JOURNAL OF mumn KESEARCH 
Vol. XXIX Washington, D. C., July 15, 1924 No. 2 
BACTERIAL PUSTULE OF SOYBEAN 1 
By Frederick A. Wolf 
Botanist, North Carolina Agricultural Experiment Station 
INTRODUCTION 
Diseases of the soybean, Soja max 
(L.) Piper, have for several years been 
the subject of investigation by the 
writer and his colleagues at the North 
Carolina Agricultural Experiment Sta¬ 
tion (2, 8, 8, 11, 16, 17). 2 Among 
those which have been given special 
study is a leafspot to which the ap¬ 
propriate name “bacterial pustule” 
has been applied. This leafspot dis¬ 
ease was first briefly described (4) in 
1922 by Florence Hedges. In this 
preliminary report, Miss Hedges de¬ 
signated the causal organism Bac¬ 
terium phaseoli var. sojense and stated 
that a paper covering the results of her 
investigations was in preparation ( 6 ). 
It might be anticipated that the present 
report would confirm in all essential 
features that of Miss Hedges. Should 
it contribute nothing new to the 
knowledge of this disease and its 
causal organism, nevertheless it is 
believed to have a definite value since 
the investigations have been conducted 
entirely independently. It is the 
writer’s purpose, therefore, to embody 
in this paper a description of the disease, 
an account of its relation to other 
soybean leaf spots of bacterial origin, 
studies on its etiology, and on the 
morphology and physiology of the 
causal organism. 
HISTORY AND DISTRIBUTION 
A definite knowledge of the occur¬ 
rence of this disease dates from Miss 
Hedges’s isolation, from specimens sent 
from Texas in 1917, of a yellow organ¬ 
ism very closely resembling Bacterium 
phaseoli E. F. Smith. However, a bac¬ 
terial leafspot of soybean which was 
assumed to be due to Bacterium pha¬ 
seoli was mentioned as long ago as 
1904 (12). The isolations upon which 
this report was based were made two 
years earlier (18, p. 280) from diseased 
soybeans taken from two localities, one 
near Charleston, S. C., and the other 
near Washington, D. C. The organism 
isolated at that time was not proved by 
inoculation experiments to be patho¬ 
genic, and therefore its relation to the 
leafspot can not now be satisfactorily 
determined. This problem is further 
complicated by the fact that other bac¬ 
terial organisms have recently been 
found to be pathogenic to soybean. 
The first of these diseases to be care¬ 
fully investigated was a bacteriosis (9) 
which manifests itself by the formation 
of lesions both on stems and pods. 
Those on the stems are especially char¬ 
acteristic, since they girdle them in a 
manner suggesting the blackleg disease 
of potatoes. The pathogen, Bacillus 
lathyri Manns and Taubenhaus, is 
identical with the one which causes the 
“streak” disease of sweet pea, Lathyrus 
odoratus L. It is a yellow organism 
but has very different morphological 
and cultural characters from the soy¬ 
bean organism under consideration. 
As will be shown later, the appear¬ 
ance of bacterial pustule has little in 
common in any stage of development 
with that of bacterial blight as de¬ 
scribed by Miss Coerper (1) or by the 
writer (16). The causal organisms 
identified as Bacterium glycineum by 
the former and as Bad. sojae by the 
latter are both white and are thus 
easily separable from the pustule 
organism; but in the case of old 
lesions caused by Bad. sojae the tissues 
are always occupied also by a yellow, 
one-flagellate organism (16) which 
may be a source of confusion as to the 
primary cause. It might be indicated 
at this point that although the bac¬ 
terial blight diseases caused by Bad. 
glycineum and Bad. sojae are very 
similar in appearance, the causal 
organisms are readily distinguishable 
and specifically distinct, as has been 
shown by certain cultural studies (ll f 
7, 17). 
Mention has been made in several 
previously published accounts of bac¬ 
terial diseases of soybeans in the 
Orient. A bacteriosis has recently 
been recorded (10) by Miura, a Japa¬ 
nese investigator, as occurring in Man¬ 
churia. His description of the dis¬ 
ease accords with the appearance of 
1 Received for publication Feb. 25, 1924—issued January, 1925. 
2 Reference is made by number (italic) to ‘‘Literature cited,” p. 68. 
Journal of Agricultural Research, 
Washington, D. C. 
99179—25f-1 
Vol. XXIX, N 0 . 2 
July 15, 1924. 
Key No. N. C—18 
(57) 
