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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



CONTRIBUTIONS FEOM THE WISLEY LABOEATORY. 



XVI. — Bruise in Potato. 



By A. S. HoRNE, B.Sc. (Lend.), F.G.S. 



During the last few years a large number of instances have been 

 brought to my notice of potatos affected with a black discoloration of 

 the flesh. Since the trouble appears to be frequently of some economic 

 importance, it is desirable to describe the symptoms. The blackening 

 is evident immediately the tuber is cut open, and must not be confused 

 with the discoloration which often appears after the cut surface of a 

 tuber has been exposed to air, nor with that which often occurs after 

 cooking, as described by S. F. Ashby in 1905. The latter phenomena 

 are not dealt with in this paper. 



The first examples of the disease were received from Devonshire 

 in 1907. They showed small greyish-black areas (fig. 20 a) in the 

 peripheral region of the flesh. Many of them were situated between 

 the principal vascular bundles and the periderm. They did not extend 

 far internally, and none were found in the pith. The disease occurred 

 among potatos sold for cooking, and considerable waste must result 

 from the use of tubers so affected. They are very often sold at a 

 price which should warrant a supply of sound ones. Under the 

 circumstances the consumer actually pays for the sound vegetables 

 available from the purchased quantity a higher price than ought to be 

 demanded. 



In some parts of the country the disease is known as " bruise." 

 This name is aptly applied, since the discoloration resembles a bruise 

 very much in appearance. It is often, however, erroneously supposed 

 that the condition is the result of mutual pressure when potatos are 

 stored, or that it is due to blows received in tumbling or falling upon 

 the ground or upon one another. 



"With a view to discovering to what extent potatos of this descrip- 

 tion were sold for planting by local dealers in the North of England, 

 several lots were purchased in 1908. These had been obtained by the 

 dealers from Cambridgeshire and Scotland. The diseased condition 

 was found frequently in the varieties * Up-fco-Date ' and * British 

 Queen.' During the same season slightly affected tubers occurred 

 among some of the varieties grown at the Cockle Park Experimental 

 Station, in Northumberland. Additional examples were sent from 

 other parts of Northumberland. 



Diseased material was not easily obtained in the early part of the 

 next storage period, but in May (1909) — rather late in the season — 



* Ashby, S. F. " A Contribution to the Study of Factors affecting the 

 Quality and Composition of Potatos." Jour. Agr. Sci. I. (1905) p. 347. 



