562 Journal of Agricultural Research via. vi, no. t S 



able conditions decay sets in which eventually results in the partial or 

 complete destruction of the corm. 



DESCRIPTION OF SOFTROT 



Softrot is characterized by being watery and slimy, with a disagreeable, 

 repellent odor. The tissue is little or not at all changed in color under 

 natural conditions. Under sterile, artificial conditions the surface 

 becomes slightly reddish brown. Sections through diseased tissue show 

 that the middle lamella is dissolved and the intercellular spaces are filled 

 with bacteria. The cells themselves are seldom, if ever, invaded. 



CAUSE OF SOFTROT 



The softrot of dasheen is caused by the well-known softrot organism 

 of many vegetables, Bacillus carotovorus Jones. This conclusion was 

 arrived at by a comparison in culture of the growth of the organism from 

 dasheen with an authentic culture of B. carotovorus kindly furnished 

 by Dr. L. R. Jones, of the University of Wisconsin, and by a series of 

 cross-inoculations. 



The comparison of growth of B. carotovorus on different culture media 

 was made with three strains from dasheen as follows: 



3624. Bacillus carotovorus Jones (furnished by Dr. Jones). 



3595. A strain isolated from a partially softrotted Trinidad dasheen. 



3616. A strain isolated from a Pat-long-fu taro (C. esculenta). (See Plate 



LXXXIII.) 

 3626. A strain isolated from the fibrovascular bundles at the center of a big 



corm of a Trinidad dasheen. 



All these strains have produced the typical decay by inoculation. 

 After rejuvenating the strains by transferring for several consecutive 

 days to beef bouillon the following culture media were inoculated: 

 Potato cylinders, milk, litmus milk, gelatin, nitrate solution, Cohn's 

 solution, Dunham solution, Uschinsky's solution, beef bouillon, beef- 

 agar slants, beef-agar plates and saccharose, lactose, dextrose, and glycerin 

 bouillon in fermentation tubes. None of the strains grew in Cohn's 

 solution. Gelatin was promptly liquefied by all strains, and nitrates 

 were changed to nitrites when tested according to the method recom- 

 mended by Smith (8). 



Strain 3624 gave a prompt test for indol upon the addition of sul- 

 phuric acid and sodium nitrate, white strain 3595 yielded but a faint 

 pink at first, which intensified upon warming to 75 C. The other two 

 strains were doubtful. Strain 3624 was a slower grower than the others 

 on practically all media as well as the less vigorous parasite, but the 

 difference between the growths of this strain on the various media was 

 no greater than the difference between the growths of the different 

 strains from dasheens, or between the growths in different tubes of the 



