Sept. 1, 1924 
Bacterial t usiule of Soybean 
231 
are present in abundance, and that the 
swelling is caused chiefly by hyper¬ 
trophy and hyperplasia of the paren¬ 
chyma (PL 3, A, C). In some cases 
there was also striking hypertrophy of 
the epidermis cells (PL 3, D), but no 
hyperplasia was observed in this layer. 
The bacteria occur throughout the 
intumescence and there are bacterial 
cavities occupied by masses of bac¬ 
teria, also innumerable areas where 
individual rods can be clearlv seen 
(Pl. 3, B). 
The tissues of a pustule were tested 
with KI and H 2 S0 4 for cork seven weeks 
after inoculation. The cell walls gave 
the yellowish-brown reaction indicating 
suberized tissue, although none of the 
cells resembled cork cells in appear¬ 
ance. In fact, only a very small 
portion of the cell walls in the diseased 
area, whether in the swollen portion 
or not, showed the blue cellulose re¬ 
action. 
ISOLATION OF THE PARASITE 
The parasite is easily isolated from 
fresh material by means of agar poured 
plates. In some cases there was no 
previous sterilization of the leaf sur¬ 
face, but in the majority of cases 
HgCl 2 1:1000 was used, the leaf being 
dipped first in alcohol, and subsequently 
thoroughly rinsed in sterile water to re¬ 
move the HgCl 2 . It was found that 10 
to 20 seconds was a good average time for 
sterilization. The tissue was then 
crushed in a tube of sterile water or 
beef bouillon with a sterile rod and 
diffusion was allowed to take place for 
10 to 20 minutes, or longer if the tissues 
were dry or microscopical examination 
had shown comparatively few bacteria 
present. The writer has safely used 
distilled water, for rinsing the leaves 
and preparation of the dilutions, al¬ 
though this procedure has caused 
trouble with certain more sensitive 
organisms. The colonies are usually 
visible to the naked eye in 2 to 3 days 
but occasionally fail to appear until 
4 or 5 days have passed. 
INOCULATIONS ON SOYBEAN WITH 
BACTERIUM PHASEOLI SOJENSE 
The disease has been reproduced re¬ 
peatedly on sound soybean plants in 
the hothouse both by spraying and by 
rubbing with absorbent cotton wet in 
a water suspension of a culture of 
Bad. phaseoli sojense (PL 1, E to G; 
Pl. 2, B to D). The best results 
were obtained when young rapidly 
growing plants were used and were 
kept moist for at least 36 hours after 
inoculation. This was done by placing 
them in inoculating cages, the interior 
of which was thoroughly wet previous 
to inoculation. The cages were cov¬ 
ered with heavy Manila paper and the 
plants were kept moist by repeated 
sprayings with bacterial suspensions 
during the 36 to 72 hours. 3 If very 
small plants were used and the only 
available inoculation cage was large, 
pans of water or large plants with 
plenty of transpiring surface were 
added. 
Good infections were also obtained 
when the plants were covered with 
paraffined bags, but these did not hold 
the moisture as well as the cages and 
it was more difficult to respray the 
plants. Placing the.sprayed or rubbed 
plants under a bench in the shade was 
sometimes sufficient. 
The first signs of infection usually 
appeared in 5 to 9 days, although in 
some cases there was a longer incuba¬ 
tion period. Generally, the pustules 
were plainly visible in less than 10 days 
and thfe infection progressed as de¬ 
scribed under ‘ S’gns of the disease,” 
above. Under greenhouse conditions 
the leaves rarely were as badly dis¬ 
eased as in the fieM. This was prob¬ 
ably due to the fact that the soybean 
plants themselves did not thrive par¬ 
ticularly well in the conditions prevail¬ 
ing in the Washington hothouses. 
SUSCEPTIBLE VARIETIES OF SOY¬ 
BEANS 
Successful inoculations were made 
upon the following varieties of soy¬ 
beans: Ito San, Medium Yellow, 
Mammoth Yellow, Hahto, Wilson 
Black, Hollybrook Early. No infec¬ 
tion was obtained on Wilson Fine, 
although plants of Ito San and Medium 
Yellow of the same age (3 weeks) inoc¬ 
ulated at the same time with the same 
culture became badly diseased. 
Natural infection was observed in 
the fall of 1921 on the following varie¬ 
ties at Arlington Farm, Va.: Auburn, 
xVustin, Barchet (Pl. 1, C), Biloxi, 
Buckshot, Chiquita, Edna, Fairchild, 
Flat King, Hahto, Hinangdon, Holly- 
brook, Honkong, Hoosier, Laredo, 
Mammoth Brown, Mammoth Yellow 
(Pl. 1, A and D), Manchuria, Manda¬ 
rin, Midwest, Mikado, Mixture, Tar¬ 
heel Black (Pl. 1, B), Tokio, Wisconsin 
Black, S. P. I. 49832, 4 49918, 51042, 
49834, 51043 (new introductions by 
S. P. I. with no varietal names), S. P. I. 
The plants were never kept in the cages as long as 72 hours when the temperature was high. 
4 Office of Seed and Plant Introduction, U. S. Dept, of Agriculture. 
