The Bacterial Diseases of the Bean 63 



Cross inoculations 



To determine the host range of this green-fluorescent pathogene, and 

 its pathogenic relationships to others of its type, inoculation experiments 

 were conducted on a dozen species of legumes besides the common bean 

 (Phaseolus vulgaris). The experiments were made in a greenhouse at a 

 temperature of approximately 80° F. Seedlings were used in all cases, 

 and in a few instances green pods of certain species were inoculated. 

 Inoculations were made by pricking the plants with a sharp-pointed instru- 

 ment and introducing the inoculum at the same time. 



Good infection was obtained on seedlings of the following species: 

 scarlet runner bean (P. coccineus), sieva bean (P. lunatus), white-flowering 

 hyacinth bean (Dolichos lablab), cowpea (Vigna sinensis), and kudzu vine 

 ( Pueraria hirsuta) . 



While the results were negative on seedlings of the soybean (Glycine 

 max), a high degree of infection was obtained on the pods of this 

 species when these were injured (Plate IV, E). The pod spots were angular 

 in shape but very definite in outline, and were light brown in color with 

 usually a dark border. The variety of soybean used was Wilson. Good 

 pod infection was obtained also on the sieva bean. 



Negative results were obtained on seedlings of the following species: 

 white-flowering lupine (Lupinus polyphyllus) , yard-long bean (Vigna 

 sesquipedalis) , broad bean (Vicia faba), field pea (Pisum sativum var. 

 arvense), and sweet clover (Melilotus alba). Owing to the fact that in 

 culture this pathogene rapidly loses its virulence, and even its pathogenicity, 

 less satisfaction is felt with this list of plants giving negative results than 

 with any other list in the memoir. It is true that more than one set of 

 inoculations were made on the species listed above, and in all sets of experi- 

 ments certain species in the susceptible list succumbed, showing that the 

 culture used was composed of virulent organisms. Nevertheless, because 

 of the inconsistency with which the pathogene sometimes refused to infect 

 susceptible plants, the negative results were regarded with some uncer- 

 tainty. 



ETIOLOGY 



Morphology 



From a culture twenty-four hours old on beef -extract agar (pH 6.9), 

 grown at a temperature of 27° C., individual cells are large rods with 

 rounded ends. Considerable variation, however, occurs among them. 

 They measure 2.13/x (1.35 to 3.6/x) by 0.81/i (0.6 to 1.2/*). 



The organism stains well with carbol fuchsin and gentian violet. Gran- 

 ules, both central and polar, have been observed. The pathogene is Gram- 

 negative and not acid-fast. Capsules have not been demonstrated. All 

 cultures on agar showed an actively motile organism, which, when stained 

 with Loefner's flagella stain, was found to have one to two polar flagella. 



