ALTERNARIA PANAX, THE CAUSE OF A ROOT-ROT OF 

 GINSENG 



By J. RosENBAUM, specialist in Phytophthora, and C. L. Zinnsmeister, formerly 

 Agent, Cotton and Truck Disease Investigations, Bureau of Plant Industry 



While working with diseases of ginseng (Panax quinquejolium) during 

 the summer of 1913, the authors obtained from a garden near Cleveland, 

 Ohio, roots which showed a peculiar dry-rotted condition about the crown. 

 The dark-brown center of the lesion characterizing this dry-rot was more 

 or less sunken and firm to the touch and gradually shaded into the 

 yellowish white color of the healthy root. It is distinguished from 

 other root-rots by its lack of odor and the fact that the rotted roots never 

 become soft. Plate XII is a reproduction of a photograph of three roots 

 showing the typical lesions of the disease. 



When the rot is near the crown of the root, the top of the plant often 

 shows signs of the disease. These signs are a wilting and yellowing of the 

 leaves, which on being disturbed drop off readily at the point of attach- 

 ment to the main stalk. Such a condition may, however, be caused by 

 other root-rots attacking ginseng, as, for example, the rot caused by 

 Phytophthora cactorum. 



Because of the unusual character of these lesions, numerous isolations 

 were made from them, and in all cases an Alternaria-like fungus closely 

 resembling Alternaria panax Whet, was secured in pure culture. In order 

 to determine whether these two fungi were identical, a series of inocula- 

 tions on roots and tops were made with both cultures. In addition, 

 a study was made of their macroscopic and microscopic appearance. 

 This work was begun during the summer of 19 13 in Ohio and repeated 

 during the summer of 19 14 in New York. 



In the main two methods of inoculation were followed. Healthy 

 roots were taken from the garden, washed, freed from their fiber roots, 

 sterilized for 10 minutes in a i to 1,000 solution of mercuric chlorid, 

 washed in sterile distilled water, and placed in sterilized test tubes. 

 The roots were then injured by making an incision in them with a sterile 

 scalpel, and in this incision was placed a small portion of the fungus 

 from a pure culture. Roots treated in the same way but not inoculated 

 were used as checks. Six series of inoculations were made in this manner, 

 using the Alternaria-like fungus isolated from dry-rotted roots. Ninety- 

 five per cent of infection was secured, and the checks in all cases remained 

 healthy. Typical lesions (PI. XII) were produced in every instance. 

 In no case did the rotted condition involve the entire root. The time 

 necessary after inoculation for the lesion to appear varied from seven to 

 nine days. Once established the progress of the rot was also very slow. 



Journal of Agricultural Research, Vol. V, No. 4 



Dept. of Agriculture, Washington, D. C. Oct. 25, 1915 



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