BACTERIAL BLIGHT OF RYE 1 
By C. S. Reddy, Pathologist , James Godkin, formerly Assistant Pathologist, and 
A. G. Johnson, Pathologist , Office of Cereal Investigations, Bureau of Plant 
Industry , United States Department of Agriculture 
Evidently there is more than one bacterial disease of rye (Secale cereale). In' 
an earlier publication by Jones, Johnson, and Reddy 2 , a bacterial disease of rye, 
occurring near Madison, Wis., was referred to, the organism of which was patho¬ 
genic not only on rye but also on wheat, spelt, and barley. Both in pathogenicity 
and in cultural characters the organism was very similar to if not identical with 
the wheat organism which has been described by Smith, Jones, and Reddy 8 as 
Bacterium translucens var. undvlosum S. J. & R. 
In 1921 a bacterial disease of rye was observed by one of the writers (Reddy) 
near Bloomington, Ill., where it occurred on the leaves of Rosen (winter) rye. 
The leaf symptoms of the disease at Bloomington were identical with those 
previously observed on rye in the vicinity of Madison, Wis. In both cases, 
blotch-like and stripe-like water-soaked lesions (PI. 1) were noted, very similar 
to those described by Jones, Johnson, and Reddy 4 for the bacterial blight of 
barley. The rather conspicuous exudate which occurs on barley and wheat has 
also been noted on rye. ♦ 
Isolations made from , the Bloomington collections yielded a yellow organism 
to all appearances identical with the rye organism previously referred to. In 
inoculations on rye, wheat, barley, and oats this new rye organism proved to be 
pathogenic only on rye. In all of these inoculation experiments the spray method 
was employed as previously described for the barley organism. 
At Bloomington, Ill., in 1921, two inoculation experiments were conducted with 
the new rye organism. In both experiments rye and Marquis (spring) wheat 
seedlings about 4 inches high, growing in rows in the field, were inoculated. In 
each case an ample number of plants were left uninoculated as controls. In both 
of these experiments typical bacterial lesions resulted on the rye, while the wheat 
Beedlings and all of the controls remained free from bacterial infection. The 
typical rye organism was recovered from the rye lesions, and it proved pathogenic 
in subsequent inoculation experiments. 
At Madison, Wis., in 1921 and 1922, two inoculation experiments were con¬ 
ducted. In each, both the new rye organism and the barley organism, Bacterium 
translucens , were used as inocula. In both experiments, parallel inoculations 
with the two organisms were made in the greenhouse on rye, wheat, barley, and 
oat plants about finches high. In both series the new rye organism produced 
typical bacterial lesions only on rye and the barley organism, B. translucens , 
infected only barley as usual. All the uninoculated control plants remained free 
from bacterial infection. 
The morphological characters of the new rye organism were found to be identical 
with those of Bacterium translucens as described by Jones, Johnson, and Reddy. 4 
1 Received for publication April 19,1924—issued Nov., 1924. These investigations were conducted in 
cooperation with the Wisconsin Agricultural Experiment Station, Madison, Wis., and the Funk Bros. 
Seed Co., Bloomington Ill. 
1 Jones, L. R., Johnson, A. G., and Reddy, C. S. bacterial blights of barley and certain other 
cereals. Science 44: 432-433, 1916. 
3 Smith, E. F., Jones, I>. R., and Reddy, C. S. the black chaff of wheat. Science 60: 48, 1919. 
* Jones, L. R., Johnson, A. G., and Reddy, C. S. bacterial blight of barley. Jour. Agr. Research 
11: 625-644, illus. 1917. 
Journal of Agricultural Research, 
Washington, D. C. 
( 1039 ) 
Vol. XXVIII, No. 10 
June 7, 1924 
Key No. G-414 
