24 Walter H. Burkholder 



Cross inoculations 



Besides inoculation of the common bean (Phaseolus vulgaris), infection 

 was obtained also on the sieva bean (P. lunatus) and the scarlet runner 

 bean (P. coccineus). On the sieva bean, definite necrotic lesions on the 

 leaves followed inoculation of the stem. This was more likely to be the 

 result than a primary wilting. In these instances the bacteria could be 

 traced up the xylem vessels in the stem to the lesions on the leaves. Water- 

 soaked lesions were obtained also on the pods. On the scarlet runner bean, 

 the lesions were, as a rule, local about the point of inoculation, and caused 

 only a slight injury to the plant as a whole. They were usually reddish in 

 color, and extended a half inch or more up and down the stem. 



Negative results were obtained with the following species: hyacinth bean 

 (Dolichos lablab), white-flowering lupine (Lupinus polyphyllus) , kudzu vine 

 (Pueraria hirsuta), cowpea (Vigna sinensis), yard-long bean (V. sesquipe- 

 dalis), soybean (Glycine max), broad bean (Viciafaba), field pea (Pisum 

 sativum var. arvense), and sweet clover (Melilotus alba). On the green 

 pods of the cowpea a small pustule sometimes formed, as though infection 

 were going to take place, but this vanished shortly, with no further sign 

 of the disease. The bacteria introduced as the inoculum evidently caused 

 a slight disturbance, but, since they were unable to establish themselves 

 and develop, the slight lesion did not persist any longer than the introduced 

 bacteria did. Several attempts were made with this organism to obtain 

 infection of seedlings of the hyacinth bean and the white-flowering lupine, 

 since Phyt. phaseoli readily produced diseases in these two species. Under 

 the conditions of the inoculation experiments, however, the organism under 

 observation remained non-pathogenic. The host range of the two patho- 

 genes appears to be different. 



ETIOLOGY 



Morphology 



The pathogene, when grown on beef -extract agar (pH 6.9), is a fairly 

 large rod with rounded ends, occuring singly or in pairs. Chains are seldom 

 found, but during the early hours of growth long filaments are not uncom- 

 mon. Individual cells stain well with carbol fuchsin and gentian violet; 

 granules are observed at the center of the rod, or in some cases they may 

 be polar. A culture twenty-four hours old on the above medium, grown 

 at 27° C, showed the following measurements: 2.34^ (1.35 to 4/i) by 0.98/1 

 (0.6 to 1.35m). 



The organism does not form spores, and capsules have not been demon- 

 strated. When grown on a medium containing dextrose, a large amount 

 of gum is produced. The organism is motile, but those cultures with which 

 the writer has worked have not been actively so. One polar flagellum has 

 been demonstrated by the use of Loeffler's stain. 



