EFFECTS OF VARIOUS SALTS, ACIDS, GERMICIDES, ETC., 

 UPON THE INFECTIVITY OF THE VIRUS CAUSING THE 

 MOSAIC DISEASE OF TOBACCO 



By H. A. Ali^ard 



Assistant Physiologist, Office of Tobacco and Plant Nutrition Investigations, Bureau of 

 Plant Industry, United States Department of Agriculture 



In the course of the writer's investigations of the mosaic disease of 

 tobacco {Nicotiana spp.) many experiments have been carried out to 

 detennine the effects of different concentrations of salts, acids, alkalis, 

 germicides, etc., upon the infectivity of the virus. The object in view 

 was to throw some light on the question of the nature of the causal 

 infective agent and the degree of resistance of this infective principle to 

 the various chemical and germicidal treatments used. In these experi- 

 ments all concentrations stated as i gm. of reagent in loo c. c, 200 c. c, 

 etc., of solution refer to i gm. of actual water-free salt or other reagent 

 in the indicated volume of solution. The method of preparation of the 

 various concentrations has been uniform. For determining the action of 

 various concentrations of these substances, a double-strength concentra- 

 tion was first made with distilled water. Ten c. c. of virus were then 

 added to 10 c. c. of the solution, the concentration being brought down 

 to the strength desired. By using this method of preparation, the virus 

 itself is uniformly diluted to half its original strength in all solutions. 

 As the undiluted stronger concentrations (see Table I) frequently injure 

 the leaf tissues severely, or even kill the plants outright if inoculated 

 into them, it was sometimes necessary to dilute the solutions with sev- 

 eral volumes of water at the tim.e the inoculations were made. 



The results of the various concentrations of substances used are shown 

 in Table I and text following. 



Table I. — Effects of various chemicals on the infectivity of the virus of the mosaic 



disease of tobacco 



NITRIC ACID 



Concentration. 



Solution pre- 

 pared. 



Inocitlation 

 made. 



Plants used. 



Results. 



I gm. to 500 c. c. of virus solution. . 



I gm. to 800 c. c. of virus solution do . 



I gm. to 1,000 c. c. of virus solution do. 



I gm. to 1, 600 c. c. of virus solution do. 



I gm. to 1,800 c. c. of virus solution do. 



X gm. to 2,000 c. c. of virus solution do. 



I gra. to 2,600 c. c. of virus solution. .1 do. 



Virus without addition ' do. 



Tap water only (control) I do. 



June 9, 1914 



June 23, igii (14 

 days later), 

 do 



do. 

 .do. 

 .do. 

 .do. 

 .do. 

 .do. 

 .do. 



Journal of Agricultural Research, 

 Washington, D. C. 



(619) 



10 Connecticut 

 Broad leaf. 



do 



do 



do 



do 



....do 



....do 



....do 



....do 



lo plants mosaic. 



9 plants mosaic. 



Do. 



10 plants mosaic. 



Do. 

 Do. 

 Do. 

 Do. 

 All healthy. 



Vol. XIII, No. I 

 June 17, 1918 

 Key No. G-146 



