JOURNAL OF AGEICETIAL ISEARCH 



DEPARTMENT OF AGRICULTURE 

 Vol. VI Washington, D. C, May i, 1916 No. 5 



EFFECT OF CERTAIN SPECIES OF FUSARIUM ON THE 

 COMPOSITION OF THE POTATO TUBER* . 



By LoN A. Hawkins, 



Plant Physiologist, Plant Physiological and Fermentation Investigations, 



Bureau of Plant Industry 



INTRODUCTION 



Potato tubers (Solanum tuberosum) are subject to attack by various 

 parasitic fungi. Some of these organisms invade the tuber, kill the 

 cells, break down the cell walls, and cause, directly or indirectly, a 

 more or less complete disorganization of the host tissue. What con- 

 stituents of the potato are most easily destroyed by the fungus and 

 what compounds can not be utilized by it either in respiration or to 

 build up its own tissue are of considerable interest in the study of the 

 physiology of parasitism. It was to obtain information on the effect 

 of some potato tuber rot fungi upon the tissues of the host plant that 

 the present study was planned and carried out. In this investigation 

 the effect of Fusarium oxyspormn Schlecht. and F. radicicola Wollenw. 

 on the sucrose, reducing-sugar, starch, pentosan, galactan, and crude- 

 fiber content of the potato was studied. Some experiments were dupli- 

 cated also with F. coeruleum (Lib.) Sacc. 



The three species of Fusarium just mentioned are all parasites on 

 the potato tuber. Smith and Swingle (9) ^ considered F. oxysporum 

 to be the cause of a serious rot of potato tubers. Wollenweber (10) 

 did not agree with these writers, and contended that this fungus, while 

 the cause of a wilt disease of the potato plant, was not able to rot the 

 tubers. This conclusion of Wollenweber's has recently been disproved 

 by Carpenter (4), who corroborates the findings of Smith and Swingle 

 on this point. With this species and with F. radicicola, the latter con- 

 sidered by Wollenweber and by Carpenter to be the cause of a tuber-rot 

 of considerable importance, the writer experienced no difficulty in 

 obtaining well-rotted tubers in two to three weeks after inoculation. 



' The work described in this paper was carried out in cooperation with the Office of Cotton and Truck- 

 Crop Diseases. The writer thanks Mr. C. W. Carpenter, of that office, for cultures of the fungi used. 



The writer's thanks are also due Mr. A. A. Riley, of the Office of Plant Physiological and Fermentation 

 Investigations, for assistance in the experimental part of this study. 



^ Reference is made by number to " Literature cited," p. 196. 



Journal of Agricultural Research, Vol. VI, No. s 



Dept. of Agriculture, Washington, D. C. May i. 1916 



dl G— 78 



(183) 



