Bean Anthracnose 151 



with cultures from fifteen different sources. These for the most part fell 

 into two physiological forms or strains, which are designated, respectively, 

 as alpha and beta. The varieties of beans, from their behavior when 

 inoculated with these strains, showed a classification into four groups, as 

 follows: ab, those susceptible to either strain of the pathogene; Ab, those 

 resistant to alpha but susceptible to beta; aB, those susceptible to alpha 

 but resistant to beta; and AB, those showing resistance to both alpha 

 and bHa. In the first-named group, ab, belong 80 per cent of the wax 

 bush varieties inoculated, 50 per cent of the green-pod bush, 40 per cent 

 of the wax pole beans, and 30 per cent of the green-pod pole beans. It 

 appears from this, then, that the wax bush beans are, generally speaking, 

 the most susceptible to anthracnose. Five varieties are placed in the 

 resistant group AB, but of these only one, Wells' Red Kidney, has shown 

 a satisfactory resistance under all conditions. The writer (Barrus, 1915) 

 described this strain of Red Kidney as having been selected by a farmer 

 as a single healthy individual from a field where all other Red Kidneys 

 were badly affected. This strain has continued to show the same resistance 

 in the many inoculations made by the writer and by other investigators. 

 It is not a pure type, however, the seed varying somewhat in size, shape, 

 and color, and individuals appear from time to time which show some 

 susceptibility to anthracnose, varying from slight to considerable. In 

 a later paper (1918:602) the writer records the resistance of a field bean 

 called White Imperial to several inoculations made with both strains of 

 the pathogene. Recently, however (in 1921), a field of beans said to be 

 White Imperial, the pods of which were severely affected with anthracnose, 

 was observed. It seems not unlikely that strains of the pathogene exist 

 which are capable of infecting even these varieties. 



Burkholder (1918:353) has been able to produce an anthracnose-resist- 

 ant White Marrow by crossing the ordinary susceptible White Marrow 

 with the resistant Wells' Red Kidney and by subsequent selection of the 

 resistant types. In the same manner, McRostie (1919:141) has also 

 reported crossing the Wells' Red Kidney with the Michigan Robust, 

 a white pea bean, but progress had not been made beyond the F 2 generation 

 at the time of this report. In both of these crosses the character of resist- 

 ance proved to be dominant, and inoculation of the F 3 generation is 

 necessary in order to determine which individuals are homozygous and 

 which are heterozygous to resistance. 



