Section IV., 1913. [91] Trans. R.S.C. 



A Bacterial Soft Rot of Turnips. 



F. C. Harrison and Wilfrid Sadler, 



Bacteriological Laboratory, Macdonald College, P.Q. 



(Read May 28, 1913) 



Occurring more or less frequently according to season and varying 

 in destructiveness with the meteorological conditions, the so-called 

 ''Soft-Rot" of such vegetables as turnips, carrots, cauliflowers and 

 cabbages is the cause of serious economic losses to farmers and vegetable 

 growers, and hence has attracted the attention of numerous investi- 

 gators to the disease and the organisms producing it. 



As a resume of the literature has been recently published it seems 

 unnecessary to give any extensive citations. Suffice it to say that 

 M. C. Potter-, L. R. JonesS A. Spieckermann^, C. J. J. Van HalP, F. C. 

 Harrison^, H. A. Harding and W. J. Morse'', and F. C. Stewart* have 

 described in considerable detail the action of various organisms 

 associated with the soft rots of some of the fleshy vegetables. From 

 the practical standpoint it is sufficient for the grower to understand 

 that the disease is caused by a bacterial micro-organism; but from the 

 point of view of the biologist there is considerable interest in defining 

 as closely as may be the relationship of the various organisms isolated 

 and described by investigators who have worked on the disease as it 

 occurred in the field and on the various vegetables attacked. 



As a rule, organisms associated with a well defined disease are 

 recognized with a certain degree of ease, but in the case of the 'soft 

 rot' organisms there seems to be no end to the making of species and 

 varieties, and lest we should be accused of the itch of species making, 

 let us state that the present study was undertaken in order to attempt 

 to find out some facts in connection with the relationship of these 

 bacteria with a view of establishing a type, and, the proof of the patho- 

 genic nature of the organism in turnips. 



Harding and Morse' have attempted to minimise the number 

 of species by bringing these organisms into a few main groups describ- 

 ing their cultures by a plus or minus reaction in certain media, and 

 by using decimal numbers for the description of each combination. 

 This system, however, ignores the relation of the organism to its host 

 plant, and obscures the natural phylogenetic relationship of bacterial 



Sec. IV, 1913—6 



