessary conditions to make such com¬ 
parisons possible, and final judgment must await additional informa¬ 
tion. 
The experimental results for bacterial blight on many of the Ameri¬ 
can varieties, as shown in the ninth column, are supported by exten¬ 
sive observations in seedsmen’s trial grounds and in large field areas 
growing in Michigan, New York, and Vermont. 
The first column devoted to bacterial wilt gives the results of 
seed lin g inoculations in the greenhouse, the figures expressing the 
percentage of the total number of plants which showed permanent 
wilting of one or more of the first trifoliate or true leaves. The sec¬ 
ond column gives the field record. Here the occasional figures rep¬ 
resent those varieties which were inoculated by the u cotyledon 
method” and show the percentage of plants, based on a unit of 10 ; 
which either died from the effects of the disease or were so stunted as 
not to mature pods. The surviving plants generally also displayed 
varying degrees of dwarfing, but usually succeeded in ripening 
many of their pods. The words in this column expressing different 
degrees of infection refer to the inoculations on older plants by the 
needle-prick method, described in the preceding section. 
EVIDENCE OF RESISTANCE 
A review of Table II shows the comparatively small number of 
varieties which were not moderately or severely infected with both 
anthracnose and bacterial blight, the diseases given special attention 
in this study. A large proportion of those tested but one season and 
showing the extent of infection indicated by “slight” or “none” 
would doubtless also have proved more or less susceptible had they 
been tested under more favorable conditions for the development of 
disease. 
Since the evidence on resistance to anthracnose in the case of a 
number of the varieties was based largely on their behavior in the 
field, these and a number of others concerning which the information 
in Table II is uncertain or lacking were subjected to a final green¬ 
house test with all the known biologic forms of the fungus. The 
detailed results of this experiment, which was carried out in tripli¬ 
cate, are presented in Table III. 
