Sept. 1, 1924 
Bacterial Pustule of Soybean 
233 
49920, 50440, 50441, 51045, 51046, 
52345, 52346, 52347, 52348, 52349 
(Chinese varieties introduced in 1920- 
21 ). . 
Midwest was a particularly sus¬ 
ceptible variety. There were few, if 
any, sound leaves. Hollybrook, Mi¬ 
kado, Tokio, Mammoth Brown, Hahto, 
Tarheel Black (Pl. 1, B) and some of 
the Mammoth Tellows (PI. 1, A) were 
also badly infected. Buckshot was so 
slightly diseased that some search was 
required to find infected leaves. Man¬ 
darin and Biloxi also had a very small 
percentage of infection. 
INOCULATIONS ON PHASEOLUS 
WITH BACTERIUM PHASEOLI 
SOJENSE 
In an effort to determine whether 
the soybean organism was identical 
with Bad. phaseoli EFS., many cross 
inoculations were made. All inocula¬ 
tion experiments were carried on in the 
greenhouse. Infections were obtained 
on the leaves and pods of a number of 
the members of the genus Phaseolus 
with the soybean organism (Pl. 1, H 
and I; Pl. 4, A to C, E and F). On 
the other hand, repeated attempts to 
infect the soybean with Bad. phaseoli 
EFS. met with failure until inoculation 
was made under very abnormal condi¬ 
tions described later. 
Successful inoculations were made 
with the soybean organism on Climb¬ 
ing Lima, King of the Garden Lima, 
bush string bean, dwarf bush string 
bean, dwarf bountiful string bean and 
dwarf wax bean. 
INOCULATIONS ON LIMA BEAN 
On Lima bean leaves the soybean 
organism produced a reaction unlike 
that on soybean. No pustules were 
formed and sections through a spot 17 
days after inoculation showed neither 
hypertrophy nor hyperplasia. Bac¬ 
terial cavities and masses of bacteria 
were present. In only one case out of 
many was there observed even a slight 
elevation of the epidermis. Further¬ 
more, if the infection made any prog¬ 
ress after the appearance of the first 
small red spots or pale green ones with 
red centers, the spots became water- 
soaked and could not be distinguished 
from those caused by Bad. phaseoli 
EFS. In the best infections there was 
also yellowing in the later stages and a 
distortion of the very young leaves. In 
general, Bad. phaseoli sojense infected 
Lima bean leaves much more slowly 
than did the organism described from 
Phaseolus (Pl. 4, C, D, and H) except 
when the former's virulence for Lima 
was apparently increased by previous 
passage through Lima or bush string 
bean. The tiny spots sometimes did 
not appear for 2 weeks or more and 
then were very scattering and not 
infrequently failed to increase in size 
(Pl. 4, C). The plants were inoculated 
in the greenhouse by spraying and were 
kept moist in inoculation cages 48 to 72 
hours, as a hot moist atmosphere is 
very favorable to infection of Phaseolus 
with both Bad. phaseoli EFS. and 
Bad. phaseoli sojense. 
The first good infections on Lima 
beans were obtained on the green 
pods by spraying them July 13, 1917, 
with a water suspension of a 2-day-old 
potato culture of the soybean organism 
and keeping them wrapped in oiled 
paper 7 days. One side only had been 
sprayed, and when the paper was 
removed this side was covered with 
tiny water-soaked spots while the 
other was perfectly free. Three days 
later these water-soaked spots were 
very marked and there were still 
none on the unspraved side. Bacterial 
ooze was also present. Later, the 
spots turned red but they en’arged little r 
if any, after the first 10 days (PL 4, 
E, F). The parasite was reisolated, 
and one of the resulting colonies 
produced excellent infections on both 
soybean leaves and pods, and on Lima 
bean pods, which were treated as de¬ 
scribed above. The Lima bean leaves 
were not inoculated. 
INOCULATIONS ON DWARF BUSH STRING 
BEANS 
Dwarf bush string bean was much 
more susceptible than Lima (with the 
exception of the latter’s pods) to Bad. 
phaseoli sojense previous to its passage 
through a species of Phaseolus. The 
young leaves of this variety inoculated 
in the greenhouse September 30, 1919, 
were thickly covered with water-soaked 
spots on the ninth day after inoculation 
(no records made earlier). Two days 
later the center of the spot was 
becoming discolored but there was 
never much, if any, enlargement of it 
thereafter, nor was there any yellowing 
(Pl. 4, A). The spots were full of 
bacteria and the parasite was re¬ 
isolated from them. These inocu¬ 
lations were made on plants 2 weeks 
old in an inoculating cage in which 
they were kept moist for 72 hours. 
There was very slight infection on 
King of the Garden Lima plants 3 
weeks old inoculated at the same time, 
