WATERY-ROT OF TOMATO FRUITS' 
A PHYSIOTOGICAIv FORM OF OOSPORA LACTIS; EFFECT ON 
THE HOST; PENETRATION OF THE CELL WALLS BY EN¬ 
ZYMIC ACTION 
By Fred J. Pritchard, Physiologist y and W. S. Porte, Scientific Assistant, Ofiice of 
Cotton, Truck, and Forage Crop Disease Investigations, Bureau of Plant Industry, 
United States Department of Agriculture 
INTRODUCTION 
A new rot of tomato fruits closely resembling the rot caused by 
Bacillus carotovorus has frequently been found in shipments of southern 
grown tomatoes and sent to the Office of Cotton, Truck, and Forage 
Crop Disease Investigations by the Bureau of Markets' inspectors since 
the spring of 1921. It is also prevalent in the vicinity of Arlington, 
Va., and Washington, D. C. 
This rot is characterized by the extremely watery appearance and 
condition of the affected tissues, by the absence of any other discolora¬ 
tion, and by the occasional oozing of water from the surface—^features 
by which it can readily be distinguished from other fungous softrots. 
The rotted areas usually develop in the form of sectors extending from 
the stem scar toward the blossom end. In very humid air they are 
partly covered with a white velvety to granular fungous growth, but 
under average atmospheric conditions this is absent. The illustration 
shown in Plate 4, A, is fairly typical of this rot except for the low point 
of origin and the presence of a surface growth. 
That this rot has frequently been mistaken for the rot caused by 
Bacillus carotovorus is quite likely, as the two are similar in macroscopic 
appearance. However, it differs from the bacterial rot in rapidity of 
development; in fact, fruits kept in the laboratory 10 days after this rot 
had made considerable progress were not completely softened, while 
those infected by B. carotovorus usually collapsed in about 3 days. 
As an examination of the affected fruits obtained from the Bureau of 
Markets always disclosed the presence of an Oospora, experiments were 
made to determine the relation of this fungus to the disease. 
INVESTIGATION 
materiai, and methods 
The Oospora used in the inoculations was grown chiefly on carrot 
agar, as it grew better on it than on most other kinds of media. It 
grew well also on turgid raw carrots kept in a moist atmosphere, pro¬ 
ducing a distinct rot (PI. 4, C), but this material was used only for mor¬ 
phological comparisons. 
In the inoculation work, green, ripe, and partly ripe tomato fruits 
free from blemishes were submerged for 30 minutes in a i: 1000 aqueous 
solution of bichlorid of mercury, washed in distilled water, and inocu¬ 
lated with a pure culture of the Oospora obtained from the rotted fruits. 
1 Accepted for publication Jan. 22, 1923. 
Journal of Agricultural Research, 
Washington, D. C. 
aex 
(895) 
Vol. XXIV, No, II 
June 16, 1923 
Key No. (^312 
43325—23-2 
