Dec. 17,1917 
Bacterial-Blight of Barley 
637 
INOCULATION EXPERIMENTS 
On barley. —The disease has been reproduced on barley with the 
characteristic symptoms by artificial inoculation and the original organ¬ 
ism recovered. While a considerable percentage of infections have re¬ 
sulted where wound inoculations were made, the best results and those 
leading to the typical lesions have followed the spraying of the organisms 
in watery suspension upon young uninjured leaves. 
The following details of one of the earliest series of inoculations illus¬ 
trates this: 
Beldi barley was sown in 6-inch pots, and on June 28, 1915, when the 
vigorous young growth was about 4 inches high, four uniform pots, each 
containing about 25 plants, were selected for experimental uses. Of 
these pot I was inoculated by atomizer spray with a water suspension of 
the organism obtained as follows: A pure culture of the organism was 
plated out from the milky ooze squeezed from a typical leaf midvein 
lesion. Sterile water was poured into an agar tube streak culture and 
the bacterial growth allowed to diffuse into this, which was then used to 
spray upon the young barley plants. In pot II a wound inoculation was 
made on the first green leaf of each plant. This was done by touching 
with the needle the bacterial growth of a young agar streak culture of 
the same source as described above. With this needle a slight wound 
was made about midway the leaf, in the midvein or near it, the attempt 
being to puncture but one epidermal layer and to avoid a perforation 
through the entire leaf. In pot III wound inoculations were made as in 
II except that the inoculation needle was dipped directly into the milky 
ooze squeezed from a typical barley leaf midvein lesion. Pot IV was 
held as a control, the plants being wounded as in II and III, but with 
sterile needle. 
These pots of barley plants had all been grown in the greenhouse pre¬ 
vious to inoculation and were kept there in a damp chamber for 24 hours 
following this, then transferred to the open garden. The pots were here 
sunken to the soil level and thus given normal outdoor exposure, the 
weather being warm and rather dry. 
Infection was noted in pots I, II, and III on July 7, an incubation 
period of nine days. There was no infection in IV. On July 9 pot I 
showed approximately 100 per cent of plants infected, II approximately 
40 per cent, III about 20 per cent, and IV no plants infected. After the 
occurrence of splashing rains, secondary infections appeared, and at the 
end of a month, when these were at their height, pots I, II, and III 
showed a like condition, with abundant lesions on practically every plant, 
whereas the control, pot IV, showed only four or five recently developed 
lesions. Since pot IV was only 18 inches removed from the nearest in¬ 
fected pot and fully exposed for the month, splashing rains were held 
responsible for these few late infections. 
