SOME PROPERTIES OF THE VIRUS OF THE MOSAIC 

 DISEASE OF TOBACCO 



By H. A. Allard, 



Assistant Physiologist, Tobacco and Plant Nutrition Investigations, 

 Bureau of Plant Industry 



INTRODUCTION 



Several theories have been advanced to explain the physiological origin 

 of the mosaic disease of tobacco (Nicotiana tabacum.) Independently, 

 Woods (20) * and Heintzel (10) came to the conclusion that oxidizing 

 enzyms are responsible for the disease. Hunger (11) did not accept the 

 enzymic theory of the mosaic disease but considered that unfavorable 

 conditions of growth produced specific toxins within the plant which led 

 to the appearance of the disease. The writer (1) has secured data which 

 do not lend support to the physiological origin of the disease, but indicate 

 that it is dependent upon specific infection. 



Further studies of the properties of the expressed sap of mosaic plants, 

 termed the "virus" of the disease, have thrown considerable light on 

 the nature of the infective principle and its relation to some of the 

 enzymic properties of the sap of diseased plants. 



Woods (20) and other workers following him have attributed the origin 

 of the mosaic disease to oxidases and peroxidases existing normally in 

 healthy tobacco plants. Since it is a question of fundamental impor- 

 tance to determine whether or not such enzyms are the primary cause of 

 the disease, their relation to infection has been more fully investigated. 

 All data at hand indicate that infection does not depend upon the presence 

 of oxidases or peroxidases, but upon an infective principle which is not a 

 normal constituent of the sap of healthy plants. These conclusions rest 

 upon the fact that methods have been found by which the infective 

 principle may be separated from the oxidases and peroxidases present in 

 the sap of mosaic plants, as shown in the experimental work. 



FILTRATION EXPERIMENTS WITH THE VIRUS OF THE DISEASE 

 FILTRATION THROUGH THE LIVINGSTONE ATMOMETER POROUS CUP 



Earlier investigators have shown that the virus of the mosaic disease 

 of tobacco passes through the Berkefeld (normal) filter without losing its 

 infectious properties. The writer's experiments substantiate these re- 

 sults, as shown in Table I, although there is strong indication that the 

 virus becomes attenuated and is less infectious when filtered in this 



1 Reference is made by number to " Literature cited," p. 673-674. 



Journal of Agricultural Research, Vol. VI, No. 17 



Dept. of Agriculture, Washington, D. C July 24, 1916 



ep G — 83 



(649) 



