Apr. 15, 1921 
Bacterial Spot of Tomato 
141 
It was upon their suggestion that the successful cross inoculations sub¬ 
sequently reported were made. 
Since the organism known to be involved in bacterial spot of tomato 
has not been described and named, 1 it is given the following chacterization. 
TECHNICAL, DESCRIPTION 
Bacterium exitiosum, n. sp . 2 
Cylindrical rods, rounded at ends, solitary or in pairs; individual rods 1.5 to 2.7 u 
by 0.6 to 1.3 /x; motile by a single polar flagellum; aerobic, no spores; not conspicuously 
capsulated. 
Superficial colonies on potato agar, round, pulvinate, smooth, glistening; naphtha¬ 
lene yellow, with radial striae of color in peripheral zone; margin entire. 
Gelatin rapidly liquefied; no acid produced in milk; digests casein; nitrates not 
reduced; no acid or gas produced in media with various carbohydrates; Gram-negative. 
Group number 211.3332 513. 
Pathogenic on Lycopersicum esculenium Mill, forming lesions on leaf blade, rachis, 
petiole, cotyledon, stem, peduncle, and green fruit. Fruit lesions destructive. Also 
pathogenic on leaves and fruit of Capsicum annuum L. and on leaves of Solatium 
tuberosum L. 
Type locality: Frankfort, Ind. 
Distribution: Widespread. 
PATHOGENICITY 
Since the fall of 1919 numerous series of inoculations upon tomatoes 
under greenhouse conditions were attended by uniformly successful 
results. Cultures from four sources were used, but most of the work 
was done with the two strains used in the cultural tests. Repeated 
reisolations have been made, and the identity of the causal organism has 
been verified. One reisolated strain was extensively used in cultural and 
inoculation tests. Reciprocal cross inoculation upon pepper and tomato 
plants has also been successful. 
Foliage infection of tomato was readily produced by spraying plants 
with an atomizer containing a water suspension of the organism from 
agar cultures. For much of the foliage inoculation work a moist chamber 
was used, but it was found that ordinary greenhouse conditions also 
permitted infection. Infection of green fruit was obtained through 
puncture wounds. Cotyledon infection was effected by spraying flats 
of seedlings and by planting inoculated seed. The incubation period on 
foliage was three to six days and on fruit five to six days. Typical 
inoculation tests are described in the following paragraphs. 
FOUAGE INOCULATION 
On January 31 two small potted tomato plants were thoroughly 
atomized on both upper and lower leaf surfaces with a water suspension 
of the organism from an agar slant culture 8 days old. These plants were 
1 See footnote reference on page 125 to the work of Miss E. M. Doidge. 
* According to Migula’s classification and Buchanan’s revision the combination would be Pseudomonas 
exitiosa, n. sp. (Buchanan, R. E. .studies in the nomenclature and classification of the bac¬ 
teria. V. SUBGROUPS AND GENERA OF THE BACTERIACBAE. In Jour. Bact., V. 3, no. I, p. 48-51. 1918.) 
